Iguana 11.3 b&w text IGUANA • VOLUME 11, NUMBER 3 • SEPTEMBER 2004 151IGUANA • VOLUME 11, NUMBER 3 • SEPTEMBER 2004 151GRAND CAYMAN BLUE IGUANAS speckled with isolated pale cream scales and the flanks between chevrons are still marked with diffuse pale cream spots. The blue base color is progressively obscured by dark gray on the tail, where the banding becomes less distinct with age. The alternating cream and black pattern on the dorsal crest is reduced but still evident. The juvenile pattern changes to the adult form gradually, by further replacement of cream spots and speckling with the blue base color and the variable loss of the dark chevrons (some adults lose them entirely). Limbs also become blue, apart from the toes, which lose all banding and darken to black. The nuchal and dor- sal crest scales all become bright blue, with no trace of the juve- nile pattern. The lower half of the tail becomes darker, with band- ing either totally obscured or very indistinct. The sclera of the eye becomes redder and more exposed as the animal grows. Having said all of that, a Blue Iguana is only blue when it wants to be blue. All that blue is masked in dark gray when an iguana is cold, sleeping, or just trying to remain inconspicuous. The gray color closely matches the surrounding carbonate karst rock, on which iguanas seem to vanish into the landscape. Watching these iguanas in the wild, they appear to use their color selectively and carefully, as signals to each other. In the greens and earth tones of Grand Cayman’s dry shrublands, the bright blue of C. lewisi shines out like a beacon. References Burton, F.J. 2000. Grand Cayman Iguana, pp. 45–47. In A. Alberts (comp. & ed.), West Indian Iguanas: Status Survey and Action Plan. IUCN, Gland, Switzerland. Burton, F.J. 2004. Taxonomic status of the Grand Cayman Blue Iguana. Caribbean Journal of Science 40:198–203. Grant, C. 1940. The herpetology of the Cayman Islands. Bulletin of the Institute of Jamaica, Science Series (2):1–55. Malone, C.L., T. Wheeler, J.F. Taylor, and S.K. Davis. 2000. Phylogeography of the Caribbean Rock Iguana (Cyclura): Implications for conservation and insights on the biogeographic history of the West Indies. Molecular Phylogenetics and Evolution 17:269–279. Schwartz, A. and M. Carey 1977. Systematics and evolution in the West Indian iguanid genus Cyclura. Studies on the Fauna of Curaçao and other Caribbean Islands 173:15–97. S P E C I E S P R O F I L E Compared to their relatives in the families Boiidae and Pythonidae, the Ground Boas of the genus Tropidophis (Family Tropidophiidae) are relatively small and are sometimes referred to as “dwarf boas.” The largest species reaches a total length of barely over a meter and the smallest less than a third of that length. Unlike most boas and pythons, Ground Boas lack infrared sensors in interlabial pits, but, like their larger relatives, they possess vestiges of hind limbs, which are visible externally as a pair of cloacal spurs. All are live-bearers. They are ground- dwelling or semiarboreal and feed primarily on small vertebrates, mainly frogs and lizards. When disturbed, these snakes may exhibit autohemorrhaging from the eyes and mouth as well as cloacal discharge. On loose substrates, at least one species is known to employ sidewinding locomotion. Many (maybe all) species also are capable of physiological color changes, a phe- nomenon that is rare in snakes. Ground Boas apparently are unique among those snakes that can change colors in that they do so on a 24-hour cycle: they are lighter in color at night and darker during the day. All members of the genus are listed in CITES Appendix II and are rarely seen in the pet trade. Species of Tropidophis are relatively broadly distributed in the West Indies and South America, but they are secretive. Consequently, many are not well-represented in museum collec- tions and their taxonomy has been poorly understood. Previous Ground Boas (Tropidophis) of the Cayman Islands A.C. Echternacht Department of Ecology & Evolutionary Biology University of Tennessee, Knoxville Photographs by the author. Adult Grand Cayman Ground Boa, Tropidophis caymanensis. 152 IGUANA • VOLUME 11, NUMBER 3 • SEPTEMBER 2004 SPECIES PROFILE classifications recognized 13–16 species, but a recent taxonomic study conducted by S. Blair Hedges elevated several subspecies to species rank and recognized 29 species. Three of these occur only in South America (Ecuador, Brazil, and Perú) and one is known only from a single specimen. The remaining 26 species occur in the West Indies, where most are restricted to single islands. Fifteen species are found in Cuba, and only in Cuba are the geographic ranges of mul- tiple species (4–6 species, depending on the locality) known to over- lap. Three species occur in Jamaica, two in the Bahamas, and one each on Hispaniola, Navassa, the Turks & Caicos Islands, Grand Cayman, Little Cayman, and Cayman Brac. The local common name for the Ground Boas of the Cayman Islands is “lazy snake.” The name is derived from their habit of balling up when first captured rather than trying to escape. This behavior is widespread within the genus and is most likely to be exhibited by juveniles. The three Caymanian species were, until recently, considered to be subspecies of T. caymanen- sis, each endemic (restricted) to a single island. Each is now con- sidered a full species: T. caymanensis (Grand Cayman), T. parkeri (Cayman Brac), and T. schwartzi (Little Cayman). All three are relatively small snakes, usually less than 50 cm in total length. In the Cayman Islands, Ground Boas are primarily active at night and, on Grand Cayman, Grant found them to be especially active late in the summer following periods of rain. Ground Boas may occur throughout Grand Cayman and Little Cayman, but on Cayman Brac they appear to be limited in distribution to the northern and western coastal areas. Most are found on the ground, but exceptions exist: they have been found in the leaf bases of epiphytes and Richard Thomas found one 2.4 m above the ground in the roof of an outhouse! They have been found in habitats ranging from beach to dry forest and in leaf litter, rotten tree stumps, cracks in the walls of houses, and under palm fronds, rocks, slabs of limestone, logs, and boards. The diet seems to con- sist mainly of lizards of the genus Anolis and Cuban Tree Frogs, Osteopilus septentrionalis. The ends of the tails of Caymanian Ground Boas are white to yellow in color, in stark contrast to the darker coloration of the rest of the snake. This pattern is usually seen in sit-in-wait (ambush) predators. As a snake lies quietly in wait, it wiggles the tip of its tail. This may attract the attention of a sight predator, like an anole or tree frog, that mistakes it for something to eat and ends up being eaten by the snake. References Grant, C. 1941 (“1940”). The herpetology of the Cayman Islands. Bulletin of the Institute of Jamaica, Sciences Series 2: iv + 65 pp. Hedges, S.B. 2002. Morphological variation and the definition of species in the snake genus Tropidophis (Serpentes, Tropidophiidae). Bulletin of the Natural History Museum, London (Zoology) 68: 83–90. Hedges, S.B., C.A. Haas, and T.K. Maugel. 1989. Physiological color change in snakes. Journal of Herpetology 23: 450–455. Schwartz, A. and R.W. Henderson. 1991. Amphibians and Reptiles of the West Indies: Descriptions, Distributions, and Natural History. University of Florida Press, Gainesville. Seidel, M.E. and R. Franz. 1994. Amphibians and reptiles (exclusive of marine turtles) of the Cayman Islands, pp. 407–433. In: M.A. Brunt and J.E. Davies (eds.), The Cayman Islands: Natural History and Biogeography. Monographiae Biologicae. Volume 71. Kluwer Academic Publishers, Nordrecht, the Netherlands. Smith, D.D., J.S. Parmerlee, Jr., R. Powell, L.R. White, and A. Lathrop. 1991. Tropidophis haetianus. Locomotion. Herpetological Review 22: 132–133. Smith, D.D., D.J. Pflanz, and R. Powell. 1993. Observations of auto- hemorrhaging in Tropidophis haetianus, Rhinocheilus lecontei, Heterodon platyrhinos, and Nerodia erythrogaster. Herpetological Review 24: 130–131. Thomas, R. 1963. Cayman Islands Tropidophis (Reptilia, Serpentes). Breviora (195): 1–8. Tolson, P.J. and R.W. Henderson. 1993. The Natural History of West Indian Boas. R&A Publishing, Ltd., Taunton, U.K. Zug, G.R., L.J. Vitt, and J.P. Caldwell. 2001. Herpetology: An Introductory Biology of Amphibians and Reptiles. Academic Press, New York. Subadult Little Cayman Ground Boa, Tropidophis parkeri.