Chimpanzees possess a large number of behavioral and cultural traits among nonhuman species. The “disturbance hypothesis” predicts that human impact depletes resources and disrupts social learning processes necessary for behavioral and cultural transmission. We used a dataset of 144 chimpanzee communities, with information on 31 behaviors, to show that chimpanzees inhabiting areas with high human impact have a mean probability of occurrence reduced by 88%, across all behaviors, compared to low-impact areas. This behavioral diversity loss was evident irrespective of the grouping or categorization of behaviors. Therefore, human impact may not only be associated with the loss of populations and genetic diversity, but also affects how animals behave. Our results support the view that “culturally significant units” should be integrated into wildlife conservation.

African large mammals are under extreme pressure from unsustainable hunting and habitat loss. Certain traits make large mammals particularly vulnerable. These include late age at first reproduction, long inter-birth intervals, and low population density. Great apes are a prime example of such vulnerability, exhibiting all of these traits. Here we assess the rate of population change for the western chimpanzee, Pan troglodytes verus, over a 24-year period. As a proxy for change in abundance, we used transect nest count data from 20 different sites archived in the IUCN SSC A.P.E.S. database, representing 25,000 of the estimated remaining 35,000 western chimpanzees. For each of the 20 sites, datasets for 2 different years were available. We estimated site-specific and global population change using Generalized Linear Models. At 12 of these sites, we detected a significant negative trend. The estimated change in the subspecies abundance, as approximated by nest encounter rate, yielded a 6% annual decline and a total decline of 80.2% over the study period from 1990 to 2014. This also resulted in a reduced geographic range of 20% (657,600 vs. 524,100 km ). Poverty, civil conflict, disease pandemics, agriculture, extractive industries, infrastructure development, and lack of law enforcement, are some of the many reasons for the magnitude of threat. Our status update triggered the uplisting of the western chimpanzee to "Critically Endangered" on the IUCN Red List. In 2017, IUCN will start updating the 2003 Action Plan for western chimpanzees and will provide a consensus blueprint for what is needed to save this subspecies. We make a plea for greater commitment to conservation in West Africa across sectors. Needed especially is more robust engagement by national governments, integration of conservation priorities into the private sector and development planning across the region and sustained financial support from donors.

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The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu.

The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites.