American Journal of Primatology 35139-142 (1995) Comparison of Gut Proportions in Four Small-Bodied Amazonian Cebids STEPHEN F. FERRARI' AND M. APARECIDA LOPES' Departments of 'Genetics and 2Biology,Universidade Federal do Pa&, Belem, Brazil Gut proportions in four small-bodied Amazonian cebids (Callicebus caligatus, Callicebus moloch, Pithecia irrorata, and Saimiri madeirae) are reported and compared in the context of known differences in feeding ecology. The gastrointestinal tracts of both Callicebus and Pithecia were found to be relatively undifferentiated, as expected from their predominantly frugivorous diets. In Saimiri, the marked dominance of the small intestine correlates with a highly insectivorous diet. o 1995 Wiley-Liss, Inc. Key words: Cebidae, gut proportions, diet INTRODUCTION The morphology of the gastrointestinal tract in primates varies systematically in relation to feeding ecology [Chivers & Hladik, 1980; Martin e t al., 1985; MacLarnon et al., 19871. In broad terms, the relative size of the small intestine correlates negatively with the proportion of structural carbohydrates in the diet and positively with that of high quality items such as animal material and seeds. Chivers and Hladik  record the gut morphology of a number of wildcaught platyrrhines from Panama, but quantitative data on South American taxa are limited [Ayres, 1986; MacLarnon et al., 1987; Ferrari et al., 19931, especially in comparison with Old World primates. The present study reports on the gut proportions of eight wild-caught monkeys from western Brazilian Amazonia. The specimens represent three of the four smallest-bodied cebid genera, including one (Callicebus) that has not been studied previously. Gut proportions observed in all specimens were consistent with both those of related taxa [Fooden, 1964; Chivers & Hladik, 1980; Ayres, 1986; Ferrari, submitted], and the data available on feeding ecology [Kinzey, 1981; Happel, 1982; Terborgh, 1983; Oliveira et al., 1985; Setz, 1987; Boinski, 1989; Peres, 19931. METHODS The adult specimens analyzed here were collected during a survey in the Brazilian states of Amazonas and Rond6nia [Ferrari & Lopes, 19921. Two male Saimiri madeirae [sensu Thorington, 19851, a female Callicebus moloch, and a male Pithecia irrorata were collected a t Lago dos Reis, Amazonas (7"32'S, Received for publication November 16, 1993; revision received April 15, 1994 Address reprint requests to Stephen F. Ferrari, Department of Genetics, Universidade Federal do Para, Caixa Postal 8607, 66.075-150 Belem-PA, Brazil. 0 1995 Wiley-Liss, Inc. 140 I Ferrari and Lopes TABLE I. Body Size and Gut Dimensions of C. caligatus, C. moloch, P. irrorata, and S . madeirae Body weight Length of small intestine/ colon (mm) Specimen (d length (mm) Total gut area (an2) C . caligatus C. moloch Female Male Mean P. irrorata S . madeirae Male 1 Male 2 Male 3 Female Mean 880 296 9441324 352.5 1,020 860 940 1,580 290 284 287 332 1,0561521 1,1681540 1,1121530.5 1,44017 17 564.0 624.7 594.4 711.0 1,010 880 970 820 920 280 264 272 246 265.5 1,2731190 1,1601178 1,241/148 1,0381125 1,1781160.25 471.2 369.1 268.1 245.9 338.6 62"52'W), and a male C. moloch and two S . madeirae (1male, 1female) a t Calama, RondBnia (8"03'S, 62"53'W). Callicebus caligatus is represented by a male from Rio Ipixuna, Amazonas (7"31'S, 63"22'W). All specimens were weighed and measured (bregma to ischium) prior to removal of the gastrointestinal tracts. Measurements of the length and surface area of gut compartments were carried out 2 to 4 h after death, following Chivers and Hladik  and Ferrari et al. , and double-checked to ensure accuracy. Specimens (stuffed skins and skeletocs) were deposited at the Goeldi Museum in Belem [see Ferrari & Lopes, 19921. RESULTS Body weights and lengths of the eight specimens ranged between 820-1,580 g and 246-332 mm, respectively (Table I). While there is a n overall tendency for gut area to increase with body size, there are only weak correlations with body weight (Spearman rank: r, = 0.60, P > 0.05, N = 8) and length (r, = 0.59, P > 0.051, and the small size of the samples prohibits meaningful comparisons a t the species level. There are, nevertheless, some interesting contrasts between S. madeirae and the remaining specimens, especially in colon length (Table I). The contrasts between taxa are further emphasized in the data on gut proportions (Table 11).The gastrointestinal tracts of Callicebus and Pithecia are somewhat undifferentiated (coefficient of gut differentiation [CGD] of 0.89-1.131, values highly characteristic of primate frugivores [Chivers & Hladik, 19801. S. madeirae exhibits a relatively huge small intestine, by contrast, and a high degree of differentiation more typical of mammalian faunivores (CGD < 0.50). S. madezrue body size, gut area, and CGDs are in fact closely similar to those recorded for other Saimiri species [Chivers & Hladik, 1980; Ayres, 19861. DISCUSSI 0N As for other squirrel monkey species, gut proportions observed in S. madeirae are consistent with a highly insectivorous diet [see Terborgh, 1983; Boinski, i9891. The evidence presented here also suggests that Saimiri is more specialized for insectivory than the callitrichids Callithrix and Saguinus [see Ferrari et al., 19931. This is supported by differences in the foraging behavior of syntopic Saimiri and Gut Proportions in Small-Bodied Amazonian Cebids I 141 TABLE 11. Surface Area of Gut Compartments and Coefficient of Gut Differentiation of SDecimexis Described in Table I Surface area (cm’) SDecimen C. caligatus C . moloch Female Male Mean P. irrorata S . madeirae Male 1 Male 2 Male 3 Female Mean Coefficient of gut differentiation (CGD)“ Stomach Small intestine Caecum Colon 66.5 (18.9)b 165.3 (46.9) 61.3 (17.4) 59.4 (16.8) 1.13 42.7 74.5 58.6 (9.9)’ 286.1 329.7 307.9 (51.8) 180.6 165.7 173.2 (29.1) 0.97 0.89 0.93 84.0 (11.8)b 335.1 (47.1) 54.5 54.8 54.7 (9.2) 74.0 (10.4) 217.9 (30.7) 1.12 73.8 55.3 39.7 21.0 47.4 (14.0)’ 322.2 252.9 180.4 189.8 236.3 (69.8) 18.2 13.2 9.5 9.7 12.7 (3.7) 57.0 47.7 38.5 25.4 42.1 (12.5) 0.46 0.46 0.49 0.30 0.43 “CGD = surface area of stomach 19801. + caecum + colonlsurface area of small intestine [following Chivers & Hladik, bPercentage of total gut area. ‘Mean value as a percentage of mean total gut area. Saguinus in Peru [Terborgh, 1983; Terborgh & Stern, 19871, especially during the dry season period of resource scarcity. While they are known to feed on arthropods, both Callicebus and Pithecia are primarily frugivores [Kinzey, 1981; Happel, 1982; Terborgh, 1983; Oliveira et al., 1985; Setz, 1987; but see Peres, 19931, and this is reflected in their gut proportions. Gut passage rates in Pithecia, nevertheless, suggest that the digestion of low quality resources, such as leaves, may be important [Milton, 19841. Both genera are also highly similar to the fourth small-bodied cebid, Aotus [Chivers & Hladik, 19801, whose diet is basically frugivorous [Wright, 19813. Pithecia also appears to be far more similar in gut proportions to Aotus and Callicebus than to other pitheciines, Cacajao and Chiropotes [Fooden, 1964; Ayres, 1986; Ferrari, submitted], a s might be expected from differences in their degree of specialization for seed predation [Kinzey, 19921. CONCLUSIONS 1. Gut proportions in wild-caught Saimiri madeirae were typical of highly insectivorous primates, including other Saimiri species. 2. Gut proportions recorded for Callicebus moloch, Callicebus caligatus, and Pithecia irrorata were both typical of relatively unspecialized frugivores and similar to those of the fourth small-bodied cebid. Aotus. ACKNOWLEDGMENTS Data collection was authorized by IBAMA (special license 1404/90-31) and supported by the John D. and Catherine T. MacArthur Foundation. We thank 142 I Ferraii and Lopes Dionisio Pimentel Neto, David C. Oren, Cazuza Junior, Katharine Milton, and three anonymous reviewers. REFERENCES Ayres, J.M. Uakaris and Amazonian flooded forest. Ph.D. Thesis, University of Cambridge, UK, 1986. Boinski, S. The positional behavior and substrate use of squirrel monkeys: Ecological implications. JOURNAL OF HUMAN EVOLUTION 18:659-677, 1989. Chivers, D.J.; Hladik, C.M. 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