International Journal of Primatology最新文献

Mammalian mothers flexibly invest in their offspring to maximize their lifetime fitness. Flexible maternal investment may be particularly important in large-brained species with prolonged maternal care, e.g., in great apes. We investigated the effects of socioecological factors and mother–offspring characteristics on nine maternal behaviors in wild Sumatran orangutans (Pongo abelii; N = 22 mother-offspring pairs; >11,200 hr of focal data from 2007–2022) using generalized linear mixed models. The behaviors fall under four maternal functions: locomotory support (carrying), skill acquisition support (feeding in proximity, food transfer), protective proximity maintenance (body contact and proximity initiation, following), and independence promotion (body contact and proximity termination, avoiding). Mother’s parity was not significantly associated with any maternal behavior. Mothers were more likely to show locomotory support, skill acquisition support, and protective proximity maintenance toward younger than older offspring, whereas they were more likely to promote independence in older than younger offspring. Mothers with male offspring were more likely to show skill acquisition support to their offspring than those with female offspring. With increasing food availability, skill acquisition support reduced. With increasing association size (i.e., the number of individuals within 50 m of each other), mothers were more likely to show protective proximity maintenance and less likely to promote independence. When males were present, mothers were more likely to show locomotory support to their offspring. Sumatran orangutan mothers thus flexibly adjust offspring-directed behavior in response to prevailing socioecological factors and mother–offspring characteristics. Our findings add support to the evolutionary theory that mammalian mothers flexibly invest in their offspring.

Females other than the mother often handle infant primates. In some cases, this infant handling can affect the infant negatively and persist after that (excessive infant handling [EIH]). We tested two hypothesized functions (reproductive competition and social bridging) and three hypothesized mechanisms (social exchange, inexperience, and accessibility) for EIH to investigate why and how handlers perform EIH. We recorded infant handling bouts (n = 1446) involving 12 wild, 0- to 16-week-old Japanese macaques inhabiting Yakushima Island (Macaca fuscata yakui) through all-occurrence sampling. We found that aggression tended not to become EIH and that adults performed EIH more than subadults and juveniles. We also found that handlers groomed mothers less before EIH than before non-EIH. Handlers performed EIH, rather than non-EIH, toward infants who were out of contact with mothers and those of closer-ranking, higher-ranking, and unfamiliar females. These results suggest that EIH is not performed for reproductive competition but for social bridging with higher-value social partners. Social bridges with such individuals may be important in despotic species, such as that of the Japanese macaque. Our findings also suggest that EIH does not occur through proximate mechanisms of social exchange and inexperience with infants but partially through accessibility of infants. Handlers reduce the cost of EIH by choosing accessible infants (those who were out of contact with mothers and those of closer-ranking females), but at the same time, maternal tolerance allows the handlers to choose inaccessible infants (those of higher-ranking and unfamiliar females). Our study provides clear evidence of social tolerance in a despotic system and insights into natal attraction that negatively affects infants in wild primates.

The global trade in nonhuman primates represents a substantial threat to ecosystem health, human health, and primate conservation worldwide. Most of the primate trade involves trade for pet-keeping, consumption, or biomedical experimentation. We present an overview of international primate trade through five case studies; each describes a different facet of this trade. We draw on published scientific literature, media outlets, and open access datasets, including the CITES Trade Database to build these case studies. Case study 1 describes the role of introduced island populations of Macaca and Chlorocebus in trade for biomedical experimentation; case study 2 covers the global health threats posed by the primate trade, including zoonotic disease transmission once animals enter the trade pipeline; case study 3 addresses the ways that changing patterns of primate trade, from local markets to online, have increased the demand for primates as pets; case study 4 recognizes the role that local environmental activism can play in mitigating trade; and case study 5 shows variation between global regions in their contribution to the primate trade. We recommend greater oversight of primate trade, especially domestic trade within primate range countries, and real-time reporting to CITES to accurately track primate trade. Effective conservation-focused regulations that can minimise the negative effects of primate trade must be tailored to specific regions and species and require transparency, careful regulation, field research, and an understanding of the magnitude of this trade.

Studies integrating patterns of molar morphology and diet are particularly useful to address questions of evolutionary history and diet in extinct taxa. However, such studies are lacking among lorisoids compared with other primates. Lorisoidea is distinctive when considering diet as some taxa consume large quantities of gums or exudates, whereas others consume none. Although there has been previous study of the relationship between craniodental form and exudate feeding, little is known about how patterns of exudate feeding covary with variation in molar topography. We analyzed a sample (n = 52) of lorisoids representing 17 extant taxa and one extinct taxon (Karanisia clarki). We used dental topographic metrics to quantify functional aspects (i.e., curvature, complexity, and relief) of occlusal morphology. We also used ancestral state reconstruction to estimate topographic parameters for the last common ancestors (LCA) of Lorisoidea, Lorisidae, and Galagidae. As with previous studies, we found that higher topographic values characterize insectivores, whereas frugivores tend to have lower values. We reconstructed the LCA of Lorisoidea, Lorisidae, and Galagidae as insectivorous, with Lorisidae slightly more insectivorous, and potentially more exudativorous than Galagidae. Moreover, we identified a significant interaction between the primary dietary component (i.e., fruit or insects) and the level of exudate feeding in our sample, with exudate-feeding insectivores being associated with lower topographic values than exclusive insectivores. Finally, we reconstruct K. clarki as an insectivore, contrary to previous findings, although whether the animal fed on exudates remains ambiguous. Overall, our results provide a framework for testing ecological hypotheses about lorisoids and may point to a unique pattern of molar topography among exudativores.