Distribution and Habitat Utilization of Ctenosaura bakeri on Utila

Abstract

Ctenosaura bakeri, endemic to Utila (Honduran Bay Islands), is one of only two reptiles that are exclusive mangrove dwellers. With a total distribution of 1091 ha, the total size of the three mangrove areas on Utila, this species has the smallest range of any in the genus. Distribution of three species of mangroves is not homogenous in any of the three areas. Also, effects of tides and salt content vary substantially over place and time. I collected and marked 171 iguanas at three study sites. The most animals (107) were caught at the Iron Bound site, fewer than half that many (40) were caught at Big Bight Pond, and only 24 iguanas were caught at Blue Bayou. Adult iguanas totaled 125, 2.7 times the number of subadults (46). Population densities were 63 adults per ha or 103 iguanas (adults + subadults) per ha (Iron Bound), 37 adults or 39 iguanas per ha (Big Bight Pond), and 20 adults or 24 iguanas per ha (Blue Bayou). Recaptures of marked iguanas numbered from 1–14 and generated 123 distances moved involving 52 individuals (25 females and 27 males). Five animals were recaptured exclusively at initial capture sites and most (56 %) moved < 20 m from the site of initial capture. Distances moved were greater in males than females. Time between first capture and last recapture ranged from 10–323 days. Sex specific differences were not evident. The primary factor controlling population density was the abundance of tree hollows, used as retreats and found primarily in larger Black Mangroves (Avicennia germinans). These were inhabited for at least four years, regarded as territory year-round, and aggressively defended. Estimates, made using two different models, of total adult population size for the entire island were 21,820–73,097 and 38,185–85,098.