Sustainable Peeling of Kapok Tree (Ceiba pentandra) Bark by the Chimpanzees (Pan troglodytes verus) of Comoé National Park, Ivory Coast

Abstract

Primates often consume either bark or cambium (inner bark) as a fallback food to complete their diet during periods of food scarcity. Wild chimpanzees exhibit great behavioral diversity across Africa, as studies of new populations frequently reveal. Since 2014, we have been using a combination of camera traps and indirect signs to study the ecology and behavior of wild chimpanzees (Pan troglodytes verus) in Comoé National Park, Ivory Coast, to document and understand the behavioral adaptations that help them to survive in a savanna-forest mosaic landscape. We found that Comoé chimpanzees peel the bark of the buttresses of kapok tree (Ceiba pentandra) trees to eat the cambium underneath. Individuals of all sex/age classes across at least six neighboring communities peeled the bark, but only during the late rainy season and beginning of the dry season, when cambium may represent an important fallback food. Baboons (Papio anubis) also target the same trees but mainly eat the bark itself. Most of the bark-peeling wounds on Ceiba trees healed completely within 2 years, seemingly without any permanent damage. We recorded chimpanzees visiting trees in early stages of wound recovery but leaving them unpeeled. Only 6% of peeled trees (N = 53) were reexploited after a year, suggesting that chimpanzees waited for the rest of the trees to regrow the bark fully before peeling them again, thus using them sustainably. Many human groups of hunter-gatherers and herders exploited cambium sustainably in the past. The observation that similar sustainable bark-peeling behavior evolved in both chimpanzees and humans suggests that it has an important adaptive value in harsh environments when other food sources become seasonally scarce, by avoiding the depletion of the resource and keeping it available for periods of scarcity.

Trunk spines of trees: a physical defence against bark removal and climbing by mammals?

“…Species from both prickly trunk ( Bombax ceiba , Ceiba speciosa , Ceiba pentandra ) and thorny trunk syndromes ( Gleditsia microphylla , Flacourtia indica ) have been reported to have their bark targeted by mammals such as rodents, deer, elephants, cattle and primates ( Bucher, 1987 ; Wenyuan et al , 1993 ; Khan et al , 1994 ; Steinheim et al , 2005 ; Joshi and Singh, 2008 ; Jain et al , 2011 ; Lapuente et al , 2020 ), but no quantitative assessment of their effectiveness as defences has yet been attempted. Qualitative descriptions suggest that the establishment of spines on old saplings of Bombax ceiba (prickly trunk syndrome) and Dalbergia sissoo (thorny trunk syndrome) results in no further debarking by porcupines ( Khan et al , 2000 ), and make the debarking of Ceiba pentandra (prickly trunk syndrome) by chimpanzees more difficult ( Lapuente et al , 2020 ), which supports our predictions. These observations are particularly interesting as porcupines are highly specialized in debarking ( Akram et al , 2017 ), which suggests that trunk spines should induce an even stronger negative effect on less specialized herbivores.…”

Archaeology of the Perishable

“…There are reasons for hope with the archaeology of the perishable. Just as with termite fishing, other chimpanzee behaviors, for example, tortoise smashing (Pika et al 2019), crab processing (Koops et al 2019), tree drumming (Babiszewska et al 2015), accumulative stone throwing (Kühl et al 2016), or bark peeling (Lapuente et al 2020), hold potential for expanding investigations.…”

“…Carvalho goes further and suggests expanding this work to other chimpanzee behaviors that may also leave recognizable signatures, as not to do so will continue to offer partial and biased perspectives on technological evolution. We are particularly excited about the archaeological potential of tree drumming (Babiszewska et al 2015) and bark peeling (Lapuente et al 2020) as extensions of our methods to other chimpanzee behaviors. We agree with Carvalho that without knowing what features or traces to look for in the archaeological record, we will continue to be blinkered by the lithic bias.…”

Introduction to the Special Issue on Savanna Chimpanzees

“…Vink et al (2020) continue this effort by measuring party sizes using three different methods for unhabituated individuals, including counts from direct observations, nest sites, and camera trap videos. Two additional studies in this issue use camera traps as an adjunct observational method (Boyer Ontl andLapuente et al 2020b).…”

“…The late wet season in West Africa is a period of fruit scarcity for savanna chimpanzees (e.g., Fongoli: Pruetz 2006). This challenge of fruit scarcity led Lapuente et al (2020b) to deploy camera traps as a means of understanding how chimpanzees at Comoé fall back on Ceiba pentandra bark. These authors found that bark ingestion was widespread among communities and it occurred more often during the late wet season.…”