Comparison of feeding behavior between two different‐sized groups of Japanese macaques (Macaca fuscata yakui)

Abstract

Group-living animals face intragroup scramble and intergroup contest competitions. Many studies have shown that larger groups bear the costs of intragroup scramble competition, which negatively affects the reproductive success of females. Unlike most primate species, Japanese macaques in the Yakushima coastal forest show increased reproductive success with group size. However, it remains unclear how group size affects the behavior of macaques. The present study examined the effects of group size on the feeding behavior of Japanese macaques in the Yakushima coastal forest. We investigated 9-13 adult females from two different-sized groups via focal animal sampling during October 2012-August 2013. We compared the feeding behavior, including patch use, between the two groups. The larger group had a larger home range and spent more time feeding, especially on mature leaves. This suggests that intragroup feeding competition should be more intense in the larger group than in the smaller group. The feeding of mature leaves might enable the larger group to increase the number of co-feeding individuals. Contrary to the predictions that the larger group travels longer distances and spends more time moving, the smaller group traveled longer distances, and spent more time moving, although the number of visited patches did not differ between the two groups. The immediate consequences of the loss of inter-group encounters could accumulate as daily travel costs, considering that group size is associated with inter-group dominance and that intergroup aggressive encounters occur frequently in the Yakushima coastal forest. This suggests that the smaller group has increased travel costs as a result of intergroup contest competition, which leads to decline in reproductive success. Am. J. Primatol. 77:986-1000, 2015. © 2015 Wiley Periodicals, Inc.

Within-Population Variations in Home Range Use and Food Patch Use of Japanese Macaques: A Perspective of Intergroup Hostility

“…Patches outside of the home range were categorized as the border with dominant groups or subordinate groups (see "Home Range Estimation" in Data Analysis). Kurihara/Hanya DOI: 10.1159/000493574 [Kurihara and Hanya, 2015]. Meanwhile, macaques in the coastal forest did not increase co-feeding with adult males along the border, contrary to our prediction.…”

“…To control for confounding factors, we used the number of co-feeding individuals, patch size, and food type as control variables (Table 2). It has already been established that (1) the duration of feeding in one patch depends on patch size, food type, and the number of co-feeding individuals [Kazahari and Agetsuma, 2008;Chancellor and Isbell, 2009], (2) the frequency of visual scanning depends on the number of co-feeding individuals [Kazahari and Agetsuma, 2010;Suzuki and Sugiura, 2011], and (3) the number of co-feeding individuals depends on patch size and food type [Potts et al, 2011;Kurihara and Hanya, 2015]. Although several studies measured patch quality more precisely (e.g., density of food items within a patch [Kazahari and Agetsuma, 2008]), patch size and food type would be sufficient for controlling ecological characteristics of a patch in the present study.…”

“…The duration of feeding in 1 patch was log-transformed to achieve normality, and the numbers of co-feeding individuals and co-feeding adult males were rounded up to be treated as a zero-inflated Poisson distribution [Kurihara and Hanya, 2015]. We included "food patch location" as a fixed effect and the identity of the focal animal as a random effect in all models (Table 2).…”

Positional Behaviours of François’ Langur (Trachypithecus francoisi) in the Limestone Forest of Nonggang, Guangxi, South-West China

“…Annual and seasonal percentages were obtained by averaging relative monthly values. Following Huang et al [2017] and Kurihara and Hanya [2015], we built generalised linear mixed models to explain locomotion, posture, stratum and substrate use by the langurs and then examined seasonal variations. For this purpose, we set seasons as fixed factors and sample sizes as random factors in the models.…”

Effect of Group Size on Time Budgets and Ranging Behavior of White-Headed Langurs in Limestone Forest, Southwest China

“…However, it is much more difficult to directly observe scramble competition and measure foraging efficiency [Liu et al, 2013]. Many researchers inferred scramble competition from the significant effect of group size on day range length and time budgets [Dunbar, 1992;Overdorff, 1996;Steenbeek and van Schaik, 2001;Teichroeb et al, 2003;Snaith and Chapman, 2005;Fashing et al, 2007;Saj and Sicotte, 2007;Isbell, 2012;Liu et al, 2013;Fan et al, 2015;Kurihara and Hanya, 2015]. The ecological constraints model proposes that intragroup feeding competition should increase as group size increases, and the larger groups should travel further and spend more time moving and/or feeding, and/or less time resting than smaller groups [Janson, 1988;Wrangham et al, 1993;Chapman et al, 1995;Chapman and Chapman, 2000;Chapman and Pavelka, 2005;Teichroeb and Sicotte, 2009;Liu et al, 2013;Gogarten et al, 2014].…”