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  • 1
    ISSN: 1573-8604
    Keywords: callitrichids ; polyandry ; helping ; twinning ; paternal care
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tamarins and marmosets (callitrichids) present an unusual opportunity for study of the determinants of primate social systems, because both the mating and infant care patterns of callitrichids are variable, even within individual populations. In this paper, I briefly describe three characteristics of callitrichid social systems that distinguish them from most other primates: extensive male parental care, helping by nonreproductive individuals, and variable mating patterns. I then discuss the evolution of these characteristics and of the frequent twinning exhibited by callitrichids. I suggest that an ancestor of modern callitrichids gave birth to a single offspring at a time, mated monogamously, and had significant paternal care. The idea that males of this ancestral form must have provided paternal care, even though only single infants were born, derives from a comparison of litter/mother weight ratios in modern primate species. Twinning perhaps then evolved because of a combination of dwarfing in the callitrichid lineage, leading to higher litter/mother weight ratios, and a high infant mortality rate, and because the extensive paternal care already present facilitated the raising of twins. I propose that the helping behavior of older offspring may have coevolved with twinning, because helpers would have increased the chances of survival of twins, and the presence of twins would have increased the benefits of helping. Finally, the high costs of raising twins and the variability of group compositions, especially the fact that some groups would not have had older offspring to serve as helpers, may have selected for facultative polyandry in saddle-back tamarins (Saguinus fuscicollis) and perhaps in other callitrichid species. Both helping and cooperative polyandry have been extensively studied in bird species, and I apply some of the conclusions of these studies to the discussion of the evolution of callitrichid social systems.
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  • 2
    ISSN: 1573-8604
    Keywords: baboons ; greetings ; coalitions ; cooperation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Greetings involving exchanges of ritualized sexual gestures are a common form of interaction among adult male baboons, although relatively little attention has been paid to them. In this study, we investigate how greetings reflect important aspects of the male's social relationships, including dominance rank, age/residence status, and cooperative tendencies. The results are based on over 600 greetings among 12 adult males recorded during a 4-month study of a troop of wild olive baboons near Gilgil, Kenya. Four of the adult males were older, lower-ranking, long-term residents, which frequently formed coalitions to take estrous females away from the eight young, higher-ranking males. Virtually all dyads greeted: greetings occurred more than twice as often as other types of male-male interactions; and nearly all greetings occurred in a neutral context, in which there was no resource at stake. The percentage of greetings completed, the frequency with which different gestures were employed, and the roles adopted by each male varied significantly across old-old, old-young, and young-young dyads. Greetings between young adult males were often interrupted or actively resisted, consistent with their unstable and ambiguous dominance relationships. Greetings between old-old dyads were usually completed and appeared consistent with their cooperative relationships. One pair of old males formed a stable, reciprocal coalition against young males, and this pair's greetings showed remarkable symmetry of roles. Greetings, we hypothesize, function to allow males to negotiate important aspects of their relationships, including cooperation.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of primatology 11 (1990), S. 237-282 
    ISSN: 1573-8604
    Keywords: brain evolution ; brain growth ; allometry ; encephalization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fundamental ambiguities in the interpretation of brain/body allometric trends can only be resolved by analyzing relationships between ontogenetic brain/body growth processes in different groups. The ambiguous concept of adult encephalization confuses at least three distinct types of transformation of a common mammalian growth curve: scalar magnification, total curve didplacement, and changes in proportions of the pre- and postnatal phases of the curve. The conservative ratio between pre- and postnatal growth phases determines the apparent linearity of comparative brain/body allometry and can be explained by assuming that embyological neurogenetic processes ultimately determine both target brain and body size—the first directly and the second indirectly via neurohormonal regulation of somatic growth. Uneven taxonomic distribution of different ontogenetic growth patterns may explain many differences in the allometric trends at different taxonomic levels of analysis. The human brain grows exactly as if it was in a giant ape body; however, because of decoupled growth in different brain regions, it regulates body growth as though it were the size of a chimpanzee brain. Human encephalization exhibits an ontogenetic transformation not found in other mammalian groups.
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  • 4
    ISSN: 1573-8604
    Keywords: baboon ; Papio ; demography ; population dynamics ; ecology ; altitude
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Twenty-seven troops were counted during a 1989 census of the mountain baboon population at Giants Castle Game Reserve. In contrast to earlier findings, and despite a similar population structure, we found no relationship between group size and altitude. We argue that this is a consequence of long-term population processes whereby groups split as they grow larger and, in some cases, as their home ranges expand upward. At these high altitudes, smaller groups are eventually subjected to environmental conditions that destroy them. We propose that the high-altitude slopes act as a demographic sink.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of primatology 11 (1990), S. 399-399 
    ISSN: 1573-8604
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-8604
    Keywords: Saguinus ; tamarin ; diet ; foraging ; seasonality ; feeding ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From June through December, data were collected on the diet and ranging patterns of moustached (Saguinus mystax) and saddle-back (Saguinus fuscicollis) tamarin monkeys in the Amazon Basin of northeastern Peru. During this 7-month period, insects and nonleguminous fruits accounted for 83% of tamarin feeding and foraging time. Despite marked seasonal variation in rainfall and forest productivity, patterns of habitat utilization, day range, dietary diversity, resource exploitation, and activity budget remained relatively stable throughout the year. Moustached and saddle-back tamarins appear to solve problems of food acquisition and exploit patchily distributed feeding sites using a relatively limited set of foraging patterns. In general, these primates concentrate their daily feeding efforts on several trees from a small number of target plant species. These feeding sites are uncommon, produce only a small amount of ripe fruit each day, and are characterized by a high degree of intraspecific fruiting and flowering synchrony. Trees of the same species are frequently visited in succession, and individual feeding sites are revisited several times over the course of 1–2 weeks. This type of foraging pattern occurred during both dry and wet seasons and when exploiting fruit, nectar, legume, and exudate resources. Seasonal variation in the percentage of feeding and foraging time devoted to insectivory was also limited. In this investigation, there was no consistent evidence that temporal changes in overall forest fruit production had a major impact on the feeding, foraging, or ranging behavior of either tamarin species.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-8604
    Keywords: Barbary macaques ; fecundity ; reproductive senescence ; maternal investment ; menopause
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reproductive history of 207 female Barbary macaques, living in a large outdoor enclosure in Southwest Germany, was studied during an 11-year period. The results yielded a significant relationship between female age and fecundity, with fertility rates lower than expected among young and old females. Analysis of the reproductive history of individual females revealed a significant decline in fertility from prime age (7–12 years) to mid age (13–19 years), and from mid age to old age (20–25 years). The proportion of long interbirth intervals increased steadily among aging females. Infant survival was not significantly related to maternal age, but offspring of old females showed the highest survivorship. Behavioral observations revealed that old mothers weaned their offspring significantly later than younger mothers, suggesting that prolongation of interbirth intervals is due not only to deteriorating physical condition but also to increased maternal investment, as life history theory predicts. Reproduction ceased during the middle of the third decade of life. Final cessation of estrous cycling invariably occurred 3 or 4 years after the birth of the last offspring, but a postreproductive life span of ≥5 years appears to be common in this population. Available data suggest that reproductive senescence and menopause are more common among nonhuman primates than widely believed and that both traits are part of an adaptive life history strategy.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    International journal of primatology 11 (1990), S. 611-612 
    ISSN: 1573-8604
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-8604
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-8604
    Keywords: handedness ; hemispheric specialization ; great apes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present data on hand preference in great apes and discuss them in the context of theoretical models of hand preference in nonhuman primates presented by MacNeilageet al. (1987) and by Fagot and Vauclair (1991). We also discuss several methodological and statistical issues as they pertain to the assessment of hand preference in great apes and other primate species. Finally, we present a comparative framework for the study of hand preference, emphasizing the importance of studies with great apes in developing evolutionary models of hemispheric specialization.
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