Craig B. Stanford

Social learning is essential to the development of culture in humans, non-human primates, and other cultural species. Transmission biases (social learning strategies), the cognitive processes that guide conscious and subconscious decisions about when and from whom to learn, are a key branch of social learning. Primatological research has primarily explored single biases in isolation, such as chimpanzee bias toward adopting behavior demonstrated by higher-ranking individuals. However, few studies have considered how simultaneous strategies interact when subjects are given a conflicting choice involving two potentially adaptive biases. This study used a token-reward task with 35 sanctuary-housed chimpanzees at Ngamba Island Sanctuary in Uganda to determine whether chimpanzees more frequently adopt behaviors from high- or low-ranking female demonstrators when those behaviors differ in payoff, providing either a preferred pineapple piece (high-payoff) or a less favored carrot piece (low-payoff). Individuals in Group 1 observed a low-ranking demonstrator collecting the high-payoff reward (pineapple) and a high-ranking demonstrator collecting the low-payoff reward (carrot). Chimpanzees in Group 1 did not adopt one behavior significantly more frequently than the other. In Group 2, the demonstrator roles were reversed, and the frequency of high-payoff selection was higher. This suggests that high-payoff behaviors are more likely to propagate when presented by higher-ranking demonstrators. Additionally, adoption of high-payoff behaviors may be constrained by the presence of alternative, lower-payoff behaviors demonstrated by socially preferred individuals. In turn, this may contribute to explanations of why chimpanzee culture is relatively simple compared to that of humans.

While spoken language is unique to humans, many features of human communication are shared with great apes, including the use of signals in multiple modalities such as vocalizations, gestures, and facial expressions. Communication signals can be unimodal (involving a single modality) or multimodal (combining multiple modalities simultaneously). Here, we examined age-related differences in bonobo ( Pan paniscus) unimodal and multimodal communication signals. We assessed all vocalizations, gestures, facial expressions, and multimodal combinations produced by captive bonobos across a variety of behavioral contexts. All occurrences of communication signals were collected via focal observations from 12 individuals ranging from 6 months to 44 years of age. All individuals produced multimodal communication signals but all bonobos, regardless of age, produced multimodal signals at lower frequencies than unimodal signals. Age had a significant effect with younger bonobos producing more multimodal signals than older individuals ( p < 0.001). The infant and juveniles produced the most multimodal signals and there was an approximately 6% increase in unimodal signals per age year increase. These findings indicate a developmental shift toward unimodal signals as bonobos age. Behavioral context was predictive of signal type usage with an increase of multimodal signals in agonistic ( p < 0.001), play ( p < 0.001), and sexual contexts ( p = 0.001). This indicates that context is important for bonobo modality with multimodal signaling occurring more in “high-risk/high-reward” contexts where proper signal comprehension is vital. This study represents an overview of multimodal communication across bonobo life stages, offering further insights into primate communication patterns and developmental trajectories.

We created a database of lost and rediscovered tetrapod species, identified patterns in their distribution and factors influencing rediscovery. Tetrapod species are being lost at a faster rate than they are being rediscovered, due to slowing rates of rediscovery for amphibians, birds and mammals, and rapid rates of loss for reptiles. Finding lost species and preventing future losses should therefore be a conservation priority. By comparing the taxonomic and spatial distribution of lost and rediscovered tetrapod species, we have identified regions and taxa with many lost species in comparison to those that have been rediscovered—our results may help to prioritise search effort to find them. By identifying factors that influence rediscovery, we have improved our ability to broadly distinguish the types of species that are likely to be found from those that are not (because they are likely to be extinct). Some lost species, particularly those that are small and perceived to be uncharismatic, may have been neglected in terms of conservation effort, and other lost species may be hard to find due to their intrinsic characteristics and the characteristics of the environments they occupy (e.g. nocturnal species, fossorial species and species occupying habitats that are more difficult to survey such as wetlands). These lost species may genuinely await rediscovery. However, other lost species that possess characteristics associated with rediscovery (e.g. large species) and that are also associated with factors that negatively influence rediscovery (e.g. those occupying small islands) are more likely to be extinct. Our results may foster pragmatic search protocols that prioritise lost species likely to still exist.

Natural disasters can negatively affect primate population demography and social group structure. A clear understanding of these effects has important implications for wildlife conservation. The worst snow storms in nearly five decades hit portions of southern and central China between January 10 and February 6, 2008, presenting a unique opportunity to observe their immediate effects on a previously studied group of Hubei Golden Snub‐nosed Monkeys (Rhinopithecus roxellana hubeiensis) in temperate forests in Shennongjia Nature Reserve, Hubei Province, China. We recorded social and demographic characteristics of the group before and after the snow storms. The average group size decreased from 270 individuals before the storms to 197 individuals after the storms, a reduction of 27.2%. Adult females (30.1%), juveniles (38.1%) and infants (55.4%) suffered higher mortality than did adult males (15.7%). Despite age and sex‐based differences in mortality, the ratios of adult males to adult females, adults to immatures and adult females to immatures remained similar before and after the storms. However, higher mortality among females, juveniles and infants may reduce the group's long‐term potential for growth. Am. J. Primatol. 71:523–526, 2009.

Chimpanzees and traditional human foragers are among the few higher primates that actively hunt mammalian prey for a part of their subsistence. Both hunt socially, and meat is a relatively small part of the overall diet for both chimpanzees and most human hunter-gatherers. Most attempts to understand the hunting and meat-eating behavior of chimpanzees have likened these apes to social carnivores, such as wolves and lions. Those species are, however, obligate meat-eaters and, therefore, make hunting decisions daily based on where to find prey and how to capture, not whether to forage for it versus plant foods. A more appropriate comparison is with traditional human foragers of the tropics and subtropics because both hunter-gatherers and chimpanzees forage primarily for plant foods, making decisions about whether to pursue meat on an hourly or daily basis. Seeing both chimpanzees and humans as omnivores that have evolved separate suites of adaptations valuable for foraging, including meat foraging, allows us to pose a number of theoretical questions relating to the ecology of meat procurement. Because the last common ancestor of chimpanzees and modern humans likely resembled a chimpanzee in at least some important ways (Wrangham 1987; Moore 1996), a comparison of the meat-foraging adaptations of the two species should help us understand key behaviors involved in the divergence of the hominid phylogeny as well as the behavioral ecology of the common ancestor.