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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.


