Facial and genital lesions in baboons (Papio anubis) of Kibale National Park, Uganda

Primates and disability: Behavioral flexibility and implications for resilience to environmental change

Congenital malformations, conditions, injuries, and illness can lead to long-term physical impairment and disability in nonhuman primates. How individual primates change their behaviors flexibly to compensate for their disabilities can inform our understanding of their resilience and ability to adjust to environmental change. Here, we synthesize the literature on nonhuman primates and disability, addressing the questions: how does disability influence behavior in primates? What insights can we take from the literature to better understand and predict the capacity of primates to modify their behaviors in the face of human-induced environmental change? We conducted a systematic review of the literature on spontaneous physical impairment and disability in captive, free-ranging, and wild primates. We surveyed 2807 articles on Web of Science and Scopus and identified 114 studies that fit our predetermined inclusion criteria. Behavioral plasticity, maternal and conspecific care, and the potential for innovation of novel behaviors allow many primates with disabilities to compensate when faced with challenges that are outside the scope of usual circumstances. We also found that 60% of the publications connected primate physical impairment and disability to human activities, suggesting an entangled relationship among humans, the environment, and primate disability. Disability and physical impairments provide an opportunity to examine how primates modify their behavior when presented with challenging conditions, and their potential resilience to a changing environment.

The life of a naturalist

This essay summarizes some of my findings while studying primates in the field from 1962 to 2018. Although I have studied primates throughout the tropics, I focused on Africa, primarily the Kibale Forest of Uganda. My research began in the early days of primate field studies when very little was known about the behavior and ecology of most species. Consequently, I was able to study nearly anything that could be observed under natural conditions. It was not necessary to specialize, and I opted to be a generalist. In much of my work I have attempted to understand the relationships between habitat quality, social organization, and population dynamics, emphasizing the great intraspecific variability that exists over time and between areas. Vocalizations have also long been of interest to me, starting with a description of predator-specific alarm calls and later showing how vocalizations among African monkeys appear to be evolutionarily stable. As my field experience progressed, I became increasingly involved with the conservation of tropical rain forests. In the last part of this essay I offer my thoughts on current trends in field primatology and some advice to the next generation of field biologists, stressing the importance of being a naturalist.

Constraints on population growth of blue monkeys (Cercopithecus mitis) in Kibale National Park, Uganda

Changes in population size are driven by environmental and social factors. In spite of repeated efforts to identify the constraints on an unusually low-density population of blue monkeys (Cercopithecus mitis), it remains unclear why this generalist species fails to thrive in Kibale National Park in Uganda. While an unidentified disease may occasionally obstruct conception, it does not seem to limit overall reproductive rates. Infanticide at this site is infrequent due to the long tenures of resident males. Our analyses indicate that the single biggest constraint on blue monkey densities may be feeding competition with grey-cheeked mangabeys (Lophocebus albigena): across Kibale, the densities of these two species are strongly and negatively correlated. Though further analysis is needed to understand the timing and strength of feeding competition between them, we conclude that blue monkeys at Ngogo experience competitive exclusion from grey-cheeked mangabeys, possibly resolving the 50-year mystery surrounding this population.