Habitat loss and mongoose predation threatening the St. Croix ground lizard

St. Croix Ground Lizard

As happens with some anoles and other reptiles in the Caribbean, the St. Croix ground lizard is seriously endangered because of human encroachment and exotic predators. For all their speed and quick reflexes, a number of ameivas are easy prey to mongooses. On June 03, 1977, the St. Croix ground lizard was designated as endangered in the St. Croix area. There are currently only two islands where the St. Croix ground lizard, now extinct on St. Croix and listed as an endangered species, still exists -- Green Cay and Protestant Cay.

About the St. Croix Ground Lizard

Croix Ground Lizard is a small species of Ameiva that measures approximately 35 to 77 millimeters in snout-vent length (UFWA, 1992). The lizard is easily distinguished by its parallel longitudinal black, white, and light-brown stripes. Its belly is light gray with lateral blue margins, and pinkish undersides of legs, throat, and chest. Its tail also has alternating rings of blue and black. Currently, nothing is known of this species' reproductive biology.

Formerly, the St. Croix ground lizard was found exclusively on St. Croix, U.S. Virgin Islands and its offshore islands and cays (UFWA, 1992). Today, Green Cay and Protestant Cay, which are located off the north coast of St. Croix, are the only sites where this lizard is located. The population probably does not exceed 2,500 individuals on Green Cay and 50 on Protestant Cay.

The lizard's habitat consists of beach areas and upland forests of the Hippomane-Tabebuia woodland (UFWA, 1992). This lizard is drawn to exposed and canopied areas, leaf or tidal litter, loose substrate, and crab burrows. Currently, both Green and Protestant Cays have been designated as Critical Habitat for the St. Croix ground lizard, although protestant Cay provides less protection.

Research on the St. Croix ground lizard is limited, due to the rarity of the species. The lizard primarily eats amphipods (sandfleas) found in beach debris, small white moths taken from under the litter, and hermit crabs. There is little behavioral information on the speacies and information on home range or territoriality is nonexistent.

Like most Ameivas, the St. Croix ground lizard is diurnal, when it can be seen foraging for ants and other insects, and occasionally resting and sunning itself. It appears that the species is non-migratory.

Endangered species release surveys conducted in 1980-81, shortly after the lizard was declared an endangered species, revealed that the population of St. Croix ground lizards could be between 360-4300 on Green Cay and 50 on Protestant Cay, although the population on Green Cay today probably does not exceed 2500 individuals.

Conclusion

The future of the St. Croix ground lizard populations depends on these cays. Future threats to the species include the danger of accidental invasion of said cays by the mongoose, and the Ameivas vulnerability to natural catastrophes such as hurricanes, mainly due to their small size and reduced habitat area. An increase in human disturbance or habitat alteration at important habitats, resulting from recreational activities, could also harm the future of the lizards.

When the lizard was declared an endangered species in 1977, Green Cay was purchased by the U.S. Fish and Wildlife Service and designated the Green Cay National Wildlife Refuge. This area currently provides protection for 14 of the 18 acres of designated Critical Habitat for the ground lizard. Plans include a retrapping effort to remove mongoose that remain after an intensive trapping effort on Buck Island, the proposed experimental release site of wild-caught lizards.

The main purpose of the Green Cay project is to maintain the natural island ecosystem and protect the endangered St. Croix ground lizard and colonial nesting birds. To accomplish this, the U.S. Fish and Wildlife Service uses rigid law enforcement and conducts wildlife surveys. In addition, it removes wildlife that poses danger to the endangered species.

Basically, as far as current and future efforts to protect this endangered species are concerned, the Fish and Wildlife Service and the National Park Service signed a cooperative agreement in 1982 for the National Park Service to provide protection to Green Cay National Wildlife Refuge. In addition, a mongoose eradication program is in the works at Buck Island Reef National Monument to provide an experimental release site for the St. Croix ground lizard.

The question of whether the St. Croix ground lizard will make it on this planet largely depends on human efforts to continue the species. Without help from humans, the St. Croix ground lizard would be extinct. However, it is important to remember that human interference with the natural habitat of the lizard was what caused it to be endangered in the first place. If we had not introduced the rats to the island and build new development on the lizards' habitat, it would have been able to continue living and breeding on the island.