Date of Award


Document Type



College of Arts and Sciences

Degree Program


Degree Name

Master of Science

Thesis Advisor

Dr. Janice Chism

Committee Member

Dr. William Rogers

Committee Member

Dr. Matthew Heard


Monk Saki, Equatorial Saki, Pithecia, Habitat Partitioning, Niche Theory


Researchers previously reporting equatorial and monk sakis (Pithecia aequatorialis and P. monachus) occurring sympatrically north of the Amazon River in Peru raised the question of whether the two species were syntopic or separated by habitat. I encountered both species of saki south of the Amazon in Peru in the Área de Conservación Regional Comunal Tamshiyacu Tahuayo (ACRCTT). Initial observations and local lore suggested that in this area equatorial sakis occur predominantly in flooded forests and monk sakis in terra firme. I conducted a six-week survey (324 hours effort, a minimum of 18 groups observed) to test this hypothesis, collecting data on location and habitat preference of the two species using both terrestrial line transect surveys and canoe-based sampling. My findings indicate that the two species are syntopic, with both species occurring in igapó forest adjacent to rivers, but only equatorial sakis observed in terra firme forest. These results indicate that if the two species segregate by habitat, it is based on features other than a simple dichotomy between igapó and terra firme forest. In my study area, equatorial sakis significantly outnumber monk sakis (x2=10.889, d.f.=1, p=0.0010), despite previous surveys that only reported monk sakis in the reserve. My census data also confirmed the presence of atypically colored adult females in some equatorial saki groups, supporting earlier suggestions that the two species may be hybridizing.