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General Information on Boa Constrictors

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General Information on Boa Constrictors

    BOA CONSTRICTORS (BOA CONSTRICTOR)

    SIAR ANTHRANIR REPTILES

    CHARLES R. SMITH

    AUSTIN, TX

    EMAIL: CRinAustin@att.net

    ?1999 Siar Anthranir Reptiles

    TABLE OF CONTENTS

    GENERAL BACKGROUND INFORMATION ............................................................................................ 1

    Systematics ........................................................................................................................................... 1

    Color and Pattern Variation ................................................................................................................ 1

    Natural History .................................................................................................................................... 4

    Use by Man ........................................................................................................................................... 5

    HERPETOCULTURE .................................................................................................................................... 5

    Temperament and Handling ................................................................................................................ 5

    Housing ................................................................................................................................................. 6

    Food and Water.................................................................................................................................... 7

    Growth .................................................................................................................................................. 8

    Reproduction ........................................................................................................................................ 9

    Health ................................................................................................................................................. 13

    Colds ........................................................................................................................................ 13

    Pneumonia ................................................................................................................................ 13

    Mouth Rot (Stomatitis) ............................................................................................................. 13

    Starvation (Inanition) ................................................................................................................ 14

    Inclusion Body Disease ............................................................................................................ 14

    Amoebiasis ............................................................................................................................... 14

    Cryptosporidium spp. ............................................................................................................... 14

    Cestodes, Nematodes, Trematodes, and Lingulatids .................................................................. 14

    Mites, Ticks, and Lice .............................................................................................................. 15

    Scale Infections (Blister Disease orVesicular Dermatitis) ......................................................... 15

    Problems with Shedding (Dysecdysis) ...................................................................................... 15

    REFERENCES .............................................................................................................................................. 16

    TABLES AND FIGURES

    Table 1. Distribution and Dorsal Pattern of Subspecies of Boa Constrictor. .............................................. 2 Table 2. Meristics of Subspecies of Boa Constrictor. .................................................................................... 3

    Figure 1. Range Map of Boa Constrictor Subspecies and Other New World Boids. ..................................... 3

    Table 3. Feeding Schedule. ............................................................................................................................ 7

    Figure 2. Weight-Length Relationship of Boa Constrictors in Colony. ........................................................ 8

    Figure 3. Growth in Length through Time. .................................................................................................... 9

    Figure 4. Growth in Weight through Time. .................................................................................................... 9

    Table 4. Sexual Dimorphism in Boa Constrictors. ....................................................................................... 9

    4.1. Literature Records of Caudal Plate Numbers in Males and Females. .......................................... 9

    4.2. Caudal Plate Numbers of Males and Females in the Colony. .................................................... 10

    4.3. Tail Length as a Percentage of Total Length for Males and Females in the Colony. ................. 10 Figure 5. Caudal Plate Numbers for Males and Females in the Colony. .................................................... 10

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Figure 6. Tail Length as a Proportion of Total Length for Males and Females in the Colony. ................. 10

    Figure 7. Period of Gestation from Time of Ovulation to Parturition for Six Females in the Colony. ...... 11

    Figure 8. Numbers of Live Births and Other Eggs (Unfertilized Ova or Stillbirths) Produced in the

    Colony. ........................................................................................................................................... 12

    PHOTOGRAPHS

    Photo 1. Boa constrictor imperator from coastal Tamaulipas, Mexico. ......................................................... 4 Photo 2. Two-year-old Boa constrictor constrictor born in captivity. ............................................................ 4 Photo 3. Fatty tumors. .................................................................................................................................... 6

    Photo 4. Midbody swelling in an ovulating boa constrictor. ....................................................................... 11

    Photo 5. Copulation in boa constrictors. ...................................................................................................... 11

    Photo 6. Late-term pregnancy in a thermoregulating boa constrictor. ...................................................... 11 Photo 7. 40 baby B.c. constrictor................................................................................................................... 11 Photo 8. Identical twin neonates. .................................................................................................................. 12

    Photo 9. Operation to remove retained eggs and uterine horns/oviducts ................................................... 12 Photo 10. Uterine horns with retained eggs. Oviducal torsion preventing passage of the ova.................. 13

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General Background Information

Systematics

    The boa constrictor (Boa constrictor) is a heavy-bodied lowland tropical snake ranging from northern Mexico through Central America to northern Argentina. Forcart (1951) treats the Genus Constrictor as a

    synonym of Boa with the single species constrictor. Surprisingly, the boa constrictor is closely related to three species of Malagasy boas. This biogeographic distribution of reptiles in both tropical America and Madagascar also occurs in iguanine lizards and sideneck turtles. The relationship is so close that Kluge (1991) recommends the transfer of the Malagasy boas to the Genus Boa. Because of various taxonomic conventions, he suggests the

    following names: Boa madagascarensis (Acrantophis madagascarensis) for the Madagascar ground boa, B.

    dumerili (Acrantophis dumerili) for Dumeril's boa, and B. manditra (Sanzinia madagascarensis) for the

    Madagascar tree boa.

    Systematists currently recognize nine or ten poorly differentiated constrictor subspecies (Forcart 1951,

    Stimson 1969, Peters and Orejas-Miranda 1970, Langhammer 1983, Price and Russo 1991), three of which occur only on individual islands in the Gulf of Panama and the Lesser Antilles (Tables 1 and 2, Figure 1). The Mexican or Central American boa constrictor, imperator (Daudin 1803), is the northernmost race found from

    Mexico to northwestern South America. The common boa constrictor, B. c. constrictor Linnaeus 1758, is the

    most frequently imported subspecies, lives throughout Amazonian South America, and includes several "redtail" forms. B. c. ortonii Cope 1877, the Peruvian "redtail" boa constrictor, represents a restricted coastal population with a pale coloration but otherwise very similar to imperator. Langhammer (1983) suggests that it

    might best be relegated to the synonymy of imperator. B. c. occidentalis (Philippi 1873), the Argentine or

    pampas boa constrictor, and amarali, the Amaral's (or Brazilian or Bolivian) boa constrictor, occur to the south of constrictor as fairly widespread races.

    The remaining subspecies have very restricted ranges and, in most cases, questionable statuses. B. c.

    orophias (Linnaeus 1758), the St. Lucia boa constrictor, and nebulosa Lazell 1964, the clouded or Dominica

    boa constrictor, occur on Caribbean islands. B. c. sabogae (Barbour 1906), the Taboga Island boa constrictor, is

    restricted to an island in the Gulf of Panama and represents a reddish color variant of the mainland imperator.

    Synonymy with imperator has been suggested, but supporting data have not yet been published (Langhammer 1983). B. c. melanogaster Langhammer 1983, the black-bellied boa constrictor, occurs in the upper Amazon rainforest of eastern Ecuador, but Price and Russo (1991) question the validity of this subspecies. B. c.

    longicauda Price and Russo 1991, the long-tailed boa constrictor, has a dark anerythristic coloration and proportionately long tail compared to other boa constrictor races. It has been reported only from Tumbes Province, Peru.

    Several previously described races have been synonymized with adjacent subspecies. Peters and Orejas-Miranda (1970) include B. c. mexicana (Jan 1863) from Mexico, B. c. isthmica Garman 1883 from Panama, and

    B. c. eques (Eydoux and Souleyet 1842) from Peru in the synonymy of imperator. Zweifel (1960) synonymized

    the Mexican race sigma, the Tres Marías Islands boa constrictor described from María Madre Island by Smith (1943), with the mainland form imperator, though others have questioned this action (Langhammer 1983).

    Lazell (1964) refers B. c. diviniloqua (Duméril and Bibron 1844) to orophias, the St. Lucia boa constrictor.

    Color Pattern and Meristic Variation

    Considerable variation in color pattern exists both within and between subspecies (Table 1), especially with regard to insular and coastal forms. Many Boa constrictor populations exhibit reddish coloration of the tail

    and elsewhere (see below), but the redtail forms have no taxonomic status. Some amazing varieties, including albino and patternless forms, recently have been reported for boa constrictors (Barker 1993, Anonymous 1997, de Vosjoli 1997, Barnes and Dillon 1998). The imperator race tends to have a darker and less distinct color

    pattern than does constrictor. Hogg Island boa constrictors from cays off the Atlantic coast of Honduras exhibit pale patterns that may respond to light levels. The Taboga Island boa constrictor (sabogae) in Panama has an

    indistinct reddish brown pattern and most likely represents an aberrant population of imperator (Langhammer

    1983). Some specimens of ortonii possess wine-red blotches on the rear of the body and are called Peruvian redtails. In the Lesser Antilles, the clouded boa constrictor (nebulosa) of Dominica has many narrow obscure

    dark blotches on a dusky ground color, while the St. Lucia boa constrictor (orophias) simply has a higher blotch

    count than does the mainland constrictor. Some individuals of constrictor from the Guianas and northeastern

    Brazil have wine-red blotches similar to those in some Peruvian boas and represent the other major group of redtails. The Argentine or pampas boa constrictor (occidentalis) is a small dark boa with the blotches forming a

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    reticulate pattern. The Brazilian or Amaral's boa constrictor (amarali) in southern Brazil and Bolivia is virtually identical to constrictor, but it has a few more dorsal spots that differ slightly in shape from those in

    constrictor.

    TABLE 1. DISTRIBUTION AND DORSAL PATTERN OF SUBSPECIES OF BOA CONSTRICTOR.

    Subspecific range and pattern information on Boa constrictor extracted from Boulenger (1893), Stull (1935), Lazell (1964), Stimson (1969), Peters and Orejas-Miranda (1970), Schwartz and Thomas (1975), do Amaral

    (1977), Vanzolini et al. (1980), Langhammer (1983), and Price and Russo (1991). SUBSPECIES GEOGRAPHIC RANGE PATTERN CHARACTERISTICS

    Middorsal head stripe without lateral projections, black amarali - Amaral's rings around dorsal spots separated from one another, (or Brazilian or S and SE Brazil, SE midbody spots with vertebral extensions directed toward Bolivian ) boa Bolivia. head and tail, more than 21 saddle-shaped dorsal spots constrictor on body.

    constrictor - Amazonian South America Middorsal head stripe without lateral projections, black

    common boa to Argentina and Paraguay; rings around dorsal spots separated from one another, 14

    constrictor Trinidad, Tobago. to 22 subrectangular dorsal spots on body.

    imperator - N Mexico to NW South Middorsal head stripe with lateral projections, black Mexican or Central America; W of Andes in rings around dorsal spots separated from one another, 22 American boa Colombia, Ecuador, and N to 30 dorsal spots on body. constrictor Peru.

    Middorsal head stripe with lateral projections, black longicauda - rings around dorsal spots separated from one another, 19 long-tailed boa Tumbes Province, Peru. to 21 dorsal spots on body, anerythristic dark coloration, constrictor tail length greater than 12% of total length in males.

    melanogaster - Black rings around dorsal spots separated from one black-bellied boa E Ecuador. another, 20 to 21 dorsal spots on body, venter black in

    constrictor adults.

    nebulosa - clouded Middorsal head stripe without lateral projections, 31 to or Dominica boa Dominica, Lesser Antilles. 35 obscure irregular transverse dorsal markings on

    constrictor clouded grey-brown ground of body.

    occidentalis -

    Argentine or NW Argentina and Middorsal head stripe without lateral projections, black

    pampas boa Paraguay. rings around dorsal spots in contact with one another.

    constrictor

    Middorsal head stripe without lateral projections, black orophias - St. Lucia St. Lucia, Lesser Antilles. rings around dorsal spots separated from one another, 27 boa constrictor to 31 saddle-shaped dorsal spots on body.

    ortonii - Peruvian NW coastal Peru. Dorsal pattern inconspicuous, color pale and sandy. boa constrictor

    sabogae - Taboga

    Island boa Taboga Island, Panama. Dorsal pattern inconspicuous, color dark reddish brown.

    constrictor

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TABLE 2. MERISTICS OF SUBSPECIES OF BOA CONSTRICTOR.

    Midbody Lori- Ventral Caudal Supra- Circum- Inter- Dorsal Subspecies Scale Labial References Plates Plates Labials Orbitals Oculars Spots Rows Rows

    amarali 226-237 43-52 71-79 20-24 15-20 1 >21 35,52,65

    constrictor 231-250 43-62 77-95 20-25 16-20 16-22 2-3 14-22 8,15,27,35,36,52,56,65 imperator 225-260 47-70 55-79 17-23 14-20 13-16 1-2 22-30 8,12,25,35,61,63,64,65,70,72 longicauda 223-247 50-67 60-76 19-21 54

    melanogaster 237-252 45-54 86-94 20-21 35

    nebulosa 258-273 59-69 19-21 31-35 35,36

    occidentalis 242-251 45 64-87 21-22 16-20 13-16 2-3 22-30 8,35,53

    orophias 258-288 55-69 65-75 14-19 16-18 1-2 25-31 8,35,36

    ortonii 246-252 46-59 57-72 19 19 1 15-19 11,35,54,58

    sabogae 241-247 49-70 65-67 ------ 2,35,65

    FIGURE 1. RANGE MAP OF BOA CONSTRICTOR SUBSPECIES AND OTHER NEW WORLD BOIDS (MODIFIED FROM SAVAGE 1966).

    Savage (1966) recognizes three groups of New World boid genera: Young Northern (Charina, Lichanura), Middle American (Boa, Loxocemus, Ungaliophis), and South American (Corallus, Epicrates, Eunectes, Trachyboa, Tropidophis, Xenoboa). The range of the ten boa constrictor races encompasses the distributions of

    all Middle and South American genera except for the Caribbean forms. Boa constrictors occur from northern

    Argentina to northern Mexico.

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    I started with one female imperator from the Gulf Coast of Tamaulipas Province, Mexico, and one male

    and one female constrictor. Hence, the young I obtain are either constrictor or constrictor-imperator

    intergrades. The constrictor's show the influence of imperator in some characters, so they probably were

    imported from Colombia or Venezuela. The female constrictor is quite dark, while the male has a light tan

    ground color washed with considerable pink. The imperator possesses an unusual dark red and black pattern

    that appears to be characteristic of the Gulf of Mexico coastal populations. Neill and Allen (1962) describe the situation for Belíze populations as follows:

    Elsewhere we mentioned the dark coloration of lowland boas, especially coastal ones, in British

    Honduras. We have since obtained 2 examples of a red phase from the mangrove swamps at

    Belíze. In these, all the darker elements of the pattern are dark red or cinnamon, and the

    background is pinkish. The specimens accord with the suggestion that reptiles from supratidal

    situations tend to be either unusually dark or reddish.

Photo 1. Boa constrictor imperator from coastal Tamaulipas, Mexico.

    Photo 2. Two-year-old Boa constrictor constrictor born in captivity.

Natural History

    Ranging from the pampas of western Argentina to both northern coasts of Mexico (Figure 1), the boa constrictor probably represents the commonest, widest ranging snake in the Western Hemisphere, if not the world. This heavy-bodied species primarily inhabits lowland tropical rainforest, but also occurs in arid pampas grasslands and scrub, mountainous tropical rainforest, coastal scrubs and marshes, thorn scrubs in the Yucatan, and second-growth forests on Caribbean islands and elsewhere in the range. The cryptic color pattern corresponds to a sit-and-wait style of predation and includes fine striping through the eye and its pupil to obscure the eye's outline. de Vosjoli (1998) observed a juvenile boa constrictor twitch its tail in an attempt to lure a lizard housed in an adjacent cage. Boa constrictors feed mostly on birds and mammals, but have been reported to take lizards also (Greene 1983). Body temperature of a free-ranging telemetered boa constrictor in Mexico averaged 26.4?C (79.5?F) with a range of 24 to 38.5?C (75.2 to 101.3?F) (McGinnis and Moore 1969), while another individual investigated in Panama maintained a body temperature from 24.4 to 29.4?C (75.9 to 84.9?F) over twelve days (Montgomery and Rand 1978). Basking temperatures of wild boa constrictors vary from 26 to 34?C (79 to 93?C) (Brattstrom 1965, Myres and Eells 1968).

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    Boa constrictors range from 40 to 55 cm (16 to 22 in.) at birth and can grow to one meter (39 in.) in the first year, one and a half (five feet) in the second, two (six and a half feet) in the third, and two and a half meters (over eight feet, females only) in the fourth year. Maturity typically does not occur until at least four years of age. Growth rate depends greatly upon the surrounding temperature and the amount of food given. Though literature reports of 4 to 5.5 m (13 to 18 ft.) exist (Greene 1983), average size attained in most populations and in captivity is considerably less. For the probable Colombians in this colony, females reach average maximum sizes of 2.4 m (94 in.) and 10.4 kg (23 lb.), while males average 1.9 m (75 in.) and 5 kb (11 lb.) (Figures 3 and 4). A mature imperator female from northern Mexico only reached 1.9 m (74 in.) and 5.4 kg (12 lb.). Growth virtually stops by the third year in males and the fifth year in females. The Growth section provides more

    detailed biometric data. Maximum size may vary geographically with smaller boa constrictors occurring in northern Mexico and Argentina, while larger ones are found in Amazonian South America. The length-weight relationship for colony animals estimates that an 18-foot boa would weigh better than 300 lbs. The only other large boids with such heavyset bodies are the green anaconda and blood python. Maximum lifespan reported in the literature is at least forty years (Bowler 1977, Huff 1980). The oldest individuals in this colony have reached the low twenties.

    Literature information on boa constrictor reproduction is spotty and largely anecdotal. The mating period extends from December to March in Trinidad (Mole and Ulrich 1894, Mole 1924). Females ovulate large 2-3 inch yolked eggs. "Placentation" occurs in boa constrictors and represents a process by which oxygen, carbon dioxide, water, and perhaps other small molecules are exchanged between the maternal and neonatal blood streams. The energy used for development probably comes exclusively from the yolk sac. Gestation appears to last from five to six months in Colombia (Otero de la Espriella 1978). Litters have been obtained during August in Belíze (N=2, Neill 1962) and from November to February in Peru (N=4, Dixon and Soini 1986). The reproductive cycle may vary geographically. Six Mexican and Central American boa constrictor litters averaged 17.8 young with a range of 10 to 36, while six South American (Trinidad and Peru) litters had a mean of 30.3 and range from 6 to 63 (Fitch 1985). Otero de la Espriella (1978) gives a range of 40 to 80 young per litter in Colombia. The higher mean litter size in South America may reflect variation in size of the reported females. Hoover (1936) described a Central American female that gave birth to two live young and 13 leathery "eggs," two of which produced viable young. Boa constrictors may often produce infertile eggs with solid yolks or eggs with partially or fully developed stillborn young. The membrane of such eggs usually becomes thickened, translucent, and tough compared to the clear, delicate membrane containing a viable neonate. Use by Man

    The boa constrictor today represents one of the most heavily exploited reptile species. Dodd (1986, 1987) reports on legal importation of snakes into the United States. From 1977 to 1983, over 113000 live boas were imported; this amounted to nearly half of all the imported snakes listed for protection by the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Live imports decreased 97 percent from 1979 to 1983 as more animals were used for production of ornamental leather. In 1983, 6572 whole boa constrictor skins, 1714 large leather pieces such as briefcases, and 165843 small pieces, mostly shoes, were brought into the United States. The only other snake species that supplies more skins and leather is the reticulated python (Python reticulatus). Though Otero de la Espriella (1978) describes a culture operation for

    boa constrictors in Colombia, the vast majority of imports must arise from natural populations whose status is completely unknown.

HERPETOCULTURE

Temperament and Handling

    Boa constrictors tend to be very easy-going snakes. Disposition varies among individuals, between races (imperator's have a nasty reputation), with age, and in response to handling. If a boa constrictor is in a bad mood, the head and neck usually are thrown back in an S-curve and the animal may hiss long and very loudly. It is not hard to tell when a boa constrictor wishes to be left alone. After biting, the snake may let go immediately or clamp down with its jaws and coil tightly around anything available, including arms and legs. Holding the animal's head under a running tap may convince it to release its hold. Otherwise, a flat card or blade must be forced between one of the jaws and whatever it is biting. At this point, the other jaw can be unhooked.

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    Boa constrictors seem to become more familiar with people as a result of handling and so are less likely to bite if taken out of their cages every now and then. All of the young which I have raised can be handled freely. My boa constrictors have bitten me in two situations. One is during or just after feeding, and the second is during their "adolescence." Tongs for holding the food item help greatly in avoiding mistakes on the snake's part during feeding. Handling the snake after feeding is not recommended, since it is prone to bite and also may regurgitate. Putting your hand in front of a boa constrictor after you have been holding food is asking for trouble. Boa constrictors feed very reliably and initially seize prey on the basis of smell rather than vision. Thereafter, their sense of smell seems to be swamped and they may bite anything that moves suddenly in their vicinity. Further details on feeding are given below.

    I have noticed that one to one and a half meter (three to five feet) boa constrictors sometimes become nervous when handled. They also may bite lightly if touched suddenly on the body. These bites may startle you, but are not serious and do not hurt much at all (though you will bleed a bit). They can be avoided by handling the snake in a gentle manner without any sudden moves on your part. In general, boa constrictors should be supported fully and allowed to wrap around your hands and arms. They fear situations where they might fall. Holding an animal around the body at an arm's length definitely tends to make it feel insecure. In any event, this proclivity to biting seems to be part of an "adolescent" stage that the snake will grow out of. Bites of boa constrictors less than one and a half meters (five feet) generally have the severity of a cat scratch, but those from larger boas can require a few stitches if the skin tears when the person or snake pull back. If you feel apprehensive about the size and/or temperament of your snake, you should sell it and get a smaller and/or nicer one.

    Housing (Vivarium Research Group, Inc. 1998)

    Cages or aquaria made with wood, plastic, fiberglass, glass, etc. serve well for boa constrictors. No

    screen should be used for the top or anywhere else in the cage. Using screen in the cage is a common mistake.

    Some individuals will rub their noses on screen or other rough surfaces until they develop abrasions and infections (see mouth rot under Health), will not feed, and starve to death. Even if the snake recovers, the

    disfigurement will be permanent since the scales will not grow back. Sometimes the abrasions can even cause fatty tumors (see Photo 3 below) to develop. Snakes can be remarkably quick in rubbing their snouts raw, say several hours. I recommend pegboard for tops as it is readily available, cheap, and easy to work with. Since snakes require very little air circulation, cages can be closed off to make them easier to heat (which is a great deal more important for tropical snakes like boa constrictors). Cages should be large enough for the snake to stretch out in, if possible. Large animals should be kept in cages with a long dimension at least two thirds of the snake's length. Though boa constrictors like to climb, floor area is more important than height in a cage, particularly for large individuals.

    Much controversy exists over what to put in the cage

    besides the snake. The following is my personal preference. In

    general, I like to keep the interior of the cage as simple as

    possible, since it facilitates cleaning, changing water, and taking

    the snake out of the cage. Naturalistic tropical vivaria can be

    used for small boa constrictors (Vivarium Research Group, Inc.

    1998). Careful consideration should be given to rocks, branches,

    and such that are placed in the cage as the inhabitant's safety

    depends upon it. Boa constrictors are not bright nor are they

    adapted to living in cages. As a consequence, they potentially

    can get caught in rock holes or branch forks that can cause injury

    or death. Movement through tight spots also can scar the boa

    when done during the shedding period. Photo 3. Fatty tumor that probably resulted from Many people use newspaper, cedar shavings, Astro-Turf, abrasions caused by rubbing the snout on screen.

    dirt, sand, etc. in the bottom of the cage: I recommend pine These tumors typically float more or less freely under

    shavings. Some boa constrictors, particularly small ones, like to the skin and can be removed easily. However, they

    burrow, and pine shavings are the only substrate other than cedar usually are not dangerous from a health standpoint

    unless they begin to invade the eye or nose areas and shavings that allow them to do this. A depth double the diameter

    interfere with shedding, breathing, or feeding. Of of the snake suffices for burrowing. Aside from being more

    course, most people do not find them very expensive than pine shavings, cedar shavings are too aromatic

    aesthetically pleasing. and some people assert that they are detrimental to the health of

    snakes. Pine shavings are absorbent and dry out quickly. A damp cage leads to scale mite population

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explosions and blister disease (see under Health, Wright 1995). Feces and surrounding shavings can be easily

    removed and replaced with fresh bedding. Spot cleaning should be carried out at least once a week. All bedding should be replaced and the cage cleaned thoroughly at least twice annually. The one disadvantage of shavings is that snakes can accidentally ingest them while feeding; see Food and Water for further discussion

    of this problem. Many ranch and feed stores carry bale-size packages of pine shavings for around ten dollars.

    Placing a layer of plastic sheeting in the bottom of a wooden cage will prevent water and other fluids from wetting the lumber and causing irremovable odors. The plastic must be firmly attached to the cage with no holes or free edges; otherwise, a boa constrictor may be depended upon to get under it. Boric acid power can be sprinkled beneath the plastic to control mites, ants, and other arthropod pests.

    Since boa constrictors are tropical poikilotherms, their cages must be heated. Otherwise, they develop colds and pneumonia, have trouble with digesting food, may regurgitate after eating, and become more susceptible to many diseases and pests, in particular amoebiasis, blister disease, and scale mite infestations (see under Health). Individuals will form aggregations in captivity, evidently in order to retain heat (Myres and Eells 1968). Particularly while digesting food, boas attempt to maintain a temperature from 31 to 32?C (88 to 90?F) (Regal 1966, Myres and Eells 1968). Wild caught boa constrictors should be maintained above 27?C (81?F), but my captive-born animals do well at temperatures as low as 24?C (75?F). Some kind of localized heat source should also be present, so the snake can achieve a temperature appropriate for digestion. If the room cannot be maintained at a temperature higher than 24?C (75?F), supplemental heat must be provided for the cage. Hot rocks are made of plaster with an embedded electric heating element and work well in a small cage if they can be obtained. Heating pads that are placed in the bottom of the cage can get wet and sometimes do not provide sufficient heat. Subfloor heating with light bulbs, heater tape or ribbon, or heating pads may work in some situations. An incandescent light or space heater near the cage are also viable solutions. Incandescent lights and other filament heaters can be wired to a transformer or light dimmer to control their heat output (Logan 1972). Care must be taken to avoid cracking glass or overheating the cage with the heat source. An aquarium heater or incandescent reflector may be used inside the cage, but it should be suitably isolated so the boa cannot touch it and burn itself. Light reflectors used within a cage should be set up so that no hot areas, wires, or sharp edges are exposed. Whatever heating option is selected, the temperature should be checked every few days to confirm that an appropriate temperature range is being maintained. Boa constrictors quickly develop colds and their susceptibility to other diseases also increases at low temperatures.

    Boa constrictors also require high relative humidity, preferably around 70 to 80%. This can be a real problem in the winter when heating the cage drops the humidity. Boas often have problems with shedding and may develop blister disease if the humidity is too low (see under Health). The most direct way to raise the

    humidity is to spray the boa and its cage every day or two. Care must be taken so the cage does not become excessively damp, as this condition will encourage scale mite infestations and blister disease. The presence of plants in the cage or use of a humidifier may also help.

    Food and Water

    One advantage of a boa constrictor as a pet is that it can go without food and water for weeks, thus freeing its owner for fairly extended trips. The concomitant disadvantage is that snakes will not beg for food as a cat or dog will, so many owners neglect the snake's feeding. In combination with their elongated morphology and the difficulty of recognizing that the animal is indeed becoming thin, this results in many captive snakes getting so weak that they can no longer feed. For these and other reasons, starvation is probably the most common cause of death in captive snakes (see under Health).

    Water should be present in the cage at least a few days out of the week. Boas like very much to soak in water on occasion, so the container should be large enough to hold snake and water without overflow. I keep water containers a third to half full. Large boas will tip over containers, unless they are heavy or are fastened in place. Water should be changed once or twice a week or whenever feces are deposited in it.

    Considerable latitude exists in food item size, amount of food per feeding, and frequency of feeding for snakes. Table 3 provides a rough guide for boa constrictors of different sizes. Overall amount of food eaten can vary easily from one half to twice as much as indicated in the table. Amount of food given will depend upon temperature and how high a growth rate is desired. Boa constrictors typically eat much less in winter than in summer.

?1999 Siar Anthranir Reptiles, 2309 Aldford Drive, Austin, TX 78745-4817, 512-462-3845

    8

TABLE 3. FEEDING SCHEDULE.

    LENGTH OF BOA Size and Type of Food Item Frequency of Feeding

    40-60 cm (16-24 in) baby to 3-week-old rats, mice 1 mouse per week

    0.6-1 m (2-3.3 ft) 3-week-old rats, mice 2-4 mice per week

    1-1.5 m (3.3-4.9 ft) half-grown rats, chicks 2 rats per week

    1.5-2 m (4.9-6.6 ft) rats, 1-month-old chickens 2 rats per week

    2-2.5 m (6.6-8.2 ft) rats, half-grown chickens 3-4 rats every two weeks

    2.5 m (8.2 ft) or more rats, chickens, rabbits 1 rabbit every 3 weeks

    Since boa constrictors feed very readily, some precautions are necessary, particularly if more than one animal are present. It is best to separate individuals to different containers, since they will attempt to seize anything that moves nearby when they are feeding and will also try to bite and constrict food that another snake already has. Heavy leather or rubber gloves that extend to the elbows are useful for handling large boa constrictors during feeding sessions. Boa constrictors feed so readily (and sloppily) that they sometimes engulf shavings, gravel, or other indigestible materials as well as the food. The snake may not be able to pass or regurgitate the foreign matter if it is large enough relative to the animal's size. These items can cause stomach ulcers that will kill the snake. The only sure way to avoid this problem is to feed the boa constrictor in a container having only the snake and food present. Any aquarium or plastic box will serve for small boa constrictors, but styrofoam boxes are the cheapest and most handleable alternative for large individuals.

    I recommend that only animals that already have been killed be given to boa constrictors. The most important reason for this is to prevent injury to the snake as a result of bites or scratches from the prey (Klingenberg 1998). Fry (1973), a veterinarian with extensive experience in reptile treatment, states that the most common traumatic lesions he deals with in snakes are rat bites in boa constrictors. Deaths rarely result from these bites, but permanent scars do since destruction of underlying soft tissues usually occurs. Killing the food animal beforehand is also more humane for the prey. Boa constrictors do not care whether the animal they are eating is alive or dead; they usually constrict it as if it were alive. Food items can be offered to a boa constrictor with tongs, by dropping the food into the snake's container, or by leaving the food in its cage. Shavings should be swept clear of the area in the cage where feeding takes place.

    If a boa constrictor refuses to eat, it is either too cold, already full, frightened, shedding, sick, or pregnant. Full, shedding, and pregnant boa constrictors should not be fed, cold boas should be kept warmer, frightened individuals may have to be left with their food overnight, and sick animals may require treatment or force-feeding (see under Health). Live food should never be left with a snake, unless the situation is kept under

    observation. Rats and mice can and will chew patches of skin off of a snake (Klingenberg 1998). Newborn boas have a substantial amount of yolk in the gut and spend their initial one to two weeks shedding. They should never be fed until after their natal shed, as doing so increases the risk of amoebiasis or other intestinal infections (see under Health).

    Since boa constrictors readily will accept dead animals, it is often convenient to obtain a large amount of food, kill and freeze it, and defrost suitable portions at the time of future feeding sessions. The food only needs to be at room temperature. The method of choice for euthanasia is carbon dioxide asphyxiation with cervical dislocation as an alternative. Freezing destroys parasites which might be passed on to the snake, but it may also be deleterious for vitamins. I doubt that this is true, since I have fed frozen animals to captive born boa constrictors for years, and the snakes exhibit normal growth and no overt vitamin deficiencies. For whatever reason, if a snake should refuse to eat, the food should always be discarded and never refrozen. The

    convenience of frozen food is another strong reason for giving boa constrictors dead animals to eat.

    Snake food may be obtained from a variety of places. Pet shops carry rats and mice. Ranch and feed stores often stock chicks, chickens, and rabbits. These animals also are advertised in the classified section of newspapers, though they may be intended as pets. I do not recommend succumbing to the temptation of obtaining animals such as puppies or rabbits that are being advertised only as pets. Laboratories sometimes get rid of large numbers of research animals and do not mind if they are used to feed snakes. Experimental animals from laboratories should be free of toxic substances and should not have been killed with ether, phencyclidine (Sernalyn), sodium pentobarbital (Nembutal), or other barbiturates. Using animals with questionable origins or edibility is not worth the risk. Wild animals should be avoided as a source of food. The need for snake food will not justify the expense and effort required to maintain a rodent colony, rabbit hutch, or chicken coop.

?1999 Siar Anthranir Reptiles, 2309 Aldford Drive, Austin, TX 78745-4817, 512-462-3845

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