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  • Articles  (14,510)
  • Oxford University Press  (14,510)
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  • 1
    Publication Date: 2020-08-27
    Description: We present CO observations towards a sample of six H i-rich Ultradiffuse galaxies (UDGs) as well as one UDG (VLSB-A) in the Virgo Cluster with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope. CO J = 1–0 is marginally detected at 4σ level in AGC 122966, as the first detection of CO emission in UDGs. We estimate upper limits of molecular mass in other galaxies from the non-detection of CO lines. These upper limits and the marginal CO detection in AGC 122966 indicate low mass ratios between molecular and atomic gas masses. With the star formation efficiency derived from the molecular gas, we suggest that the inefficiency of star formation in such H i-rich UDGs is likely caused by the low efficiency in converting molecules from atomic gas, instead of low efficiency in forming stars from molecular gas.
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  • 2
    Publication Date: 2020-07-16
    Description: We find that the minor axes of the ultra-diffuse galaxies (UDGs) in Abell 2634 tend to be aligned with the major axis of the central dominant galaxy, at a $gtrsim 95{{ m per cent}}$ confidence level. This alignment is produced by the bright UDGs with the absolute magnitudes Mr 〈 −15.3 mag, and outer-region UDGs with R 〉 0.5R200. The alignment signal implies that these bright, outer-region UDGs are very likely to acquire their angular momenta from the vortices around the large-scale filament before they were accreted into A2634, and form their extended stellar bodies outside of the cluster; in this scenario, the orientations of their primordial angular momenta, which are roughly shown by their minor axes on the images, should tend to be parallel to the elongation of the large-scale filament. When these UDGs fell into the unrelaxed cluster A2634 along the filament, they could still preserve their primordial alignment signal before violent relaxation and encounters. These bright, outer-region UDGs in A2634 are very unlikely to be the descendants of the high-surface-brightness dwarf progenitors under tidal interactions with the central dominant galaxy in the cluster environment. Our results indicate that the primordial alignment could be a useful probe of the origin of UDGs in large-scale structures.
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  • 3
    Publication Date: 2020-07-11
    Description: We present a detailed analysis of the gaseous component of the Si K edge using high-resolution Chandra spectra of low-mass X-ray binaries. We fit the spectra with a modified version of the ISMabs model, including new photoabsorption cross-sections computed for all Si ionic species. We estimate column densities for Si i, Si ii, Si iii, Si xii, and Si xiii, which trace the warm, intermediate temperature, and hot phases of the Galactic interstellar medium. We find that the ionic fractions of the first two phases are similar. This may be due to the physical state of the plasma determined by the temperature or due to the presence of absorber material in the close vicinity of the sources. Our findings highlight the need for accurate modelling of the gaseous component before attempting to address the solid component.
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  • 4
    Publication Date: 2020-07-11
    Description: Using state-of-the-art high-resolution fully GPU N-body simulations, we demonstrate for the first time that the infall of a dark matter-rich satellite naturally explains a present black hole offset by subparsecs in M31. Observational data of the tidal features provide stringent constraints on the initial conditions of our simulations. The heating of the central region of M31 by the satellite via dynamical friction entails a significant black hole offset after the first pericentric passage. After having reached its maximum offset, the massive black hole sinks towards the M31 centre due to dynamical friction and it is determined to be offset by subparsecs as derived by observations.
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  • 5
    Publication Date: 2020-06-12
    Description: In two recent papers published in MNRAS, Namouni and Morais claimed evidence for the interstellar origin of some small Solar system bodies, including: (i) objects in retrograde co-orbital motion with the giant planets and (ii) the highly inclined Centaurs. Here, we discuss the flaws of those papers that invalidate the authors’ conclusions. Numerical simulations backwards in time are not representative of the past evolution of real bodies. Instead, these simulations are only useful as a means to quantify the short dynamical lifetime of the considered bodies and the fast decay of their population. In light of this fast decay, if the observed bodies were the survivors of populations of objects captured from interstellar space in the early Solar system, these populations should have been implausibly large (e.g. about 10 times the current main asteroid belt population for the retrograde co-orbital of Jupiter). More likely, the observed objects are just transient members of a population that is maintained in quasi-steady state by a continuous flux of objects from some parent reservoir in the distant Solar system. We identify in the Halley-type comets and the Oort cloud the most likely sources of retrograde co-orbitals and highly inclined Centaurs.
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  • 6
    Publication Date: 2020-06-18
    Description: Strong gravitational lensing has been a powerful probe of cosmological models and gravity. To date, constraints in either domain have been obtained separately. We propose a new methodology through which the cosmological model, specifically the Hubble constant, and post-Newtonian parameter can be simultaneously constrained. Using the time-delay cosmography from strong lensing combined with the stellar kinematics of the deflector lens, we demonstrate that the Hubble constant and post-Newtonian parameter are incorporated in two distance ratios that reflect the lensing mass and dynamical mass, respectively. Through the re-analysis of the four publicly released lenses distance posteriors from the H0LiCOW (H0 Lenses in COSMOGRAIL’s Wellspring) collaboration, the simultaneous constraints of Hubble constant and post-Newtonian parameter are obtained. Our results suggest no deviation from the general relativity; $gamma _{t {PPN}}=0.87^{+0.19}_{-0.17}$ with a Hubble constant that favours the local Universe value, $H_0=73.65^{+1.95}_{-2.26}$ km s−1 Mpc−1. Finally, we forecast the robustness of gravity tests by using the time-delay strong lensing for constraints we expect in the next few years. We find that the joint constraint from 40 lenses is able to reach the order of $7.7{{ m per cent}}$ for the post-Newtonian parameter and $1.4{{ m per cent}}$ for the Hubble constant.
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  • 7
    Publication Date: 2020-07-10
    Description: One of the proposed channels of binary black hole mergers involves dynamical interactions of three black holes. In such scenarios, it is possible that all three black holes merge in a so-called hierarchical merger chain, where two of the black holes merge first and then their remnant subsequently merges with the remaining single black hole. Depending on the dynamical environment, it is possible that both mergers will appear within the observable time window. Here, we perform a search for such merger pairs in the public available LIGO and Virgo data from the O1/O2 runs. Using a frequentist p-value assignment statistics, we do not find any significant merger pair candidates, the most significant being GW170809-GW151012 pair. Assuming no observed candidates in O3/O4, we derive upper limits on merger pairs to be ∼11–110 yr−1 Gpc−3, corresponding to a rate that relative to the total merger rate is ∼0.1−1.0. From this, we argue that both a detection and a non-detection within the next few years can be used to put useful constraints on some dynamical progenitor models.
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  • 8
    Publication Date: 2020-07-10
    Description: We present extremely deep upper limits on the radio emission from 4U 1957+11, an X-ray binary that is generally believed to be a persistently accreting black hole that is almost always in the soft state. We discuss a more comprehensive search for Type I bursts than in past work, revealing a stringent upper limit on the burst rate, bolstering the case for a black hole accretor. The lack of detection of this source at the 1.07 μJy/beam noise level indicates jet suppression that is stronger than expected even in the most extreme thin disc models for radio jet production – the radio power here is 1500–3700 times lower than the extrapolation of the hard state radio/X-ray correlation, with the uncertainties depending primarily on the poorly constrained source distance. We also discuss the location and velocity of the source and show that it must have either formed in the halo or with a strong asymmetric natal kick.
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  • 9
    Publication Date: 2020-06-12
    Description: Swift J004427.3−734801 is an X-ray source in the Small Magellanic Cloud (SMC) that was first discovered as part of the Swift S-CUBED programme in 2020 January. It was not detected in any of the previous 3 yr worth of observations. The accurate positional determination from the X-ray data has permitted an optical counterpart to be identified that has the characteristics of an O9V−B2III star. Evidence for the presence of an infrared excess and significant I-band variability strongly suggests that this is an OBe-type star. Over 17 yr worth of optical monitoring by the OGLE (Optical Gravitational Lensing Experiment) project reveals periods of time in which quasi-periodic optical flares occur at intervals of ∼21.5 d. The X-ray data obtained from the S-CUBED project reveal a very soft spectrum, too soft to be that from accretion on to a neutron star or black hole. It is suggested here that this is a rarely identified Be star–white dwarf binary in the SMC.
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  • 10
    Publication Date: 2020-07-10
    Description: Gravitational microlensing can detect isolated stellar-mass black holes (BHs), which are believed to be the dominant form of Galactic BHs according to population synthesis models. Previous searches for BH events in microlensing data focused on long time-scale events with significant microlensing parallax detections. Here we show that, although BH events preferentially have long time-scales, the microlensing parallax amplitudes are so small that in most cases the parallax signals cannot be detected statistically significantly. We then identify OGLE-2006-BLG-044 to be a candidate BH event because of its long time-scale and small microlensing parallax. Our findings have implications to future BH searches in microlensing data.
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  • 11
  • 12
    Publication Date: 2007-06-01
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  • 13
    Publication Date: 2007-06-01
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  • 14
    Publication Date: 2015-08-14
    Description: We present a sub-100 pc-scale analysis of the CO molecular gas emission and kinematics of the gravitational lens system SDP.81 at redshift 3.042 using Atacama Large Millimetre/submillimetre Array (ALMA) science verification data and a visibility-plane lens reconstruction technique. We find clear evidence for an excitation-dependent structure in the unlensed molecular gas distribution, with emission in CO (5–4) being significantly more diffuse and structured than in CO (8–7). The intrinsic line luminosity ratio is r 8–7/5–4  = 0.30 ± 0.04, which is consistent with other low-excitation starbursts at z  ~ 3. An analysis of the velocity fields shows evidence for a star-forming disc with multiple velocity components that is consistent with a merger/post-coalescence merger scenario, and a dynamical mass of M (〈1.56 kpc) = 1.6 ± 0.6  x  10 10 M . Source reconstructions from ALMA and the Hubble Space Telescope show that the stellar component is offset from the molecular gas and dust components. Together with Karl G. Jansky Very Large Array CO (1–0) data, they provide corroborative evidence for a complex ~2 kpc-scale starburst that is embedded within a larger ~15 kpc structure.
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  • 15
    Publication Date: 2015-08-24
    Description: Regardless of the physical origin of stellar magnetic fields – fossil or dynamo induced - an inclination angle between the magnetic and rotation axes is very often observed. Absence of observational evidence in this direction in the solar case has led to generally assume that its global magnetic field and rotation axes are well aligned. We present the detection of a monthly periodic signal of the photospheric solar magnetic field at all latitudes, and especially near the poles, revealing that the main axis of the Sun's magnetic field is not aligned with the surface rotation axis. This result reinforces the view of our Sun as a common intermediate-mass star. Furthermore, this detection challenges and imposes a strong observational constraint to modern solar dynamo theories.
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  • 16
    Publication Date: 2015-08-21
    Description: We use the ‘Evolution and Assembly of GaLaxies and their Environments’ ( eagle ) suite of hydrodynamical cosmological simulations to measure offsets between the centres of stellar and dark matter components of galaxies. We find that the vast majority (〉95 per cent) of the simulated galaxies display an offset smaller than the gravitational softening length of the simulations (Plummer-equivalent  = 700 pc), both for field galaxies and satellites in clusters and groups. We also find no systematic trailing or leading of the dark matter along a galaxy's direction of motion. The offsets are consistent with being randomly drawn from a Maxwellian distribution with  ≤ 196 pc. Since astrophysical effects produce no feasible analogues for the $1.62^{+0.47}_{-0.49}$  kpc offset recently observed in Abell 3827, the observational result is in tension with the collisionless cold dark matter model assumed in our simulations.
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  • 17
    Publication Date: 2015-08-24
    Description: The solar wind magnetic field contains rotations at a broad range of scales, which have been extensively studied in the magnetohydrodynamics range. Here, we present an extension of this analysis to the range between ion and electron kinetic scales. The distribution of rotation angles was found to be approximately lognormal, shifting to smaller angles at smaller scales almost self-similarly, but with small, statistically significant changes of shape. The fraction of energy in fluctuations with angles larger than α was found to drop approximately exponentially with α, with e-folding angle 9.8° at ion scales and 0 $_{.}^{\circ}$ 66 at electron scales, showing that large angles (α 〉 30°) do not contain a significant amount of energy at kinetic scales. Implications for kinetic turbulence theory and the dissipation of solar wind turbulence are discussed.
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  • 18
    Publication Date: 2015-08-12
    Description: We report the broad-band spectral properties of the X-ray pulsar Cep X-4 by using a Suzaku observation in 2014 July. The 0.8–70 keV spectrum was found to be well described by three continuum models – Negative and Positive power-law with Exponential cut-off (NPEX), high-energy cut-off power-law and CompTT models. Additional components such as a cyclotron line at ~28 keV and two Gaussian components for iron lines at 6.4 and 6.9 keV were required in the spectral fitting. Apart from these, an additional absorption feature at ~45 keV was clearly detected in residuals obtained from the spectral fitting. This additional feature at ~45 keV was clearly seen in phase-resolved spectra of the pulsar. We identified this feature as the first harmonic of the fundamental cyclotron line at ~28 keV. The ratio between the first harmonic and fundamental line energies (1.7) was found to be in disagreement with the conventional factor of 2, indicating that the heights of line-forming regions are different or viewed at larger angles. The phase-resolved spectroscopy of the fundamental and first harmonic cyclotron lines shows significant pulse-phase variation of the line parameters. This can be interpreted as the effect of viewing angle or the role of complicated magnetic field of the pulsar.
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  • 19
    Publication Date: 2015-08-14
    Description: The spin-down of a neutron star, e.g. due to magneto-dipole losses, results in compression of the stellar matter and induces nuclear reactions at phase transitions between different nuclear species in the crust. We show that this mechanism is effective in heating recycled pulsars, in which the previous accretion process has already been compressing the crust, so it is not in nuclear equilibrium. We calculate the corresponding emissivity and confront it with available observations, showing that it might account for the likely thermal ultraviolet emission of PSR J0437–4715.
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  • 20
    Publication Date: 2015-08-14
    Description: New insights into the formation of interstellar formamide, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction NH 2 + H 2 CO -〉 NH 2 CHO + H. Contrarily to what previously suggested, this reaction is essentially barrierless and can, therefore, occur under the low temperature conditions of intestellar objects thus providing a facile formation route of formamide. The rate coefficient parameters for the reaction channel leading to NH 2 CHO + H have been calculated to be A = 2.6 x 10 –12  cm 3  s –1 , β = –2.1 and = 26.9 K in the range of temperatures 10–300 K. Including these new kinetic data in a refined astrochemical model, we show that the proposed mechanism can well reproduce the abundances of formamide observed in two very different interstellar objects: the cold envelope of the Sun-like protostar IRAS16293–2422 and the molecular shock L1157-B2. Therefore, the major conclusion of this Letter is that there is no need to invoke grain-surface chemistry to explain the presence of formamide provided that its precursors, NH 2 and H 2 CO, are available in the gas phase.
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  • 21
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    Oxford University Press
    Publication Date: 2015-09-23
    Print ISSN: 1366-8781
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  • 22
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    Oxford University Press
    Publication Date: 2015-09-23
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  • 23
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    Oxford University Press
    Publication Date: 2015-09-23
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  • 24
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    Oxford University Press
    Publication Date: 2015-09-23
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  • 25
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    Oxford University Press
    Publication Date: 2015-09-23
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  • 26
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    Oxford University Press
    Publication Date: 2015-09-23
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  • 27
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    Oxford University Press
    Publication Date: 2015-09-23
    Description: Sheila Peacock reports on a meeting that explored the UK's contribution to seismology in the past, present and future.
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  • 28
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    Oxford University Press
    Publication Date: 2015-09-23
    Description: Jenny Collier , marine geophysicist and President of the BGA, explains why she is addicted to science.
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  • 29
    Publication Date: 2015-09-25
    Description: Recent Low-Frequency Array (LOFAR) observations at 115–175 MHz of a field at medium Galactic latitudes (centred at the bright quasar 3C196) have shown striking filamentary structures in polarization that extend over more than 4° across the sky. In addition, the Planck satellite has released full sky maps of the dust emission in polarization at 353 GHz. The LOFAR data resolve Faraday structures along the line of sight, whereas the Planck dust polarization maps probe the orientation of the sky projected magnetic field component. Hence, no apparent correlation between the two is expected. Here we report a surprising, yet clear, correlation between the filamentary structures, detected with LOFAR, and the magnetic field orientation, probed by the Planck satellite. This finding points to a common, yet unclear, physical origin of the two measurements in this specific area in the sky. A number of follow-up multifrequency studies are proposed to shed light on this unexpected finding.
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  • 30
    Publication Date: 2015-09-25
    Description: Protoplanetary discs are now routinely observed and exoplanets, after the numerous indirect discoveries, are starting to be directly imaged. To better understand the planet formation process, the next step is the detection of forming planets or of signposts of young planets still in their disc, such as gaps. A spectacular example is the Atacama Large Millimeter/submillimeter Array (ALMA) science verification image of HL Tau showing numerous gaps and rings in its disc. To study the observability of planet gaps, we ran 3D hydrodynamical simulations of a gas and dust disc containing a 5 M J gap-opening planet and characterized the spatial distribution of migrating, growing and fragmenting dust grains. We then computed the corresponding synthetic images for ALMA. For a value of the dust fragmentation threshold of 15 m s –1 for the collisional velocity, we identify for the first time a self-induced dust pile-up in simulations taking fragmentation into account. This feature, in addition to the easily detected planet gap, causes a second apparent gap that could be mistaken for the signature of a second planet. It is therefore essential to be cautious in the interpretation of gap detections.
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  • 31
    Publication Date: 2015-09-25
    Description: Recent observations have discovered a number of extremely gas-rich very faint dwarf galaxies possibly embedded in low-mass dark matter haloes. We investigate star formation histories of these gas-rich dwarf (‘almost dark’) galaxies both for isolated and interacting/merging cases. We find that although star formation rates (SFRs) are very low (〈10 –5 M  yr –1 ) in the simulated dwarfs in isolation for the total halo masses ( M h ) of 10 8 -10 9 M , they can be dramatically increased to be ~10 –4 M  yr –1 when they interact or merge with other dwarfs. These interacting faint dwarfs with central compact H ii regions can be identified as isolated emission line dots (‘ELdots’) owing to their very low surface brightness envelopes of old stars. The remnant of these interacting and merging dwarfs can finally develop central compact stellar systems with very low metallicities ( Z /Z  〈 0.1), which can be identified as extremely metal-deficient (‘XMD’) dwarfs. These results imply that although there would exist many faint dwarfs that can be hardly detected in the current optical observations, they can be detected as isolated ELdots or XMD dwarfs, when they interact with other galaxies and their host environments. We predict that nucleated ultrafaint dwarfs formed from the darkest dwarf merging can be identified as low-mass globular clusters owing to the very low surface brightness stellar envelopes.
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  • 32
    Publication Date: 2015-09-28
    Description: The BRITE ( BRIght Target Explorer ) constellation of nanosatellites performs seismology of bright stars via high-precision photometry. In this context, we initiated a high-resolution, high signal-to-noise, high-sensitivity, spectropolarimetric survey of all stars brighter than V = 4. The goal of this survey is to detect new bright magnetic stars and provide prime targets for both detailed magnetic studies and asteroseismology with BRITE . Circularly polarized spectra were acquired with Narval at TBL (Bernard Lyot Telescope, France) and HARPSpol at ESO (European Southern Observatory) in La Silla (Chile). We discovered two new magnetic B stars: the B3V star i Car and the B8V component of the binary star Atlas. Each star was observed twice to confirm the magnetic detections and check for variability. These bright magnetic B stars are prime targets for asteroseismology and for flux-demanding techniques, such as interferometry.
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  • 33
    Publication Date: 2015-11-20
    Description: Females of many animal species seek mating opportunities with multiple males, despite being able to obtain sufficient sperm to father their offspring from a single male. In animals that live in stable social groups, females often choose to mate outside their group resulting in extra-group paternity (EGP). One reason proposed to explain female choice for extra-group males is to obtain compatible genes, for example, in order to avoid inbreeding depression in offspring. The benefits of such extra-group paternities could be substantial if they result in fitter, outbred offspring. However, avoiding inbreeding in this way could be costly for females, for example, through retaliation by cuckolded males or through receiving aggression while prospecting for extra-group mating opportunities. We investigate the costs and benefits of EGP in the banded mongoose Mungos mungo , a cooperatively breeding mammal in which within-group mates are sometimes close relatives. We find that pups born to females that mate with extra-group males are more genetically heterozygous are heavier and are more likely to survive to independence than pups born to females that mate within their group. However, extra-group matings also involve substantial costs as they occur during violent encounters that sometimes result in injury and death. This appears to lead femalebanded mongooses to adaptively adjust EGP levels according to the current risk of inbreeding associated with mating within the group. For group-living animals, the costs of intergroup interactions may help to explain variation in both inbreeding rates and EGP within and between species.
    Print ISSN: 1045-2249
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  • 34
    Publication Date: 2015-11-20
    Description: Many species living in developed areas adjust the timing of their activity and habitat selection to avoid humans, which may reduce their risk of conflict, including vehicle collisions. Understanding the behavioral adaptations to vehicles exhibited by species that thrive in urban areas could improve the conservation of many species that are threatened by road-caused mortality. We explored these behaviors using the seasonal distribution of 80 road-killed coyotes ( Canis latrans ) collected by civic employees and by comparing the activity patterns (step lengths) and road crossings made by 19 coyotes fitted with GPS collars with 3-h fix rates, 7 of which were killed in vehicle collisions. Coyotes were collected on roads most often in spring and fall, which corresponded to the most rapid changes in day length in our northern study area and when collared road-killed coyotes were more active during rush hour. Among collared coyotes, those that were killed on roads were most active and crossed roads most frequently at dusk. By contrast, surviving animals were most active and crossed roads most often near midnight year round and surprisingly, exhibited less avoidance of roads than did road-killed coyotes. Our results suggest that risk of vehicle collision is lower for coyotes that restrict the times at which they cross roads but some coyotes do not or cannot. Such behavioral flexibility to adapt to the timing of human activity relative to exogenous cues such as dawn and dusk may contribute to differences both among and within wildlife species in rates of coexistence with humans.
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  • 35
    Publication Date: 2015-11-20
    Description: Group living in animals is a well-studied phenomenon, having been documented extensively in a wide range of terrestrial, freshwater, and marine species. Although social dynamics are complex across space and time, recent technological and analytical advances enable deeper understanding of their nature and ecological implications. While for some taxa, a great deal of information is known regarding the mechanistic underpinnings of these social processes, knowledge of these mechanisms in elasmobranchs is lacking. Here, we used an integrative and novel combination of direct observation, accelerometer biologgers, and recent advances in network analysis to better understand the mechanistic bases of individual-level differences in sociality (leadership, network attributes) and diel patterns of locomotor activity in a widespread marine predator, the lemon shark ( Negaprion brevirostris ). We found that dynamic models of interaction based on Markov chains can accurately predict juvenile lemon shark social behavior and that lemon sharks did not occupy consistent positions within their network. Lemon sharks did however preferentially associate with specific group members, by sex as well as by similarity or nonsimilarity for a number of behavioral (nonsimilarity: leadership) and locomotor traits (similarity: proportion of time swimming "fast," mean swim duration; nonsimilarity: proportion of swimming bursts/transitions between activity states). Our study provides some of the first information on the mechanistic bases of group living and personality in sharks and further, a potential experimental approach for studying fine-scale differences in behavior and locomotor patterns in difficult-to-study organisms.
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  • 36
    Publication Date: 2015-11-20
    Description: Sexually selected traits are often driven to costly extremes by persistent directional selection. Energy acquisition and allocation can therefore influence variation in traits subject to both precopulatory and postcopulatory sexual selection, though the later have received much less attention. We tested the condition dependence of sperm morphology, sperm count, and fertilization success in a promiscuous lizard ( Anolis sagrei ) by 1) collecting sperm samples from wild males that varied naturally in body condition, 2) experimentally altering the body condition of captive males through dietary restriction, and 3) analyzing genetic paternity data from competitive mating trials between captive males that differed in body condition. In both wild and captive males, the length of the sperm midpiece decreased with body condition. Experimental food restriction decreased sperm production, decreased length of the sperm head, increased length of the sperm midpiece, and increased variance in sperm morphology within individuals. When restricted to a single copulation, males on high-intake diets exhibited a slight but nonsignificant fertilization advantage. Reanalysis of a previous experiment in which high- and low-condition males were sequentially allowed to copulate ad libitum for 1 week revealed a significant fertilization bias in favor of high-condition males. When controlling for mean treatment effects on the proportion of offspring sired and on sperm phenotypes, multiple regression revealed negative correlations between fertilization success and sperm head length, midpiece length, and sperm count. Collectively, our results suggest that condition-dependent fertilization success in A. sagrei may be partially mediated by underlying condition dependence of sperm morphology and sperm count.
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  • 37
    Publication Date: 2015-11-20
    Description: The postfledging dependence period (PFDP) is a crucial stage in the development of altricial birds. This period is regulated by parental investment, in terms of food provisioning and protection, and the demands of young associated with their development and physical condition. We examine the relative role of parental investment, food provisioning, and offspring decisions on the PFDP regulation in the Spanish imperial eagle ( Aquila adalberti ) by comparing the PFDP timing among young from non-manipulated territories, food supplemented territories, and birds translocated by hacking methods in the absence of adults and with ad libitum food supply. We found that extra food homogenized the nutritional condition of young and reduced the length of the first stage of PFDP, which is related to flight development and thus dependent on body condition. However, hacked birds did not reduce this stage despite ad libitum food, likely due to the lack of parental stimulus to develop advanced flights. Although the presence of adults might accelerate young becoming independent, hacked birds did not extend significantly the whole PFDP and all birds eventually started dispersal. Thereby, the PFDP regulation was primarily under offspring control, and modulated secondarily by parental effects independently of food provisioning and laying date. The length of this period seems to be constrained mainly by the inherent benefits of early dispersal on ultimate fitness in accordance with ontogenic hypotheses. In addition, hacking was shown to be an effective translocation method when properly used, without negative drawbacks for young development during the PFDP.
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  • 38
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    Publication Date: 2015-11-21
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  • 39
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    Publication Date: 2015-11-21
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  • 40
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    Publication Date: 2015-11-21
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  • 41
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    Publication Date: 2015-11-21
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  • 42
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  • 43
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    Publication Date: 2015-11-21
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  • 44
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    Publication Date: 2015-11-21
    Description: Simon Mitton summarizes the RAS Specialist Discussion Meeting that examined from a historical perspective Hoyle's remarkable career and the impact of his science, in the first of two articles on his scientific legacy.
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  • 45
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  • 46
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    Publication Date: 2015-11-21
    Description: Fred Hoyle's interest in geophysics has been largely forgotten; Helge Kragh takes another look.
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  • 47
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  • 48
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    Publication Date: 2015-11-21
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  • 49
    Publication Date: 2015-11-21
    Description: Assessments of the risk posed by near-Earth objects ignore the possibility of a giant comet entering the inner solar system. Bill Napier, David Asher, Mark Bailey and Duncan Steel examine the likelihood and potential consequences of the appearance of such a centaur.
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  • 50
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    Publication Date: 2015-11-21
    Description: Toby Samuels and Natasha Nicholson report on a debate over the pros and cons of turning humans into martians.
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  • 51
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    Publication Date: 2015-11-21
    Description: Nevil Maskelyne became the fifth Astronomer Royal 250 years ago, at a time when science and politics were intertwined. Paul Edwards maps his career.
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  • 52
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    Publication Date: 2015-11-21
    Description: Space physicist Mike Lockwood , who was awarded the RAS Gold Medal in 2015, was inspired by his school physics teacher, JFK and Feynman.
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  • 53
    Publication Date: 2015-11-23
    Description: Accreting neutron stars exhibit Type I X-ray bursts from both frequent hydrogen/helium flashes as well as rare carbon flashes. The latter (superbursts) ignite in the ashes of the former. Hydrogen/helium bursts, however, are thought to produce insufficient carbon to power superbursts. Stable burning could create the required carbon, but this was predicted to only occur at much larger accretion rates than where superbursts are observed. We present models of a new steady-state regime of stable hydrogen and helium burning that produces pure carbon ashes. Hot CNO burning of hydrogen heats the neutron star envelope and causes helium to burn before the conditions of a helium flash are reached. This takes place when the mass accretion rate is around 10 per cent of the Eddington limit: close to the rate where most superbursts occur. We find that increased heating at the base of the envelope sustains steady-state burning by steepening the temperature profile, which increases the amount of helium that burns before a runaway can ensue.
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  • 54
    Publication Date: 2015-11-23
    Description: We present new late-time near-infrared imaging of the site of the nearby core-collapse supernova SN 2012aw, confirming the disappearance of the point source identified by Fraser et al. and Van Dyk et al. as a candidate progenitor in both J and Ks filters. We remeasure the progenitor photometry, and find that both the J and Ks magnitudes of the source are consistent with those quoted in the literature. We also recover a marginal detection of the progenitor in H -band, for which we measure H = 19.67 ± 0.40 mag. Comparing the luminosity of the progenitor to stellar evolutionary models, SN 2012aw appears to have resulted from the explosion of a 12.5 ± 1.5 M red supergiant.
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  • 55
    Publication Date: 2015-11-26
    Description: We derive the carbon monoxide (CO) luminosity function (LF) for different rotational transitions [i.e. (1–0), (3–2), (5–4)] starting from the Herschel LF by Gruppioni et al. and using appropriate L CO – L IR conversions for different galaxy classes. Our predicted LFs fit the data so far available at z 0 and 2. We compare our results with those obtained by semi-analytical models (SAMs): while we find a good agreement over the whole range of luminosities at z 0, at z 1 and z 2, the tension between our LFs and SAMs in the faint and bright ends increases. We finally discuss the contribution of luminous active galactic nucleus ( L X 〉 10 44 erg s – 1 ) to the bright end of the CO LF concluding that they are too rare to reproduce the actual CO LF at z 2.
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  • 56
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    Oxford University Press
    Publication Date: 2015-11-20
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  • 57
    Publication Date: 2015-11-20
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  • 58
    Publication Date: 2015-11-20
    Description: In antagonistic encounters, the primary decision to be made is to fight or not. Animals may then possess adaptations to assess fighting ability in their opponents. Previous studies suggest that humans can assess strength and fighting ability based on facial appearance. Here we extend these findings to specific contests by examining the perception of male faces from paired winners and losers of individual fights in mixed martial arts sporting competitions. Observers, unfamiliar with the outcome, were presented with image pairs and asked to choose which of the 2 men was more likely to win if they fought while other observers chose between the faces based on masculinity, strength, aggressiveness, and attractiveness. We found that individuals performed at rates above chance in correctly selecting the winner as more likely to win the fight than the loser. We also found that winners were seen to be more masculine, stronger, and more aggressive than losers. Finally, women saw the winners as more attractive than the losers. Together these findings demonstrate that 1) humans can predict the outcome of specific fighting contests based on facial cues, 2) perceived masculinity and strength are putative cues to fighting success available from faces, and 3) facial cues associated with successful male–male competition are attractive to women.
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  • 59
    Publication Date: 2015-11-20
    Description: Assessing an opponent’s strength is an important component of attack strategies in territorial combats between males. Body size is often considered to directly influence an individual’s strength, but other honest visual signals may also affect the assessment of opponents. Among such visual signals are the so-called egg-spots, a conspicuous ovoid marking on the anal fin of male haplochromine cichlid fishes, made up of carotenoid-containing and other pigment cells. It has long been assumed that egg-spots are mainly relevant in courtship and spawning behavior, and previous work has focused primarily on their function in intersexual selection. Recently, however, both body size and egg-spots have been suggested to play a role in male–male interactions. To test whether egg-spots function in female choice or whether egg-spots and/or body size function as a predictor of strength and the subsequent attack strategy in male–male interactions, we performed a series of behavioral experiments in the haplochromine cichlid Astatotilapia calliptera . The trials revealed a limited involvement of egg-spots in female choice, yet a much stronger influence in male interactions. Territorial males combined information from the strength assessment based on body size and egg-spots to adopt their attack strategies. They launched more attacks against the larger intruder with many egg-spots compared with the smaller intruder without or with fewer egg-spots. Our study provides evidence that egg-spots serve as honest visual signal and that the level of asymmetries in egg-spot pattern and body size determines the relative impact of each trait in strength assessment.
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  • 60
    Publication Date: 2015-11-20
    Description: Evaluating the costs and benefits of dispersal on individual life history is critical to understanding its importance to ecology and evolution. In feral horses ( Equus ferus caballus ), females may permanently move among breeding groups (bands) during their lifetime (termed social dispersal). Here, we assess costs and benefits of adult female social dispersal using 7 years of movement and life history data from an individual-based study of feral horses on Sable Island. Using path and survival analyses, we explored relationships between social dispersal, female reproduction, and survival of offspring. Dispersal negatively correlated with a female’s next reproduction (probability to produce a living foal that was observed during our summer census) and reproductive success (RS) over the longer term (probability of producing foals in subsequent years). Females that dispersed had longer latency before next reproduction than nondispersing (philopatric) females. We could not measure costs in terms of induced abortions or neonatal survival, but we observed no evidence of infanticide during our summer censuses. Furthermore, overwinter survival of foals to 3 years of age was not affected by either dispersal of its mother before conception or as pregnant. Despite a 10% higher rate for foals dispersing with mothers to survive to 3 years compared with those of philopatric females, the difference was not statistically significant. Overall, our results suggest that dispersing individuals have lower RS that may be a cost of social dispersal on future reproduction.
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  • 61
    Publication Date: 2015-11-20
    Description: Large mammalian carnivores create areas perceived as having high and low risk by their ungulate prey. Human activities can indirectly shape this landscape of fear by altering behavior and spatial distribution of carnivores. We studied how red deer perceive the landscape of fear in an old-growth forest system (Białowieza Primeval Forest, Poland) both at large and fine spatial scale. Camera traps were placed at locations with and without tree logs (fine-scale risk factor) and at different distances from the core of a wolf territory and human settlements (large-scale risk factor). Red deer avoided coming close to large tree logs and increased their vigilance levels when they were present in close vicinity. The strength of these effects depended on the distance to the wolf core area; deer perceived tree logs as more risky when wolves were more often present. Hence, tree logs inside wolf core areas create fine-scale patches of fear with reduced deer browsing pressure, thereby enhancing chances for successful tree recruitment. Human presence shapes this landscape of fear as wolf core areas are located far from human settlements. This "human shadow" on predator–prey interactions is therefore an important component that should be taken into account in human-dominated landscapes.
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  • 62
    Publication Date: 2015-11-20
    Description: Why do females faced with the same array of potential mates often select different males? Variation in choosiness, defined as investment in mate search, is an important potential source of variation in mating decisions. Experimental work suggests such variation is driven by the costs of searching, but data from natural populations are scarce and few studies have addressed explicitly the counteracting benefits expected from search investment. We tracked male visitation behavior of free-ranging females on a lek of lance-tailed manakins ( Chiroxiphia lanceolata ) using automated telemetry at dispersed male display sites. We assessed relationships of female age, experience, body condition, and parasite load with variation in choosiness, quantified as males visited, number of visits, and visit duration. Young females visited more males and made more total visits before choosing a mate, whereas older females conducted longer visits for first nests of the year. Renesting females searched less, but the few monitored females mating faithfully between years nevertheless sampled several males. We found little support for effects of condition on choosiness. Results suggest females sample more widely when they lack information about the distribution of available mates. Though previous work in the study population has shown both female preference for and offspring fitness benefits from heterozygous sires, genetic tests of paternity revealed choosier females did not choose more heterozygous mates. Females’ investment in mate search varied in relation to their own age and within-year experience, but mate search investment did not independently determine variation in choice among individuals.
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  • 63
    Publication Date: 2015-11-23
    Description: The formation of the Milky Way stellar halo is thought to be the result of merging and accretion of building blocks such as dwarf galaxies and massive globular clusters. Recently, Deason et al. suggested that the Milky Way outer halo formed mostly from big building blocks, such as dwarf spheroidal galaxies, based on the similar number ratio of blue straggler (BS) stars to blue horizontal branch (BHB) stars. Here we demonstrate, however, that this result is seriously biased by not taking into detailed consideration on the formation mechanism of BHB stars from helium-enhanced second-generation population. In particular, the high BS-to-BHB ratio observed in the outer halo fields is most likely due to a small number of BHB stars provided by globular clusters (GCs) rather than to a large number of BS stars. This is supported by our dynamical evolution model of GCs which shows preferential removal of first-generation stars in GCs. Moreover, there are a sufficient number of outer halo GCs which show very high BS-to-BHB ratio. Therefore, the BS-to-BHB number ratio is not a good indicator to use in arguing that more massive dwarf galaxies are the main building blocks of the Milky Way outer halo. Several lines of evidence still suggest that GCs can contribute a significant fraction of the outer halo stars.
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  • 64
    Publication Date: 2015-11-20
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  • 65
    Publication Date: 2015-11-20
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  • 66
    Publication Date: 2015-11-20
    Description: Urban animals often show differences in aggression relative to their rural counterparts, but the ultimate and proximate origins of these differences are poorly understood. Here, we compared urban and rural song sparrows ( Melospiza melodia ), a species for which higher levels of aggression in urban populations have previously been reported. First, we confirmed elevated territorial aggression levels in urban birds relative to rural birds over multiple years. To begin to identify the environmental variables contributing to these differences, we related aggression to features of the social and physical environment, specifically population density and the availability of suitable nesting vegetation. Population distribution and the availability of suitable nest vegetation were not correlated with territorial aggression levels. Subsequently, we conducted a food supplementation experiment to determine whether potential differences in the relative availability of food between the 2 habitats might drive differences in aggression. Food supplementation increased territorial aggression significantly, particularly in rural birds. Thus, it appears that the availability of food could play a role in determining territorial aggression in song sparrows. The specific combination of these features found in urban areas may cause the increased levels of territorial aggression seen in these populations.
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  • 67
    Publication Date: 2015-11-20
    Description: A critical question in the study of the evolution of cognition and the brain concerns the extent to which variation in cognitive processes and associated neural mechanisms is adaptive and shaped by natural selection. In order to be available to selection, cognitive traits and their neural architecture must show heritable variation within a population, yet heritability of cognitive and neural traits is not often investigated in the field of behavioral ecology. In this commentary, we outline existing research pertaining to the relative influences of genes and environment in cognitive and underlying neural trait variation, as well as what is known of their heritable genetic architecture by focusing on several cognitive traits that have received much attention in behavioral ecology. It is important to demonstrate that cognitive traits can respond to selection, and we advocate for an increased emphasis on investigating trait heritability for enhancing our understanding of the ecological, genetic and neurobiological mechanisms that have shaped interspecific and intraspecific variation in cognitive traits.
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  • 68
    Publication Date: 2015-11-20
    Description: Two recent observations in behavioral biology have sparked great interest and have already yielded many novel and intriguing insights. Bacteria appear to live lives of unforeseen behavioral complexity, and the consistent behavioral variation among individual animals is often not "noise" but turns out to be a highly relevant ecological and evolutionary feature in itself. Research covering these 2 phenomena has proceeded largely in isolation, and the rich behavioral lives of bacteria have not yet been studied with consistent interindividual behavioral differences in mind. Yet, the parallels between animal and bacterial behavior that are increasingly being uncovered, as well as the particular characteristics of bacteria, point toward a new approach in the study of consistent individual variation in behavior. Using bacteria can bring fruitful opportunities to the field and allows researchers to address questions that are very difficult to pursue using animal model systems. Notwithstanding a few challenges, bacteria can provide an alternative study system that may elucidate several evolutionary and ecological aspects of consistent individual behavioral variation.
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  • 69
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  • 70
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    Publication Date: 2015-11-21
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  • 71
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    Publication Date: 2015-11-21
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  • 72
    Publication Date: 2015-11-21
    Description: Alexander Russell , Anthony Yeates and Jonathan Eastwood review the state of the art and interesting future directions in this developing field, drawing on the RAS discussion meeting held on 12 December 2014.
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  • 73
    Publication Date: 2015-11-25
    Description: Nuclear star clusters (NCs) are found to exist in the centres of many galaxies and appear to follow scaling relations similar to those of supermassive black holes. Previous analytical work has suggested that such relations are a consequence of feedback-regulated growth. We explore this idea using high-resolution hydrodynamical simulations, focusing on the validity of the simplifying assumptions made in analytical models. In particular, we investigate feedback emanating from multiple stellar sources rather than from a single source, as is usually assumed, and show that collisions between shells of gas swept up by feedback leads to momentum cancellation and the formation of high-density clumps and filaments. This high-density material is resistant both to expulsion from the galaxy potential and to disruption by feedback; if it falls back on to the NC, we expect the gas to be available for further star formation or for feeding a central black hole. We also note that our results may have implications for the evolution of globular clusters and stellar clusters in high-redshift dark matter haloes.
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  • 74
    Publication Date: 2015-08-27
    Description: We explain the axisymmetric gaps seen in recent long-baseline observations of the HL Tau protoplanetary disc with the Atacama Large Millimetre/Submillimetre Array (ALMA) as being due to the different response of gas and dust to embedded planets in protoplanetary discs. We perform global, three-dimensional dusty smoothed particle hydrodynamics calculations of multiple planets embedded in dust/gas discs which successfully reproduce most of the structures seen in the ALMA image. We find a best match to the observations using three embedded planets with masses of 0.2, 0.27 and 0.55 M J in the three main gaps observed by ALMA, though there remain uncertainties in the exact planet masses from the disc model.
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  • 75
    Publication Date: 2015-08-27
    Description: Using deep Herschel and ALMA observations, we investigate the star formation rate (SFR) distributions of X-ray-selected active galactic nucleus (AGN) host galaxies at 0.5 〈  z  〈 1.5 and 1.5 〈  z  〈 4, comparing them to that of normal, star-forming (i.e. ‘main-sequence’, or MS) galaxies. We find that 34–55 per cent of AGNs in our sample have SFRs at least a factor of 2 below that of the average MS galaxy, compared to 15 per cent of all MS galaxies, suggesting significantly different SFR distributions. Indeed, when both are modelled as lognormal distributions, the mass and redshift-normalized SFR distributions of X-ray AGNs are roughly twice as broad, and peak 0.4 dex lower, than that of MS galaxies. However, like MS galaxies, the normalized SFR distribution of AGNs in our sample appears not to evolve with redshift. Despite X-ray AGNs and MS galaxies having different SFR distributions, the linear-mean SFR of AGNs derived from our distributions is remarkably consistent with that of MS galaxies, and thus with previous results derived from stacked Herschel data. This apparent contradiction is due to the linear-mean SFR being biased by bright outliers, and thus does not necessarily represent a true characterization of the typical SFR of X-ray AGNs.
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  • 76
    Publication Date: 2015-08-29
    Description: We investigate the density–shear instability in Hall-magnetohydrodynamics (Hall-MHD) via numerical simulation of the full non-linear problem in the context of magnetar activity. We confirm the development of the instability of a plane-parallel magnetic field with an appropriate intensity and electron density profile, in accordance with analytic theory. We find that the instability also appears for a monotonically decreasing electron number density and magnetic field, a plane-parallel analogue of an azimuthal or meridional magnetic field in the crust of a magnetar. The growth rate of the instability depends on the Hall properties of the field (magnetic field intensity, electron number density and the corresponding scaleheights), while being insensitive to weak resistivity. Since the Hall effect is the driving process for the evolution of the crustal magnetic field of magnetars, we argue that this instability is critical for systems containing strong meridional or azimuthal fields. We find that this process mediates the formation of localized structures with much stronger magnetic field than the average, which can lead to magnetar activity and accelerate the dissipation of the field and consequently the production of Ohmic heating. Assuming a 5  x  10 14  G magnetic field at the base of crust, we anticipate that magnetic field as strong as 10 15  G will easily develop in regions of typical size of a few hundred metres, containing magnetic energy of 10 43  erg, sufficient to power magnetar bursts. These active regions are more likely to appear in the magnetic equator where the tangential magnetic field is stronger.
    Print ISSN: 1745-3925
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  • 77
    Publication Date: 2015-05-31
    Description: Long expected transition states between the rotation powered and accretion powered non-thermal emission in the millisecond pulsar binary systems have been recently observed in the case of three objects PSR J1023+0038, PSR J1824–2452, and PSR J1227–4859. Surprisingly, the transition is related to the significant change in the -ray flux being a factor of a few higher with the presence of an accretion disc. The origin of this enhanced emission seems to be related to the penetration of the inner pulsar magnetosphere by the accretion disc. We propose that the radiation processes, characteristic for the rotation powered pulsar, can co-exist with the presence of an accretion disc in the inner pulsar magnetosphere. In our scenario additional -ray emission is produced by secondary leptons, originated close to the acceleration gap, which Compton up-scatter thermal radiation from the accretion disc to GeV energies. The accretion disc penetrates deep into the pulsar magnetosphere allowing the matter to fall on to the neutron star surface producing pulsed X-ray emission. We show that the sum of the rotation powered pulsar -ray emission, produced by the primary electrons in the curvature process, and the -ray emission, produced by secondary leptons, can explain the observed high-energy radiation from the redback binary pulsar PSR J1227–4853 in the state with evidences of the accretion disc.
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  • 78
    Publication Date: 2016-07-14
    Description: The fitness and survival of organisms ultimately depend on their feeding. Therefore, foraging behaviors should be selected to maximize cost-benefit ratio. Wind may restrict and modify animal movements increasing the cost of foraging, especially when the animal carries resources that intercept wind. We quantified the effect of wind on the foraging of leaf-cutting ants and evaluated whether this effect varies with 1) leaf fragment traits, such as area, mass, and shape, and 2) the characteristics of the foraging trail system. We also tested whether these ants show a short-term response to wind by selecting loads with characteristics that reduce wind interception, and a long-term response, by arranging the spatial design of the trail system in a way that reduces that effect. We found that in windy conditions, the speed of loaded ants was reduced by 55%, and ants were blown off the trail 28 times more than in windless conditions. However, wind only affected ants walking along trails that were perpendicular to wind direction or parallel upwind. Wind effect increased with area, mass, and shape of loads. At the short term, ants reduced the negative effect of wind by selecting smaller, lighter, or more elongated loads. However, trails showed no particular spatial distribution in relation to wind direction. This is the first study that quantifies the negative consequences of wind on leaf-cutting ants’ foraging and reports behaviors that can reduce this effect. Our work illustrates how short-term behavioral responses can mitigate the negative effect of an understudied environmental factor on ant foraging.
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  • 79
    Publication Date: 2016-07-14
    Description: The temporal partitioning hypothesis suggests that the evolution of different diel activity rhythms in animals might facilitate the coexistence between prey and predators. However, the temporal shift of habitat use induced by predation has rarely been observed. The study of such a mechanism is particularly relevant for introduced species because it might explain how native species can persist or decline in response to the presence of alien species. The introduction of fish into ponds inhabited by amphibians has severe consequences for their occurrence and abundance. Fish particularly affect an alternative newt phenotype, the paedomorph, which does not undergo metamorphosis and maintains larval traits such as gills at the adult stage. In a laboratory design, we assessed the diel patterns of habitat use in the 2 distinct morphological phenotypes of palmate newt ( Lissotriton helveticus ) in the presence or absence of goldfish ( Carassius auratus ). Both newt phenotypes avoided a risky habitat more in the presence than in the absence of fish. This habitat shift was more pronounced during the daytime (i.e., when the risk could be considered higher for the newts) than during nighttime. However, in contrast to metamorphs, paedomorphs showed less adaptive changes according to temporal risk and remained in their shelter for most of the time. Temporal and habitat partitioning at the diel scale between native and alien species might promote their coexistence, but diel change can also imply a cost in the overall reduction of the time allocated to essential activities, showing that species interactions remain complex.
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  • 80
    Publication Date: 2016-07-14
    Description: Translocation is an important conservation management tool. However, not all individuals are equally suited to translocation, and temperament traits (e.g., boldness, reactivity, exploration, sociability, and aggression) are likely to influence survival in a new environment. A few empirical studies have examined the consequences of personality differences on captive-bred translocated animals, but this has not been done for wild-caught animals. We compared behavioral responses to trapping, processing, holding, and release for 56 wild common brushtail possums ( Trichosurus vulpecula ). Twenty individuals were captured twice, once to attach radio-tracking collars, the second time (2 weeks later) for the translocation. Consistency of behavioral responses was compared between capture events and radio-tracking allowed estimates of pretranslocation home range, rest site selection, and foraging behavior. Survivors ( n = 10 survivors, 5 months later) were individuals showing the most fear or emotional reactivity during holding (less likely to have slept, eaten, defecated, or nested) and those that had the smallest home ranges and selected the safest den sites in their original habitat. Conversely, the greatest increase in body mass was recorded for individuals that had demonstrated "unsafe" behavior in their original habitat. To our knowledge, this is the first time this type of behavioral screening during handling and holding prior to release as part of a translocation has been undertaken. These methods have broad applicability for screening potential translocation candidates and are easily translated to a range of threatened and vulnerable animal species.
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  • 81
    Publication Date: 2016-07-14
    Description: The distribution and abundance of food resources are among the most important factors that influence animal behavioral strategies. Yet, spatial variation in feeding habitat quality is often difficult to assess with traditional methods that rely on extrapolation from plot survey data or remote sensing. Here, we show that maximum entropy species distribution modeling can be used to successfully predict small-scale variation in the distribution of 24 important plant food species for chimpanzees at Gombe National Park, Tanzania. We combined model predictions with behavioral observations to quantify feeding habitat quality as the cumulative dietary proportion of the species predicted to occur in a given location. This measure exhibited considerable spatial heterogeneity with elevation and latitude, both within and across main habitat types. We used model results to assess individual variation in habitat selection among adult chimpanzees during a 10-year period, testing predictions about trade-offs between foraging and reproductive effort. We found that nonswollen females selected the highest-quality habitats compared with swollen females or males, in line with predictions based on their energetic needs. Swollen females appeared to compromise feeding in favor of mating opportunities, suggesting that females rather than males change their ranging patterns in search of mates. Males generally occupied feeding habitats of lower quality, which may exacerbate energetic challenges of aggression and territory defense. Finally, we documented an increase in feeding habitat quality with community residence time in both sexes during the dry season, suggesting an influence of familiarity on foraging decisions in a highly heterogeneous landscape.
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  • 82
    Publication Date: 2016-07-14
    Description: Despite parents are equally related to all of their progeny, they may differentially invest in offspring that provide the highest fitness return. Sons and daughters can differ in reproductive value, especially in species where fitness is predicted by the expression of sexually selected traits. In many birds, offspring plumage coloration functions as a honest signal of individual quality, thus allowing parents to differentially invest in offspring of either sex accordingly. Here, we tested whether parents allocate different amounts of food depending on plumage color of their male and female offspring. As a model, we used the barn swallow ( Hirundo rustica ), a species where large among- and within-brood variation in ventral plumage color exists and male reproductive success varies according to ventral plumage coloration. We recorded the proportion of feedings obtained and body mass variation by dyads of same-sex and similar-sized nestlings subjected to either experimental darkening of their ventral plumage color or to a sham treatment. Plumage darkening enhanced food provisioning and body mass gain of males but not of females. Because darker ventral coloration is associated with larger reproductive success in male barn swallows, these results suggest that parents tune their effort toward more valuable male offspring that are likely to provide the greatest fitness returns. Our study thus suggests that parents are selected to differentially invest in offspring of either sex according to a trait expressed in early life, which is relevant to intrasexual competition for access to mates at sexual maturity.
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  • 83
    Publication Date: 2016-07-14
    Description: The iconic red hourglass of the black widow spiders (genus Latrodectus ) is traditionally considered an aposematic signal, yet experimental evidence is lacking. Here, we present data that suggest that black widow coloration may have evolved to be an aposematic signal that is more conspicuous to their vertebrate predators than to their insect prey. In choice experiments with wild birds, we found that the red-and-black coloration deters potential predators: Wild birds were ~3 times less likely to attack a black widow model with an hourglass than one without. Using visual-system appropriate models, we also found that a black widow’s red-and-black color combo is more apparent to a typical bird than a typical insect. Additionally, an ancestral reconstruction reveals that red dorsal coloration is ancestral in black widows and that at some point some North American widows lost their red dorsal coloration. Behaviorally, differences in red dorsal coloration between 2 North American species are accompanied by differences in microhabitat that affects how often a bird will view a black widow’s dorsal region. All observations are consistent with a cost–benefit trade-off of being more conspicuous to predators than to prey. We suggest that limiting detection by prey may help explain why red and black aposematic signals occur frequently in nature.
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  • 84
    Publication Date: 2016-07-14
    Description: While conducting a toxicity assessment of the antidepressant paroxetine (Paxil®), in wild-derived mice ( Mus musculus ), we observed that exposed dams (P 0 ) produced female biased litters (32:68 M:F). Though numerous experimental manipulations have induced sex ratio bias in mice, none have assessed the fitness of the offspring from these litters relative to controls. Here, we retrospectively analyze experimentally derived fitness data gathered for the purpose of toxicological assessment in light of 2 leading hypothesis (Trivers–Willard hypothesis [TWH] and cost of reproduction hypothesis [CRH]), seeking to test if this facultative sex ratio adjustment fits into an adaptive framework. Control F 1 males were heavier than F 1 females, but no differences in mass were detected between exposed F 1 males and females, suggesting that exposed dams did not save energy by producing fewer males, despite producing 29.2% lighter litters relative to controls. F 1 offspring of both treatments were released into seminatural enclosures where fitness was quantified. In enclosures, the relative reproductive success of F 1 -exposed males (compared with controls) was reduced by ~20% compared with the relative reproductive success of F 1 -exposed females. Thus, exposed dams increased their fitness by adjusting litters toward females who were less negatively affected by the exposure than males. Collectively, these data provide less support that the observed sex ratio bias results in energetic savings (CRH), and more support for the TWH because fitness was increased by biasing litters toward female offspring. These mammalian data are unique in their ability to support the TWH through the use of relevant fitness data.
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  • 85
    Publication Date: 2016-07-14
    Description: Understanding how seabirds and other central place foragers locate food resources represents a key step in predicting responses to changes in resource abundance and distribution. Where prey distributions are unpredictable and ephemeral, seabirds may gain up-to-date information by monitoring the direction of birds returning to the colony or by monitoring the foraging behavior of other birds through local enhancement. However, search strategies based on social information may require high population densities, raising concerns about the potential loss of information in declining populations. Our objectives were to explore the mechanisms that underpin effective search strategies based on social information under a range of population densities and different foraging conditions. Testing relevant hypotheses through field observation is challenging because of limitations in the ability to manipulate population densities and foraging conditions. We therefore developed a spatially explicit individual-based foraging model, informed by data on the movement and foraging patterns of seabirds foraging on pelagic prey, and used model simulations to investigate the mechanisms underpinning search strategies. Orientation of outbound headings in line with returning birds enables departing birds to avoid areas without prey even at relatively low population densities. The mechanisms underpinning local enhancement are more effective as population densities increase and may be facilitated by other mechanisms that concentrate individuals in profitable areas. For seabirds and other central place foragers foraging on unpredictable and ephemeral food resources, information is especially valuable when resources are spatially concentrated and may play an important role in mitigating poor foraging conditions.
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  • 86
    Publication Date: 2016-07-14
    Description: Experiments designed to quantify the effects of increasing numbers of carers on levels of offspring care are rare in cooperative breeding systems, where offspring are reared by individuals additional to the breeding pair. This paucity might stem from disagreement over the most appropriate manipulations necessary to elucidate these effects. Here, we perform both carer removal and brood enhancement experiments to test the effects of numbers of carers and carer:offspring ratios on provisioning rates in the cooperatively breeding chestnut-crowned babbler ( Pomatostomus ruficeps ). Removing carers caused linear reductions in overall brood provisioning rates. Further analyses failed to provide evidence that this effect was influenced by territory quality or disruption of group dynamics stemming from the removals. Likewise, adding nestlings to broods caused linear increases in brood provisioning rates, suggesting carers are responsive to increasing offspring demand. However, the 2 experiments did not generate quantitatively equivalent results: Each nestling received more food following brood size manipulation than carer removal, despite comparable carer:offspring ratios in each. Following an at-hatching split-design cross-fostering manipulation to break any links between prehatching maternal effects and posthatching begging patterns, we found that begging intensity increased in larger broods after controlling for metrics of hunger. These findings suggest that manipulation of brood size can, in itself, influence nestling provisioning rates when begging intensity is affected by scramble competition. We highlight that carer number and brood size manipulations are complimentary but not equivalent; adopting both can yield greater overall insight into carer effects in cooperative breeding systems.
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  • 87
    Publication Date: 2016-07-14
    Description: Dispersal affects the social contexts individuals experience by redistributing individuals in space, and the nature of social interactions can have important fitness consequences. During the vagrancy stage of natal dispersal, after an individual has left its natal site and before it has settled to breed, social affiliations might be predicted by opportunities to associate (e.g., distance in space and time between natal points of origin) or kin preferences. We investigated the social structure of a population of juvenile great tits ( Parus major ) and asked whether social affiliations during vagrancy were predicted by 1) the distance between natal nest-boxes, 2) synchrony in fledge dates, and 3) accounting for spatial and temporal predictors, whether siblings tended to stay together. We show that association strength was affected predominantly by spatial proximity at fledging and, to a lesser extent, temporal proximity in birth dates. Independently of spatial and temporal effects, sibling pairs associated more often than expected by chance. Our results suggest that the structure of the winter population is shaped primarily by limits to dispersal through incomplete population mixing. In addition, our results reveal kin structure, and hence the scope for fitness-related interactions between particular classes of kin. Both spatial-mediated and socially mediated population structuring can have implications for our understanding of the evolution of sociality.
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  • 88
    Publication Date: 2016-07-14
    Description: Cultural transmission in nonhuman animals is often sex biased, with females more frequently or efficiently learning cultural behaviors than males. The evolutionary origins of sex-biased cultural transmission have been a mystery, though it has been proposed that female offspring may gain greater reproductive benefit from cultural traits than sons—the "disparate benefits" hypothesis. I propose a different, "uniparental teaching," hypothesis where sex-biased transmission evolves in uniparental species if mothers teach, that is, invest in their offsprings’ learning. I show, with theoretical models, that mothers evolve to invest more in teaching daughters than sons because teaching daughters results in greater inclusive fitness benefits. Teaching a son gives him a reproductive benefit for one generation. However, I show that because daughters may teach future generations, teaching a daughter can be a better long-term investment. I also model the disparate benefits hypothesis and show that the uniparental teaching hypothesis better fits the empirical patterns of sex-biased transmission in the well-studied example of "sponging" in bottlenose dolphins. Uniparental teaching may also explain sex-biased transmission in other species, including chimpanzees. My findings suggest that controversial mechanisms of cultural transmission in nonhumans, such as teaching, may be inferred from population-level patterns of transmission even when it is difficult to observe transmission directly in the field or laboratory.
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  • 89
    Publication Date: 2016-07-14
    Description: Iteroparous organisms face a trade-off between reproduction and survival, but knowledge of whether how and when costs of long-term increases in workload are paid is scant. We increased locomotion costs for a whole year by equipping male great tits with a backpack during breeding, removing the backpacks 1 year later. We applied 3 different treatments: control (without backpack), light ("empty" backpack, 0.1g), and heavy ("full" backpack, 0.9g, ~5% of body mass). Backpacks were administered in 3 cohorts, and we monitored effects on mass of nestlings and the male, wing length, reproduction, and survival. Added mass had a negative effect on nestling mass in both the starting year of the experiment and 1 year later, but not on production of fledglings or recruits. In winter and the next breeding season, males equipped with heavy backpacks had a higher (net) body mass and had shorter third primary feathers than the other 2 groups. Heavy backpack males were less likely to sleep in a nest box in winter. Nest boxes are optimal roosting sites, and we interpret this finding as a treatment effect on success in competition over this resource. However, there was no effect of the manipulation on survival. Overall, we found no long-term fitness consequences, and we discuss possible explanations and implications for the "starvation–predation theory" of optimal body mass. However, we found short-term effects of carrying extra weight suggesting that behavioral studies using small devices should consider the effects of equipping small non-migratory passerines with devices such as transmitters.
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  • 90
    Publication Date: 2016-07-14
    Description: Behavior is usually the first line of defense against parasites. Antiparasite behaviors, such as grooming, or outright avoidance, have been shown to reduce the risk of parasitism in a wide variety of host–parasite systems. However, despite the central importance of antiparasite behavior, little is known about the extent to which prior exposure to parasites improves effectiveness. Here, we report the results of a 2-year study designed to test whether exposure to parasites can "prime" behavior, loosely analogous to priming of the immune system. We tested whether preening improves with experience by infesting captive-bred rock pigeons ( Columba livia ) with 2 common species of rock pigeon feather lice. We infested "primed" birds in Years 1 and 2 of the study and "nonprimed" birds only in Year 2. Birds with lice preened about a third more, on average, than birds without lice. Birds subsequently cleared of lice resumed preening at the same rate as birds that never had lice. Thus, our results confirm that preening is an inducible, reversible defense that is partly triggered by the presence of lice. Surprisingly, primed birds did not differ significantly from nonprimed birds in the overall rate or the efficacy of preening. Primed and nonprimed birds preened at similar rates and had similar numbers of lice at the end of the study. Our results therefore provide little evidence that antiparasite behavior improves with experience, at least in the case of preening as a defense against feather lice.
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  • 91
    Publication Date: 2016-07-14
    Description: Acoustic communication signals are often involved in mate-choice decisions. The decision for the best mating partner can become difficult when the available parameters of a signal are not positively correlated. Rational choice theory predicts that animals assign each signal a fixed value on a single dimension. The probability of choosing one signal over the other should be a monotonic function of the respective values and result in transitive choices. A violation of transitivity in choice behavior would suggest comparative rather than absolute decision making. Here, we tested the transitivity of preferences of female crickets for male calling songs. We conducted a series of binary choice experiments and compared their outcome to female preferences measured in no-choice experiments. To test transitivity, every choice pair had to differ in 2 parameters of the calling song. The parameter pairs used were 1) pulse rate and sound intensity, 2) chirp rate and sound intensity, and 3) pulse rate and chirp rate. The results revealed that females acted transitively if chirp rate and sound intensity or pulse rate and chirp rate of the patterns were varied. But females violated transitivity if pulse rate and sound intensity of signals differed as they mostly chose the louder pattern, although it was less attractive in the no-choice situation. This implies that sound intensity was weighted differently by females in the decision process in no-choice and choice experiments. The violation of transitivity suggests a comparative evaluation of available signals by female crickets.
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  • 92
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    Oxford University Press
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  • 93
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    Oxford University Press
    Publication Date: 2016-07-20
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  • 98
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  • 99
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  • 100
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