Nutritional composition of the diet of the western gorilla (Gorilla gorilla): Interspecific variation in diet quality

Abstract

To meet nutritional needs, primates adjust their diets in response to local habitat differences, though whether these dietary modifications translate to changes in dietary nutrient intake is unknown. A previous study of two populations of the mountain gorilla (MG: Gorilla beringei) found no evidence for intraspecific variation in the nutrient composition of their diets, despite ecological and dietary differences between sites. One potential explanation is that nutritional variability in primate diets requires greater ecological divergence than what was captured between MG sites, underpinning environmental differences in the nutrient quality of plant foods. To test whether Gorilla exhibits interspecific variation in dietary composition and nutrient intake, we studied the composition and macronutrients of the western gorilla (WG: Gorilla gorilla) staple diets and compared them with published data from the two MG populations. We recorded feeding time and food intake of four adult female WGs from one habituated group over a period of 11 months (December 2004-October 2005) at the Mondika Research Center, Republic of Congo, allowing for assessment of seasonal patterns of nutrient intake. Staple diets of WGs and MGs diverged in their dietary and macronutrient composition. Compared to MGs, the staple diet of WGs (by intake) contained higher proportions of fruit (43%) and leaf (12%) and a lower proportion of herb (39%), resulting in a higher intake of total nonstructural carbohydrate and fiber and a lower intake of crude protein. Staple gorilla fruits and herbs differed in nutrient quality between sites. Gorillas exhibit nutritional flexibility that reflects ecological variation in the nutrient quality of plant foods. Since dietary quality typically affects rates of growth and reproduction in primates, our results suggest that interspecific differences in nutrient intake and food quality may shape differences in gorilla nutrient balancing and female life history strategies. K E Y W O R D S ape, ecology, feeding, nutrition, primate

Facial asymmetry tracks genetic diversity amongGorillasubspecies

“…Virunga mountain gorillas rely on an almost entirely folivorous diet that is both spatio-temporally abundant and high in protein, while western lowland gorillas rely most heavily on unpredictable, seasonal fruit in addition to herbs and leaves. The western lowland gorilla diet is comparatively lower in protein, but high in non-protein energy during periods of high fruit consumption [ 20 , 23 , 45 ]. When fruit-feeding, gorillas spend more time travelling and less time resting [ 45 ], which, in addition to competition with other apes and the comparative unpredictability of their ecological conditions, might provide differential sources of environmental stress.…”

“…Second, we assess whether gorillas that experience more environmental stress exhibit more pronounced facial FA. While environmental stress encompasses many factors, one main axis of variation among gorilla subspecies lies in dietary and ecological variability, with western lowland gorillas being exposed to the highest level of seasonal unpredictability in food resources and competition [ 20 ]. Western lowland gorillas have also experienced major population declines due to human activity and infectious diseases, most notably Ebola, resulting in approximately 90% casualties in affected populations [ 21 ].…”

“…By contrast, Virunga mountain gorillas eat a reliable, almost entirely folivorous diet, and have experienced increased population growth over the past several decades [ 22 ]. Grauer gorillas fall between these two extremes, with those from highland areas eating a more folivorous diet, and those from lowland areas eating a similar proportion of fruit as western lowland gorillas [ 20 , 23 ]. Grauer gorillas have also experienced major population declines in the last century, losing up to 77% of their total population [ 24 ].…”

Hand preference in unimanual and bimanual coordinated tasks in wild western lowland gorillas (Gorilla gorilla gorilla) feeding on African ginger (Zingiberaceae)

“…b . graueri ), and mountain gorillas in several study sites (western lowland gorillas: Mondika in Lodwick & Salmi, 2019, Bai Hokou in Goldsmith, 1999; Remis, 1997, Nouabalé‐Ndoki in Nishihara, 1995, Lopé in Rogers et al, 1990; Williamson et al, 1990, Rio Muni in Sabater Pi, 1997, Belinga in Tutin & Fernandez, 1985, reviewed in Rogers et al, 2004, and eastern lowland gorillas: Kahuzi‐biega in Yamagiwa et al, 1994; Yamagiwa et al, 2005, and mountain gorillas: Bwindi in Rothman et al, 2006). Furthermore, it is also reported that chimpanzees and bonobos in multiple study sites feed on piths of African gingers in the wild (chimpanzees: Belinga in Tutin & Fernandez, 1985, Bulindi in McLennan, 2013, Kahuzi‐biega in Yamagiwa & Basabose, 2006, Kalinzu in Furuichi et al, 2001, Kibale in Potts et al, 2011, Lopé in Tutin & Fernandez, 1993, Mahale in Nishida & Uehara, 1983, and bonobos: Bolobo in Maloueki et al, 2016, Lake Tumba in Horn, 1980, Wamba in Ishizuka et al, 2019, and Yalosidi in Kano, 1983; Uehara, 1990).…”

“…b. graueri), and mountain gorillas in several study sites (western lowland gorillas: Mondika in Lodwick & Salmi, 2019, Bai Hokou in Goldsmith, 1999Remis, 1997, Nouabalé-Ndoki in Nishihara, 1995, Lopé in Rogers et al, 1990Williamson et al, 1990, Rio Muni in Sabater Pi, 1997, Belinga in Tutin & Fernandez, 1985 in Rogers et al, 2004, and eastern lowland gorillas: Kahuzi-biega in Yamagiwa et al, 1994;Yamagiwa et al, 2005, and mountain gorillas:…”