Iguana 10.2 36 IGUANA Volume 10, Number 2 In addition to an already remarkable three native iguanas, tiny Utila (only 41 km2) supports a phenome- nal reptilian diversity: 15 lizards (including the three iguanas), 11 snakes, a freshwater turtle, and a croco- dilian. Most are representatives of widely ranging Central American species, but two are endemic to Utila (Anolis utilensis and Ctenosaura bakeri) and three oth- ers are found only on the Bay Islands (Anolis bicaorum, Phyllodactylus palmeus, Sphaerodactylus rosaurae). The American Crocodile (Crocodylus acutus) pop- ulation on Utila may be extirpated already and the tur- tle, a Slider (Trachemys sp.), is known to occur in only very small numbers in a single, largely freshwater pond in the undeveloped western half of the island. The snakes range in size from the Boa constric- tor and Indigo Snake (Drymarchon corais), which may exceed 2 m in length, to the tiny Thread Snake (Leptotyphlops goudotii), a termite- and ant-eating specialist that reaches a maximum known total length of 18.5 cm. Swamp Snakes (Tretanorhinus nigroluteus) are highly aquatic and the very slender Vine (Oxybelis aeneus and O. fulgidus) and Tree snakes (Imantodes cenchoa) are adapted for a largely arboreal existence. The remaining snakes tend to be habitat and prey generalists of moderate size. These include the Tropical Ratsnake (Pseudelaphe flavirufa) and three “racers” (Coniophanes imperialis, Dryadophis melanolomus, and Leptophis mexicanus). The lizards include a beach-dwelling racerunner (Cnemidophorus lemniscatus), a skink (Mabuya uni- marginata), the Common or Brown Basilisk (Basiliscus vittatus), three anoles (Anolis bicaorum, A. sericeus, and A. utilensis, all of which are sometimes assigned to the genus Norops), and six geckos (Coleonyx mitratus, Hemidactylus frenatus, Phyllodactylus palmeus, Sphaerodactylus millepunctatus, S. rosaurae, and Thecadactylus rapicauda). SPECIES PROFILE: UTILA’S REPTILES Robert Powell The Boa constrictor usually is considered a predator of mammals, but it will readily hunt and consume iguanas and is relatively common in the mangroves, where Ctenosaura bakeri would seem to be the primary prey. Photograph by Robert Powell. The Green-headed Parrot Snake (Leptophis mexicanus) is a habitat generalist that is equally at home on the ground or in trees and bushes. Although it will feed on birds and small mammals, its preferred prey is lizards. This may be the most common snake on Utila. Photograph by Robert Powell. Like most skinks, the local species (Mabuya unimarginata) has smooth scales well-adapted to foraging in leaf litter. They are most frequently encoun- tered when they climb vegetation to bask. Photograph by Robert Powell. Tiny Dwarf Geckos (Sphaerodactylus millepunctatus) are abundant inside rotten logs and in surface debris, where they feed on a variety of small arthropods. Photograph by Joe Burgess. 37IGUANAJune 2003 Anolis bicaorum is the most common anole on Utila, but is abundant only in the forest-mangrove interfaces, where pairs occupy most of the larger trees. This male is responding to an intruder in its territory. Photograph by Joe Burgess. Basilisks (Basiliscus vittatus) are known best for their ability to run quickly on their hindlegs, to the extent of being able to run on water. However, they are abundant in a variety of habitats, many of which are not associated with streams or ponds. Photograph by Robert Powell. This brightly colored racerunner (Cnemidophorus lemniscatus) is some- times referred to as the Rainbow Lizard. Because of a tendency to twitch an elevated forelimb when it pauses in its search for food (as this individual is doing), this lizard is known locally as the “Shaky-paw.” They are locally abundant on sandy beaches. Photograph by Robert Powell. The Tropical Rat Snake (Pseudelaphe flavirufa) is a capable climber. In addition to rodents and other mammals, this species, like all rat snakes, also will consume birds and lizards. Photograph by Robert Powell. The very tiny Striped Thread Snakes (Leptotyphlops goudotii) are most frequently encountered in association with termite and ant nests, where they feed preferentially on eggs, larvae, and pupae. This specimen, however, was discovered in the open on a sandy beach. Photograph by Robert Powell. 38 IGUANA Volume 10, Number 2 The Turnip-tailed Gecko (Thecadactylus rapicauda) is named for the shape of its regenerated tail (the original is more typically tapered). These large geckos are abundant on trees and, more rarely, buildings. They are unusual among lizards in that they can retract their claws into “sheaths” when not in use. Photograph by Robert Powell. This Leaf-toed Gecko (Phyllodactylus palmeus) is abundant on trees and buildings, but is being displaced on the latter by the recently introduced House Gecko (Hemidactylus frenatus). Photograph by Robert Powell. Coleonyx mitratus is an unusual gecko in that it lacks adhesive lamellar scales on the undersides of its digits and doesn’t climb. These lizards are common in and around surface debris and trash. Photograph by Robert Powell. Anolis utilensis, like the other Utila endemic, Ctenosaura bakeri, is a mangrove specialist. Common only in the Black Mangroves of the Big Bight, these well-camou- flaged lizards behave in a very gecko-like fashion, crawling on the tree trunks and adpressing themselves tightly against the bark when threatened. Photograph by Robert Powell.