Do male African elephants, Loxodonta africana, signal musth via urine dribbling?

Abstract

The phenomenon of musth in male elephants involves increased sexual activity, heightened aggression and nearly continuous dribbling of pungent smelling urine. Urine chemistry during musth is altered, suggesting that urine may signal the musth status of the individual. Signalling musth remotely may benefit individuals if it reduces the likelihood of physical confrontation between males, which can lead to injury and even death. Few studies, however, have asked whether and how male elephants respond to urine of other males. We tested two predictions of the hypothesis that urine signals musth status to male conspecifics: (1) that male African elephants differentiate musth and nonmusth urine, and (2) that males differentiate between urine dribbled during early and late musth. The second prediction stems from the observation that males lose weight and presumably body condition during musth. We conducted two related bioassays with 26 captive nonmusth males ranging from 13 to 52 years of age. In each assay, subjects were simultaneously presented with three urine samples (nonmusth, early musth, late musth), each from a different donor male, and a control. We found that subjects differentiated between musth and nonmusth samples using their vomeronasal organ system, but did not discriminate between the samples using their main olfactory system. Males did not differentiate early from late musth. In addition, we found that subject contextual factors, specifically age, dominance status and social grouping, significantly predicted response. We discuss these results within the framework of male elephant longevity and social relationships and their importance to reproductive success.