Chemical composition of axillary odorants reflects social and individual attributes in rhesus macaques

Abstract

Scents play an important role in the life of most terrestrial mammals and may transmit valuable information about conspecifics. Olfaction was long considered of low importance in Old World monkeys due to their relative reduction of olfactory structures and low incidence of scent-marking behavior but has been increasingly recognized for mediating social relationships in recent years. Yet, studies investigating the composition of their chemical cues remain scarce. In the present study, we analyzed the potential information content of chemicals present on the skin of rhesus macaques (Macaca mulatta). We collected axillary secretions from 60 animals of the semifree-ranging population on Cayo Santiago (Puerto Rico, USA) with precleaned cotton swabs from which the secretions were subsequently extracted and analyzed by gas chromatography–mass spectrometry. Rhesus macaque axillary odorants varied in their overall similarity and composition. This variation was attributable to differences in sex, group membership, and kinship and further appeared to reflect age and rank in parts of our sample. The compounds most strongly associated with this variation primarily comprised larger molecular weight aldehydes and steroids. Such compounds are considered to be perceivable by the primate olfactory system through close-range interactions or through breakdown into smaller molecules by bacterial fermentation. Overall, our results provide additional evidence that odors of Old World monkeys reflect a wealth of potential information about their carrier, which provides the basis for chemical communication via body odors; however, its use by conspecifics needs to be confirmed in bioassays.Significance statementOne prerequisite for olfactory communication is the presence of systematic variation in animal odors that is related to attributes such as age, sex, or kinship. The composition of odors has been examined in numerous mammals but, with the exception of humans, remains poorly understood in Old World monkeys and apes, taxonomic groups in which most species do not show scent-marking behavior. In the present study, we show that the composition of axillary secretions of an Old World monkey, the rhesus macaque, reflects sex, group membership, relatedness, and possibly also age and rank. This variation thus provides a basis for olfactory communication in Old World monkeys.Electronic supplementary materialThe online version of this article (10.1007/s00265-018-2479-5) contains supplementary material, which is available to authorized users.

On the trail of primate scent signals: A field analysis of callitrichid scent‐gland secretions by portable gas chromatography‐mass spectrometry

“…These findings led to the emergence of research on primate chemosignaling, at behavioral (e.g., Greene & Drea, 2014;Henkel & Setchell, 2018), chemical (e.g., Setchell et al, 2010;Weiß, Kücklich, et al, 2018), and genetic levels (e.g., Knapp et al, 2006;Setchell et al, 2011). Yet, our knowledge of primate chemosignaling is still limited (Heymann, 2006a).…”

“…At present, two approaches are used in field semiochemistry. The first approach is to collect odor samples via swabs (e.g., Leclaire et al, 2017;Weiß, Kücklich, et al, 2018) or thermal desorption tubes (e.g., Kücklich et al, 2017;Weiß, Marcillo, et al, 2018), or to collect deposited secretions (e.g., scent marks left on a surface, T. E. Smith et al, 2001), or excretions such as urine (e.g., DelBarco-Trillo et al, 2011) directly into a container, and transport them to a laboratory for analysis by chromatography. Though thermal desorption tubes can be transferred from the field to the laboratory without any need for cold shipment, swabs, secretions, and excretions have to be stored at a sufficiently low temperature, which can be challenging (Drea et al, 2013).…”

Comparative chemical analysis of body odor in great apes

“…Analyses of odor samples with gas chromatography mass spectrometry (GC‐MS) revealed sex differences in the chemical composition of scents for example in Aotus spp . (Spence‐Aizenberg, Kimball, Williams, & Fernandez‐Duque, ), Eulemur ; Simons and Rumpler, ; delBarco‐Trillo et al, ), mandrills ( Mandrillus sphinx ; Linnaeus, ; Setchell et al, ; Vaglio et al, ), and rhesus macaques ( Macaca mulatta ; Zimmermann, ; Weiß, Kücklich, et al, ). In human body odor, variance was also found between the sexes (Penn et al, ; Zeng, Leyden, Spielman, & Preti, ).…”

Group and kin recognition via olfactory cues in chimpanzees (Pan troglodytes)

“…[76 -78]). In primates, chemical profiles reflect group membership in scent gland secretions in mandrills, Mandrillus sphinx [20] and body odour in rhesus macaques, Macaca mulatta [21]. Given our results, it is likely that chimpanzee urinary olfactory profiles also encode information about group membership and kinship [79].…”