The smaller boas and pythons concerned herein are taxonomically placed within the Bolyeriidae, Erycinae, Tropidophiidae and Loxocemidae.
To the average person, the word "python" or "boa" evokes an image of a snake of massive proportions. Even to seasoned herpetologists, snakes such as reticulated pythons (Python reticulatus), Burmese pythons (Python molurus), or boa constrictors (Boa constrictor) might spring to mind. Yet, of the 92 or so species of snakes (comprising five separate families) that are commonly referred to as pythons or boas, only a handful reach lengths of 12 feet or more.
Outside the realm of the "big guys," however, exist a number of other boids that tend to be small, terrestrial or burrowing snakes. These include some that are well known to herpetoculturists, like the popular rosy and rubber boas of the American West and the Old World sand boas. Others, such as the eyelash boas, are rarely seen lowland-dwelling, fish-eaters. Still others, like the Round Island boa (Bolyeria multocarinata), have not been encountered in the in the wild since 1975 and are thought to be extinct.
The smaller boas and pythons concerned herein are taxonomically placed within the Bolyeriidae, Erycinae, Tropidophiidae and Loxocemidae. The Bolyeriidae consists of two insular species confined to the Mauritius Islands in the western Indian Ocean. In a recent revision that was accepted by many herpetologists (see Greene, 1997; McDiarmid et al. 1999), the North American rubber and rosy boas and the West African burrowing python are now found in the genus Charina (Kluge, 1993). These, along with the sand boas (genus Eryx and Gongylophis) are collectively placed within the group of snakes known as the Erycinae. The dwarf boas of the family Tropidophiidae consist of the four neotropical genera, including Exiliboa, Tropidophis, Trachyboa, and Ungaliophis. And, finally, the New World burrowing python (Loxocemus bicolor) is the lone member of the family Loxocemidae.
Bolyeriidae
The Bolyeriidae is represented by two species that are now confined to a small volcanic outcropping in the Indian Ocean by the name of Round Island. Seriously threatened by the introduction of goats and rabbits onto the island (and thus the loss of native vegetation), one species, Bolyeria multocarinata, is believed to have gone extinct in the 1970s. The other species, the Round Island or keel-scaled boa (Casarea dussumieri), is threatened but has fortunately increased its population size since the removal of rabbits from the island (Garbutt, 1992). Several other islands have both historical and fossil records of these small boids, but rats are believed responsible for their demise (Tonge, 1990).
Between 1977 and 1982, the Jersey Wildlife Preservation Trust received a group of 11 Casarea dussumieri on loan by the Mauritian government in efforts to establish a captive-breeding program. Captive animals were set up on a dry peat substrate and maintained individually until they were thoroughly established. Although feeding predominately on the Round Island skink (Leiolopisma telfairii) and the Round Island gecko (Phelsuma guentheri) in the wild, it was found that Casarea could be persuaded to accept mice in captivity. Clutch sizes have ranged from three to 11 eggs, with newly hatched neonates averaging about 7 inches in length (Bloxam, 1984; Bloxam and Tonge, 1988). Several zoological institutions now participate in the management of the captive population.
Erycinae
With shortened to club-like tails, the erycines form an interesting group of Old and New World snakes which share a number of anatomical, osteological and behavioral characteristics in common. In 1993, Arnold Kluge of the University of Michigan placed both Calabaria and Lichanura within the Charina genus, unpopular within herpetocultural circles but in reality accepted by a number of professional herpetologists (see Greene, 1997; McDiarmid et al. 1999). For sake of clarity, though, the former genus names of Calabaria and Lichanura will be used alongside Charina in this article. As a group, the Erycinae includes the rosy (Charina [Lichanura] trivirgata) and rubber boas (Charina bottae) of western North America, the West African burrowing python (Charina [Calabaria] reinhardtii) and the Old World sand boas of the Eryx and Gongylophis genera.
Small and heavy-bodied, the rubber boa (Charina bottae) has a remarkable tolerance for cold climates. Frequenting moist habitat, it favors temperate coniferous forest and grassland ranging from British Columbia, Canada into the Pacific Northwest, through to Southern California. Recorded from near sea level upward into montane habitat (to 9,000 feet), these snakes have actually been observed to be active when there is snow on the ground (Wright and Wright, 1957).
Involved in Native American folklore, rubber boa tails were worn as a charm by hunters among the Thompson Indian group of British Columbia in the belief that it would protect them from grizzly bears (Shaw and Campbell, 1974). Infrequently kept in captivity, keepers should maintain rubber boas on a substrate that will allow for their burrowing tendencies. Specimens will do well at temperatures ranging from the low 70s to the low 80s Fahrenheit, with the allowance for a warm area for thermoregulation. Rubber boas are primarily rodent and lizard feeders in the wild and will usually accept mice in captivity. This species will reproduce at 2 to 3 years of age and brood size averages four to five per litter.
The rosy boa (Charina [Lichanura] trivirgata) is the boa of the American Southwest. Distributed from Southern California and Arizona southward through Baja California and Sonora, Mexico, this 2- to 3-foot-long snake is found in several forms (subspecies).
The taxonomy of the rosy boa on the subspecific level is confusing, and various forms are known by different names from several authors. The rosy boa is a terrestrial snake characteristic of rocky and boulder-strewn areas in the desert. Primarily feeding on rodents and small birds in the wild, rosy boas are also known to occasionally feed on snakes in captivity. Specimens do well on substrates ranging from sand or aspen shavings to plain newspaper and should have access to a warm spot for proper thermoregulation. An extremely easy snake to reproduce in captivity, litters range from one to 12 in size.
The Calabar burrowing python (Charina [Calabaria] reinhardtii) or "boa," as perhaps it should now be called, is a commonly encountered species in tropical rain forest and cultivated areas in western Africa. Known for its habit of rolling into a defensive ball, this inoffensive burrowing species is believed to cause young women to become pregnant, according to a Cameroon myth (Lawson, 1993).
Captive specimens should be kept on a lightly moistened burrowing medium of cypress mulch, peat moss or potting soil that should be at least several inches or more in depth. Hide boxes can be provided, though this shy, retiring species will more than likely utilize the substrate for hiding places. Recently imported burrowing pythons may be somewhat reluctant to feed at first, but most will eventually begin taking rat pinkies and mouse fuzzies. Captive reproduction has occurred on a number of occasions with clutch size ranging from one to five eggs.
The sand boas of the Eryx and Gongylophis genera form a unique group of small, highly specialized burrowing snakes that are distributed in Africa, Europe and Asia. With a distinct preference for arid regions, 11 species are found in semi-desert to clay steppe areas, but have even been recorded from sandy beaches (Bellairs and Shute, 1954).
Predominately rodent feeders in captivity, other reported prey items include such things as birds, lizards, frogs, insects, carrion, snake eggs and even slugs. Efficient constrictors, sand boas (like many other erycines) will often take multiple prey items simultaneously. Captives do well on both wood shaving and dry sand substrates, which should be kept deep enough to allow for burrowing. A warm basking area will allow for proper thermoregulation. Commonly reproduced in captivity, these snakes reach maturity within two to three years, and litters range from one to over 20 young per brood.
Tropidophiidae
On the afternoon of August 10, 1967, the late Charles M. Bogert and J. Stuart Rowley were collecting near the headwaters of the Rio Valle Nacional on the northern slopes of the Sierra da Juarez in Oaxaca, Mexico. At an elevation of approximately 2,300 meters, a few species of reptiles, including garter snakes (Thamnophis sp.), fence lizards (Sceloporus sp.) and alligator lizards (Barisia sp.) were known to occur in the cool, moist cloud forest habitat. What the collectors discovered foraging underneath a large rock, however, proved puzzling. A small black snake, later described as Exiliboa placata, turned out to be not only a new species, but a new genus as well (Bogert, 1968).
More than 30 years have passed since the original description of Exiliboa placata, a discovery that immediately redefined the boundaries within the family Tropidophiidae. Entirely New World in origin, three other genera are found within the dwarf boa complex, including the largely insular Tropidophis genus, the arboreal to fossorial snakes of the Ungaliophis genus, and the lowland fish-eating Trachyboa. Of the few Oaxacan dwarf boas (Exiliboa placata) that have reached North American institutions, none have been maintained for any length of time in captivity. Captives have fed on frogs of the Eleutherodactylus genus and both salamander and amphibian eggs were taken from the digestive tracts of recently collected animals. Litter size ranges from eight to 16 young per brood (Campbell and Camarillo, 1992).
Perhaps the most well-known group of dwarf boas are the wood snakes of the genus Tropidophis. Distributed through the Caribbean to South America, 18 species of wood snakes are currently recognized, the newest additions (T. celiae and T.spiritus) being described from Cuba as recently as 1999 (Hedges et al, 1999; Hedges and Garrido, 1999). Although the Cuban species T. melanurus can exceed 3 feet in length, most wood snakes are relatively small (12 to 24 inches), secretive and predominately terrestrial in habits. Ronald Crombie (pers. comm.), however, noted that the Brazilian species (T. paucisquamus) is perhaps strongly arboreal and, in fact, found a number of specimens 1 to 3 meters high in the branches of trees around streams or ponds. Many wood snakes have a peculiar defensive habit of expelling blood from the mouth, nares and eyes when disturbed.
Wood snakes are easily maintained on a cypress mulch substrate, with the addition of a few pieces of bark for cover. Keepers should provide a moist area as a shedding cycle or ecdysis nears. Feeding mainly on lizards and amphibians in the wild, most specimens can be switched over to rodents in captivity. Occasionally bred in captivity, litters range from two to 10 young per brood. Short, stout and roughly scaled, the eyelash boas (genus Trachyboa) are distributed in tropical lowland habitat from Panama to Ecuador. Two species are recognized: Trachyboa boulengeri occurs in the Choco forests of Panama, Colombia and Ecuador; Trachyboa gularis is found in the dryer coastal areas of Ecuador. Both species are largely terrestrial, sedentary snakes in nature and have peculiar defensive strategies of balling into flattened circles as well as forming rigid pencil-like postures when disturbed.
Eyelash boas are easy to maintain on substrates ranging from newsprint to cypress mulch, with the addition of a hiding place. Successful maintenance requires cool ambient temperatures. Arnett et al. (1992) noticed that Trachyboa boulengeri went off feed at temperatures above 70 degrees Fahrenheit, while T. gularis does well at temperatures from about the mid-60s to near 80 degrees Fahrenheit (Arnett et al. 1992; pers. obs.). Although both species take frogs and toads, they will actually thrive on live fish in captivity. Litters average about five to six young per brood.
Up until the 1960s, only a handful of snakes of the genus Ungaliophis were known to exist in museum collections. Relatively small (18 to 24 inches) and slender, these snakes are collectively referred to as the bromeliad, banana or neotropical dwarf boas. Ranging from southern Mexico to northern Colombia, they are distributed in tropical low to moderate elevations. Both species are arboreal in habits and have been collected under bark, in epiphytic growth and in the vicinity of recently fallen trees.
Easily maintained in captivity, keepers should provide them with branches and pieces of bark to accommodate their arboreal and secretive habits. Live plants such as pothos, Philodendron or bromeliads are aesthetically pleasing, but more important, offer moist microhabitats for these cryptic snakes. Captive specimens can be fed small mice or lizards (Anolis sp.). Occasionally bred in captivity, males have an interesting habit of biting the females' tails during reproductive encounters (Burger, 1995). Brood size averages about three to four offspring per litter.
Loxocemus Bicolor
Occasionally referred to as the New World burrowing python, Loxocemus bicolor has long been an enigma in taxonomic circles. It is generally now considered to have arisen from an independent lineage and has been afforded its own family, the Loxocemidae. Not actually a true python, this interesting "sunbeam-like" snake is distributed from low to moderate elevations along the Pacific coast from Mexico through Central America. Inhabiting tropical dry forest formations, Loxocemus bicolor has been collected in leaf litter, rockpiles, under logs and along roads at night (Nelson and Meyer, 1967).
Not especially common in captivity, Loxocemus bicolor is a secretive snake that can be maintained on a thick substrate of cypress mulch where it will usually remain hidden from view. Males should not be kept together due to their propensity to fight. While rodents, lizards, and eggs are preyed upon in the wild, captives will usually accept mice and small rats. Considered a fall to winter breeder, this species has reproduced on several occasions in both North American and Russian collections. Loxocemus averages fewer than six eggs per clutch.
The author wishes to express sincere appreciation to Ronald I. Crombie of the Smithsonian Institution for sharing correspondence regarding the southeastern Brazilian dwarf boa (Tropidophis paucisquamis).
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