The Function of Howling in the Ring-Tailed Lemur (Lemur catta)

Long calls are sex-specific vocalizations used for mate attraction or mate defense in many animal species. Ring-tailed lemurs (Lemur catta), female-dominant strepsirrhines, have a male-specific long call termed a howl, with proposed functions that have never been empirically tested. I aimed to investigate why ring-tailed lemur males howl and to test whether the mate defense and mate attraction hypotheses for long-calling were applicable to this species. From March to July 2010, I collected 600 h of focal data on 25 males aged ≥3 year at Beza Mahafaly Special Reserve, Madagascar. I observed each male continuously for 30 min at a time and noted all agonism using one–zero sampling at 2.5-min intervals. I calculated male dominance rank from these data. I recorded days when female estrus occurred and noted howling and intergroup encounters using all-occurrences sampling. Howling rate was not significantly related to female estrus or male dominance rank, providing no support for the mate attraction hypothesis or the intragroup mate defense hypothesis. In contrast, the intergroup mate defense hypothesis was strongly supported. During intergroup encounters, male howling rate significantly increased compared to howling rate at times without other groups present, and a greater number of males participated in multimale howling choruses when compared to times without nongroup members present. My results suggest that male ring-tailed lemurs howl to advertise their presence and location to other groups, but not to male or female members of their own group. Howling could discourage male immigration by advertising the number of males already present in a group. Long calls are used for similar mate defense purposes during intergroup encounters by other primates, including Thomas langurs (Presbytis thomasi) and chacma baboons (Papio ursinus).