Olfactory Sensitivity for Aliphatic Esters in Spider Monkeys (Ateles geoffroyi)

Using a conditioning paradigm, the authors investigated the olfactory sensitivity of 3 spider monkeys (Ateles geoffroyi) for a homologous series of aliphatic esters (ethyl acetate to n-octyl acetate) and isomeric forms of some of these substances. With all odorants, the monkeys significantly discriminated concentrations below 1 ppm from the odorless solvent, and in several cases, individual monkeys even demonstrated thresholds below 1 ppb. The results showed spider monkeys to have a high olfactory sensitivity for aliphatic esters, which for the majority of substances matches or even is better than that of species such as the rat, the mouse, or the dog. These findings support the assumption that between-species comparisons of neuroanatomical features are poor predictors of olfactory performance. There is a long-standing tradition in olfactory research of as-signing animal species or even whole orders of animals as being “macrosmatic, ” that is, having a keen sense of smell, or as being “microsmatic, ” that is, having a poor sense of smell. This dichot-omy is mainly, if not exclusively, based on an interpretation of neuroanatomical features such as the relative size of olfactory brain structures or the absolute size of olfactory epithelia (Farb