The ecology, evolution and natural history of the endangered carnivores of Cozumel Island, Mexico

Understanding the basic ecology and evolutionary history of a species is important for the conservation and management plans of endangered species. This dissertation examined the phylogenetic uniqueness, feeding ecology, population size and morphological variation found in two endemic carnivores, they pygmy raccoon (Procyon pygmaeus) and dwarf coati (Nasua nelsoni), on Cozumel Island, Mexico. Data was collected by trapping 78 individual pygmy raccoons (38 males and 42 females) for three field seasons from 2001--2003. Results from the mtDNA analyses suggest that island coatis are distinct from their mainland sister taxa, while the mainland and island raccoons seem more closely related. Using a molecular clock and the average sequence divergence between island and Yucatan coatis and raccoons these species are estimated to have diverged from their mainland conspecific s in the last 46--51,000 years. Using data derived from stable carbon and nitrogen isotope analyses combined with scat data, feeding ecology analyses indicate that the pygmy raccoon utilizes an omnivorous diet in which the three most prevalent food items were crab, which constitutes >50% of the diet, followed by fruits and insects. Trapping efforts identified the most northwestern section of the island, despite what appears to be suitable habitat elsewhere, as the location of the main populations of the pygmy raccoon on Cozumel Island. Using mark-recapture models, the current population of pygmy raccoons on Cozumel Island is estimated to be fewer than 250 mature individuals at this time. Results from this study indicate that both the pygmy raccoon and dwarf coati should be listed as critically endangered by the World Conservation Union (IUCN). Data from morphological measures indicated that like most species of Procyon, the pygmy raccoon exhibits significant male biased sexual dimorphism in the form of increased mass and canine length. The average mass for adult male and female pygmy raccoons was 3.68 and 3.28 kg, respectively, and male canines were approximately 1 cm longer than females. Adult and subadult morphometric values, including mass, did not fluctuate seasonally. In comparing the island and mainland raccoons, a 15% size reduction was estimated for the pygmy raccoon species.