Rebecca J Lewis

My field work currently focuses on Verreaux's sifaka (Propithecus verreauxi verreauxi) in the Kirindy Mitea National Park. This park provides a unique opportunity to study sifaka socioecology because the park is the transition zone for three different ecosystems: the dry, deciduous forest of the west, the spiny desert of the south, and the coastal mangroves. I have created a 1 km2 grid system of trails in the forest. Trails are 25 meters apart and marked for easy navigation. This grid system also allows us to measure home range size and use without the use of a GPS. Eight social groups are habituated and marked with nylon collars and tags. One individual per group has a radio collar.

Demography, Morphology, & Genetics 

 Censuses of the social groups are conducted regularly to allow for studies of demography. Captures are conducted twice a year in order to monitor body condition. I am also collaborating with Dr. Deborah Bolnick to conduct genetic analyses of the population.

Alternative Mating Strategies

 Adult male sifaka are bimorphic: some males have a dark brown, greasy staining on their chests, while others have chests that are clean and white. This variation is related to dominance status. The goal of my study is to document the striking variation in sifaka male chest status and to evaluate the hypotheses that chest status represents alternative mating tactics. To this end, I am studying (1) male social and mating behavior, (2) variability in chest staining, (3) the morphological and hormonal correlates of chest status, (4) female mate choice, (5) how the chest staining acts as a visual and olfactory signal, (6) whether chest status is related to male dispersal strategies, and (7) male reproductive success.

Feeding Ecology

Verreaux's sifaka are medium-sized folivores that live in habitats ranging from dry, deciduous forest to spiny desert. Because Kirindy Mitea National Park is located in the transition zone for three ecosystems, this field site is ideal for examining the effects of ecology on behavior. I am studying how the sifaka in Kirindy Mitea National Park use their habitat, what plants they eat, and the within- and between- group competition that arises as a result of the availability of their food.