Olfactory sensitivity for aliphatic alcohols in squirrel monkeys and pigtail macaques

Area of Science:

• Primate Olfaction
• Sensory Neuroscience
• Animal Behavior

Background:

• Primates are often classified as microsmatic based on neuroanatomy, but physiological evidence for poor smell is lacking.
• Previous assumptions about primate olfactory capabilities are largely based on brain structure size rather than functional performance.

Purpose of the Study:

• To physiologically assess the olfactory sensitivity of squirrel monkeys (Saimiri sciureus) and pigtail macaques (Macaca nemestrina).
• To investigate primate olfactory perception of aliphatic alcohols and compare it to other species.
• To evaluate the correlation between olfactory detection thresholds and chemical properties like carbon chain length.

Main Methods:

• A conditioning paradigm was employed to test olfactory sensitivity.
• Subjects included three squirrel monkeys and four pigtail macaques.
• Homologous series of aliphatic alcohols and isomeric forms were used to determine detection thresholds.

Main Results:

• Both primate species detected alcohol concentrations below 1 part per million.
• Individual detection thresholds for 1-hexanol were below 10 parts per billion.
• Olfactory sensitivity in these primates matched or exceeded that of rats for most tested alcohols.
• A negative correlation was observed between olfactory detection threshold and alcohol carbon chain length.

Conclusions:

• Primates exhibit well-developed olfactory sensitivity, contradicting the 'microsmatic' label.
• Neuroanatomical comparisons are poor predictors of olfactory performance across species.
• Olfaction may play a significant, underestimated role in primate behavior regulation.