hydrolyzed to chitobiose by chitinase, and chitobiose can be hydrolyzed to N-acetyl-D-glucosamine by chitobiase (Stevens and Hume, 1995). Because these enzymes are found in many indigenous gut microorganisms, their presence in the gastrointestinal tract does not infer endogenous production. However, chitinase has been found in the gastric mucosa of a number of animal species (Jeuniaux, 1962), including the primates, Cebus capucinus (Jeuniaux and Cornelius, 1978) and Perodicticus potto (Beerten-Joly et al., 1974).
Few studies of carbohydrates in wild food plants have identified or measured the specific carbohydrates found in plant parts consumed by free-ranging primates. In some instances, analytic procedures were used to measure concentrations of moisture, crude protein, ether extract, ash, NDF, ADF, and ADL in consumed plant parts (fresh basis). When the sum of moisture, crude protein, ether extract, ash, and NDF percentages was subtracted from 100% of fresh weight, the residual fraction was presumed to be mostly nonstructural carbohydrates, largely sugars, starch, and soluble fiber not included in NDF. NDF includes mainly cellulose, hemicelluloses, and lignin, so NDF minus ADL would approximate the structural-carbohydrate concentration; and NDF minus ADL plus nonstructural carbohydrates would yield an approximate measure of total carbohydrates. Of course, such estimates are subject to the errors associated with inaccuracies, imprecision, or lack of specificity in analyses of the other plant components. In addition, the category total carbohydrates combines carbohydrate fractions that differ tremendously in digestibility by endogenous alimentary enzymes. Carbohydrates in the insoluble fiber fraction (NDF-ADL) are relatively low in digestibility, those in the soluble fiber fraction (TDF-NDF) generally are moderately to highly digestible, whereas soluble sugars and starch are highly digestible.
Calvert (1985) collected 36 samples of stems, leaves, shoots, and fruits from 27 species of plants eaten by western gorillas (Gorilla g. gorilla) in Cameroon, West Africa. Mean nonstructural-carbohydrate concentrations (dry basis) were estimated to be 28, 5, 24, and 20% in leaves, shoots, stems, and fruits, respectively. Estimates of mean structural-carbohydrate concentrations (cellulose plus hemicelluloses) were 27, 62, 45, and 38%, respectively. Thus, total carbohydrate concentrations were about 55, 67, 69, and 58% in leaves, shoots, stems, and fruits, respectively. Edwards (1995) collected plant parts (representing 90% of feeding time) consumed by red howlers (Alouatta seniculus) in the central llanos of Venezuela. Mean dietary nonstructural-carbohydrate concentrations (dry basis) were 29% during the wet season and 37% during the dry season. Structural carbohydrate concentrations (dry basis) were 32% and 31% during the wet and dry seasons, respectively. Thus, total carbohydrate concentrations were 61% and 68%. Conklin-Brittain et al. (1997) analyzed 408 samples of 194 plant parts representing 94% of the plant-feeding time among chimpanzees (Pan troglodytes), gray-cheeked mangabeys (Cercocebus albigena), blue monkeys (Cercopithecus mitis), and redtail monkeys (Cercopithecus ascanius) in the Kibale Forest, Uganda. Reported mean concentrations (dry basis) of simple sugars were 10-15% and of total nonstructural carbohydrates from 34-39%. (Conklin-Brittain et al., 1998). Mean concentrations of structural carbohydrates (cellulose plus hemicelluloses) were 23-26%. Thus, total carbohydrate concentrations in the plant parts eaten were 57-65%.
Others have conducted nutrient analyses of the natural foods of gorillas in the Lopé Reserve, Gabon (Rogers et al., 1990), baboons (Papio anubis) on the Laikipia Plateau in Kenya (Barton et al., 1993) (Table 3-2), red colobus (Colobus badius) and black-and-white colobus (C. guereza) in the Kibale Forest in Uganda (Baranga, 1982), and silvered leaf monkey (Trachypithecus auratus) in the Pangandaran Nature Reserve, West Java (Kool, 1992) (Table 3-3). The proportions of items in wild diets that were analyzed are lower in Table 3-3 than in Table 3-2. The data generated do not permit estimates of total nonstructural carbohydrates or total carbohydrates, but measurements of ADF make it clear that fiber concentrations were variable in chosen foods and often high compared with those in fruits and vegetables cultivated for human consumption and in commercial primate diets.
Rogers et al. (1990) noted that plant diversity was high in the mature forest inhabited by gorillas in Gabon compared with the impoverished disturbed forest occupied by gorillas in Cameroon (Calvert, 1985). Fruit availability in Gabon was much greater, and Lopé Reserve gorillas eagerly consumed ripe fruits, particularly succulent flesh that tended to be more sugary and less fibrous than unripe fruit or the fruit parts that were uneaten. Mean water-soluble carbohydrate concentration in the dry matter of 46 fruits and fruit parts that were eaten was 35%, and mean ADF concentration 24%. Surprisingly, consumed fruit parts often were higher than nonconsumed fruit parts in condensed tannins and total phenols. Conklin and Wrangham (1994) analyzed nine fig species eaten by frugivorous primates in the Kibale Forest, Uganda, and found that water-soluble carbohydrates (free simple sugars) in the pulp organic matter (dry matter minus ash) were present at 7-23%, whereas NDF was present at 24-65%. For purposes of comparison, total sugar concentrations exceed 33% in the dry matter of the edible portion of raw figs consumed by humans when calculated by adding analytic