American Journal of Primatology 48:153–160 (1999) © 1999 Wiley-Liss, Inc. BRIEF REPORT Taste Difference Thresholds for Sucrose in Two Species of Nonhuman Primates MATTHIAS LASKA, 1 * HEINZ-PETER SCHEUBER, 2 EDITH CARRERA SANCHEZ, 3 AND ERNESTO RODRIGUEZ LUNA 3 1 Department of Medical Psychology, University of Munich Medical School, Munich, Germany 2 Department of Surgery, University of Munich Medical School, Munich, Germany 3 Instituto de Neuro-Etologia, Universidad Veracruzana, Xalapa, Mexico The purpose of this study was to determine taste difference thresholds for sucrose in frugivorous spider monkeys and omnivorous baboons. Us- ing a two-bottle 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 ability to discriminate these from lower concentrations of this carbohydrate. The just noticeable differences (JNDs), expressed as Weber ratios (∆/I), were found to range from 0.075–0.25 in the spider monkeys, with a tendency for lower values with higher RCs. In contrast, the baboons showed the reverse trend, with the lowest Weber ratio of 0.10 at the two lowest RCs and higher values of up to 0.25 with the highest RC tested. Thus, the JNDs were found 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 may use sweetness as a criterion for food selection. The different patterns of differential sen- sitivity for sucrose across the range of concentrations tested suggest a correlation between the ability to discriminate between different concen- trations of sucrose and the dietary habits of the two species. Am. J. Primatol. 48:153–160, 1999. © 1999 Wiley-Liss, Inc. Key words: taste difference thresholds; sucrose; spider monkeys; Ateles geoffroyi; baboons; Papio hamadryas anubis INTRODUCTION The ability to judge the sugar content of potential food is particularly impor- tant for species which at least partly meet their energy requirements by using easily metabolizable carbohydrates. Apart from a sufficiently high sensitivity en- Contract grant sponsor: Deutsche Forschungsgemeinschaft; Contract grant number: La 635/6-2; Con- tract grant sponsor: Volkswagen Foundation; Contract grant number: I 71/285; Contract grant spon- sor: Conacyt Mexico; Contract grant number: 4316P-H9608. *Correspondence to: Matthias Laska, Department of Medical Psychology, University of Munich Medi- cal School, Goethestr. 31, D-80336 Munich, Germany. E-mail: Laska@imp.med.uni-muenchen.de Received 15 July 1998; revision accepted 23 November 1998