Recent Trends in Recruitment and Environmental Limiting Factors for the Sister Islands Rock Iguana, Cyclura nubila caymanensis

Jeanette Moss


Other projects

12 Aug 2015

Evaluating Population Recruitment and Hatchling Survivorship in Cyclura nubila caymanensis at Communal Nesting Sites on Little Cayman Island

21 Aug 2017

Natal Ecology of the Sister Islands Rock Iguana (SIRI): Radio-Tracking and Long-Term Monitoring of Juveniles on Little Cayman and Cayman Brac

This project, set to take place in late summer 2016, accomplishes several aims of ongoing research into the population dynamics and nesting ecology of the critically endangered Sister Islands Rock Iguana (SIRI) on Little Cayman (LC). By focusing efforts on hatchling and yearling SIRI during the emergence season, we will be able to estimate first-year survivorship in addition to examining specific environmental and community covariates that could be driving habitat selection and nesting behaviours.

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In August 2015, a RSG supported nesting studies on LC to evaluate population recruitment and hatchling survivorship of SIRI. A major outcome of this project was the tagging of nearly 230 hatchlings for long-term monitoring of growth, survivorship, and dispersal. Moreover, effective protocols for hatchling capture and nest excavations were established, which will facilitate the testing of new hypotheses related to recruitment limiting factors and nesting strategies. Preliminary data point to the importance of environmental and community covariates as well as female mate choice in maintaining recruitment. These factors should be more closely examined to better inform management strategies for SIRI.

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The first major contribution of our work in 2016 will be to estimate the survivorship and population size of 2015’s cohort based on recapture rates of PIT-tagged yearlings. In combination with molecular insights and additional years of nest surveys, this data will be instrumental in exposing recent trends in recruitment. In addition to mark-recapture efforts, a return trip in 2016 will be an opportunity to further explore questions of nesting ecology. By testing new predictions about SIRI’s nesting strategies, we aim to identify the most critical limiting factors in population recruitment. New environmental and community covariates to be investigated include incubation conditions of nest chambers, site-specific predation risk, and nest clustering and synchronization. Understanding how these factors contribute to variation in nesting strategies, specifically to the maintenance of communal sites, will be of great value to management planning. Concurrently, increased genetic sampling efforts will advance ongoing investigations into female mate choice via estimation of polyandry rates as well as degree of reproductive skew. Polyandry has been proposed as a possible strategy for inbreeding avoidance in small, isolated populations and may play an important role in maintaining healthy levels of recruitment in periods of decline.

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In addition to continuing our scientific investigations on LC, another major contribution of ongoing conservation research will be to engage the local community to inspire and guide initiatives for long-term monitoring and management of SIRI. Together with valued partner organizations, including the Cayman Islands National Trust and the Cayman Islands Department of Environment (DoE), our research team will strive to educate and foster a sense of pride in the Sister Islands’ endemic iguana. Among developing initiatives is a concerted feral cat eradication effort. Addressing this suspected significant threat to local fauna will depend upon the involvement and support of the local community and government.

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