Male and female western gorilla diet: Preferred foods, use of fallback resources, and implications for ape versus old world monkey foraging strategies

Abstract

Most of what is currently known about western gorilla (Gorilla gorilla) diet is based on indirect studies using fecal samples and trail signs rather than measures based on direct observations. Here we report results on adult male and female western gorilla foraging behavior, based on systematic focal observations and nutritional analyses of foods. We found that western gorillas, like other apes, are highly selective ripe fruit specialists, seeking fruit high in energy, low in antifeedants, and rare in the environment. During seasonal fruiting peaks, fruit accounted for up to 70% of feeding time. When ripe fruit was scarce, gorillas increased time spent feeding on leaves and nonpreferred fruits and herbs. Leaves were the major fallback food, accounting for up to 70% of feeding time in males and 50% in females during periods of fruit scarcity. In spite of large differences in body size, the sexes were remarkably similar in their overall diet, not differing in time spent feeding on fruit or preferred herbs. However, the male consistently fed more often and on a greater variety of leaves than did females, whereas females fed more often on fallback herbs and termites. Our findings, when considered in light of previous findings on sympatric mangabeys, indicate that the foraging strategy of western gorillas is broadly similar to that of chimpanzees and orangutans, and distinct from that of old world monkeys.

Hominids adapted to metabolize ethanol long before human-directed fermentation

“…Although ripe fruit is generally the preferred food of all hominoids (58)(59)(60)(61), those without an ethanol-oxidizing ADH4 (orangutans and gibbons) differ from chimpanzees and gorillas in several important regards. Unlike chimpanzees and gorillas, gibbons and orangutans rely primarily on arboreal fallback foods, and, whereas gibbons and orangutans have unique strategies to buffer against ripe-fruit scarcity, these strategies bear important similarities to the cercopithecines.…”

Dental microwear texture analysis of late Pliocene Procynocephalus subhimalayanus (Primates: Cercopithecidae) of the Upper Siwaliks, India

“…In addition, semi-terrestriality does not always indicate a reliance on USOs. African apes such as gorillas and chimpanzees are partially terrestrial but actively search for fruit [43,44]. However, the marked similarity in enamel surface texture properties between Procynocephalus and Parapapio, and the inferred USO consumption in Parapapio [38], suggests that Procynocephalus is likely to have also consumed the underground parts of plants in the C 4 grasslands of late Pliocene northern India.…”

“…Both male and female Gorilla gorilla actively search for ripe fruit and two rare herbs even when fruit is abundant [43]. When fruit is scarce, fallback foods are consumed, including leaves and second choice fruits and herbs, bark, pith and insects (particularly among females).…”

“…Herbs are close to ground level and may be covered with fracture resistant particles more often than arboreal leaves and fruits [25]. The two Gorilla that approximate Procynocephalus on the first canonical scores axis ( Figure 7) may exhibit extremes in textural complexity values (Asfc) from the consumption of abrasive grit on preferred herbs such as the shoots of Haumania danckelmaniana and the swamp herb Hydrocharis chavalieri both of which are eaten year round [43].…”

“…In contrast, Lophocebus eats ripe and unripe fruit as well as fruit rotting on the ground, and includes seeds, legumes and fruit equipped with a range of defensive toxins. Old World monkeys differ from the great apes in having less differentiated diets, often including lower quality leaves than can be consumed by hominoids [43]. Like its tropical forest relative Lophocebus, Procynocephalus probably also exhibited a less differentiated diet than characterized by the great apes, and may have included durophagy (hard-object feeding) as a fallback strategy in the grasslands of the Upper Siwaliks of the late Pliocene.…”