Record Details

Thornton, Benjamin J
Nesting Ecology of the Endangered Acklins Bight Rock Iguana, Cyclura rileyi nuchalis, in The Bahamas
Andrews University
Master's Thesis
Cyclura rileyi nuchalis
Virtually nothing is known regarding the reproductive ecology of Cyclura rileyi. I studied the least threatened of its three subspecies, C. r. nuchalis, on North Cay in the Acklins Bight, where several thousand females reside. Before and during the nesting season, I equipped 18 females with radio transmitters to follow their movements. Nesting density was greatest along the sandy beachfront dunes. Critical reproductive size was approximately 20 cm SVL and 300 g. Females excavated up to seven burrows, 69-235 cm in length, before depositing 2-5 eggs. The number of eggs laid was proportional to the size of the female. Home range sizes of nongravid (smaller) and gravid (larger) females, evaluated by fixed kernel methods and minimum convex polygon, were similar. Most females (65%) nested within their home range but some moved up to 1 km to nest. Copulation ended in the second week of June. Forced copulation was common at the end of the mating season. Gravid females may be copulated by more than one male. Males often defended females with which they copulated. Nesting burrows may be used for more than one season (23%, n = 3), as indicated by old eggshells found in nesting chambers along side new clutches. Some nesting burrows were used by more than one iguana in the same season. In most cases, gravid females were entombed in their nesting chamber overnight to oviposit. Nesting burrows were completely filled with sand, unlike the egg chamber which remained open before and after ovipositing. Clutch size (3 - 5 eggs) was positively correlated with snout to vent length (SVL). Relative reproductive investment was positively associated with SVL. Body condition after parturition was negatively correlated with SVL. Larger females oviposited later than smaller females. As clutch size increased, individual egg size decreased. Mature females, captured and equipped with transmitters 14-25 days (n = 6) and 1-3 days (n = 8) before oviposition, showed no apparent deleterious effects from handling and disturbance. Some females (29%) remained in close proximity for several days or more to defend their nest from other females digging nearby.