Museum of Science
Lizard Island: Cuba is a study in saurian richness
by Alfonso Silva Lee
Some scientists have all the luck. Naturalist Alfonso Silva Lee has spent much of his life exploring the Caribbean, a world of deserts and rainforests, of insects, snails, fish, frogs, and birds. And lizards. On February 4, 2000, at the Museum, Silva Lee presents Lizard Island: Anoles, Curlytails, Geckos, Galliwasps, and Iguanas of the Caribbean as part of the free First Friday Lecture Series sponsored by the Lowell Institute. Here, Silva gives memebers a preview of one islands' amazing diversity of lizard inhabitants.
Cuba holds a larger share of lizards than it should. Much larger. If the world's saurian richness were to follow the density of species packed on the island&emdash;82 species&emdash;the planet would host not just 3,750 or so species, but an amazing 107,370, give or take a few dozen. Of Cuba's total, 73 are found only on the archipelago. Lizard Island, to be sure. And the number of species know to live there is growing, with 14 newly described in the last ten years.
Day and night, lizards are part of every Cuban Landscape. From southern coastal deserts to the wettest swamps and mountain forests, it is virtually impossible to scrutinize a Cuban tree or bush without discovering a lizard in a matter of seconds.
The great majority of Cuba's lizards, 54 species, belong to a single genus, Anolis, which includes a total of over 250 species scattered throughout the American tropics and subtropics. Measured from the snout to the base of the tail (herpetologists don't measure lizard tails because they detach so easily), these anoles range from 30-millimeter (1.2-inch) jumping whips to heavyweights as long as 191 millimeters (7.5 inches). Most Cuban anoles are arboreal, feed upon a wide variety of insects, and hide in their throats a colored fold of skin&emdash;the throat fan, or dewlap&emdash;that they expand in social interactions. Generally full-sized and strongly pigmented only in males, the dewlap of each species has a distinct color.
The best-known local lizard is the ubiquitous Cuban brown anole. A saurian equivalent to the house sparrow, it is common in sunny environments, from beaches and mangrove stands to mountain forests, and especially in gardens and parks. Like the sparrow, this lizard is well adapted to take advantage of human surroundings&emdash;and maritime transprotation. It has managed to invade a number of neighboring islands and isolated coastal localities from Honduras to Texas, and it is firmly established in the Florida peninsula.
The brown anole spends most of the day in full view under the sun's scorching rays. Its preferred body temperature is around 33° C (91.4° F), quite close to our own and positively warm. These lizards perch on the lower portions of tree trunks, or on fence posts and bushes, jumping to the ground to pursue recently alighted insects. Throughout the summer, adult males are seen flashing their colorful dewlaps every few minutes, their minds more attuned to social affairs than to invertebrate morsels. They do not tolerate the sight of each other, and physical clashes featuring head-bobbing, push-ups, and tail lashings are common.
Rivaling the abundance of brown anoles are the closely related green and blue anoles, denizens of the branches further off the ground. These are of greater size, with proportionally larger heads and oversized back teeth that are probably handy for subduing grasshoppers and cockroahces. A groove in front of each eye makes these lizards look ill-intentioned. But it is actually a simple anatomical adaptation: it allows the anoles to look straight ahead when advancing on their prey.
Green anoles can be quite fearless around humans. At home on my hammock, I have watched these lizards boldly take possession of every string&emdash;and most of my body&emdash;as feeding grounds. As anyone can guess, I always sided with the lizards&emdash;which, happily, scored in at least eight out of ten strikes at pestering flies.
The largest of all anoles are the Cuban chipojos, known in English as knight anoles or giant anoles. Their sizes range from the female dark-cheeked giant anole at 122 millimeters (4.8 inches) to the 191-millimeter (7.5-inch) western giant anole. In the wild, these giants generally sport a standard, mostly vivid-green costume, but all are capable of turning dark green or dark brown, and different species may show at times a variety of colorful bands and blotches. One Cuban giant anole is entirely sky blue.
Giant anoles spend their hunting hours among the highest branches. As their size suggests, they are not nimble-footed. Their hunting tactics are odd: they seem to lurch carelessly at prey, often overlooking the fact that the target may be in mid-air. Rambling through rainforests where chipojos are abundant, I have several times been startled by a sound like a dropping mango, only to discover that the heavy object crashing through the foliage was a Baracoan giant anole with a bird in its mouth. Quiescence, along with camouflaging colors and markings, helps makes these huge lizards invisible to birds.
Along the edges of the many creeks and rivulets that scar the northern, more forested and hilly half of Pinar del Río province, lives the Cuban stream anole. This handsome lizard is stricly tied to the waterways, usually perching low on overhanging vegetation or amoung boulders lying in the streams.Well adapted to this humid, shady environment, the stream anole rarely basks. It swims, dives, runs over the surface like a basilisk, and has been reported to remain underwater for close to one hour. Its countenance resembles that of a crocodile&emdash;a miniature version to be sure, with the supplemental gratuity of charming blue eyes. Luxury possessions in a tropical environment, blue eyes are common among other deep-forest anoles, resulting from loss of darker pigments commonly present to protect retinal cells from intense solar radiation.
There is no definitive answer as to where or why any of these creatures evolved, but we do have a general explanation for Cuba's lizard wealth. During the last tens of millions of years, a number of huge natural rafts must have crossed the water gap between Central and South America to Cuba, and some of these randomn craft undoubtedly carried lizards among the crew. Other, shorter sea voyages must have departed from nearby islands, like Jamaica and Hispaniola. Once each invader was firmly established, Cuba's patchy distribution of soil types, along with sea level changes that have repeatedly multiplied and divided the number of islands comprising the Cuban archipelago, set the groundwork for evolution in different directions.
George Bernard Shaw wrote, "The worst sin towards our fellow creatures is not to hate them, but to be indifferent to them; that is the essence of inhumanity." When it comes to lizards, sadly, we fit the description. Lately, however, through scientists' interest in their behavior and laypeople's affection for them as pets, lizards seem to be gaining cultural points. If the trend continues, lizards and humans alike will benefit. The natural history of Cuba's anoles is but one reptile tale. There's a whole world of lizards waiting for us to explore.
Copyright 2000, Museum of Science, Boston