A Comparison of Eulemur Social Systems and Vocal Communication During the Mating Season: Implications for the Speciation and Conservation of Blue-Eyed Black Lemurs and Black Lemurs

  • Caitlin Eschmann

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


Within the last ten years, two closely-related, parapatric species of lemurs, the blue-eyed black lemur (Eulemur flavifrons) and the black lemur (E. macaco), were classified as distinct taxa. Despite this, morphologically intermediate forms have been reported from an area of potential overlap in the two species’ distributions. If hybridisation between E. flavifrons and E. macaco is, or was, ongoing in this region, pre-mating barriers reinforcing reproductive isolation between the two species may be incomplete. No published studies compare comprehensively their behavioural ecology. Therefore, the overall aims of this study were to identify an area of contact between the two species and to illuminate the role of species-specific behaviours as potential pre-mating isolation mechanisms. The social systems and vocal communication of three distinct populations of E. flavifrons (Ef-1, Ef-2, and Ef-3) and three distinct populations of E. macaco (Em-1, Em-2, and Em-3) were examined over three mating seasons (May-July 2015-2017). Each population, which could contain multiple groups, was selected to be representative of a unique allopatric (Ef-1, Em-1, and Em-3) or parapatric location (Ef-2, Ef-3, and Em-2) within the two taxa’s geographic distributions. In addition, the two species’ potential contact zone was surveyed. Although E. flavifrons was observed outside of its established range during this time, I was unable to conclusively determine whether the two species currently overlap. The comparisons of the social organisation, social structure, and mating systems of E. flavifrons populations and E. macaco populations did not reveal clear interspecific differences. Instead, one E. macaco population (Em-1) was found to differ from the others consistently. Preliminary findings suggest that social system plasticity in these species may be partially related to local ecological conditions. The comparison of the vocal repertoires and acoustic parameters of specific calls also revealed no clear interspecific differences. The lack of evidence supporting E. flavifrons and E. macaco social system and acoustic communication divergence suggests that it is unlikely that these characters serve as mate recognition mechanisms between the two species or prevent their interbreeding in natural settings. Based on these findings, possible modes of speciation for E. flavifrons and E. macaco are evaluated.
Date of Award26 Jun 2019
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorGrainne Mccabe (Supervisor) & Marc W Holderied (Supervisor)

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