Taste difference thresholds for sucrose in two species of nonhuman primates

The purpose of this study was to determine taste difference thresholds for sucrose in frugivorous spider monkeys and omnivorous baboons. Using a two-b ottle preference test of brief duration, we presented four Ateles geoffroyi and four Papio hamdryas anubis with six different reference concentrations (RCs) of 25, 50, 100, 200, 300, and 400 mM sucrose and tested their abilit y to discriminate these from lower concentrations of this carbohydrate. The just noticeable differences (JNDs), expressed as Weber ratios (Delta/I), w ere found to range from 0.075-0.25 in the spider monkeys, with a tendency f or lower values with higher RCs. In contrast, the baboons showed the revers e trend, with the lowest Weber ratio of 0.10 at the two lowest RCs and high er values of up to 0.25 with the highest RC tested. Thus, the JNDs were fou nd to be generally similar in both species and at least as low as in humans . The results support the assumption that both spider monkeys and baboons m ay use sweetness as a criterion for food selection. The different patterns of differential sensitivity for sucrose across the range of concentrations tested suggest a correlation between the ability to discriminate between di fferent concentrations of sucrose and the dietary habits of the two species . (C) 1999 Wiley-Liss, Inc.