Coprophagy by the semi-habituated chimpanzees of Semliki, Uganda
C.L.R. Payne1, T.H. Webster1,2 and K.D. Hunt3
2Departments of Anthropology and Zoology, Miami University
3Department of Anthropology, Indiana University
This report adds to the growing published literature on coprophagy in wild chimpanzees. We present observational and circumstantial evidence of this behavioural pattern, and test the utility of current hypotheses for explaining coprophagy in wild chimpanzees.
Eating one's own feces (autocoprophagy) and eating the feces of others (allocoprophagy) occurs in wild populations throughout the animal kingdom1. Yet in apes, coprophagy is commonly considered to be abnormal behaviour in captive populations. It often appears in lists of problematic behaviours2,3, and is thought to be a response to boredom or stress4.
Yet wild chimpanzee populations also engage in coprophagy: Autocoprophagy has now been reported from several long term study groups, including Assirik5, Gombe6, Mahale7, Bossou8, and Fongoli (Bertolani et al., unpublished data). Interspecific allocoprophagy has been reported from Kibale, where chimpanzees consume elephant dung9. The cause of this pattern remains uncertain, but several hypotheses have been proposed.
The Toro-Semliki Reserve is in western Uganda, near the eastern edge of the Great Rift Valley (0° 50’ to 1° 05’ N, 30° 20’ to 30° 35’ E), and supports several chimpanzee communities14. Habituation efforts have been ongoing since 199615, and progress is being made.
We made observations and collected fecal samples opportunistically from May-November 2008. Feces were washed and sieved through a 1 mm mesh, and the contents recorded.
We saw five episodes of autocoprophagy during the study period (See details in Table 1). No allocoprophagy was observed directly, but circumstantial evidence of coprophagy comes from one case of discarded (presumably spat-out) seeds (Table 1), and from seed fragments in eight fecal samples (Table 2).
Table 1. Observed cases of coprophagy by Semliki chimpanzees.
Table 2. Chimpanzee fecal samples containing Saba florida seed fragments.
At least three individuals, including adult and juvenile males, showed coprophagy (Table 1). Individuals were observed to defecate directly into their own hand and raise the feces to their mouth. They then manipulated the feces in their mouths using their lips, spitting out seeds and indeterminate fecal matter. These cases occurred when groups ate low-quality food items, such as bark, pith and seeds (Table 1). Case 6 occurred when at least one individual was in poor health, as evidenced by vomit found on leaves, although no evidence of disease or infection was found at any other time during the study.
The presence of seed fragments in feces may be indirect evidence of coprophagy, because the apes were never seen or heard to crush the hard Saba florida seeds when eating the fruits whole. In every case in which coprophagy was observed, we could hear the sounds of seeds being crunched and cracked. We presumed these to be Saba, since these seeds were predominant and were found more consistently in fecal samples than any other seeds during the study period. We found crushed seeds in samples in the latter half of the Saba fruiting season (Fig. 1), shortly before Saba seeds disappeared from feces altogether.
The decline in the presence of whole seeds and increase in the presence of fragments in feces between Weeks 1-8 and Weeks 9-16 (Fig. 1) differs significantly from chance (χ2 (df=1) = 10.7, N=78, p<0.01).
Fig. 1. Indirect evidence of coprophagy from fecal analysis: S. florida consumption.
The hypotheses (a)-(b) cannot explain coprophagy by the Semliki chimpanzees. (a): Unlike barren captive environments, the habitat at Semliki reserve is rich and stimulating; the chimpanzees engage in various kinds of extractive foraging. (b): Fibrous materials often feature in the diet of the Semliki chimpanzees14, and were consumed during every case of observed coprophagy. (c): Insects occurred regularly in fecal samples at Semliki during the study period, so coprophagy need not supply Vitamin B12.
Instead, hypotheses (d) and (e) seem likely variables which may interact to cause the chimpanzees of Semliki to engage in coprophagy. Given the significant relationship between the presence of crushed seeds in feces and declining Saba availability, we propose a tentative hypothesis that coprophagy in Semliki chimpanzees is caused by the pressure to exploit added nutrients from reingesting Saba seeds when availability of the fruit is in decline. There is a possibility that seed fragments in feces may not reflect coprophagy but instead the occasional crunching of the seeds during Saba fruit consumption that is never seen at Semliki, but observed at Mahale (Nakamura, personal communication). Further observational data are needed to clarify this.
The lack of coprophagy during times when Saba was consumed in abundance, and the presence of many whole, non-reingested seeds in feces in the early half of the fruiting season, suggests that coprophagy may be a fallback or seasonal strategy for Semliki chimpanzees. It may be a response to a decreasing resource, as a way of more efficiently exploiting the nutrients available from this high quality food item. It may also be specific to individuals who find it harder to acquire high quality foods (Table 1). However, further behavioural data is needed to test this, particularly since coprophagy was only observed in adult and juvenile males and these individuals are better habituated to human observation than female chimpanzees at Semliki.
Hypothesis (f) cannot be assessed from the data gathered thus far. As habituation efforts progress, it is hoped that more information on unusual behavioural patterns in this population will come to light.
We thank the National Science Foundation, University of Indiana, Rebecca Jeanne Andrew Memorial Fund, and Bedford and Durham Funds of King's College, Cambridge for financial support; WC McGrew and LF Marchant for help with data collection and analyses; and the rangers of the Ugandan Wildlife Authority and the staff of Semliki Chimpanzee Research Camp, for field assistance.
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