Chimpanzee ranging responses to fruit availability in a high‐elevation environment

Abstract

Most primates experience seasonal fluctuations in the availability of food resources and face the challenge of balancing energy expenditure with energy gain during periods of resource scarcity. This is likely to be particularly challenging in rugged, montane environments, where available energy is relatively low and travel costs are high. Chimpanzees (Pan troglodytes) show extensive behavioral diversity across study sites. Yet, as most research has focused on low-and mid-elevation sites, little is known on how chimpanzees respond to periods of low fruit availability in harsh montane environments. We use focal follow and phenology data to investigate how fruit availability influences daily path length and monthly home range in chimpanzees living in Nyungwe National Park, a montane forest in Rwanda. Nyungwe chimpanzees decreased their daily travel distances during periods of fruit scarcity. However, this decrease in travel effort did not correspond with a decrease in foraging area. Instead, monthly homes ranges shifted location across the study period. Nyungwe chimpanzees occupy a relatively wide altitudinal range and the shifts in monthly home range location may reflect differences in the altitudinal distribution of food resources.Chimpanzee monthly diet was often dominated by one or two species and each of these species were confined to different elevation zones. One important species, Podocarpus latifolius, grew only at high elevations (2,600-2,950 m) and chimpanzees ranged at the altitudinal peak of their range for 2 consecutive months while feeding on this species. Thus, while high elevations are often thought to be harsh environments for primates, they can be an important part of a species' home range when they provide a refugium for densely distributed, important food species. K E Y W O R D S3D home range, chimpanzee, ecological constraints, montane forest, path length, seasonality

Comparisons of Activity Budgets, Interactions, and Social Structures in Captive and Wild Chimpanzees (Pan troglodytes)

“…In contrast, previous studies have shown that there are large regional differences in the activity budgets for traveling in wild chimpanzees, from 6% in Budongo to 22% in the Tai Forest [ 51 , 52 , 53 ], depending on socio-ecological factors, such as individual density or food availability [ 54 ]. The values of activity budgets for traveling in Tama (12.0 ± 3.6%) and Mahale (15.4 ± 2.9%) in this study were within this range.…”

Daily Travel Distances of Unhabituated Grauer’s Gorillas (Gorilla beringei graueri) in a Low Elevation Forest

“…Primates are known to not only alter their total DTD depending on seasonal resource availability, but they may also show variation in the directionality of movement patterns Janson, 2007, 2013;Green et al 2020aGreen et al , 2020b. In particular, folivorous species tend to show largely random movement patterns, whereas species that rely on food resources that are heterogeneously distributed in space, such as fruits, move in relatively straight lines [Reyna-Hurtado et al, 2018;Jang et al, 2019;Green et al, 2020aGreen et al, , 2020bSalmi et al, 2020]. Thus, we formulated an additional hypothesis that daily displacement distances (DDD; the Euclidian distance between 2 successive night nests) and linearity of movements (Linearity Index, LI) would also reflect temporal fluctuations, possibly related to changes in fruit consumption or availability.…”

Ranging patterns of Japanese macaques in the coniferous forest of Yakushima: Home range shift and travel rate

“…Habitat shift seems common among New World primates due to the widespread pattern of a habitat mosaic of inundated and non‐inundated forests in the Amazon basin (Hemingway & Bynum, 2005). In montane habitats, the environment changes gradually along an elevational gradient, and many species exhibit altitudinal seasonal migration (Buij, Wich, Lubis, & Sterck, 2002; Green, Boruff, Niyigaba, Ndikubwimana, & Grueter, 2020; Li et al, 2008; Tan, Guo, & Li, 2007). Human disturbance may also bring about a small‐scale spatial heterogeneity that enables seasonal habitat shift for primates (Gazagne et al, 2020; Ruppert, Holzner, See, Gisbrecht, & Beck, 2018).…”

“…Preferred, high‐quality foods are usually sparsely distributed, so animals often range a long distance when eating such foods (Campera et al, 2014; Hill & Agetsuma, 1995). On the contrary, when animals eat fallback foods during periods of scarcity of such preferred foods, their ranging distance decreases if the fallback food is abundant in the habitat (Green et al, 2020). However, other types of ranging patterns have also been reported.…”