Evaluating headstarting as a management tool: Post-release success of green iguanas (Iguana iguana) in Costa Rica

Abstract

Headstarting has become a popular tool employed by wildlife managers to help animal species, specifically those lacking or providing minimal parental care-offset extinction. However, many researchers challenge the conservation value of headstarting and urge proponents to monitor headstarted individuals following release into the wild to evaluate the success of headstart programs. As part of an experimental headstarting program managed by the Iguana Verde Foundation in Costa Rica, we conducted a 1.5-month radiotelemetry study of 11 headstarted 2 year old green iguanas (Iguana iguana) following their release into the wild at the Gandoca-Manzanillo Wildlife Refuge. Headstarted iguanas were compared to their wild counterparts (two radiotelemetered and 18 opportunistically-encountered) with respect to changes in growth, arboreal microhabitat use, social aggregation, activity ranges and movements. Male and female headstarted iguanas exhibited similar behaviours and headstarted iguanas were similar to wild iguanas for most variables measured. Thus, the headstarted green iguanas were clearly capable of short-term (1.5-month) survival in the wild and their apparently normal behaviours reflected the suitable conditions under which they were raised. The results provide insight into the ecology of green iguanas and will help guide headstarting and reintroduction programs for iguanas at this location and endangered iguanas elsewhere. Key words: Captive-breeding, conservation, headstarting, home range, lizard, radiotelemetry, reptilian, spatial use.