BOA CONSTRICTORS (BOA CONSTRICTOR)
SIAR ANTHRANIR REPTILES
CHARLES R. SMITH
AUSTIN, TX
EMAIL: [email protected]
©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
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©1999 Siar Anthranir Reptiles, 2309 Aldford Drive, Austin, TX 78745-4817, 512-462-3845
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Caudal Plate Numbers for Males and Females in the Colony..........................................................10
Tail Length as a Proportion of Total Length for Males and Females in the Colony....................10
Period of Gestation from Time of Ovulation to Parturition for Six Females in the Colony........11
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 OrejasMiranda (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
amarali - Amaral's
(or Brazilian or
Bolivian ) boa
constrictor
S and SE Brazil, SE
Bolivia.
constrictor common boa
constrictor
imperator Mexican or Central
American boa
constrictor
Amazonian South America
to Argentina and Paraguay;
Trinidad, Tobago.
N Mexico to NW South
America; W of Andes in
Colombia, Ecuador, and N
Peru.
longicauda long-tailed boa
constrictor
melanogaster black-bellied boa
constrictor
nebulosa - clouded
or Dominica boa
constrictor
occidentalis Argentine or
pampas boa
constrictor
orophias - St. Lucia
boa constrictor
ortonii - Peruvian
boa constrictor
sabogae - Taboga
Island boa
constrictor
Tumbes Province, Peru.
E Ecuador.
Dominica, Lesser Antilles.
PATTERN CHARACTERISTICS
Middorsal head stripe without lateral projections, black
rings around dorsal spots separated from one another,
midbody spots with vertebral extensions directed toward
head and tail, more than 21 saddle-shaped dorsal spots on
body.
Middorsal head stripe without lateral projections, black
rings around dorsal spots separated from one another, 14
to 22 subrectangular dorsal spots on body.
Middorsal head stripe with lateral projections, black
rings around dorsal spots separated from one another, 22
to 30 dorsal spots on body.
Middorsal head stripe with lateral projections, black
rings around dorsal spots separated from one another, 19
to 21 dorsal spots on body, anerythristic dark coloration,
tail length greater than 12% of total length in males.
Black rings around dorsal spots separated from one
another, 20 to 21 dorsal spots on body, venter black in
adults.
Middorsal head stripe without lateral projections, 31 to
35 obscure irregular transverse dorsal markings on
clouded grey-brown ground of body.
NW Argentina and
Paraguay.
Middorsal head stripe without lateral projections, black
rings around dorsal spots in contact with one another.
St. Lucia, Lesser Antilles.
Middorsal head stripe without lateral projections, black
rings around dorsal spots separated from one another, 27
to 31 saddle-shaped dorsal spots on body.
NW coastal Peru.
Taboga Island, Panama.
Dorsal pattern inconspicuous, color pale and sandy.
Dorsal pattern inconspicuous, color dark reddish brown.
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TABLE 2.
Subspecies
amarali
constrictor
imperator
longicauda
melanogaste
r
nebulosa
occidentalis
orophias
ortonii
sabogae
MERISTICS OF SUBSPECIES OF BOA CONSTRICTOR.
Ventral
Plates
226-237
231-250
225-260
223-247
Cauda Midbody
LoriSupra- Circum- InterDorsal
l
Scale
Labial
References
Labials Orbitals Oculars
Spots
Plates Rows
Rows
43-52 71-79 20-24 15-20
1
>21
35,52,65
43-62 77-95 20-25 16-20 16-22
2-3 14-22
8,15,27,35,36,52,56,65
47-70 55-79 17-23 14-20 13-16
1-2 22-30 8,12,25,35,61,63,64,65,70,72
50-67 60-76
19-21
54
237-252 45-54
86-94
258-273
242-251 45
258-288 55-69
246-252 46-59
241-247 49-70
59-69
64-87
65-75
57-72
65-67
19-21
21-22
19
16-20
14-19
19
13-16
16-18
2-3
1-2
1
20-21
35
31-35
22-30
25-31
15-19
------
35,36
8,35,53
8,35,36
11,35,54,58
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.
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.
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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).
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
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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.
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
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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
Photo 3. Fatty tumor that probably resulted from
when done during the shedding period.
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
they begin to invade the eye or nose areas and
shavings that allow them to do this. A depth double the diameter unless
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
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
©1999 Siar Anthranir Reptiles, 2309 Aldford Drive, Austin, TX 78745-4817, 512-462-3845
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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.
TABLE 3.
FEEDING SCHEDULE.
LENGTH OF BOA
40-60 cm (16-24 in)
0.6-1 m (2-3.3 ft)
1-1.5 m (3.3-4.9 ft)
1.5-2 m (4.9-6.6 ft)
2-2.5 m (6.6-8.2 ft)
2.5 m (8.2 ft) or more
Size and Type of Food Item
baby to 3-week-old rats, mice
3-week-old rats, mice
half-grown rats, chicks
rats, 1-month-old chickens
rats, half-grown chickens
rats, chickens, rabbits
Frequency of Feeding
1 mouse per week
2-4 mice per week
2 rats per week
2 rats per week
3-4 rats every two weeks
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
©1999 Siar Anthranir Reptiles, 2309 Aldford Drive, Austin, TX 78745-4817, 512-462-3845
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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 Figure 2 Weight-Length Relationship of Boa
as a source of food. The need for snake food will not justify the
Constrictors in Colony
expense and effort required to maintain a rodent colony, rabbit ln [Weight (lb)] = 3.216 ln [Total Length (ft)] -0.5065
hutch, or chicken coop. However, if excess animals are ln [Weight (kg)] = 3.216 ln [Total Length (m)] - 3.537
available from one of these sources, they can be fed directly to
Weight (lb) = 0.0291 [Total Length (ft)] 3.216
a snake or frozen for later use.
Weight (kg) = 0.6026 [Total Length (m)] 3.216
Growth
Like most animals, boa constrictors have a cubic lengthweight relationship. Figure 2 is based on 360 observed weights
for snakes of different lengths in English units. Note that the
length and weight axes have logarithmic scales with linear
numeric labels. The equations were derived from data on 81
newborn and 15 older boas that ranged from 1.3 to 8.3 feet
(0.41 to 2.53 meters) in length and from 0.062 to 30.5 pounds
(0.028 to 13.84 kilograms) in weight. Multiple measurements
were taken on specimens that had grown substantially. Boas
were measured and weighed just prior to being fed.
Intermediate values can be determined by working through one
of the equations with any calculator having logarithm and
©1999 Siar Anthranir Reptiles, 2309 Aldford Drive, Austin, TX 78745-4817, 512-462-3845
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exponentiation functions. The natural logarithm formulae can be converted to base ten logarithm versions by
dividing the intercepts (-0.5065 or -3.537) by 2.3. Alternatively, the graph itself can be used to obtain a direct
estimate of weight for a particular length.
Since length "explains" 99 percent of the variation in weight, the relationship of length and weight is
very tight. The standard deviation of weight about the regression line amounts to about fifteen percent of the
weight predicted for a particular length, so the predicted weight plus or minus fifteen percent is an appropriate
range to maintain an animal's weight within. If a boa constrictor weighs less than two standard deviations
(thirty percent) below the weight calculated for its length, more feeding is required. Conversely, if the snake is
thirty percent or more heavier than its predicted weight, it is too obese. It should be noted that the weight data
for the above regression relationship were obtained for snakes just before feeding. A boa constrictor easily can
eat without harm up to a quarter of its body weight during a feeding session.
Figure 3 Growth in Length through Time.
Figure 4 Growth in Weight through Time.
Growth rates over time are a great deal messier than the length-weight relationship, since growth is
affected strongly by temperature, amount of food, sex of the boa constrictor, and probably the snake's area of
origin. Figures 3 and 4 show age isoclines based on seven females and four males whose age is either known or
can be estimated closely. The graphs show that the highest growth rates occur in the first three or four years of
life. After this, males appear to approach a maximum of about 75 inches (191 centimeters) and eleven pounds
(five kilograms). Females continue to grow to much larger sizes, and their data points indicate that a maximum
has not been reached by sixteen years of age. The data include a ten-year-old imperator female that measures
around six feet (two meters), weighs about nine pounds (four kilograms), and comes from Mexico, an area
where individuals may attain a smaller maximum size than do the constrictor's of South America.
Reproduction
Only a spotty and somewhat puzzling literature on reproduction in boa constrictors currently exists.
This is particularly surprising, since the species is an abundant, widely occurring snake that is often bred in
captivity. Males may be distinguished from females by their greater development of the "spurs,"
proportionately longer and fatter tails, and higher numbers of caudal plates (Table 4, Figures 5 and 6). Data on
the true sex were obtained by dissection, spur development, or breeding. "N" indicates neonates and "N*"
denotes constrictor-imperator intergrade neonates in the Figures. Newborns can be sexed by a technique used
for small boids. The technique involves catching the base of the tail between the thumb tip and index finger,
applying light pressure, and pulling the tail through the opening. In males, blood seems to get caught in the
hemipenes within the tail and the heads of the hemipenes can be palpated as they pass beneath the thumb tip.
Eversion of the hemipenes or probing is unnecessary in sexing boa constrictors. Both approaches also seem to
be inaccurate and potentially dangerous to the animal.
TABLE 4.
SEXUAL DIMORPHISM IN BOA CONSTRICTORS.
4.1.
Literature Records of Caudal Plate Numbers in Males and Females.
SUBSPECIES Males Females
constrictor
52 - 58 43 - 59
REFERENCES
15,27
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imperator
4.2.
48 - 61
61,63,64
Caudal Plate Numbers of Males and Females in the Colony.
Sex
Male
Female
4.3.
55 - 70
N
1
3
1
7
Mean Std. Dev.
Range
95% Confidence Interval
57.85
2.91
54 – 64
56.26 - 59.43
50.76
1.68
47 – 53
49.97 - 51.56
Tail Length as a Percentage of Total Length for Males and Females in the Colony.
Sex
N Mean Std. Dev.
Range
95% Confidence Interval
1
Male
11.55%
0.99%
9.76 - 13.68%
11.08 - 12.02%
7
Female 20 9.85%
0.63%
8.70 - 10.64%
9.58 - 10.13%
Figure 5 Caudal Plate Numbers for Males and Females in
the Colony.
Figure 6 Tail Length as a Proportion of Total Length for
Males and Females in the Colony.
Males do not show aggression toward one another, though they do have typical boid courtship behavior
involving topping and titillation of the females with their spurs. I keep pairs together throughout the year and
have never used male combat as a stimulus for mating. Colony males have never needed any encouragement to
court. Individuals in my colony reproduce under the natural diurnal cycle observed at about 30° Latitude N. I
have never purposely cooled my boa constrictors in the Fall, though their ambient temperature does drop from
the 28-34°C (82-93°F) range to 25-29°C (77 to 84°F). My animals breed annually from August to March with a
peak in January, nearly the same as the December to March mating period observed in Trinidad (Mole and
Ulrich 1894, Mole, 1924).
My impression is that females require relatively high body weight to assure ovulation. Reproductive
females accumulate huge abdominal fat bodies in the latter third of their bodies that can increase their normal
body weight 25 to 30%. Owners often mistake this fat accumulation for pregnancy and then assume the eggs
are "reabsorbed" when no birth occurs. Egg resorption is known only in certain mammals such as people.
Resorption can only take place in animals with small eggs, not in those groups with large yolks like reptiles and
birds. In boa constrictors, the presumed resorption only involves the slow utilization of the accumulated fat
bodies when ovulation fails to occur. Soon before or after a female mates, I have noticed a large localized
swelling three-fifths of the way down the body that lasts several days and marks the time immediately before
ovulation (see Photo 4 below). Since this happens only during a restricted time when the female is receptive, it
probably results from yolking and/or aggregation of the eggs prior to ovulation. This phenomenon also has
been noted in various other pythons, boas, and even some colubrids (Van Mierop and Bessett 1981, Barker and
Barker 1995). It probably provides the best indicator of the start of gestation. Egg yolking evidently occurs
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very quickly in birds and reptiles (chickens do it in nine days). Up to sixty 2 to 3 inch eggs may by yolked in
the boa constrictor's ovaries during this short period. The large fat bodies serve as the source for yolk
production.
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Figure 7 Period of Gestation from Time of Ovulation to
Partruition for Six Pregnancies in the Colony.
Photo 4. Midbody swelling in an ovulating boa
constrictor.
Photo 5. Copulation in boa constrictors.
Five females in my collection have given birth from 119 to 133 days after swelling of the midbody was
observed (Figure 7). Actual mating serves as a poor indicator of the beginning of pregnancy, since ovulation
may not happen simultaneously with mating or at all. Boa constrictors generally have their young four and a
half to six months after copulation, as has been reported from a commercial culture operation in Colombia
(Otero de la Espriella 1978) and for constrictor and imperator females that have mated in captivity in
Switzerland (Gensch 1969, Meyer-Holzapfel 1969). Mated females probably store sperm in the two uterine
horns. Females eat little or nothing during the last half of pregnancy. Pregnant females may remain tightly
coiled and thermoregulate at 27 to 32°C (80 to 90°F) (see Photo 6 below). Pregnant boa constrictors should be
maintained at 28 to 34°C (82 to 93°F). Extreme temperatures for even a short time during pregnancy can cause
deformities, primarily in the caudal region. Stillbirths and unfertilized or partially developed ova are not
uncommon, especially in initial, low temperature, or disturbed pregnancies.
Photo 6. Late-term pregnancy in a
thermoregulating boa constrictor.
Photo 7. 40 baby B.c. constrictor. What
you finally get 5 months after ovulation.
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Litters have been obtained during August in Belíze (Neill
1962), from November to February in Peru (Dixon and Soini
1986), and in June and July from imperator and constrictor
females that mated in captivity in Switzerland (Gensch 1969,
Meyer-Holzapfel 1969). Females in my colony have given birth
from February to August with a tendency toward May and June
(Figures 7 and 8). This only leaves September and October. The
reproductive cycle may vary both geographically and in response
to conditions of captivity. Live births in my colony have
numbered from four (in a constrictor-imperator cross) to forty- Photo 8. These twins have a common yolk sac and
nine with a mean of 31.3 per litter in fifteen pregnancies. Litters “placenta.” Developmental (probably mechanical)
from pregnancies with no complications have yielded from problems have prevented the usual transfer of yolk to
sixteen live births and one infertile egg to forty-nine live births the babies and have caused them to be significantly
and six stillbirths or infertile eggs. All of the litters in my colony smaller than the usual neonate. Though these two
could be fraternal twins with fused
have included at least a few eggs resulting from unfertilized ova conceivably
yolks, their high pattern concordance suggests that
or embryos that die during development. Examination of these they are identical. No obvious birth defects other
eggs has always revealed solid yolk or dead embryos or fetuses. than small size were present, but they were poor
One set of identical twins (see Photo 8 at right) has been feeders and died several months later. Other
identified in approximately 600 births. This pair had a common neonates with large yolks usually die as well.
yolk sac and extremely high pattern concordance. Live births
have comprised 60% (469 out of 776) of the total production of eggs in this colony (Figure 8).
Many problems can accompany pregnancy. Four Figure 8 Numbers of Live Births and Other Eggs
(Unfertilized Ova or Stillbirths) Produced in the
unsuccessful pregnancies, due either to genetic incompatibility
Colony.
or premature termination, and one in which twenty-eight
unfertilized eggs were produced, have also occurred in my
colony. Low temperature and other adverse prenatal conditions
contribute to congenital defects that include eye hydrocele,
scoliosis, prolapsed hemipenes, cleft palate, incomplete
umbilical closure, and spina bifida. Newborns normally
measure 46 to 56 cm (18 to 22 in.) in length, but may be
considerably smaller if the six inch umbilicus twists and
prevents transfer of yolk to the developing boa constrictor.
Structural twisting of an oviduct can prevent the passage of
young and eggs from both horns anterior to the block. Retained
eggs and young encyst, but can be removed surgically (see
Photo 9 below). Feeding a large meal to a pregnant female can
cause her to abort. An obviously pregnant female should be fed
lightly or not at all.
Photo 9. Surgical removal of uterine horns with retained ova.
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Photo 10. Uterine horns with retained eggs. Closeup of oviducal torsion preventing passage of the ova.
This boa survived for about a year after the operation.
Health
Very little therapeutic knowledge exists for diseases of reptiles and many medicines known to be
effective in treatment are not generally available, so the key to keeping a boa constrictor healthy is prevention.
A captive-born animal is advantageous in that one starts off with a clean slate, but they are nevertheless subject
to a wide range of ailments. The discussion below covers most commonly encountered problems. Hoff et al.
(1984) have presented a recent comprehensive review of reptilian diseases. Frye (1973) provides an excellent
practical guide to medical treatment of captive reptiles.
Colds
Since they are tropical animals, boa constrictors are highly susceptible to colds. Symptoms are mostly
as in people: lethargy, depressed appetite, labored open-mouth breathing, wheezing, congestion, and oral
discharge. Simply raising the temperature to the 27 to 30°C (81 to 86°F) range solves the problem. My two
wild caught constrictors, like myself, often developed sporadic colds during the winter. However, the
imperator from Mexico and all of the captive-born individuals never catch colds, even when kept around 24°C
(75°F). Place of origin and amount of acclimation apparently play a part in determining degree of susceptibility
to colds.
Pneumonia
Pneumonia is very serious and requires treatment with antibiotics. An infected animal exhibits
extremely severe cold symptoms and will be too weak to shed or eat. It should be isolated immediately and
given intramuscular injections of ampicillin trihydrate (Polyflex, 3-6 mg/kg), oxytetracycline HCl (Liquamycin,
6-10 mg/kg), or chloramphenicol (Chloromycetin, 10-15 mg/kg) once a day (Frye 1973). Murphy (1973) has
reported that tylosin is extremely effective for respiratory problems in a wide variety of reptiles. It is
administered in a daily 25 mg/kg dose as either an oral solution (Tylan) or intramuscular injection (Tylocine)
for seven days. Well stocked ranch and feed stores generally carry both Liquamycin and Tylan. Force-feeding
as described below under Starvation may be required. Snakes that are kept warm and well fed will not contract
pneumonia.
Mouth Rot (Stomatitis)
Mouth rot can be disfiguring and, if it leads to starvation, lethal. The oral mucosa presents a cottony
appearance and swells till the animal cannot fully close its mouth. This bacterial infection ( Aeromonas,
Pseudomonas, Pasteurella) is treated effectively by swabbing the oral cavity twice a day with mild antiseptic
solutions such as Listerine, 3% hydrogen peroxide, thimerosal (Merthiolate), benzalkonium chloride, or
Betadine (Frye 1973, Marcus 1980). Severe cases may require antibiotics. Force-feeding as described below
may be necessary if the condition has progressed far enough. Mouth rot is prevented easily by proper cage
construction and hygiene (see under Housing).
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Starvation (Inanition)
Starvation is usually a secondary effect of another disease but frequently the primary cause of death. A
thin snake will be lethargic and weak. An emaciated snake will exhibit prominent bones, sunken eyes, and a
shriveled skin as well. Curing the disease and force-feeding, if necessary, comprise the treatment. Diluted and
beaten egg yolk mixed with canned cat food or a commercial nutritional replacement product such as PetKalorie
or Nutrical (Frye 1973) is tube fed to the snake to gain back or maintain body weight. A flexible tube attached
to a syringe filled with food is passed down the esophagus and the food is then injected into the stomach.
Force-feeding small food items to a sick snake is a last resort. The food should be lubricated with beaten egg
yolk and pushed down the throat with a flexible blunt probe. Injuring the snake's cervical vertebra is easy to do
when force-feeding. Sometimes a nonfeeding animal will complete eating unassisted if the food item simply is
pushed into its mouth.
Inclusion Body Disease (Schumacher et al. 1994; Klingenberg 1996, 1997a, 1997b)
This viral disease has only recently been characterized and little is known about it. Clinical symptoms
include poor condition, weight loss, anorexia, regurgitation, chronic secondary infections, and neurological
problems such as tremors and stargazing. Many other reptile diseases also can cause these symptoms, but
inclusion body disease appears to be much more common in collections than previously hoped. The pathogen is
thought to be a retrovirus that is transmitted primarily by mites and ticks. Diagnosis requires blood analysis and
organ biopsy. No treatment exists for the disease. Infected animals that show symptoms can be given
supportive care, but remission has never been observed. Because of the deadly nature of this disease, the lack
of any effective treatment, and the high chance that it will spread to other snakes in a collection, infected
individuals should be euthanized.
Amoebiasis
By the time amoebiasis can be diagnosed, it is usually too late to save the individual. The rear half of an
infected animal's body may swell greatly, movement becomes difficult, a hard plug may form in the colon
anterior to the cloaca, anorexia develops, and the snake can only pass blood-tinged mucus. The snake generally
can only drag the rear half of its body around. After diagnosis, animals usually die a few days later from
gastrointestinal enteritis and liver abscesses. Infected individuals should be isolated immediately, preferably to
a different room. The cage must be disinfected thoroughly. Since the pathogen, Entamoeba invadens, occurs in
a cyst form, it is extremely infectious and can be transported in bedding or on the hands. Amoebiasis is the
worst infectious disease of herpetological collections (Donaldson et al. 1975, Bihn and Napolitano 1980).
Metronidazole (Flagyl) is given orally at a dosage of 250 mg/kg (Donaldson et al. 1975, Napolitano et
al. 1979). Another drug that has been used is emetine HCl as a daily 0.5 mg/kg intramuscular injection for ten
days (Frye 1973, Napolitano et al. 1979). High temperatures in the 35 to 37°C (95 to 99°F) range evidently
cause Entamoeba invadens infections to die out (Barrow and Stockton 1960; Meerovitch 1960, 1961; Bihn and
Napolitano 1980). Control and eradication of infection may be possible by holding animals at this temperature
range for one to two days. Conversely, quick drops in temperature to around 25°C (77°F) such as occur in the
Fall, may trigger a latent infection into the full blown disease (Meerovitch 1961). Prevention requires
avoidance of crowded community cages with many snakes, an appropriate temperature regime, good cage
hygiene, and food that is not old or refrozen. Lesions of the intestinal wall caused by ingestion of shavings or
other rough indigestible matter may increase susceptibility to infection.
Cryptosporidium spp. (McAllister et al. 1995)
Cryptosporidium infections in reptiles have only been described in the past twenty years. Snakes
become infected through oral ingestion of oocysts in the environment. As in people, reptiles may become
resistant to infection or may simple tolerate the parasite. Snakes with moderate to severe cryptosporidiosis
exhibit anorexia, pneumonia, gastroenteritis, lethargy, midbody swelling, weight loss, and regurgitation. No
effective medicinal treatment for Cryptosporidium has been found. Oral hydration and tube feeding (see
Starvation above) represent the only supportive therapeutic intervention.
Cestodes, Nematodes, Trematodes, and Lingulatids
These parasites usually never become a problem unless the infected animal becomes weakened for some
other reason. Use of some cat or dog medicines can kill snakes. My original male constrictor regularly used to
pass tapeworms, but never seemed to be bothered by them. He eventually appeared to become clear of them.
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Captive-born boa constrictors will never have tapeworms or other similar types of parasites, unless they are fed
a wild-caught animal or bird that is infected, or a cross-infection occurs with a cagemate. Only domesticated
animals should be used for snake food. Captive-born boa constrictors should not be kept with other snakes that
may have a parasitic infestation.
If a boa constrictor somehow gets internal parasites, I recommend that nothing is done unless the animal
shows chronic weight loss. Zoo and veterinary personnel may be of some help for diagnosis, treatment, and
medicines such as niclosamide (Yomesan, 150 mg/kg orally) or bunamidine HCl (Scolaban, 25-50 mg/kg
orally) for cestodes, piperazine citrate (40-60 mg/kg orally) or thiabendazole (Thibenzole, 50 mg/kg orally) for
nematodes, and emetine HCl (0.5 mg/kg/day intramuscularly for ten days) for trematodes (Frye 1973). I have
also noted that snakes sometimes pass tapeworms when treated with DDVP (phosphoric acid 2,2-dichlorovinyl
dimethyl ester) for mites. The standard veterinary use for DDVP turns out to be as a gastrointestinal wormer for
livestock. Ranch and feed stores may stock some of these drugs. No treatment is available currently for
lingulatid (tongue or lung worms of the Genus Armillifer) infestations.
Mites, Ticks, and Lice
Mites (Ophionyssus) and ticks (Ornithodoros and Amblyomma) are parasitic arachnids dangerous for
their ability to transmit viral and bacterial pathogens. Book and wood lice (Psocoptera), however, are only
nuisance insect pests. Unfortunately, keeping snakes free of mites can be like trying to keep mammals free of
fleas. The ideal solution is prevention through the strict quarantine of any new incoming animals. Rubbing
snakes with paraffin oil does not kill eggs in the cage and the desiccant silica-aerogel powder Dri-Die 67 has
been unavailable for a long time to my knowledge. Silica-aerogel products also are reported to cause longterm
pulmonary problems (Frye 1973). DDVP (phosphoric acid 2,2-dichlorovinyl dimethyl ester), better known as
Vapona in No-Pest Strips and others, has been used as an airborne miticide to control mites and ticks, but
reptiles and people are known to be sensitive to DDVP, a cholinesterase inhibitor with cumulative effects, and
must be kept out of contact with the strips if they are used. If mites or lice get out of hand, small pieces of a
pest strip can be enclosed in containers punched with holes and placed in the cage for several days. A thorough
cleaning of the cage and soaking of its occupants in water should also be carried out at the end of this period.
My strategy has been to keep the arthropod populations as low as possible (preferably at zero) by using
pine shavings and keeping the cages clean, dry, and uncrowded. Prompt removal of feces and sheds also
prevents conditions conducive to their reproduction. Rarely do I have to resort to pest strips and soaking. The
presence of mites and lice can be determined most easily by examining the inner surface of a recent shed
(actually the outer surface of the skin). Since they will be moving around and are whitish gray (lice) to black
(mites) in color, even small mites and lice will be visible against the light background of the shed. They also
turn up in the water container after an infested boa has been soaking in it. Large mites can be seen easily when
they are running around on the head and other body parts of a captive snake. Some of the most impressive mite
and lice populations I have ever seen were on snakes kept on damp, dirty newspaper.
Large ticks usually survive exposure to DDVP and must be removed manually. Very hot forceps are the
only way I have found to convince ticks to back out; yanking out ticks without heating the forceps usually
leaves the mouthparts in place where they can cause infections. The wound should be treated with an
antibacterial cream or solution such as Neosporin, hydrogen peroxide, thimerosal (Merthiolate), benzalkonium
chloride, or Betadine.
Scale Infections (Blister Disease or Vesicular Dermatitis) (Wright 1995)
Bacterial or fungal scale infections result from the combined effects of high mite populations, cool
temperature, and damp, dirty cage conditions. In some circumstances, low humidity can also cause this
condition. The infections themselves are small upraised areas covering one or two scales. Severe infections are
suppurating. In combination with the conditions causing them, the infections cause an animal to weaken, stop
eating, and forego shedding. The cage must be cleaned and dried out. The snake can be soaked in a fifty
percent Listerine or dilute organic iodine solutions for an hour a day. Very weak snakes must be given
something to support their head out of the solution and should be monitored so they do not drown. Scarring
usually does not result from scale infections. Force-feeding as described under Starvation may aid recovery in
weakened snakes that refuse food.
Problems with Shedding (Dysecdysis)
The reason that snakes shed their skins often is said to be that shedding permits growth. This idea has
arisen because they shed their skins as a single piece and the situation has been analogized with the molting of
©1999 Siar Anthranir Reptiles, 2309 Aldford Drive, Austin, TX 78745-4817, 512-462-3845
17
insects and crustaceans. Snakes actually grow in the same way as the majority of other organisms, i.e., cell
division. The true reason they shed their skins is the same one that people have for shedding: to replace the
outer damaged layer of the skin. The only difference is that snakes do it all at once; people and other animals
tend to do it in patches (dandruff is the most visible evidence of this). Shedding frequency increases with
temperature and feeding rate, since the overall metabolic rate increases. Snakes with skin injuries also usually
increase shedding frequency, a response apparently associated with the healing process.
Boa constrictors undergo a well defined physiological sequence when they shed their skins. The first
indication is dulling of the overall pattern. The snake may refuse to feed from this point until after it has shed.
Animals should not be fed or handled during the shedding period, as the skin is very soft and susceptible to
injuries causing scars. Within a few days, the skin becomes quite dull and the eye spectacles assume an opaque
milky appearance for a day or two. Snakes can be quite nervous during this period when they cannot see well.
They often develop a proclivity for soaking in the water container at this time. The skin and spectacles then
clear up. Shedding occurs three to seven days later. As mentioned before, sheds should be removed promptly
to prevent mite infestations. The new skin exhibits bright vivid markings.
Unhealthy snakes or those under poor cage conditions often have problems with shedding their skins.
Low humidity and/or temperature can cause a boa constrictor to forego shedding its skin even though it has
completed the preparatory stages. Shedding boa constrictors should be kept warm and under high humidity
with daily spraying, if necessary. Recalcitrant individuals can be soaked in an appropriate container to keep the
old skin from drying and adhering to the new one. Wetting of the snake and shedding by hand should be done
when areas of old skin have loosened and the snake still refuses to shed on its own. Even healthy individuals
occasionally have difficulties with certain areas, usually the spectacles and the tail. If patches of old skin are
still adhering to the new one after a snake sheds out, removing the old skin is a fairly simple procedure. A
finger moistened with water or mineral oil is rubbed over the free anterior edge of the old skin toward the tail.
The old skin should come off fairly easily. Care must be taken with removing an old spectacle, since the edges
of it may be adhering tightly and trauma to the underlying new spectacle and eye may occur. Very rarely, it is
better just to leave the old spectacle or other unshed skin in place until the next shedding.
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