After short interbirth intervals, captive callitrichine monkeys have higher infant mortality

Agricultural habitat use affects infant survivorship in an endangered macaque species

Infant survival is a major determinant of individual fitness and constitutes a crucial factor in shaping species' ability to maintain viable populations in changing environments.1 Early adverse conditions, such as maternal loss, social isolation, and ecological hazards, have been associated with reduced rates of infant survivorship in wild primates.2,3,4 Agricultural landscapes increasingly replacing natural forest habitats may additionally threaten the survival of infants through exposure to novel predators,5 human-wildlife conflicts,6,7 or the use of harmful chemicals.8,9 Here, we investigated potential links between agricultural habitat use and high infant mortality in wild southern pig-tailed macaques (Macaca nemestrina) inhabiting a mosaic landscape of rainforest and oil palm plantation in Peninsular Malaysia. Longitudinal data revealed that 57% of all infants born during the study period (2014-2023) died before the age of 1 year, far exceeding mortality rates reported for other wild primates.10,11,12,13,14 Importantly, prolonged time spent in the plantation during infancy decreased the likelihood of infant survival by 3-fold, likely caused by increased exposure to the threats inherent to this environment. Further, mortality risk was elevated for infants born to primiparous mothers and predicted by prolonged maternal interbirth intervals, suggesting potential long-term effects attributed to the uptake and/or accumulation of pesticides in mothers' bodies.15,16,17 Indeed, existing literature reports that pesticides may cross the placental barrier, thus impacting fetal development during pregnancy.18,19,20 Our findings emphasize the importance of minimizing anthropogenic threats to wildlife in agricultural landscapes by establishing environmentally friendly cultivation practices that can sustain wildlife populations in the long term.

Life history impacts on infancy and the evolution of human social cognition

Greater longevity, slower maturation and shorter birth intervals are life history features that distinguish humans from the other living members of our hominid family, the great apes. Theory and evidence synthesized here suggest the evolution of those features can explain both our bigger brains and our cooperative sociality. I rely on Sarah Hrdy's hypothesis that survival challenges for ancestral infants propelled the evolution of distinctly human socioemotional appetites and Barbara Finlay and colleagues' findings that mammalian brain size is determined by developmental duration. Similar responsiveness to varying developmental contexts in chimpanzee and human one-year-olds suggests similar infant responsiveness in our nearest common ancestor. Those ancestral infants likely began to acquire solid food while still nursing and fed themselves at weaning as chimpanzees and other great apes do now. When human ancestors colonized habitats lacking foods that infants could handle, dependents' survival became contingent on subsidies. Competition to engage subsidizers selected for capacities and tendencies to enlist and maintain social connections during the early wiring of expanding infant brains with lifelong consequences that Hrdy labeled "emotionally modern" social cognition.

Review of Environmental and Health Factors Impacting Captive Common Marmoset Welfare in the Biomedical Research Setting

As a small-bodied neotropical nonhuman primate species, common marmosets have unique requirements for adequate husbandry and veterinary care to ensure proper maintenance and to promote good animal welfare in a biomedical research setting. Environmental conditions, as well as medical and research-related manipulations, can impact marmoset welfare. Research focus areas, including basic neuroscience, transgenics, and aging, involve additional implications for marmoset welfare. This manuscript provides a comprehensive review of factors that should be considered and mitigated as needed by clinical and research staff working with marmosets in biomedical research facilities to optimize the welfare of captive marmosets.

Linking personality traits and reproductive success in common marmoset (Callithrix jacchus)

Animal personality can affect individual fitness and population growth. Personality traits of either parent or parents' combination may facilitate reproduction and offspring survival across species. However, previous studies focused mainly on the role of only one sex, and the link between personality and fitness has not been confirmed in primates. We examined this link in both sexes of captive common marmosets (Callithrix jacchus), a cooperatively breeding primate with extensive paternal care. We studied the effects of five personality traits of the parents (Agreeableness, Assertiveness, Conscientiousness, Inquisitiveness, and Patience), including their absolute and directional differences within pairs, on key components of reproductive performance. We expected pairs with more similar personality scores to have higher reproductive success as found in other species with long-term pairs and biparental care, but found no evidence for this hypothesis. Instead, we detected strong effects of female traits on inter-birth intervals, which were shorter in more agreeable females, and fecundity rates, which were higher in more inquisitive females. Male traits appeared to have only a limited effect on reproductive success of the pair. Our study demonstrates that various aspects of animal personality underpin reproductive performance in captive common marmosets and provides novel insights into the possible ultimate causes of personality in cooperatively breeding species.