Complex Variation in Afrotropical Mammal Communities With Human Impact.

The diversity and composition of mammal communities are strongly influenced by human activities, though these relationships may vary across broad scales. Understanding this variation is key to conservation, as it provides a baseline for planning and evaluating management interventions. We assessed variation in the structure and composition of Afrotropical medium and large mammal communities within and outside protected areas, and under varying human impact.

Nonhuman primates and cattle: a camera trap survey of inter-specific spatial and temporal overlap.

Nonhuman primates are threatened across their distribution, with habitat loss, disease, poaching, and the pet trade causing widespread population decline. An understudied threat is the growing presence of cattle in primate habitat, with the increased exposure to human and bovid pathogens, domestic dogs that accompany herders, and habitat degradation. We investigated cattle-primate spatial and temporal overlap using 13 motion triggered cameras over a 16-month period (2023-2024).

Wild chimpanzee termite mound inspections converge with the onset of rain.

How and when to inspect for hidden and ephemeral food sources presents a cognitive challenge for wild animals. Observational data suggests a high degree of seasonality in the chimpanzees' preferred termite prey at the site of Issa Valley, Tanzania. This allows us to consider hypotheses on chimpanzees' ability to predict termite activity and to efficiently forage for termites based on seasonal rainfall trends.

Chimpanzees () Indicate Mammalian Abundance Across Broad Spatial Scales.

Ongoing ecosystem change and biodiversity decline across the Afrotropics call for tools to monitor the state of biodiversity or ecosystem elements across extensive spatial and temporal scales. We assessed relationships in the co-occurrence patterns between great apes and other medium to large-bodied mammals to evaluate whether ape abundance serves as a proxy for mammal diversity across broad spatial scales. We used camera trap footage recorded at 22 research sites, each known to harbor a population of chimpanzees, and some additionally a population of gorillas, across 12 sub-Saharan African countries.

Strontium isoscape of sub-Saharan Africa allows tracing origins of victims of the transatlantic slave trade.

Strontium isotope (Sr/Sr) analysis with reference to strontium isotope landscapes (Sr isoscapes) allows reconstructing mobility and migration in archaeology, ecology, and forensics. However, despite the vast potential of research involving Sr/Sr analysis particularly in Africa, Sr isoscapes remain unavailable for the largest parts of the continent. Here, we measure the Sr/Sr ratios in 778 environmental samples from 24 African countries and combine this data with published data to model a bioavailable Sr isoscape for sub-Saharan Africa using random forest regression.

Sex differences in positional behavior of chimpanzees (Pan troglodytes schweinfurthii) living in the dry and open habitat of Issa Valley, Tanzania.

Objectives: Many early fossil hominins are associated with savanna-mosaic paleohabitats, and high sexual dimorphism that may reflect differences in positional behavior between sexes. However, reconstructions of hominin behavior and the selective pressures they faced in an open habitat are limited by a lack of studies of extant apes living in contemporary, analogous habitats. Here, we describe adult chimpanzee positional behavior in the savanna-mosaic habitat of the Issa Valley, Tanzania, to test whether Issa chimpanzees show larger sex-differences in positional behavior than their forest-dwelling counterparts.

Chimpanzee gestural exchanges share temporal structure with human language.

Humans regularly engage in efficient communicative conversations, which serve to socially align individuals. In conversations, we take fast-paced turns using a human-universal structure of deploying and receiving signals which shows consistent timing across cultures. We report here that chimpanzees also engage in rapid signal-to-signal turn-taking during face-to-face gestural exchanges with a similar average latency between turns to that of human conversation.

Many morphs: Parsing gesture signals from the noise.

Parsing signals from noise is a general problem for signallers and recipients, and for researchers studying communicative systems. Substantial efforts have been invested in comparing how other species encode information and meaning, and how signalling is structured. However, research depends on identifying and discriminating signals that represent meaningful units of analysis.

A case of suspected chimpanzee scavenging in the Issa Valley, Tanzania.

Like humans, chimpanzees (Pan troglodytes) are well known for their vertebrate and invertebrate hunting, but they rarely scavenge. In contrast, while hunting and meat consumption became increasingly important during the evolution of the genus Homo, scavenging meat and marrow from carcasses of large mammals was also likely to be an important component of their subsistence strategies. Here, we describe a confrontational scavenging interaction between an adult male chimpanzee from the Issa Valley and a crowned eagle (Stephanoaetus coronatus), which resulted in the chimpanzee capturing and consuming the carcass of a juvenile bushbuck (Tragelaphus scriptus).

A case of intercommunity lethal aggression by chimpanzees in an open and dry landscape, Issa Valley, western Tanzania.

Intercommunity (lethal) aggression is a familiar component of the behavioural repertoire of many forest-dwelling chimpanzee (Pan troglodytes) communities. However, until now, the absence of intercommunity attacks - including killings - in communities that live in open, mosaic environments has supported hypotheses of reduced resource competition in drier habitats, and informed referential models of early hominin social dynamics in a similar habitat. In June 2020, we observed the first instance of intercommunity lethal aggression, a male-committed infanticide, by the Issa chimpanzee community, which live in a savannah-mosaic habitat in the Issa Valley, western Tanzania.

Barriers to chimpanzee gene flow at the south-east edge of their distribution.

Populations on the edge of a species' distribution may represent an important source of adaptive diversity, yet these populations tend to be more fragmented and are more likely to be geographically isolated. Lack of genetic exchanges between such populations, due to barriers to animal movement, can not only compromise adaptive potential but also lead to the fixation of deleterious alleles. The south-eastern edge of chimpanzee distribution is particularly fragmented, and conflicting hypotheses have been proposed about population connectivity and viability.

Wild chimpanzee behavior suggests that a savanna-mosaic habitat did not support the emergence of hominin terrestrial bipedalism.

Bipedalism, a defining feature of the human lineage, is thought to have evolved as forests retreated in the late Miocene-Pliocene. Chimpanzees living in analogous habitats to early hominins offer a unique opportunity to investigate the ecological drivers of bipedalism that cannot be addressed via the fossil record alone. We investigated positional behavior and terrestriality in a savanna-mosaic community of chimpanzees () in the Issa Valley, Tanzania as the first test in a living ape of the hypothesis that wooded, savanna habitats were a catalyst for terrestrial bipedalism.

Understanding External Influences on Target Detection and Classification Using Camera Trap Images and Machine Learning.

Using machine learning (ML) to automate camera trap (CT) image processing is advantageous for time-sensitive applications. However, little is currently known about the factors influencing such processing. Here, we evaluate the influence of occlusion, distance, vegetation type, size class, height, subject orientation towards the CT, species, time-of-day, colour, and analyst performance on wildlife/human detection and classification in CT images from western Tanzania.

Localizing wild chimpanzees with passive acoustics.

Localizing wildlife contributes in multiple ways to species conservation. Data on animal locations can reveal elements of social behavior, habitat use, population dynamics, and be useful in calculating population density. Acoustic localization systems (ALS) are a non-invasive method widely used in the marine sciences but not well established and rarely employed for terrestrial species.

Chimpanzee (Pan troglodytes schweinfurthii) grouping patterns in an open and dry savanna landscape, Issa Valley, western Tanzania.

Fission-fusion societies are social systems in which individuals belonging to the same community are rarely all together but rather spend most of their time in temporary parties. This flexible social organization is assumed to be an adaptation that balances advantages and costs of group living in a fluid way as resources and constraints shift through space and time. It has been argued that this flexibility freed hominins from the foraging constraints caused by living in large groups.

Association of human disturbance and gastrointestinal parasite infection of yellow baboons in western Tanzania.

Human disturbance is an ongoing threat to many wildlife species, manifesting as habitat destruction, resource overuse, or increased disease exposure, among others. With increasing human: non-human primate (NHP) encounters, NHPs are increasingly susceptible to human-introduced diseases, including those with parasitic origins. As such, epidemiology of parasitic disease is becoming an important consideration for NHP conservation strategies.

Vocal communication in wild chimpanzees: a call rate study.

Background: Patterns of vocal communication have implications for species conservation: a change in calling behaviour can, for instance, reflect a disturbed habitat. More importantly, call rate is a parameter that allows conservation planners to convert call density into animal density, when detecting calls with a passive acoustic monitoring system (PAM).

Methods: We investigated chimpanzee () call rate during the late dry season in the Issa Valley, western Tanzania by conducting focal follows.

Quantitative estimates of glacial refugia for chimpanzees (Pan troglodytes) since the Last Interglacial (120,000 BP).

Paleoclimate reconstructions have enhanced our understanding of how past climates have shaped present-day biodiversity. We hypothesize that the geographic extent of Pleistocene forest refugia and suitable habitat fluctuated significantly in time during the late Quaternary for chimpanzees (Pan troglodytes). Using bioclimatic variables representing monthly temperature and precipitation estimates, past human population density data, and an extensive database of georeferenced presence points, we built a model of changing habitat suitability for chimpanzees at fine spatio-temporal scales dating back to the Last Interglacial (120,000 BP).