The Appearance and Spread of Ant Fishing among the Kasekela Chimpanzees of Gombe

Abstract

Chimpanzees exhibit cultural variation, yet examples of successful cultural transmission between wild communities are lacking. Here we provide the first account of tool-assisted predation (“ant fishing”) on Camponotus ants by the Kasekela and Mitumba communities of Gombe National Park. We then consider three hypotheses for the appearance and spread of this behavior in Kasekela: (1) changes in prey availability or other environmental factors, (2) innovation, and (3) introduction. Ant fishing was recognized as habitual in the Mitumba community by 1992, soon after their habituation began. Apart from one session in 1978, Camponotus predation (typically with tools) was documented in the Kasekela community beginning only in 1994, despite decades of prior observation. By February 2010, ant fishing was customary in Kasekela and with one exception was practiced exclusively by chimpanzees born after 1981 and immigrant females. We hypothesize that changes in insect prey availability over time and/or the characteristics of one popular ant-fishing site may have influenced the establishment of ant fishing. Though innovation cannot be completely ruled out, the circumstantial evidence suggests that a Mitumba immigrant introduced ant fishing to Kasekela. We submit that this report represents the first documented case of successful transmission of a novel cultural behavior between wild chimpanzee communities.

Primate archaeology reveals cultural transmission in wild chimpanzees (Pan troglodytes verus)

“…So far only chimpanzees and humans have been found to converge on the behaviour variant that is most common in the group, even if they have alternative behaviours in their individual repertoires that accomplish the same goal just as efficiently [67]. Conformist transmission has been proposed to restrict the accumulation of traditions in non-human [27,37,49] and human [62,68] populations. Therefore, local differences between populations remain despite individual exchange through marriage and migration [69], preventing cross cultural homogenization but protecting cultural diversity among neighbouring communities.…”

“…Only if innovators persist can they add to the behavioural pool by disseminating their innovations once they are older [48,76]. However, the ontogeny of cultural traits within a community remains a topic of investigation as only a few studies have reported the spread of new behaviours within a chimpanzee community [13,49]. In those cases, the spread of the innovations were reported for nonarbitrary behaviours and implied increased fitness through additional foraging sources.…”

“…Conformist transmission mechanisms in chimpanzees are supported by an increasing body of research that shows how conformity plays an important role in social learning strategies in a variety of wild ranging animal species [45][46][47]. Some studies have begun to thoroughly investigate how cultural transmission in wild chimpanzees may occur [42,48,49], yet how and why chimpanzees adopt certain behavioural traits and abandon their previous behaviour remain largely unknown [50,51]. With this study, we are aiming to investigate further whether immigrating females actively change their nut-cracking behaviour to match the tool selection of their new groups despite previously having acquired different preferences.…”

“…At times of emigration, they are skillful nutcrackers and display the tool selection pattern of their natal community. Observing immigration is a rare occurrence, and only very few cases of female immigration have been described [44,49,52]. However, these cases do indicate that social learning follows migration events.…”

The Evolution of Individual and Cultural Variation in Social Learning

“…This can have important implications for cultural diversity, 16 with the number of cultural traits in chimpanzee societies correlating with the number of females, 17 not males [89]. Sex-specific social learning will also determine the spread of cultural traits between 18 groups in species with sex-specific dispersal patterns [90]. In humans, socially proscribed roles (e.g.…”