Vertebrate DNA in Fecal Samples from Bonobos and Gorillas: Evidence for Meat Consumption or Artefact?

Abstract

BackgroundDeciphering the behavioral repertoire of great apes is a challenge for several reasons. First, due to their elusive behavior in dense forest environments, great ape populations are often difficult to observe. Second, members of the genus Pan are known to display a great variety in their behavioral repertoire; thus, observations from one population are not necessarily representative for other populations. For example, bonobos (Pan paniscus) are generally believed to consume almost no vertebrate prey. However, recent observations show that at least some bonobo populations may consume vertebrate prey more commonly than previously believed. We investigated the extent of their meat consumption using PCR amplification of vertebrate mitochondrial DNA (mtDNA) segments from DNA extracted from bonobo feces. As a control we also attempted PCR amplifications from gorilla feces, a species assumed to be strictly herbivorous.Principal FindingsWe found evidence for consumption of a variety of mammalian species in about 16% of the samples investigated. Moreover, 40% of the positive DNA amplifications originated from arboreal monkeys. However, we also found duiker and monkey mtDNA in the gorilla feces, albeit in somewhat lower percentages. Notably, the DNA sequences isolated from the two ape species fit best to the species living in the respective regions. This result suggests that the sequences are of regional origin and do not represent laboratory contaminants.ConclusionsOur results allow at least three possible and mutually not exclusive conclusions. First, all results may represent contamination of the feces by vertebrate DNA from the local environment. Thus, studies investigating a species' diet from feces DNA may be unreliable due to the low copy number of DNA originating from diet items. Second, there is some inherent difference between the bonobo and gorilla feces, with only the later ones being contaminated. Third, similar to bonobos, for which the consumption of monkeys has only recently been documented, the gorilla population investigated (for which very little observational data are as yet available) may occasionally consume small vertebrates. Although the last explanation is speculative, it should not be discarded a-priori given that observational studies continue to unravel new behaviors in great ape species.

Broad-scale phylogenomics provides insights into retrovirus–host evolution

“…2), which is the taxonomic group containing the highest overall representation of gamma-ERVs. It may be possible that these euarchontoglire hosts are not strictly vegetarian because recent studies suggest that several of these taxa do occasionally eat meat (22,23), given that even rare carnivorous acts may be sufficient to expose hosts to retroviral infection. Other life-history and ecological traits may also influence susceptibility to infection by gammaretroviruses.…”

Monocultures: A Blight on Human and Planetary Health

“…Humans have a long history of meat consumption, although our closest primate relatives are vegetarian (Gorilla gorilla) or low, but clearly not zero, meat consumers (Pan troglodytes and Pan paniscus) (Nishida and Uehara, 1983;Stanford, 1996;Hofreiter et al, 2010). Further, there is good evidence that some of our hominin cousins (Australopithecus bahrelghazali, Paranthropus robustus and Australopithecus sediba) were largely plant eaters (Balter et al, 2012;Henry et al, 2012a;Lee-Thorp et al, 2012).…”

A cautionary note on fecal sampling and molecular epidemiology in predatory wild great apes

“…Gorillas have never been observed to hunt, nor have remains of prey been observed in their feces. A first molecular study of gorilla diet, also in Loango, identified mammal DNA sequences in their feces [Hofreiter et al, 2010]. The authors carefully discussed this finding and mentioned the possibility of environmental or laboratory contamination.…”

“…Measuring the frequency of hunting through direct observations is possible but only where great apes have been habituated [Boesch and Boesch-Achermann, 2000]; and to our knowledge, parasite nucleic acid persistence through the digestive tract of great apes has never been assessed (whatever the parasite). By means of molecular tools, it is possible to screen fecal samples for prey DNA [Symondson, 2002], as previously done to study the diet of great apes [Hofreiter et al, 2010] and many other predators [O'Rorke et al, 2012]. Here, we use molecular methods to detect prey DNA in fecal samplings of two distinct chimpanzee communities, using fecal samples of western lowland gorillas as negative control (as they are not carnivorous), to assess to what extent this is prevalent ("prey prevalence") and could effectively pose a risk of false interpretation in fecal epidemiology studies.…”