Field Ecology of the Exotic Mexican Red-Bellied Squirrel in Florida

Abstract

An introduced population of the Neotropical red-bellied squirrel ( Sciurus aureogaster ) from Mexico was studied in the Florida Keys. Live-trapping on Elliott Key, Florida, revealed the mean population density of squirrels in a mature subtropical hammock over a 12 month period in 1972 was 2.47 squirrels per hectare. Two pelage color phases present on the island (totally black, and gray with a red belly) occur in the population in a ratio of nearly 50 percent (based on 99 squirrels sampled by live-trapping). Visual censusing of the two color phases in the dense habitat resulted in an incorrect estimate favoring the more highly visible melanistic color phase. The average home range size calculated for 18 adult males was 2.3 hectares, and for nine adult females was 0.9 hectare. Reproduction occurred intermittently throughout the year with no tendency for a synchronized breeding season. Based on limited data from four nestling litters, one or two young may be the normal litter size for the species. The squirrels exhibited a high degree of nest box utilization in the tropical habitat characterized by few natural tree hollows. The species is largely frugivorous and was observed utilizing the fruit or seeds of sixteen different species of tropical trees and shrubs including wild mastic, papaya, coconut, sea grape, and thatch palm. There is little predation pressure on the population, but competition for food and denning sites by black rats, raccoons, frugivorous birds, owls, and other species seems primary limiting factors on the island's squirrel density.