Determinants of Variation in Tropical Forest Primate Biomass: New Evidence from West Africa

Abstract

To explore sources of variation in tropical forest primate biomass, and, in particular, to test the hypothesis that soil conditions are a major ultimate determinant of the biomass of colobine monkeys and other primates, we compared data on the soils, vegetation, and primate community at a site in West Africa (Tiwai Island, Sierra Leone) with information from other sites, especially two other African sites (Douala—Edea in Cameroon, and Kibale Forest in Uganda). The biomass of eight anthropoid primate species in old secondary high forest on Tiwai was estimated from data on population densities assessed by transect samples combined with data on social group densities and individual body masses. Samples of soil and tree foliage were collected at the same site, and subjected to a variety of chemical and mechanical analyses. Our estimate of anthropoid biomass at Tiwai is 1229—1529 kg/km2, including 682—889 kg/km2 of colobines. This is one of the highest primate biomasses recorded anywhere. The soils at Tiwai were found to be relatively high in sand content and low in pH, and to have low levels of mineral nutrients. Levels of condensed tannins in the mature foliage of the trees comprising a major part of the forest canopy were higher than at other sites, but the ratio of protein to fiber in this foliage was also higher than at any other site except Kibale. It is argued that a wide range of environmental factors affect primate population densities, and that nutrient—poor soils and high tannin levels in tree foliage do not necessarily produce a low primate (or colobine) biomass, as some earlier studies had suggested. Furthermore, seeds (an important food source for Tiwai colobines) are apparently a common part of the colobine dietary repertoire and are not consumed largely as a response to a scarcity of digestible foliage.

Anti-predator strategies of free-ranging Campbell's monkeys

“…Although Gaboon vipers have been documented to prey on juvenile guenons (Foerster, 2008), to our knowledge no attempt to eat an adult has been observed in the Taï forest. Campbell's monkeys are among the smallest guenons in Taï forest (Oates et al, 1990) and could, therefore, be potential prey. Campbell's monkeys appear to be aware of their dangerousness and respond with ascending in tree and threatening at a safe distance, a behavioural pattern not observed to the mamba model.…”

Linking feeding ecology and population abundance: a review of food resource limitation on primates

“…Furthermore, nitrogen is the limiting nutrient in many terrestrial ecosystems and since it is found primarily in protein, herbivores should compensate for this limitation by choosing high protein foods (White 1993). These important ideas proposed by Milton have been applied at the population level by others (McKey et al 1981;Waterman et al 1988;Oates et al 1990;Davies 1994;. For example, Waterman et al (1988) proposed that the weighted contributions of the protein-to-fiber ratios of the mature leaves of the most abundant trees in a particular area could predict the biomass of folivorous colobines.…”

“…For example, Waterman et al (1988) proposed that the weighted contributions of the protein-to-fiber ratios of the mature leaves of the most abundant trees in a particular area could predict the biomass of folivorous colobines. This index of dietary quality has been applied successfully to predict the biomass of folivorous monkeys at local Ganzhorn 2002) and regional (Waterman et al 1988;Oates et al 1990;Ganzhorn 1995;Chapman et al 2004;Fashing et al 2007) scales. Davies (1994) suggested that the year-round availability of digestible mature leaves with high protein-to-fiber ratios, which are used by colobus species when other, more preferred foods are unavailable, serves to limit the size of colobine populations (i.e., high protein-to-fiber mature leaves are important fallback foods).…”

Understanding long‐term primate community dynamics: implications of forest change

“…We thus incorporated data on the nutrient composition of items used by red colobus to examine habitat quality , 2004a. We used the protein : fiber ratio as an index of food quality because it has been found to be a good predictor of folivore leaf choice (Milton 1979) and biomass (Waterman et al 1988, Oates et al 1990, 2004a, Ganzhorn 2002. These relationships have been demonstrated using the overall protein : fiber ratio of mature leaves in an area.…”