SAMPLE ABSTRACTS
EFFECTS OF COLOR VISION PHENOTYPE ON INSECT CAPTURE BY FREE-RANGING WHITE-FACED CAPUCHIN MONKEYS (CEBUS CAPUCINUS) IN SANTA ROSA NATIONAL PARK, COSTA RICA |
A. Melin1, L. Fedigan1, C. Hiramatsu2 and S. Kawamura2
1Department of Anthropology, University of Calgary, 2500 University Avenue NW, Calgary, Alberta, T2N 1N4, Canada, 2Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Japan |
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| Like many platyrrhine primates, white-faced capuchins (Cebus capucinus) are characterized by polymorphic color vision, which is enabled via multiple alleles for a single-locus, X-linked opsin. In combination with an autosomal opsin, this arrangement provides trichromatic vision to heterozygous females, whereas homozygous females and males are dichromats. Because trichromatic vision enables visual differentiation among red, orange, yellow and green, trichromacy may be advantageous for finding edible fruits or leaves among mature foliage. Currently most researchers attribute the evolution and maintenance of polymorphic color vision to trichromat (= heterozygote) advantage. However, dichromacy may be better for achromatic tasks, such as penetrating color camouflage, especially under low-light conditions. We evaluated whether dichromats were better able to capture camouflaged invertebrates. Through fecal analysis, we determined the genotypes for each individual (N = 35) in two groups of capuchins living in Santa Rosa National Park. Foraging data were collected for seven months, encompassing both wet and dry seasons. Insect capture rates were affected by foliage density, height in forest and time of day. Dichromatic monkeys were significantly more efficient at capturing surface-dwelling insects (repeated-measures ANOVA, p < 0.05), especially under conditions of low ambient light. However, trichromats were significantly more efficient in extracting embedded insects from substrates (Mann-Whitney U test, p < 0.05). Our findings do not support heterozygote advantage as the mechanism maintaining polymorphic color vision in this population. |
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MARKET FORCES PREDICT GROOMING RECIPROCITY IN RHESUS MACAQUES UNDER DIVERSE POPULATION DENSITIES |
P. G. Judge1 and F. B. de Waal2
1Bucknell University, Psychology Department and Animal Behavior Program, Lewisburg, PA, 17837, USA, 2Living Links, Yerkes National Primate Research Center, Emory University |
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| A biological market perspective proposes that primates use grooming for reciprocal exchange to cultivate valuable social partners and to interchange commodities such as grooming for tolerance near resources. At high population density with increased risk of aggression, subordinates might trade grooming for tolerance, while at lower density grooming may be more reciprocal to maintain preferred social relationships. Predictions were tested by examining grooming reciprocity and rank distance among adult females in six similar-sized groups of rhesus macaques (Macaca mulatta) living under three different density conditions (low = free-ranging, medium = outdoor corrals, and high = small enclosures). Pearson correlations of all paired dyads in each condition evaluated for significance through resampling indicated that grooming was not reciprocated at high density (r=-0.03, N=166, ns) but was reciprocated (p<0.05) at medium density (r=+0.15, N=211) and low density (r=+0.42, N=143). Comparison of the slopes of the regression lines indicated that grooming was significantly more reciprocal at low density than at medium and high density (p<0.01). Rank distance was not related to the degree of grooming reciprocity at low and medium density, but at high density grooming was negatively reciprocated among distantly ranked animals (r=-0.54, N=15, p<0.03). Grooming became less reciprocal as density increased particularly among distantly ranked partners, suggesting that market forces may have promoted grooming for tolerance at higher density. Support: NIH RR05276, RR00165, RR00167. |
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Revised: 17 December 2006
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