Chemical communication in Eurasian deer (Cervidae): do individual odours also code for attributes?

Abstract

Evidence for signal coding for attributes such as age, sex or population of origin, was sought in odour profiles derived from natural secretions of the preorbital gland of red deer Cervus elaphus (n = 26), sika deer C. nippon (15), Chinese muntjac Muntiacus reevesi (23) and Chinese water deer Hydropotes inermis (53); from metatarsal secretions from red deer (n = 35), sika (30), fallow (193) and roe deer Capreolus capreolus (26); and from roe deer interdigital glands (n = 48). Volatiles were eluted from sample materials at body temperature, to restrict analysis to those elements which would occur within the natural odour profile; the different volatile elements were then separated by gas chromatography. Initial results of these analyses were strongly suggestive of some level of signal-coding for attributes of the signaller. Few secretions (species × gland) contained many volatiles which differed significantly between deer from different populations of origin and, except in the muntjac preorbital and sika deer metatarsal secretions, separation of populations was generally rather poor in formal discriminant function analyses (DFA). However, where no constraint is imposed on the number of volatiles allowed to enter the analysis, secretions from at least one gland accurately discriminated between the sexes in the original sample for most species; separation of sexes was only ineffective for Chinese water deer and fallow deer. Discrimination between deer of different age-classes was similarly effective in the original sample for red deer preorbital and roe deer metatarsal secretions and fair for preobital secretions of Chinese water deer; unbalanced age-structure of samples did not permit analysis for muntjac or sika deer. Sometimes the actual predictive power of discrimination was poor; it is notable that this was characteristically associated with small sample sizes and the evidence indicates that scent secretions from most species sampled here offer the potential for coding for at least the sex and age of the signaller. Although chromatographic analysis of odours from some glands reveals consistent differences between odour profiles characteristic of sex, age or population, this does not imply that the signal is deliberately coding for such information, or that the deer use the information available. It is possible that differences in the composition of secretions in relation to age or sex of the signaller, for example, is coincidental or of secondary significance.