Record Details

Cyril Jr, Samuel
Behavioral Ecology of the Endangered San Salvador Rock Iguana (Cyclura rileyi rileyi) in the Bahamas
Loma Linda University
Master's Thesis
Cyclura rileyi rileyi
In this thesis I present the results of a study on the reproductive ecology, activity levels, population estimates, home range size and diet of the endangered San Salvador rock iguana (Cyclura r. rileyi). This lizard is one of three subspecies of C. rileyi that are endemic to the Bahamas. With fewer than 600 individuals remaining in 7 populations on small, remote islands, this iguana is one of the rarest lizards in the world. During the summer of 1999, I studied the population on Green Cay, a 5.1 ha island that supports the largest remaining population (roughly 200 animals). Nesting took place during the month of July, with larger females ovipositing earlier in the month than smaller females. Minimum reproductive size was approximately 22 cm snout-vent length (SVL) and 340 g. Many females dug exploratory burrows in microhabitats similar to nesting burrows. The nesting burrows were located in loose sand, though some were found in rock crevices. Three of five excavated nest burrows contained old eggshell fragments from previous years. Clutch size ranged from 3-6 eggs. Relative parental investment was positively correlated with SVL. Egg dimensions were negatively associated with clutch size. Females that defended their nests for more than five days (n=13 were found in areas of higher nest density than those defending their nests fewer than 5 days (n = 8). Male and female iguanas exhibited similar levels of activity. However, iguanas were more active during morning and evening hours than at mid-day. Population estimates based on mark-resighting ratios (Lincoln-Petersen estimates) were more precise than those based on numbers of iguanas observed during daily surveys. Detectability rate during the surveys averaged 33%. Estimates of home range size were similar for males and females, as evaluated by fixed kernel methods and minimum convex polygons. Vegetation on Green Cay was comprised of only ten species, of which seven were utilized by iguanas. Borrichia arborescens, Rhachicallis americana, and Conocarpus erectus were the most frequent food items in the diet. Compared to its relative abundance, Opuntia stricta was also browsed heavily.