Nocturnal behavior by a diurnal ape, the West African chimpanzee (Pan troglodytes verus), in a savanna environment at Fongoli, Senegal

Abstract

Animals in highly seasonal habitats often exhibit thermoregulatory adaptations but, like other primates, chimpanzees lack physiological mechanisms to combat thermal stress. This study provides evidence that they may exhibit behaviors that allow them to avoid high temperatures in a savanna environment, such as feeding and socializing at night during the hottest time of year and in the brightest moon phases. The results support theories invoking thermal stress as a selective pressure for hominins in open environments where heat would constrain temporal foraging niches, and suggest an adaptability of sleeping patterns in response to external factors.

Advancing conservation planning for western chimpanzees using IUCN SSC A.P.E.S.—the case of a taxon-specific database

“…There is little information for dispersal distances between chimpanzee communities, for example when females transfer from their natal group. Published maximum daily travel distances range from 9 km in rainforest habitat (Herbinger et al 2001) to 16 km in drier habitat (Humle et al 2011), and may be larger in very dry areas where chimpanzees have larger home ranges (Pruetz 2018). However, this is likely only the case within suitable habitat and in the absence of barriers such as areas densely populated by humans.…”

Temporal patterns of chimpanzee loud calls in the Issa Valley, Tanzania: Evidence of nocturnal acoustic behavior in wild chimpanzees

“…Finally, by definition, fission–fusion animals are dispersed at various times during the day and night, and thus calls may serve coordination and cohesive mechanisms (Leighty, Soltis, Wesolek, & Savage, ), advertising a caller's location and facilitating reunions (e.g., fusion events) later the next day. Environmentally, primates that live in hot climates may forage at night to avoid high day‐time temperatures (Pruetz, ). By being active during periods of the night, animals can increase their foraging time and ultimately, increase their caloric intake.…”

Sleep and nesting behavior in primates: A review

“…At Seringbara, Koops et al () found chimpanzee nest height increased with increasing humidity. Temperature during the day can also affect great ape sleeping patterns at night, as shown in Fongoli by Pruetz (), whereby increased nocturnal activity appeared to be the result of compensating for thermal stress experienced during the day. Evidence provided in this issue suggests that chimpanzees adjust nest shape and architecture in response to local weather conditions (Stewart, Piel, Azkarate, & Pruetz, ).…”

“…Temperature is another environmental factor that has been shown to influence pattern and quality of sleep in lemurs (Samson, Bray, & Nunn, ). and chimpanzees (Pruetz, ). While the external drivers mentioned above may trigger nocturnal activity in diurnal great apes, internal factors, such as the need to defecate (K. Zamma, pers.…”

“…An ape will usually build a new nest each evening and, despite lack of systematic investigation, is assumed to use it for rest from dusk until dawn (but see Tagg et al, ; Piel, , Pruetz, ; Stewart, Piel, Azkarate, & Pruetz, ; in this volume). Occasionally, nests are also built during the day, usually for rest, but have also been observed to serve functions of grooming, play, sex, nursing, and giving birth.…”