Temporal variation of white rhino dung odours

Abstract

In order for an olfactory signal to be effective, it must persist in the environment for an extended period. White rhino dung odours transmit information about sex, age, territorial and oestrous states. As these odours relay important information, temporal changes in the odour emission rate and/or composition may be critical in order for other individuals to obtain this information. Here, we examine how the dung odours of adult white rhinos (male: territorial and non-territorial; female: oestrous and non-oestrous) change over the short (hours) and long (seasons) term using headspace extraction. Additionally, we measure seasonal midden visitation and defecation frequency to link behaviours to seasonal changes in odour longevity. We found that during the dry season, territorial male dung odours persisted for 48 hours, while the odours of all other adults persisted for >48 hours. The high temperature and humidity of the wet season did not affect odour longevity of oestrous females, but decreased dung odour longevity (i.e. increased emission) of territorial males, non-territorial males, and non-oestrous females. Despite this reduction, neither males nor females adjusted their seasonal visitation or defecation frequency. With regard to a temporal indicator, 3,7-dimethly-1,6-octadiene signalled dung age during the wet season, while acetophenone signalled dung age during the dry season. Ultimately, our results provide the first detailed account of temporal changes of dung VOCs, and highlight the limitations of dung as a signalling medium.