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

Area of Science:

• Primate Olfaction
• Sensory Neuroscience
• Animal Behavior

Background:

• Primates are traditionally considered primarily visual animals with limited olfactory capabilities ('microsmatic').
• The role of olfaction in primate behavior regulation is often underestimated.
• Understanding olfactory sensitivity in primates is crucial for revising these assumptions.

Purpose of the Study:

• To investigate the olfactory sensitivity of squirrel monkeys to various odorants.
• To determine the detection thresholds for different chemical classes and homologous series.
• To assess the correlation between odorant structure and olfactory perception.

Main Methods:

• A conditioning paradigm was employed to train three squirrel monkeys.
• Olfactory sensitivity was tested using nine odorants across different chemical classes.
• Detection thresholds were determined by presenting serial dilutions of odorants against a solvent control.

Main Results:

• Squirrel monkeys demonstrated high olfactory sensitivity, detecting substances at dilutions as low as 1:10,000 to 1:30,000,000.
• Sensitivity for some odorants matched or exceeded that of rats and dogs.
• A negative correlation was found between olfactory detection thresholds and the carbon chain length of carboxylic acids.

Conclusions:

• Squirrel monkeys exhibit unexpectedly high olfactory sensitivity, challenging the 'microsmatic' primate concept.
• Olfaction likely plays a significant, underestimated role in primate behavior.
• The study necessitates a revision of the traditional view of primates as predominantly visual animals.