Male forehead gland scent may encode multiple information in the great Himalayan leaf-nosed bat, Hipposideros armiger

Abstract

Intrasexual competition favours the evolution of pronounced individual identity and competitive ability badges. However, although olfactory signals play a role in territorial conflicts of many animals, the information content encoded in olfactory signals in the context of territorial conflicts is relatively unknown. Here, we used male great Himalayan leaf-nosed bats, Hipposideros armiger, to explore whether olfactory signals from the forehead gland encoded reliable information about a signaller's individual identity, physical condition, dominance status and physiological quality. We did this by using gas chromatography–mass spectrometry to quantify the chemical composition of the gland exudate and by examining the relationships between the proportions of 24 volatile compounds and physical condition (body condition index), dominance status (David's score) and physiological quality (immunocompetence, hormonal levels and resting metabolic rate). The results showed that there were significant differences in the concentrations and categories of compounds between individuals. Moreover, the proportions of many compounds correlated with David's score and neutrophil/lymphocyte ratio. Our results indicate that olfactory signals of H. armiger could transmit information about individual identity, dominance rank and physiological quality and may work as a reliable ‘chemical ornament’ for male–male competition.