Cyclura rileyi is amongst the most threatened of the West Indian rock iguanas, with two of its three recognised subspecies being listed as critically endangered by the IUCN, and the third as endangered (6). One of the most devastating impacts has been the large-scale habitat destruction by European and American colonialists, who cleared forests for conversion to agriculture, and introduced many non-native plants and animals (6). The San Salvador iguana now has a relatively remote distribution away from most human settlements, but a large and varied range of threats nevertheless continue to make their prospects of long-term survival tenuous (4) (8).
The species is vulnerable to introduced predators and feral animals such as cats, dogs and rats, with rats recently discovered on Guana, Low, High, and Pigeon Cays, and juvenile iguanas noticeably scarce on Guana and Low Cays (4) (8). Habitat degradation is also a concern, with vegetation being damaged by catastrophic storms and hurricanes in the areas, as well as by the larvae of an introduced moth (Cactoblastis cactorum), which are devastating the prickly-pear cacti (Opuntia stricta), an important food source for iguanas on several cays (4) (8). Sadly, there are no known means of controlling the moth (4) (8). A mysterious ‘die-off’ also occurred on Guana Cay in spring 1994, possibly as the result of disease (4). However, it has also been suggested that mosquito control chemicals, which had recently been implemented to aid a growing tourism industry, could have been the culprit (4). Disease could potentially be catastrophic to many of the subpopulations due to their small and isolated nature (8). Small populations are also likely to suffer from the negative effects of inbreeding, diminishing their viability (4). A further threat to most, if not all, populations, is rising sea levels, which threaten to swamp much of the iguana’s existing habitat in the future (6).
An additional threat to the small population of White Cay iguanas (C. r. cristata) is the invasion of Australian pine trees (Casuarina), which have begun to dominate the vegetation on White Cay, attracting numerous birds of prey (falcons) during winter and migration (6). There is also evidence of illegal smuggling of the White Cay iguana (C. r. cristata), which probably poses the greatest threat to this subspecies, together with the possibility of introduced animals (4). Indeed, a raccoon discovered on White Cay apparently killed a significant proportion of the small iguana population, particularly juveniles and females (4), before it was removed in 1997 (6).
Fortunately, the Acklin’s iguana (C. r. nuchalis) populations seems to be fairly stable, although introduced hutia (Geocapromys ingrahami) on a neighbouring cay may be affecting the vegetation available to the subspecies, and the potential for illegal poaching remains a threat (4).