Sex differences in tool use acquisition in bonobos (Pan paniscus)

Abstract

All the great ape species are known tool users in both the wild and captivity, although there is great variation in ability and behavioral repertoire. Differences in tool use acquisition between chimpanzees and gorillas have been attributed to differing levels of social tolerance as a result of differences in social structure. Chimpanzees also show sex differences in acquisition and both chimpanzees and bonobos demonstrate a female bias in tool use behaviors. Studies of acquisition are limited in the wild and between species comparisons are complicated in captivity by contexts that often do not reflect natural conditions. Here we investigated tool use acquisition in a captive group of naïve bonobos by simulating naturalistic conditions. We constructed an artificial termite mound fashioned after those that occur in the wild and tested individuals within a social group context. We found sex differences in latencies to attempt and to succeed where females attempted to fish, were successful more quickly, and fished more frequently than males. We compared our results to those reported for chimpanzees and gorillas. Males across all three species did not differ in latency to attempt or to succeed. In contrast, bonobo and chimpanzee females succeeded more quickly than did female gorillas. Female bonobos and female chimpanzees did not differ in either latency to attempt or to succeed. We tested the social tolerance hypothesis by investigating the relationship between tool behaviors and number of neighbors present. We also compared these results to those reported for chimpanzees and gorillas and found that bonobos had the fewest numbers of neighbors present. The results of this study do not support the association between number of neighbors and tool behavior reported for chimpanzees. However, bonobos demonstrated a similar sex difference in tool use acquisition, supporting the hypothesis of a female bias in tool use in Pan.

Laterality of Grooming and Tool Use in a Group of Captive Bonobos (Pan paniscus)

“…The bonobos were slowly habituated to an artificial termite mound. A full description of the habituation process can be found in Boose et al [2013]. The mound featured 8 holes formed by PVC pipe that were filled daily with mashed fruit, mashed vegetables, honey, or peanut butter.…”

“…We stress that while this behavior is ethologically similar to termite fishing that is well documented in chimpanzees, the tool use behavior reported in this study should be treated as an analog to termite fishing, rather than an identical behavioral pattern. A tool use bout was defined as the time during which an individual continuously fished or attempted to extract bait [Boose et al, 2013]. When an individual departed to a distance of 1 m or more of the mound, or stopped tool use behaviors for more than 30 s but remained within 1 m or more of the mound, the bout was scored as finished [Boose et al, 2013].…”

“…Sex, age, and kinship are displayed for individuals that provided enough data for analysis in Table 2 . Bonobos are exhibited in an outdoor exhibit and 2 indoor enclosures (see Boose et al [2013] and Brand and Marchant [2015] for exhibit descriptions and dimensions). Individuals form temporary parties that last for 1 or 2 days without compositional changes.…”

“…A tool use bout was defined as the time during which an individual continuously fished or attempted to extract bait [Boose et al, 2013]. When an individual departed to a distance of 1 m or more of the mound, or stopped tool use behaviors for more than 30 s but remained within 1 m or more of the mound, the bout was scored as finished [Boose et al, 2013]. While other research on manual laterality has analyzed data at the unit level, e.g., a single insertion and withdraw of a probe, these cannot be considered statistically independent of one another, whereas bouts are independent with respect to hand use [McGrew and Marchant, 1992].…”

“…Tool use is closely scrutinized given its cultural variation among wild chimpanzees [Whiten et al, 1999] and has also been invoked as a potential selective pressure for human handedness [Kimura, 1979]. In contrast to their sister species, wild bonobos are not known to use tools in food-processing tasks [Furuichi et al, 2011;Koops et al, 2015]; however, their capacity to use tools in captivity is well documented [Gruber et al, 2010;Chapelain et al, 2011;Boose et al, 2013;Bardo et al, 2015]. Thus, studies of tool use laterality in bonobos have focused on captive individuals.…”