Spatial and reproductive biology of the Mona Island iguana: Implications for conservation

The iguana (Cyclura cornuta stejnegeri) is endemic to Mona Island, Puerto Rico and it is listed as endangered by the UICN. Two demographic traits of the species are intriguing: (a) its low densities compared with other Cyclura iguanas, and (b) the low representation of juveniles stages in the population. I studied three aspects of the Mona iguana—its social system, its reproductive biology and the evaluation of an ongoing management action, a headstart program. The headstart program seeks to increase the relative abundance of hatchlings in the population by keeping them in captivity until they reach a safe size to avoid predation. I found that the Mona iguana is highly territorial, and that the levels of territoriality it expresses are strongly related to human disturbance. These results suggest that territoriality can exert a strong density-dependent effect on this iguana and that the current low population densities can be partially explained by this behavior. In addition, many aspects of the reproductive biology of this species were quantified. A surprising result was that nesting areas for iguanas appear to be a limiting resource in Mona Island. However, management actions taken by the Natural Resources Department of Puerto Rico such as the creation of additional nesting areas by clearing vegetation in the Casuarina plantation highlight the effective actions that can be undertaken to increase the nesting-hatch success of the Mona iguanas. I found that the headstart program started by the DRNA in 1999 is successful in terms of increasing the post-release survival and general health of the young iguanas. A major contribution of this research is the acquisition of critical information to examine the susceptibility of extinction of this species via population modeling. Also, the large number of individuals permanently marked opens the possibility of conducting further long-term population research which is necessary to answer several important outstanding questions.