The Boa Constrictor
According to Daniel Webster's New Unabridged 20th Century Dictionary, boa constrictor is defined as "a large and powerful species of boa that attains a length of 10 to 15 feet."
This definition is straightforward and simple, but somehow I can't get over the idea that the term should mean so much more. Take, for instance, a person who is afraid of snakes. Doesn't the term also convey an image of a dangerous creature that is to be feared and reviled? So, if you agree that Webster's definition is in need of a little assistance, let's venture to see what else the term can mean to different people. To indigenous people in tropical America, a boa constrictor (or whatever local name is used, and there are many) is a common inhabitant of the forest, a snake that over the ages has been used as a source of food, oil, medicine, leather, ornamentation, and in religious ceremonies.
To the herpetologist, Boa constrictor is a wide-ranging species (or complex of species) whose taxonomy, relationships and other aspects of its biology remain poorly understood. To the pet owner, it is a wonderful and beautifully marked creature that doesn't require daily maintenance. To the herpetoculturist, boa constrictors are a group of snakes that differ in size, color, pattern and value according to their area of origin, classification, variant, morph or genetic makeup.
The boa constrictor is perhaps the most recognizable snake in the New World.
As I was coming up with these definitions, I thought about providing my own. I began reminiscing about my involvement with B. constrictor, which began one fateful morning on a grassy hillside in Costa Rica, long before the Beatles became popular-the first of many encounters that I've had with this species in Latin America. From my earliest recollection, what I always considered special about B. constrictor was not its extent of variation in color, pattern or size, but the knowledge that this species has been around for a very long time and conquered a tremendous range and variety of habitats. This old-timer has survived to become the most prevalent ophidian in Latin American forests, an extraordinary feat that commands a certain air of respectability. I know that it's just me, but whenever I run across a specimen, this little voice inside my head always seems to say, "It is a privilege and a pleasure to have made your acquaintance." But getting back to the definition, it's like explaining why I love the Beatles-I just couldn't put it into words.
Ask Me Why
Information on the boa constrictor abounds. If you peruse the literature, however, you'll find little summary information regarding Boa constrictor on islands. But it is on islands that B. constrictor undergoes dramatic changes in color, size and body structure, and for the breeder or hobbyist certain traits in insular (island dwelling) populations have increased their popularity. Because of their growing notoriety, I am taking this opportunity to present historical information on some captive populations. I will also present an overview of their geographical distribution, but more importantly, will attempt to provide an insight into the world of B. constrictor on small cays or islands. On some islands, B. constrictor is precariously close to extinction, and it is important that we understand the pressing need to conserve these unique boas and their fragile habitats for posterity.
The boa constrictor is perhaps the most recognizable snake in the New World. Early explorers to tropical America were captivated by tales of its enormous size, ferocity and crushing abilities, and exaggerated accounts of its prowess were common in the nature books of the times. Branded with a tabloid-like reputation, the stage was set for B. constrictor to become a star attraction in zoos, exhibits, circuses, traveling shows and, eventually, the motion picture business. The continental range of Boa constrictor extends from northern Mexico south to Peru, Bolivia and Argentina. From the late 1960s to early 1970s, prior to the implementation of import and export regulations, large numbers of boas were imported into the United States from export centers such as Colima (Mexico), Barranquilla (Colombia), Leticia (Colombia), Iquitos (Peru), and Belem (Brazil). Occasionally boas would also arrive from other areas. It was during that era, which has been called "the heyday of the animal trade," that I was fortunate to work for Bill Chase in Miami, who ran what was perhaps the most interesting animal compound that ever existed. Unlike other animal dealers of his day, Bill carried nearly every form of wildlife possible. His selection of amphibians and reptiles was the largest in the country, and since boas were a staple in the trade large numbers were always on hand-from all available areas and in all sizes. Some were real giants. I once unpacked a shipment from Peru that contained two boas about 14 1/2 feet long, one over 15 feet and one well over 16 feet-the largest I ever saw!
Nearly every shipment of boas received at Chase's had large specimens. Thus, it came as a surprise when, in 1970, a group of students led by the late E. Ross Allen came through Miami from Belize with about three dozen small boas (all under 3 1/2 feet), most which appeared to be adults! The snakes had been collected on Crawl Cay, a small barrier reef island located about 11 miles northeast of Placencia. The students could have brought back additional specimens, but decided to release the ones that were scarred or darker in color.
Compared with specimens of Boa constrictor from mainland Central America, these insular boas were much smaller, paler in color (from pale gray to pink) and suffused with varying degrees of black speckling. Even the eyes were speckled. The eye color ranged from pale pink to nearly black, and the eye size was larger, but varied from specimen to specimen. The snout was more elongate, the body dorsolaterally compressed (some were a little thin), and the tail longer. Unlike most mainland specimens, these boas were gentle in disposition, but an even more interesting characteristic was their ability to change color. This color shift, known as metachrosis, was the character that led them to be marketed in the trade as "chameleon boas." The following year, some members of the group returned to Belize and brought back additional specimens. Interestingly, only a handful of snakes were as colorful as the ones collected the previous year.
A few years later (in February of 1978) an animal dealer returned from the Cayos Cochinos (a group of small cays located approximately 10 miles north of Nueva Armenia, Honduras) with a small, unusual boa constrictor. The boa seemed to share some of the characteristics present in the Crawl Cay specimens, but was paler in color and not as heavily speckled. Before long, a collecting station was set up on the islands and within weeks other animal dealers got into the act. Since these insular boas were readily distinguishable from the ones on the mainland and the Spanish word "cochino" means pig or hog, their commercial name soon became "Hog Island boas."
During the early 1980s, hundreds (if not thousands) of Hog Island boas were exported from Honduras to the United States and Europe. By 1986, however, the numbers began to dwindle, and instead of the small, pale (often pink) boas, larger and darker specimens began to take their place. Rumor through the commercial grapevine was that the intensive collecting on the Cayos Cochinos had nearly depleted the population, and dealers had to turn their efforts to other areas-like the Bay Islands. Almost immediately there were widespread concerns as to how commercial collecting on the Cayos Cochinos may have affected the population of Boa constrictor. This led two prominent field biologists to conduct a herpetofaunal survey of the islands in March of 1988 (Wilson and Cruz, 1993). The results were staggering-not a single specimen of B. constrictor was found! Given the amount of boas that were collected for the commercial trade, it is interesting to note that as of 1993 not a single specimen of B. constrictor from the Cayos Cochinos was available for study in a museum collection! The specimen from the Cayos Cochinos pictured in the book by Wilson and Meyer (1985) is the boa brought to Miami by an animal dealer in 1978, which alerted commercial dealers to the existence of the population.
During the early 1990s, tourists reported seeing specimens of Boa constrictor on the Cayos Cochinos (G. Brewer, pers. comm.). More recently, however, specimens bearing a strong resemblance to Hog Island boas have been imported from Nicaragua and marketed as "white boas" (R. MacInnes, pers. comm). Perhaps the population on the Cayos Cochinos has started to make a comeback, but nevertheless, there is no doubt that during the past two decades what was once a thriving population of B. constrictor has been severely depleted.
There's a Place
The late Bob Sears was one of the most interesting herpers I ever met. Not only was he one hell of a stunt pilot that for years flew in air shows under the name "The Avenger," but he liked and kept all kinds of herps. Bob's true passion, however, was Boa constrictor, and since he owned an airplane, on occasion he would take off for some tropical destination and go adventuring. About 20 years ago, he came through Miami from St. Lucia (in the Lesser Antilles) with a bag full of gorgeous boas, and we had a great time swapping snake stories. Years later when I moved to Utah, he would occasionally fly up for the weekend, and as usual our conversation would turn to boas. It was during one of those forays that the topic of Crawl Cay boas came up. I can still recall the gleam in his eyes when he turned and said, "Belize! Now there's a place I can fly to!"
Just to the east of the Península de Yucatán lies the longest barrier reef in the Atlantic tropics. The reef extends intermittently for about 400 miles from near the northeastern corner of the peninsula south to the Golfo de Honduras. Off the coast of Belize the reef is composed of hundreds of sand cays or islets which enclose an extensive shallow lagoon (West, 1964). In February of 1988, with permits on hand to collect a few specimens for the Institute for Herpetological Research, Bob took off for Belize. Logically, he first went to a locality where Boa constrictor was known to occur-Crawl Cay. The island was smaller than he expected (less than half a square mile) and consisted of a mangrove swamp bordered by low-lying trees along the coast, and mangroves and scattered buttonwoods in the interior. On the southwest part of the island was a narrow strip of sand about 200 yards long and a few yards wide that supported a thicket of palms and buttonwoods. Everywhere on the island was swarms of mosquitoes and all kinds of ants, insects and crabs. The crabs even made their way up the lower portion of the trees. After searching through much of the island, the only place where Bob found B. constrictor was on the small, sandy strip. Most specimens were thin and looked rather emaciated, weighing from 1 to 3 pounds and ranging in size from 3 to 4 feet (a single specimen was nearly 5 feet). The snakes were similar in body shape and proportion, eye size and other characteristics to the ones collected a decade earlier, except that their color varied from dark reddish-brown to black. Most specimens had some degree of speckling, but no pink or brightly marked ones were found. Although the evidence is inconclusive, it appears that the selective capture of about three dozen colorful specimens a decade earlier may have affected the color variation in this population.
Get Back In July 1990, Bob returned to Crawl Cay, this time in association with the Milwaukee Public Museum. Again he found a few specimens, took a sampling for the museum and released the rest. Interestingly, all of the boas that Bob found on Crawl Cay were in trees or logs and none were on the ground.
In December 1990, Bob went back to Belize. This time he teamed up with the Belize Center for Environmental Studies and went to Wee Wee Cay, a privately held small island (about 300 yards across) located about 14 miles southeast of Dangriga. Bob found the vegetation of Wee Wee similar to that of Crawl Cay-primarily a mangrove swamp with a small spit of sand. Unlike Crawl Cay, however, humans had significantly impacted the vegetation. The sandy area had been cleared for habitation, there were four dogs on the island, and the residents claimed that the boas had been pushed back from their sandy habitat into the swamp. Nonetheless, Bob found, photographed and released four boas, noting that they were similar in appearance to those from Crawl Cay except not as heavily speckled.
The next stop was Coco Plum Cay, which is located about 7 miles southeast of Dangriga. The cay is approximately 1,000 yards long by 100 yards wide, and periodically was occupied by people in a partially cleared sandy thicket. In was in this habitat that Bob found a boa about 3 feet off the ground, where he photographed and released it. The specimen was a female with a pale gray ground color, and it appeared similar to the boas he had found on the other cays.
At first, the few snakes Bob brought back from Crawl Cay were finicky feeders. Most would only accept birds, and it took a long time before they would accept other food items. One male fasted for 18 months without showing any ill effects, but it eventually fed on rodents. In time, all specimens adjusted to captivity, and their progeny constitutes the bulk of today's captive population.
Here, There and Everywhere
On account of the extensive range and the variety of habitats occupied by Boa constrictor, it is not surprising that the species is found on many islands. On the Pacific coast of Mexico, B. constrictor has been reported off the coast of Sinaloa from Ensenada de Pabellón and Isla de las Iguanas, and off the coast of Nayarit from Isla de Bahía las Varas, and from three of the four islands in the Tres Marías Islands chain-Isla María Madre, Isla María Magdalena, and Isla María Cleofas (Henderson et al.,1995; Slevin,1926; Smith, 1943; and Zweifel,1960). The Tres Marías population was originally described as an endemic subspecies (B. c. sigma) by Smith, but Zweifel provided meristic and mensural information and concluded that although the boas were obviously different, he questioned the significance of the differentiation and relegated sigma to the synonomy of B. c. imperator. Subsequent authors have followed this arrangement.
In June of 1976 in the company of Randy McCrainie and Larry David Wilson, I visited Isla Zacate Grande in the Golfo de Fonseca (off the south coast of Honduras). The heat in this volcanic island was unbearable during the day, but during the evening we were able to find six specimens of Boa constrictor, mostly along rock walls. Although the island is separated from the coast only by a narrow channel, the boas were slightly different from those on the mainland-their ground color was paler and their eyes were larger and noticeably darker.
Off the southwest coast of Costa Rica, Boa constrictor was reported by Boza (1988) as occurring on the Isla de Caño, a relict mountain located about 12 miles west of the Península de Osa. To the east in Panama, an unusual population of Boa constrictor from the Archipélago de las Perlas in the Golfo de Panamá was described by Barbour (1906) from Isla Saboga [as Epicrates sabogae]. Cochran (1946) extended the range of B. c. sabogae to Isla San José by recording six specimens. Peters and Orejas-Miranda (1970) note, however, that the spelling of Saboga has been changed to Taboga, but any confusion as to the distribution of B. constrictor on those islands should now be clear, as Henderson (et al.,1995) reports B. constrictor as occurring on both Saboga and Taboga. Isla Saboga is located at the northern tip of the Archipiélago de las Perlas, whereas Isla Taboga lies approximately 35 miles to the northwest in the Bahía de Panama. It is in that bay and close to the entrance to the Panama Canal that Henderson (et al., 1995) also recorded B. constrictor from Isla Perico.
Off the southern coast of Colombia, Boa constrictor is known from the islands of Gorgona and Gorgonilla (Medem, 1979). Boas from those islands were not reported from museum material, but from reliable information that Medem received during investigations he conducted there in 1961. A few years later, Restrepo (1986) reported meristic information for five boas (apparently from Isla Gorgona) that were captured but later released. Since boas were unheard of on the islands until 1961, Medem concluded that they may have been recent invaders to the islands, but Restrepo later suggested that they could have been introduced by fishermen for food or to control rodents.
On the Caribbean side of Mexico, Lee (1996) reports a specimen of Boa constrictor from Isla Mujeres, which is close to the mainland at the northeastern tip of the Península de Yucatán, and a specimen from the Isla Cozumel, which lies about 50 miles to the south. Cozumel is a large limestone island that was possibly separated from the mainland by faulting, and is now a well-known tourist resort. South of Cozumel and into Belize, Lee (1996) also records B. constrictor from Ambergris Cay and Cay Corker. Schmidt (1941) provided a record for a specimen of B. constrictor from the Turneffe Islands, and Neill and Allen (1962) received information regarding the occurrence of B. constrictor on Cockroach Cay (one of the Turneffe Islands). Henderson and Hoevers (1975) further expanded the range of B. constrictor to include most of the larger cays.
Off the coast of Honduras, Boa constrictor was first reported from the Islas de la Bahía by Wilson and Hahn (1973) from a total of four specimens from the islands of Roatán, Elena and Guanaja. Those authors provided a description of the Bay Islands, noting that Utila, Roatán and Guanaja are the three major islands, but that there are also three minor islands and numerous cays. They indicated that the islands as a whole have an area of about 275 square kilometers (=106 square miles).
An excellent summary of the physiography, vegetation and herpetofauna of the Cayos Cochinos was presented by Wilson and Cruz (1993). Those authors indicate that the Cayos Cochinos are comprised of two islands (Cayo Cochino Grande and Cayo Cochino Pequeño) and a total of 13 cays. They point out that the total area of the islands (including the cays) is less than one square mile, with Cayo Cochino Grande occupying an area slightly over half a square mile and Cayo Cochino Pequeño about a quarter of a square mile. It's easy to visualize how the population of B. constrictor was severely depleted on those tiny islands. What boggles the mind, however, is how so many boas existed there!
Off the coast of Nicaragua, Barbour and Loveridge (1929) reported a single specimen of Boa constrictor from Isla de Maíz Grande, located off the southeastern coast of Nicaragua. An additional specimen from that island and one from Isla de Maíz Pequeña were reported by Villa (1972). In 1995, a group of specimens of B. constrictor from the Islas del Maíz (=Corn Islands) was imported commercially. Apparently, permits were granted for two litters of babies (21 specimens) that were born in captivity in Nicaragua, but since that time the islands have become a nature preserve and all exports have ceased (R. MacInnes, pers. comm.). Boas from the Corn Islands are small (the babies born in 1995 are still under 3 feet in length); they have a faded pattern and occasionally pink or salmon is present on their sides and/or venter.
Heading southeast along the Caribbean to northwestern Panamá, Boa constrictor was reported by Henderson (et al.,1995) from Isla Bastimientos and Isla Pastores in the Archipiélago de Bocs del Toro, and nearby from Isla Escudo de Veraguas in the Golfo de los Mosquitos. Boa constrictor has also been recorded from Isla Barro Colorado, a man-made freshwater island in Gatun lake in central Panama, created between 1912 to 1914 during the formation of the Panama Canal (Myers and Rand, 1969).
East of the Corn Islands, but still on the continental shelf and west of the Colombia Basin lie the islands of Isla San Andres, Isla Santa Catalina and Isla de Providencia (they are owned by Colombia). The occurrence of Boa constrictor on those islands was reported by Dunn (1945) and Dunn and Saxe, Jr. (1950). The latter authors considered San Andres and Providencia (with adjacent Isla Catalina) as islands that were upheaved independently from the ocean and were never connected to one another or to the mainland. By analyzing the components of the herpetofauna and comparing it with historic economic trade routes, they determined that the majority of the herpetofauna of the islands had become established as a result of human activities. They also provided meristic and mensural data for four specimens of B. constrictor, and by comparing those data with that from mainland specimens, concluded that the boas from the islands didn't demonstrate a trace of endemism and had indeed originated from the mainland.
Off the northeast coast of Venezuela lies the relatively large Isla de Margarita, from where Brongersma (1940) and Roze (1966) each report a single specimen of Boa constrictor. To the east, there are many reports of B. constrictor from the Trinidad and Tobago region, dating back to the 17th century (de Rochefort, 1665). On islands northwest of Trinidad, Boos (1984a,b) reported B. constrictor from Isla Gaspar Grande (=Gasparee Island) and three small specimens from Isla Monos. The island of Marajó is the second largest island in South America and is located at the mouth of the Amazon River system. Goulding (1990) presents an ecological picture of this area, which is often referred to as part of the Lower Amazon. This region contains thousands of islands with rain forest vegetation, and with the exception of the eastern half of Marajó nearly all are flooded twice daily with the tides. Most islands have adapted to the heavy flooding, and the volume of water traveling down the Amazon prevents intrusion from saltwater. The eastern half of Marajó consists of huge savannas studded with islands of trees and it is in that area where the specimen of Boa constrictor recorded by Muller (1969) was likely collected.
Boa constrictor is well known in the Lesser Antilles. The species has been documented from St. Lucia since the time of Linnaeus, and from Dominica since the 19th century. The evolutionary relationships of these boids was studied by Lazell, Jr. (1964), who concluded that in the Lesser Antilles the populations were members of a stepped-cline series that demonstrated geographic variation in a single species, and that the forms were subspecifically related to one another. The subspecific epithet for the St. Lucia population became the oldest name available (orophias), which was proposed by Linnaeus in 1758. Lazell, Jr. named the Dominica population nebulosus (which means clouded) in allusion to its dark appearance. Memoirs of a reptile-collecting trip to St. Lucia were provided by Reichling (1991), and extensive natural history information on a trip to Dominica, as well as reproductive and husbandry data for B. c. nebulosus were presented by Vandeventer (1992).
In My Life
Life for Boa constrictor in some of the smaller cays must be difficult, and you have to wonder how resilient these boas must be to have survived for eons. In cays like those in Belize, the morphological changes these boas have undergone may hold a clue to their survival. Since on these islands various species of crabs blanket the ground, boas must have had to adapt to an arboreal way of life. A change in body structure (from large and heavy to small and thin) is an advantage for their tree-dwelling existence, not only for locomotion but for capturing and feeding on transient birds. A smaller specimen would not require as much living space, and would feed on smaller food items and possibly less food. Another adaptation is their pale color. On a small, sun-drenched island a pale color is useful in expelling heat. The nighttime color shift could also relate to heat loss, or perhaps as a mechanism for nocturnal camouflage.
Many years ago I visited the Columbus Zoo and met with Lou Pistoia, who was in charge of the reptile collection. Lou's claim to fame was that he had established more snake longevity records at Columbus than the entire zoo world combined. His secret was to feed the snakes only sporadically, and I was amazed by how "skinny" most of the specimens were. In comparison, thin specimens of Boa constrictor on some of the islands could relate to a long life span, and perhaps some of these slender insular boas live longer than their mainland congeners. Being thin, however, could also be a double-edged sword. Without sufficient body weight females may not attain breeding condition but once every few years. The boas that Bob brought back from Crawl Cay gave birth to very small babies, and out of the first four litters there were only eight live, healthy offspring. Loss of fecundity could have resulted from specimens with improper body weight, but in view of the limited number of specimens on Crawl Cay, especially since a large part of the population was apparently removed, it could have also resulted from an inbreeding depression syndrome. It is a well-known fact that a loss of genetic diversity could have increased the chances for detrimental recessive genes to appear in the population.
You also have to wonder how these boas have survived natural calamities such as tidal waves and hurricanes, and how they have managed to colonize numerous small islands. An interesting observation was provided to Bob Sears by one of the locals. He had found boas "floating in the water between cays, curled up and with their head sticking up."
I Should Have Known Better
In captivity, breeders tend to pump-up their animals so they can quickly reach reproductive size and weight, since larger, heftier females produce larger litters. Breeders also tend to be selective in their efforts, and prefer to reproduce specimens with desirable traits, such as pronounced speckling, brighter colors or aberrant patterns. In some cases, after a few generations specimens will no longer resemble the original stock.
Herpetoculture is a valuable tool for producing animals for the commercial market, for zoos or exhibition, for study and numerous other purposes. However, where on the one hand herpetoculture may be the vehicle that will ultimately save populations of insular boas from extinction, on the other it can be viewed as the culprit that has created the commercial demand that threatens certain boa populations. Years ago, we used to think in terms of breeding specimens with the ultimate goal of restocking wild populations, a noble supposition that afforded herpetoculture a level of credibility and responsibility. In recent years, however, that premise has lost both popularity and support. Through experience and advances in veterinary medicine, we are aware that there are too many pathogens (such as Paramyxo viruses and Inclusion Body Disease) that could be detrimental to free-ranging reptiles should captive specimens be released into the wild. Captive self-sustaining populations of insular boids are meritorious in their own right and I fully support them. However, when it comes to conserving natural populations nothing will preserve these boas better than protecting the ecosystems they inhabit.
Tomorrow Never Knows
On account of the wide distribution and array of insular adaptations exhibited by Boa constrictor, this species appears to be an excellent candidate for future biogeographical, ecological and evolutionary studies. Populations of B. constrictor from cays or small islands would be an important component for such research, since it is there that B. constrictor exhibits remarkable changes in the way it looks and behaves. The problem is that we may be running out of time.
One of the reasons I developed a love for herpetology and a special interest in boa constrictors is that I was raised in an era when you could travel to remote areas and find, photograph, even collect, specimens. Times have changed, however, and not only are permits to collect specimens seldom available, but many areas have become too dangerous for people to travel. With the coming of the new millennium, perhaps we should take the time to reflect on the many changes that have happened to our planet during the 20th century, and think about what tomorrow will bring.
I grew up in areas of Costa Rica where you could walk for days in undisturbed primary rain forest. Sadly, the human demand for food and living space have taken a monumental toll on the forest, and many places have been deforested as far as the eye can see. The story is the same throughout much of Latin America. A recent and even more disturbing trend, however, is the development of coastal areas and islands for resorts and getaways. Under the guise of economic development for tourism, expanses of natural vegetation are being razed to make way for hotels, restaurants, dance floors, swimming pools, tennis courts, grassy courtyards, golf courses and airstrips. And as if to add insult to injury, instead of using native plants for landscaping and decoration, the local flora is being replaced by foreign vegetation. In countries like Belize, where tourists and divers make up such a large part of the economy, this trend is likely to continue.
As far back as a decade ago, the Belize Center for Environmental Studies had already identified 68 cays that had received substantial human alteration and development. How long Boa constrictor can withstand human pressures on these cays is anyone's guess, but unless we make a concerted effort to protect some of these fragile ecosystems these unique boas and their habitats are destined to become nothing but a memory.
As a herpetological community we must be aware of the situation and direct conservation efforts toward governmental agencies, conservation groups, or anyone in who is in a position of wealth or power. This is a huge problem that cannot be tackled alone. Our only hope is that in time a solution will come-as the Beatles once said-with a little help from our friends.
This article would not have been possible without the information, enthusiasm, support, and friendship of the late Bob Sears. Together we presented an abbreviated version as a paper at the 16th International Herpetological Symposium in St. Louis, Missouri, in 1992. For critically reviewing the manuscript and offering many helpful comments and suggestions, I am especially indebted to Bill Lamar and Gordon W. Schuett. I also wish to thank Bill Lamar, James R. McCrainie, Gordon W. Schuett , Alejandro Solorzano, Larry David Wilson and others too numerous to mention for the great times we've spent in the field in the company of Boa constrictor. For photographs, information and many other courtesies I am also grateful to Greg Brewer, Kevin and Sue Hanley, Robert W. Henderson, Rob Roy MacInnes, Dennis Sargent, Kyle Schuett and Terry Vandeventer.
Barbour[CP1], T. 1906. Vertebrata from the savanna of Panama IV. Reptilia and Amphibia. Bull. Mus. Comp. Zool. 46:224-229.
Barbour, T. and A. Loveridge. 1929. Reptiles and Amphibians. Vertebrates from the Corn Islands. Bull. Mus. Comp. Zool. 69: 138-146.
Boos, H. 1984a. A consideration of the terrestrial reptile fauna on some offshore islands north west of Trinidad. Living World Journal. J. Trinidad and Tobago Field Nat. Club. 1983/1984:19-26.
Boos, H. 1984b. The status and distribution of important reptiles and amphibians in Trinidad and Tobago. New York, FAO United Nations. 19pp.
Boza, M.A. 1988. Costa Rica: Parques Nacionales. Editorial Heliconia Fundación Neotropica. San José, Costa Rica. 271pp.
Brongersma, L.D. 1940. Snakes from the Leeward Group. Venezuela and eastern Colombia. Pp 116-137. In P.W. Hummelinck, Ed. Studies on the Fauna of Curacao, Aruba, Bonaire, and the Venezuelan Islands. Vol. 2 Utrecht, N.V. Drukkerij P. Den Boer.
Cochran, D.M. 1946. Notes on the herpetology of the Pearl Islands, Panama. Smithsonian Misc. Collect. 106(4):1-8.
de Rochefort, C. 1665. Histoire Naturelle et Morale des Ilses Antilles de Amerique. Rotterdam: Aenout Leers.
Dunn, E.R. 1945. The amphibians and reptiles of the Colombian Caribbean Islands San Andres and Providencia. Caldasia 3(4):269-271.
Dunn, E.R. and L.H. Saxe, Jr. 1950. Results of the Catherwood-Chaplin West Indies Expeditions, 1948. V. Amphibians and reptiles of San Andres and Providencia. Proc. Acad. Nat Sci. Philadelphia. 102:141-165.
Goulding, M., 1990. Amazon: The Flooded Forest. Sterling Publishing Co., Inc., New York. 208pp.
Henderson, R.W. and L.G. Hoevers. 1975. A checklist and key to the amphibians and reptiles of Belize, Central America. Milwaukee Publ. Mus. Contrib. Biol. Geol. 5:1-63.
Henderson, R.W., T.W.P. Micucci, G. Puorto and R.W. Bourgeois. 1995. Ecological correlates and patterns in the distribution of neotropical boines (Serpentes: Boidae): A preliminary assessment. Herpetol. Nat. Hist. 3(1):15-27.
Lazell, Jr., J.D. 1964. The Lesser Antillean representatives of Bothrops and Constrictor. Bull. Mus. Comp. Zool. 132(3):245-273.
Lee, J.C. 1996. The amphibians and reptiles of the Yucatan Peninsula. Cornell Univ. Press. 500 pp.
Medem, F. 1979. Los amfibios y reptiles de las Islas Gorgona y Gorgonilla. Pp. 189-218. In Prahl, F. Guhl and M. Grogl Eds. Gorgona, Bogotá, Univ. de los Andes. 179pp. Muller, P. 1969. Herpetologische Beobachtungen auf der Insel Marajo. DATZ 22(4):117-121.
Myers, Charles W. and S. Rand. 1969. Checklist of amphibians and reptiles of Barro Colorado Island, Panama, with comments on faunal change and sampling. Smithsonian Contrib. Zool. No. 10, 11p.
Neill, W.T. and E.R. Allen. 1962. Reptiles of the Cambridge Expedition to British Honduras, 1959-1960. Herpetologica 18:79-91.
Peters, J.A. and B. Orejas-Miranda. 1970. Catalogue of the neotropical squamata: Part 1. Snakes. Bull. U.S. Natl. Mus. 291:1-347.
Reichling, S.B. 1991. The serpents of St. Lucia, Bothrops caribbae and Boa constrictor orophias. The Vivarium 3(3):7-9, 22.
Restrepo, J.H. 1986. Las serpientes. Pp 148-161. In Prahl, H. von and M. Alberico Eds. Isla Gorgona. Banco Popular. Bogotá, Colombia. 252 pp.
Roze, J.A. 1966. La taxonomia y zoogeografia de los ofidios en Venezuela. Univ. Central Venezuela. Caracas. Edit Bibloiteca 28. 382 pp.
Schmidt, K.P. 1941. The amphibians and reptiles of British Honduras. Field Mus. Nat. Hist. Publ. Zool. Ser. 22:475-510.
Slevin, J.R. 1926. Expedition to the Revillagigedo Islands, Mexico, in 1925, III. Notes on a collection of reptiles and amphibians from Tres Marias and Revillagigedo Islands, and west coast of Mexico, with description of a new species of Tantilla. Proc. Acad. Sci. Ser. 4, 15:195-207.
Smith, H.M. 1943. Summary of the collections of snakes and crocodilians made in Mexico under the Walter Rathbone Bacon Traveling Scholarship. Proc. U.S. Nat. Mus. 93:393-504.
Vandeventer, T.L., 1992. In search of the Tete ?chein: Observations on the natural history of Boa constrictor nebulosus. 16th Inter. Herpetol. Symp. on Cap. Prop. and Husb. Uned. Proc.
Villa, J. 1972. Snakes of the Corn Islands. Caribbean Nicaragua. Brenesia 1:14-18.
West, R.C. 1964. Surface configuration and associated geology of Middle America. In Handbook of Middle American Indians. R. Wauchope Gen Ed. 570 pp.
Wilson, L.D. and G. Cruz. 1993. The herpetofauna of the Cayos Cochinos, Honduras. Herpetol. Nat. Hist. 1(1):13-23.
Wilson, L.D. and D.E. Hahn. 1973. The herpetofauna of the Islas de la Bahía, Honduras. Bull. Florida State Mus. Biol. Sci. 17:93-150.
Wilson, L.D. and J. Meyer. 1985. The snakes of Honduras. 2nd ed. Milwaukee Publ. Mus. 150 pp.
Zweifel, R.G. 1980. Results of the Puritan-American Museum of Natural History expedition to western Mexico. 9. Herpetology of the Tres Marias Islands. Bull. American Mus. Nat. Hist. 119:77-128.