Ground Night Nesting in Chimpanzees: New Insights from Central Chimpanzees (Pan troglodytes troglodytes) in South-East Cameroon

Abstract

Some chimpanzee populations exhibit ground night nesting, which occurs in different habitat types, is driven by a variety of interconnected factors, and may reflect cultural or social differences. This has important implications for ape conservation management, given that accurate nest builder identification is required to estimate density, crucial in monitoring, and allows inferences about environmental and social factors that may have contributed to the transition from tree to ground sleeping in early hominins. We conducted a 24-month marked nest count survey in La Belgique, Cameroon, and recorded the occurrence of chimpanzee tree and ground night nests, temperature and rainfall, predator and large mammal abundance, human activities, nesting tree species, and Uapaca spp. consumption. Ground night nesting occurred at a rate of 3.47% (n = 1,008), with more in swamps, in the dry season and with increasing human activities. We found no influence of leopard/elephant presence, but a possible influence of lack of nesting trees. We suggest chimpanzees visit swamps in the dry season (low water levels) for relief from hunting pressure and to consume Uapaca spp. fruits. Ground nesting may be enabled due to high abundance of terrestrial herbaceous vegetation, and may be favoured for inconspicuousness and safety from gun hunters.

The distribution of plant consumption traits across habitat types and the patterns of fruit availability suggest a mechanism of coexistence of two sympatric frugivorous mammals

“…However, our results are not consistent with these observations. Our seasonal analysis revealed a significant increase in swamp use by chimpanzees in the long dry season, as observed elsewhere (Morgan et al, ; Poulsen & Clark, ) and in the same site in a previous study (Tagg, Willie, Petre, & Haggis, ). We found gorillas to randomly use LG and YSF in all seasons, except in the long rainy season when they used YSF in proportion significantly less than would be expected by chance; however, a general analysis revealed that gorillas preferred LG, but again used YSF in proportion significantly less than would be expected by chance.…”

“…fruits in swamps in the long dry season, competition between gorillas and chimpanzees may be avoided in swamps by the increasing consumption of herbs by gorillas in the long dry season. Meanwhile, it has been found that herbaceous plants suitable for gorilla nest building are less abundant in mature forest than in old secondary forest in this region (Willie et al, ), while chimpanzee nesting trees are less abundant in young secondary forest than in mature forest (Tagg et al, ). Adding to the lower abundance of chimpanzee preferred fruiting plants in young secondary forest found in this study, this observation may explain the near absence of gorillas and chimpanzees in MF and in YSF, respectively, in all seasons.…”

Sleep and nesting behavior in primates: A review

“…In addition, some large‐bodied primates sleep terrestrially on bare ground or on cliffs, such as group‐sleeping baboons ( Papio spp.) (Hamilton, ), or individually sleeping great apes (Fruth & Hohmann, ; Tagg, Willie, Petre, & Haggis, ). Of particular interest in the study of primate sleep is nest‐building behavior, which has evolved independently six to eight times in primates (Kappeler, ).…”

“…Nest building is a habitual behavior in great apes, constructions are built for short periods only and never serve as a shelter for caching young. Structures are commonly built within trees, although ground nests built with terrestrial vegetation are common in gorilla and ground‐nesting is likely present at low rates across all species and subspecies (Tagg et al, ). These structures attracted the attention of early explorers such as Du Chaillu (), Hornaday (), and Savage and Wyman (1843–1844).…”

Conservation relevance of terrestrial herbaceous vegetation studies

“…Herbaceous plants also provide fallback foods for chimpanzees (Harrison & Marshall, 2011). In addition, chimpanzees occasionally sleep in ground nests built using herbaceous plants (Koops, Humle, Sterck, & Matsuzawa, 2007;Tagg, Willie, Petre, & Haggis, 2013). Both chimpanzees and bonobos frequently utilize plant materials, including herbaceous species, to make tools to extract termites from termite nests (Deblauwe, Guislain, Dupain, & Van Elsacker, 2006;McGrew et al, 2007;Sanz & Morgan, 2007).…”