ALBERT

Notes: In the Fiji Islands, female yellow-lipped sea kraits (Laticauda colubrina) grow much larger than males, and have longer and wider heads than do conspecific males of the same body length. This morphological divergence is accompanied by (and may be adaptive to) a marked sex divergence in dietary habits. Adult female sea kraits feed primarily on large conger eels, and take only a single prey item per foraging bout. In contrast, adult males feed upon smaller moray eels, and frequently take multiple prey items. Prey size increases with snake body size in both males and females, but the sexes follow different trajectories in this respect. Female sea kraits consume larger eels relative to predator head size and body length than do males. Thus, the larger relative head size of female sea kraits is interpreted as an adaptation to consuming larger prey items. Our results are similar to those of previous studies on American water snakes (natricines) and Australian file snakes (acrochordids), indicating that similar patterns of sex divergence in dietary habits and feeding structures have evolved convergently in at least three separate lineages of aquatic snakes.

Notes: Abstract  Large predators play important ecological roles, but often are sensitive to habitat changes and thus are early casualties of habitat perturbation. Pythons are among the largest predators in many Australian environments, and hence warrant conservation-orientated research. Carpet pythons (Morelia spilota imbricata) have declined across much of south-western Australia presumably because of habitat clearance and degradation. Information on habitat use, home range sizes and movements is needed to plan for the conservation of this important predator. We studied pythons at two study sites (Garden Island and Dryandra Woodland) with markedly different climates, habitat types and disturbance histories. We surgically implanted radio-transmitters in 91 pythons and tracked them for periods of 1 month to 4 years. Dryandra pythons remained inactive inside tree hollows during cooler months (May–September), whereas some (especially small) pythons on Garden Island continued to move and feed. Overall weekly displacements (mean = 100–150 m) were similar at the two study sites and among sex/age classes, except that reproductive females were sedentary during summer while they were incubating eggs. Home ranges averaged 15–20 ha. Adult male pythons had larger home ranges than adult females at Dryandra, but not at Garden Island. Radio-tracked snakes at Dryandra exhibited high site fidelity, returning to previously occupied logs after long absences and reusing tree hollows for winter shelter. Many of the logs used by snakes had been felled during plantation establishment 〉70 years ago, with little subsequent regeneration of source trees. In contrast, Garden Island snakes usually sheltered under dense shrubs. Habitat usage was similar among different sex/age classes of snakes at each site, except that juvenile pythons were more arboreal than adults. Although carpet pythons demonstrate great flexibility in habitat use, certain habitat elements appear critical for the persistence of viable populations. Fire plays a central role in this process, albeit in complex ways. For example, low-intensity fires reduce the availability of hollow logs on the ground at Dryandra and fail to regenerate shrub thickets required by prey species. Paradoxically, high-intensity fires stimulate shrub thickets and fell trees creating new logs – but might also threaten overwinter trees. Thus, the impact of disturbances (such as wildfires) on the viability of python populations will be mediated in complex ways by alteration to important microhabitats such as vegetation cover or log availability. At Dryandra, landscape management should include occasional fire events to generate new logs as well as shrub thickets used by prey. Strategic burning may also be required at Garden Island to regenerate some vegetation communities.

Notes: Abstract  There are many anecdotal reports of massive day-to-day variation in activity levels of tropical reptiles and amphibians, and intuition suggests that weather conditions may be responsible for much of that variation. Our analysis of a large data set on the activity levels of tropical snakes and frogs confirms the existence of this short-term variation in activity levels, reveals strong synchrony between sympatric taxa in this respect, but also shows that standard weather variables (temperature, humidity, precipitation, moonlight, atmospheric pressure) are surprisingly poor at predicting the numbers of individuals and species encountered during standardized surveys. We recorded the numbers of snakes and prey taxa (frogs) encountered on 349 nights over the course of one year on a 1.3-km transect in the Adelaide River floodplain, in the wet–dry tropics of Australia. Frogs, water pythons (Liasis fuscus), slatey-grey snakes (Stegonotus cucullatus) and keelbacks (Tropidonophis mairii) all showed strongly seasonal patterns of activity. After adjusting for seasonal differences, encounter rates were related to climatic conditions but different taxa responded to different weather variables. Water python activity was related to amount of moonlight, keelback activity was related to temperature, and frog activity was related to relative humidity, rainfall, temperature and moonlight. However, weather variables explained relatively little of the variation in activity levels. Strong synchrony was evident among encounter rates with various taxa (independent of season and weather conditions), suggesting that activity levels may be determined by other unmeasured factors.

Notes: Abstract  Although most reptiles have polygynous mating systems without long-term pair bonds, one lineage of large scincid lizards in Australia is exceptional in this respect. Reports of complex sociality in the genus Egernia led us to conduct the first radiotelemetric field study of a species within this group. Land mullets (Egernia major) are large (60 cm total length), viviparous lizards from rainforest habitats in south-eastern Australia. To document the spatial ecology and social organization of this species, we captured 12 adult lizards in the Barrington Tops area of eastern New South Wales and implanted them with miniature radiotransmitters. The lizards were released at their sites of capture and located daily for the next 6 weeks. All of the radiotracked lizards had discrete home ranges of approximately 10 000 m2, based around well-defined core areas (approximately 2000–3000 m2). Females tended to move further, and to range over wider areas, than did males. All of the radiotracked lizards lived in social groups consisting of one or more adult males and females plus juveniles of all age classes. Subgroups were apparent within one group of five radio-tagged lizards: individual animals consistently shared their shelter sites and home ranges with one or more specific individuals. Male/female pairings were more frequent than expected under the null hypothesis of random association among individuals. The data in the present study support anecdotal reports of pair bonds in E. major and support suggestions that the social systems of species in this genus are more complex than those of previously studied reptiles.

Notes: Abstract The oviposition site that a female mosquito selects will influence the fitness of her larvae. We conducted a series of artificial pond experiments to compare the oviposition responses of two species of mosquitoes with the presence of tadpoles, conspecifics and chemical cues from these organisms. The two mosquito species differ markedly in larval ecology. The larvae of one species, Culex quinquefasciatus, co-occur with numerous freshwater organisms, including tadpoles of Linmodynastes peronii (the striped marsh frog). Larvae of the other mosquito, Ochlerotatus australis, inhabit small brackish rock ponds where the main potential competitors are tadpoles of Crinia signifera (the common eastern froglet). In field trials, females of both mosquito species oviposited significantly more often in water that contained (or had previously contained) conspecific larvae. However, these superficially similar responses were mediated via different pathways: fungicide abolished the response by C. quinquefasciatus but not by O. australis. The two mosquito species also responded differently to cues associated with syntopic tadpoles. The presence of tadpoles did not influence oviposition by C. quinquefasciatus, but O. australis oviposited less often if tadpoles were present. These interspecific differences in oviposition behaviour may be adaptive to differences in larval ecology: competition with tadpoles is likely to be more significant for O. australis than for C. quinquefasciatus. Our findings thus support the hypothesis that mosquitoes oviposit selectively to avoid potential anuran larval competitors.

Notes: Abstract  Stephens' Banded Snakes (Hoplocephalus stephensii Krefft 1869) are large (to 1 m), highly arboreal elapid snakes, restricted to mesic forested areas along the eastern coast of Australia. Radiotelemetric monitoring of 16 individuals at Whian Whian State Forest in north-eastern New South Wales over 25 months provided the first data on spatial ecology of this threatened taxon. Two major influences on movements by Stephens' Banded Snakes were identified: the distribution of large hollow-bearing trees, and the avoidance of conspecifics. Radiotracked snakes were sedentary inside tree hollows for extended periods (mean = 8 days) during their active season, interrupted by occasional long (mean = 124 m) nocturnal movements to another shelter tree. Snakes travelled on the ground rather than within the canopy, and thus were potentially exposed to terrestrial predators. Although the home ranges of the radiotracked snakes overlapped substantially (mean = 27%), simultaneous occupancy of ‘shared’ shelter trees was less common than expected by chance. Hence, we conclude that adult Stephens' Banded Snakes generally avoid the presence of conspecifics. Snakes used from five to 30 shelter trees and home ranges of male snakes were larger than those of females (mean = 20.2 vs 5.4 ha). The large spatial scale of these movements, and limited overlap among individuals, means that a viable population of this taxon requires a large area of contiguous forest. This requirement may explain why the species has not persisted in small forest fragments.