Abstract
Olfactory communication may be particularly important to black rhinoceros, Diceros bicornis, because they are solitary living and have comparatively poor eyesight but their populations are structured by inter- and intrasexual relationships. Understanding olfactory functions and processes might achieve better conservation management but their study in rhinoceros remains anecdotal or descriptive. Experimental approaches are required but rarely possible as rhinoceros are difficult to observe and manipulate. We measured the olfactory investigation behaviour (duration and frequency of sniffing) of black rhinoceros in four experiments designed to determine the function of chemosignals in dung and urine. A habituation–dishabituation trial demonstrated that black rhinoceros discriminated individually distinctive odours from faecal signals (experiment 1). When adults (>6 years old) were presented with dung from conspecifics of different sex and age classes (adult, and subadult from 2 to 4 years old), male dung was investigated more by both sexes, and females investigated subadult dung more (experiment 2). Both dung and urine from the same adult donors were investigated by both sexes, but male dung was investigated more than female dung and female urine more than male urine, although differences were statistically weak (experiment 3). Lastly, fresh faecal samples and those aged 1, 2, 4, 16 and 32 days were similarly investigated, indicating that they still function as olfactory signals. Together the results indicate that dung or urine signalled age, sex and identity to conspecifics and signals may persist as dung decays. Chemosignals are likely to be important to the social and spatial organization of black rhinoceros.
► We tested the function of olfactory signals in rhinoceros dung and urine. ► The duration and frequency of sniffing events varied between olfactory signals. ► Donor age, sex and identify was discriminated from faecal samples. ► Both urine and dung function as signals and faecal signals persist as dung decays. ► Dung and urine chemosignals may be important to rhinoceros social organization.