Western gorilla diet: A synthesis from six sites

Abstract

The objective of this paper is to collate information on western gorilla diet from six study sites throughout much of their current range, including preliminary information from two sites (Afi and Lossi), where studies of diet have begun only recently. Food lists were available from each site, derived from indirect signs of gorilla feeding (such as feces), with some observational data. Important staple, seasonal, and fallback foods have been identified, and a number of striking similarities across sites have been revealed based on a much larger data set than was previously available. It was confirmed that the western gorilla diet is always eclectic, including up to 230 items and 180 species. The greatest diversity is found among the fruit species eaten, fruit being included in western gorilla diets from all sites and throughout most or all of the year. Eight plant families provide important foods at five, or all six, sites, suggesting that it may be possible in the future to predict which habitats are the most suitable for gorillas. Gorillas exploit both rare and common forest species. Similarities and differences among sites can be explained superficially on the basis of geography and the past history of the forest. Gorilla density across sites appears to be most affected by the density of monocotyledonous bulk food plants, but its relationship to the density of important tree food species has yet to be tested.

Temporal variation selects for diet–microbe co-metabolic traits in the gut of Gorilla spp

“…That is, seasonal shifts in their habitat forces them to rely mainly on fibrous fruits, leaves and herbaceous vegetation during the low ripe fruit season (Masi et al, 2009). These fibrous foods are low in readily digestible energy, higher in hemicellulose, cellulose and lignin than ripe fruit (Remis, 1997a,b,c Remis et al, 2001Rogers et al, 2004Rogers et al, ,1990Rothman et al, 2014), although in times of fruit scarcity fruits eaten are high in fiber and similar to vegetation (Remis et al, 2001). Thus, it is likely that bio-geographical and ecological factors across evolutionary timescales triggered both diversification of Gorilla spp., and the acquisition of distinct gut bacterial communities in mountain and lowland gorillas (Ley et al, 2008;Collins and Dubach, 2000;Gomez and Verdu, 2012;Sussman, 1991).…”

“…(Remis, 1997a;Doran and McNeilage, 1998). In contrast, the fragmented distribution of fruit and the higher nutritional diversity of fruit substrates expand foraging options in gorilla groups, causing individuals within groups to consume more diverse diets when fruit is available (Masi et al, 2009;Rogers et al, 2004). This is an interesting example of how macroecological patterns may be also reflected at microecological scales.…”

“…Study site, subjects and sample collection Western lowland gorilla (G.g.gorilla) fecal samples were collected near two research sites, Bai Hokou November and December usually correspond to periods of low fruit availability, whereas high fruit consumption takes place from May to July (Masi, 2007;Remis, 1997b;Masi et al, 2012;Rogers et al, 2004). Thus, September corresponds to a transition period between low and high fruit consumption.…”

“…G. g. gorilla experience marked shifts in the availability of preferred resources yearlong (Rogers et al, 2004); they spend about 80% of their time consuming readily digestible fruit when seasonally available, but shift to a similar percent of time feeding on vegetation (terrestrial herbs and leaves) in drier periods of the year (Masi, 2007;Masi et al, 2009), while also incorporating fibrous fruit and bark (Remis, 1997b).…”

Functional Anatomy and Adaptation of Male Gorillas (Gorilla gorilla gorilla) With Comparison to Male Orangutans (Pongo pygmaeus)

“…Gorillas range throughout their habitat foraging on vegetation and insects near the forest floor (Tutin et al, 1991;Cipolletta et al, 2007). However, when seeking preferred foods, they may travel distances to swampy areas for aquatic herbs or widely dispersed fruit sources on the ground (Nishihara, 1995;Yamagiwa et al, 1996;Remis, 1997b;Goldsmith, 1999;Rogers et al, 2004). When succulent fruits are seasonally available, their day ranges increase by several times such that their mean day journey lengths approach 3 km, similar to those of the more persistently frugivorous chimpanzees (Tutin and Fernandez, 1993;Yamagiwa et al, 1996;Remis, 1997a,b).…”