'Microsmatic' primates revisited: Olfactory sensitivity in the squirrel monkey

Using a conditioning paradigm, the olfactory sensitivity of three squirrel monkeys to nine odorants representing different chemical classes as well as members of a homologous series of substances was investigated. The animals significantly discriminated dilutions as low as 1:10 000 n-propionic acid, 1:30 000 n-butanoic acid and n-pentanoic acid, 1:100 000 n-hexanoic acid, 1:1Mio n-heptanoic acid, 1:30 000 1-pentanol, 1:300 000 1,8-cineole, 1:1Mio n-heptanal and 1:30Mio amyl acetate from the near-odorless solvent, with s ingle individuals scoring even slightly better. The results showed (i) the squirrel monkey to have an unexpectedly high olfactory sensitivity, which f or some substances matches or even is better than that of species such as t he rat or the dog, and (ii) a significant negative correlation between perc eptibility in terms of olfactory detection thresholds and carbon chain leng th of carboxylic acids. These findings support the assumptions that olfacti on may play a significant and hitherto underestimated role in the regulatio n of primate behavior, and that the concept of primates as primarily visual and 'microsmatic' animals needs to be revised.