The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Demography of the endangered Milne-Edward’s sifaka (Propithecus edwardsi) in an unprotected degraded forest


1Department of Anthropology, Stony Brook University, 2Department of Animal Biology, University of Antananarivo

March 28, 2015 , Gateway Ballroom 2/3/4/5 Add to calendar

Compared to anthropoids, lemur sociality has puzzled primatologists due to a suite of behaviors including prevalent female dominance, even adult sex ratios, and lack of sexual dimorphism. Milne-Edward’s sifaka (Propithecus edwardsi) moreover, forms groups with socionomic sex ratios consistent with monogamy, polygyny, polyandry, and polygamy in equal proportions within Ranomafana National Park (RNP), Madagascar. Data from other P. edwardsi groups however, are needed to examine the prevalence of this fluid grouping system. We examined a population of P. edwardsi in an unprotected forest north of RNP, known locally as Ampatsona and Ambohidaza (AA), which is heavily exploited for mining, timber, and agriculture. Thus, we predicted that group sizes would be smaller and compositions would differ from RNP due to habitat degradation in AA. We found 23 groups of P. edwardsi within AA, ranging in size from 1-8 individuals. Average group size was 3.9 individuals, lower than groups in RNP (5.3 individuals). 12 groups had sex ratios consistent with “monogamy” (i.e. one adult male and one adult female), 1 group with “polygyny”, 1 group with “polyandry”, 3 groups with “polygamy” and could not identify full compositions of the remaining 5 groups. These findings contrast with the more variable compositions in RNP, suggesting that anthropogenic disturbance can affect P. edwardsi group compositions. We suggest that this population merits immediate conservation action. Future work will more thoroughly examine effects of resource distribution, habitat disturbance, and kinship on group compositions using tree abundance, GPS, and fecal data collected in parallel to this study.

This research was performed with permission from the Stony Brook University IACUC and the Ministry of Environment of Madagascar and funding from Primate Conservation International.