Date of Award

Spring 5-15-2017

Author's School

Graduate School of Arts and Sciences

Author's Department


Degree Name

Doctor of Philosophy (PhD)

Degree Type



In this dissertation, I examine how two confamilial and ecologically similar indriids, indri (Indri indri), and diademed sifakas (Propithecus diadema) maintain coexistence in Betampona Nature Reserve (BNR), an eastern lowland rainforest in Madagascar. These two species occur sympatrically throughout much of their species ranges and are similarly-sized folivorous primates. As anatomic folivores, they present an opportunity to investigate how niche differentiation and resource partitioning allow two sympatric primate species with similar feeding patterns to coexist. I examined coexistence strategies and the general behavioral ecology of each species by examining their activity patterns, dietary profiles, home range use, and daily path lengths throughout an annual cycle. I also compared results from my study site to results from other long-term studies. I collected data on six indri groups and three diademed sifaka groups from April 2013 until May 2014. All indications from this study and other reports indicate that both species are diurnal. Both species spent the majority of their daily active period resting followed by feeding. I found a significantly positive relationship between the time spent active and daily maximum temperature. Diademed sifakas had a significantly shorter daily active period on days with higher rainfall but I did not find the same correlation for indri. I found species-specific difference in the time spent, and activities performed in different levels of the forest. While both species spent the majority of their time in the continuous canopy, diademed sifakas traveled to the ground and occupied the under-canopy layer more than indri. Both indri and diademed sifakas consumed young leaves more than any other plant part but dietary overlap was low. Indri primarily fed from only trees whereas diademed sifakas fed from significantly more non-trees (epiphytes, lianas, and ferns), particularly when resource availability was low. I also found significant differences in the forest level occupied while feeding. While both species primarily fed in the continuous canopy level, diademed sifakas fed on the ground and in the under-canopy layer more than indri. Indri fed in the emergent canopy layer more than diademed sifakas. Diademed sifakas had larger home ranges and significantly longer daily path lengths than indri. Both species exhibited clear preferences for some areas of their home ranges over others. Neither species used their home ranges homogenously. This was the first study to examine home range overlap using Kernel Density Estimations (KDE). Using this method, I found that, interspecifically, indri and diademed sifaka home range overlap to be low. Low spatio-temporal overlap was also evident in that interspecific encounters were rare. For both species, daily path length was shortest in the cold, rainy season, and longest in the warm, rainy season. Diademed sifakas, however, decreased their daily path length significantly in the cold, rainy season. Indri decreased their daily path length during this time but not significantly. In summary, I found that indri and diademed sifakas employ coexistence strategies in their activities, dietary profiles, home range use, and daily path lengths. For both species, activity, feeding, and ranging patterns fluctuated throughout the year. General activity, diet, and home range use patterns were consistent with other sites. Throughout primate taxa, sympatric folivorous primates exhibit several non-mutually exclusive strategies through a combination of differing activity patterns, dietary profiles, forest strata occupation, and ranging patterns. The indri and diademed sifakas at BNR exhibited a combination of coexistence strategies primarily via differing dietary profiles and low spatio-temporal overlap.


English (en)

Chair and Committee

Crickette M. Sanz

Committee Members

Kari Allen, Benjamin Z. Freed, Jane Phillips-Conroy, David Strait,


Permanent URL: https://doi.org/10.7936/K7SJ1J1B