Conservation of Caribbean Iguanas

The islands of the Caribbean support 11 species of large herbivorous lizards in the family Iguanidae, commonly called iguanas.  Ten of these iguana species are endemic to the Caribbean, which is to say they are found nowhere else on earth.  As a group, Caribbean iguanas are the most endangered group of lizards in the world. For this reason, San Diego Zoo Institute for Conservation Research and its staff have been involved with Caribbean iguana conservation and recovery programs for almost two decades.

All endemic Caribbean iguanas are adapted to tropical dry-forest or scrub habitats that are among of the region’s most imperiled ecosystems.  Iguanas are the largest native terrestrial vertebrates and dominant herbivores on most islands where they occur.  Because they eat the fruits, flowers, and leaves of many native plant species in these habitats and facilitate the dispersal and germination of seeds passing through their digestive tract, iguanas play a key role in the maintenance and perpetuation of native Caribbean plant communities.

The principal threats to the survival of Caribbean iguana species are habitat loss and predation or competition from introduced mammals, including rats, mongooses, cats, dogs, pigs, goats, sheep, cattle, donkeys, and horses.  For several iguana species, predation of juveniles by introduced mammalian predators is eliminating all recruitment to wild populations, leading to the need for intensive headstarting efforts to forestall extinction. 

Headstarting entails collecting juvenile iguanas emerging from wild nests, before introduced predators eat them, and raising them in captivity until they are large enough to survive in the wild.  For a few iguana species, wild populations are so small that captive breeding of adults and headstarting of juveniles are both necessary to avoid extinction in the wild.

There are presently dedicated captive breeding or headstarting facilities for five of the most endangered Caribbean iguana species.  All of these facilities are located on the home island of the respective imperiled species.  These programs have been instrumental to recovery efforts and, to date, more than 700 Caribbean iguanas have been raised in these facilities and released, significantly increasing the known population size for many species and reducing their immediate risk of extinction.  Nonetheless, most of the captive breeding and headstarting programs for Caribbean iguanas have been less effective than anticipated due to difficulties associated with operating and maintaining animal care facilities that are often understaffed and in remote locations with limited access to material resources.

To increase the number of captive bred and headstarted iguanas available for population supplementation and reintroduction efforts, San Diego Zoo Global and its partners have recently committed to building a large, centralized, multi-species, headstarting and captive breeding facility for endangered iguanas in the Caribbean. 

The proposed facility is expected to replace or supplement existing individual-species facilities in range countries with limited capacity and institutional support. The facility will likely be located on Puerto Rico due to its ideal climate and habitat, central Caribbean location, technological infrastructure, presence and availability of necessary human and material resources, and political stability. 

When combined with other conservation measures, including invasive species control and habitat protection, this initiative has the potential to secure the long-term survival of the most endangered Caribbean iguana species.