Taxon Management Account
Cryptobranchus alleganiensis alleganiensis (Daudin)
Compiled by: William P. Flanagan III
Compilation Date: August 2002
Introduction and Natural History
The family Cryptobranchidae contains three extant species;
Andrias japonicus, A. davidianus, and Cryptobranchus alleganiensis.
The genus Cryptobranchus contains only one extant species with two subspecies;
C. a. alleganiensis and C. a. bishopi. They are the largest salamanders in America,
with adult size ranging between 29-51 cm,and a record length of 74cm (Conant and Collins 1991, Fitch 1947).
The body form is compressed horizontally with a laterally compressed paddle-like tail.
The integument is covered in ridges and folds especially along the lateral surfaces.
Ground color is usually brown but ranges between black and bright orange
(Conant and Collins 1991, Petranka 1998, Fauth et. Al. 1996). Albinism has been reported (Dyrkacz 1981).
Mottling is often present.
C. a. alleganiesis ranges from New York south to Mississippi and west to central Missouri.
C. a. bishopi is endemic to the Ozark Mountains of southeastern Missouri and northeastern Arkansas
(Conant and Collins 1991). C. alleganiensis are found in fast- moving streams or rivers.
Large rocks are utilized as cover and seem to be a requirement (Pfingsten 1990, Siebert 1989).
Pfingsten 1990 noted that Ohio hellbender populations concentrated shortly after bends in rivers.
Bishop 1941 describes C. alleganiensis as "A great flat flabby animal…."
This fantastic amphibian’s aquatic nature and nocturnal habits (Bishop 1941, Humphries and Pauley 2000,
Noeske and Nickerson 1979) have made collecting life-history data difficult.
Daylight hours are largely spent under cover, sometimes with their heads partially exposed.
Crayfish and fish make up the bulk of the diet, but they will accept a wide variety of prey
if the opportunity presents itself. Defenses include cryptic coloration, noxious skin secretions (Brodie 1971),
the ability to flee quickly with short bursts of speed, and an intimidating bite (pers. obser.).
A variety of fish, snakes, turtles, larger C. alleganiensis, and man have been reported as predators
(Nickerson and Mays 1973, Petranka 1998, Minton 2001). Minton 2001 reported an experienced source saying,
"They tasted pretty good if you didn’t know what you were eating."
Breeding occurs in the fall (Smith 1907, Bishop 1941, Ingersol 1982, Nickerson and Mays 1973).
Breeding season is longer, September – November, in Missouri populations (Dundee and Dundee 1965, Peterson 1988).
One winter breeding has been recorded in Missouri (Peterson et. al 1989). In the east, breeding seasons generally
last 2-3 weeks, from late August to mid September or September into October (Petranka 1998).
Larvae are gilled until approximately 1.5 – 2 years of age, at which point the gills are lost
and they resemble miniature versions of the adults. Age at maturity remains somewhat unclear.
Smith 1907 estimated age at maturity to be within the range of 3-4 years.
Nickerson and Mays 1973 and Peterson 1985 estimated it to be later at, 7-8 years of age.
The longevity is recorded as 29 years (Nigrelli 1954), but it is likely they can live longer.
One of the most frequently asked questions regarding C. alleganiensis is the origin of its common name,
hellbender. Nickerson and Mays 1973 reference two sources that attribute the name hellbender to early
African-American origins. The name is believed to be a reference to the animal’s bending movements being
similar to what one must experience during the torments of Hell.
Currently C. a. alleganiensis and C. a. bishopi are not protected by the Federal Government or CITES.
However, C. a. bishopi is currently a candidate for protection from the Federal Government (Federal Register 2002).
C. alleganiensis is provided some level of protection or management in Ohio, North Carolina, South Carolina, Arkansas,
Missouri, Illinois, Alabama, and Georgia However, this animal does not enjoy protection from New York, Pennsylvania,
Kentucky, Mississippi, and West Virginia (Levell 1997, Humphries 2002a). Some states even regulate it as if it were a
Habitat destruction due to deforestation or pesticide run-off probably represents the greatest threat to C. alleganiensis.
Although rarely kept by hobbyists, limited range, specialized habitat, decreased density combine to make hellbenders
especially vulnerable to overcollection. Unfortunately, several researchers have encountered examples of collection
by the pet trade (Nickerson ?, Wilkinson?) Acquisition of specimens is the most common question posted to a hellbender
website (Humphries pers. Com.), possibly indicating an increase in collection pressure.
Recent population data are absent throughout most of the range of C. a. alleganiensis and C. a. bishopi.
Dramatic declines in numbers have been observed in Missouri and Arkansas, with little or no observed
recruitment (Mathis pers. Com. 2002, Wheeler and Trauth 2002). Microhabitat use makes locating larvae extremely
difficult in parts of the hellbender’s range (Nickerson 2001). It is clear that more intensive monitoring throughout
the animal’s range is needed.
ISIS online abstracts lists 28 animals in 14 institutions. Five institutions list Cryptobranchus alleganiensis
without identifying the subspecies, one C. a. bishopi, and ten list C. a. alleganiensis. Six facilities reported
housing only solitary animals or single sex populations. Currently Cryptobranchus alleganiensis is listed as a
priority 2 DRP with a recommendation of up grade to -1 PMP if captive reproduction occurs (Wright 2000).
Although there is considerable work done in situ, data collection is time consuming and difficult.
Large gaps still exist in our knowledge of their biology. Further research on social interactions,
reproductive physiology, and habitat selection may prove critical in the conservation of this species.
Low genetic variability between populations (Routman 1993) coupled with the fact that hellbenders have
faired well in limited repatriation attempts (Nickerson 1980) make this species a good candidate for re-release programs.
Captive management of this species could make significant contributions to the conservation of this species.
Captive reproduction has yet to be achieved. However, only about 30% of the Cryptobranchus reported to ISIS are of
known sex, and only two institutions report numbers and sex ratios suitable to make serious propagation attempts.
It is important to develop suitable propagation protocol now. Size and structure of den, social groupings,
sexing techniques, temperature, lighting, and water quality parameters are all areas of investigation that require further research.
Since hellbenders tolerate a wide of captive conditions and captive reproduction has proven elusive, a variety of
husbandry strategies may be appropriate.
Large aquatic setups with a high flow rate are required. Two or three adults can be maintained in a tank 95"x 25"x 18".
It is advisable to design enclosures with removable dividers. This will allow social groupings to be manipulated with
relative ease. Hellbenders can be territorial and will eat smaller conspecifics (Nickerson and Mays 1973).
Although they are aquatic, there are reports of terrestrial movement (Nickerson and Mays 1973).
The author maintained one adult that would routinely crawl onto the land area of the exhibit.
Recent captives have been observed making numerous attempts to escape enclosures (John Groves pers. com).
Consequently, enclosures should include either a tight fitting lid or an overhang to prevent escapes.
Underwater cover is important. Large flat rocks set at least twice the animal’s height are excellent.
Care should be taken to ensure that heavy cover is properly supported on the enclosure bottom.
Animals will dig into gravel bottoms and improperly supported cover will shift posing a significant squishing hazard.
Since hellbenders are territorial, the number of submerged cover spots should equal or exceed the
number of animals housed in the enclosure.
Peagravel is an acceptable substrate; larger gravel with average diameter of 1-3” is best.
This will help to prevent animals from accidentally ingesting gravel during feeding.
Water should be filtered to ensure excellent water quality. Flow should be strong and directional.
An adjustable standpipe will make it easy to change water levels, which seems to be important in cycling these animals.
Proper water quality and temperature are often to two biggest challenges. NH4, NO2 and NO3 should be monitored weekly.
Levels of these nitrogenous wastes should be maintained below 1.0 p.p.m., for NH4, 0.5 p.p.m. for NO2, and 5.0 p.p.m. for NO3.
Dissolved Oxygen should be over 90% saturation. Beffa 1976 found that animals increased rocking activity as dissolved oxygen
decreased until 20?% at which point animals attempted to leave the aquaria.
Temperatures should be maintained at temperatures that range between 9 and 25?C with the extremes at 1.5 to 2 month
intervals in the winter and summer. Smith 1907 recorded breeding season water temps between 14-18?C. Dundee and Dundee
1965 noted spring fed streams had temperatures that rarely varied beyond 17-12?C, whereas non spring fed streams that got
as warm as 25?C during the summer months.
Lighting is likely an important cue for reproduction of this species. Riss et. Al. 1963? Suggested that lighting
played a significant role in endocrine activity. Hellbenders are usually nocturnal (Bishop 1941, Humphries 2000)
with seasonal or occasional diurnal activity (Nickerson and Mays 1973). Like most captive herps they should be offered
a natural light cycle, 10hours light and 12dark during the winter December and January and 12 hours of light with 10 hours
on dark in the summer June and July. Many popular weather web sites offer local sunrise and sunset data.
Using this data with electronic or analog lighting timers would make it easy to closely approximate the collection
locality light cycle. A bank of lights hung directly above the tank that goes on one hour after and off one hour before
the main room lights will simulate dusk and give the animals a variety of light intensities. Although this author has offered UVB,
it is unlikely that this aquatic and largely nocturnal animal will require it in captivity.
Because behavioral data is difficult to collect in situ, this is one area where ex situ programs should be making big
contributions. Housing multiple animals in one in enclosure can pose a risk of nasty bite wounds or even cannibalism.
Multiple animal enclosures should include lots of space, multiple underwater retreats and removable dividers.
Captive animals have been observed both vigorously defending territories and tolerating other adults of both sexes.
Situations should be individually evaluated especially during change of seasons or social structure.
Keepers should watch for bite wounds, appetite loss, or any other signs of stress.
This is one aspect of the biology of this animal that has been well studied. Crayfish is clearly the most common food item
taken by wild hellbenders (Smith 1907, Bishop 1941, Nickerson and Mays 1973). However in captivity the diets of captive
hellbenders have often been more reliant on earthworms, fish, shrimp, raw meat, and even mice. Two feeding strategies are common.
One is tong feeding each animal food items. This approach allows the keeper to track food intake closely.
Unfortunately it also conditions many captives to vigorously strike at any item that is presented towards the mouth including;
keepers fingers and potential mates. The second strategy is to keep a number of live food items crayfish or feeder fish available
in the enclosure at all times. This fosters a more natural set of feeding behaviors but has several potential dangers.
Excessive numbers of crayfish will sometimes pick at captive hellbenders. The threat of introducing disease from the food
items is greater when the food items are housed this way. Obtaining frequent weights is important to insure that animals are
eating and adjusting well.
If environmental parameters are met, hellbenders tend to be hardy captives. Loss of weight or appetite should be treated
as a sign of serious illness. While a certain amount of rocking behavior is normal continuous rocking can be a sign of low
dissolved oxygen or stress and should be investigated. Physical restraint can be difficult. Hellbenders seem to have
greater patience for handling that occurs under water. Andrias and Cryptobranchus both possess a tacky spot near the tip
and towards the top of their laterally compressed tail. Grasping this spot firmly between the thumb and forefinger will
allow for limited cautious manipulation and reduce the need for more aggressive restraint. The animals will generally
tolerate this condition for several seconds before reacting at which point the animal will vigorously attempt to swim away or bite.
In both cases the animal should be released. More aggressive physically restrain may be accomplished by confining the animal
to an appropriate sized net. A pant leg made of soft cloth works very well. Opinions vary greatly on the potential danger posed by a bite.
A bite from an adult could certainly cause lacerations and caution should be used when handling large specimens.
Hellbenders can be difficult to correctly sex. During the breeding season the glands around the males’ cloacas
swell making them easy to identify as males. Absence of this swelling could indicate either a non-sexually active
male or a female. This could be especially confusing in captive settings where reproductive cycles may not be functioning
properly. Males are broader and heavier than similarly sized females (Bishop 1941). Laproscopy and ultrasound of
adults is definitive regardless of reproductive readiness. Ultrasound is less invasive but both require the
involvement of a skilled technician or veterinarian.
Any serious attempt to breed these animals should start by simulating natural light and temperature cycles.
In addition several authors suggest that rainfall plays an important role in stimulating activity during the
breeding season (Nickerson and Mays 1973, Nickerson pers. Com). During the fall water level and frequency of
fake rain showers should be increased while temperature and day length decreased. Reproductively active males
have swollen cloacas that may even ooze salamander milt and females will have swollen abdomens. Males build a
nest that is usually under a large submerged cover object. Nickerson and Tohulka 1986, and Bishop 1941 describe
nests and should give the keeper some direction. Active nests may contain large complements of eggs, approximately
2000 eggs(Bishop 1941). This large number represents the reproductive effort of several females. A single female
may produce approximately 250 eggs in a season (Smith 1907). There is insufficient data to suggest appropriate structure
of breeding groups. Although multiple female breeding groups may be more natural there is risk associated.
Larger groupings increase the chances of a detrimental territorial interaction. In addition, hellbenders have been
known to cannibalize eggs in the wild (Bishop 1941). Females may selectively target the eggs of competing females.
Enclosure size should be strongly considered before attempting larger groupings
Eggs lack pigment and may be light sensitive.
Fertilization is external. Males have been observed fanning the eggs with their tails. This is believed to spread
the milt across the surface of the eggs(Smith 1907). Males excavate an underwater nest chamber and will entice several
females to oviposit in it. Eggs are laid in the fall(Smith 1907, Siebert 1989, Nickerson and Mays 1973).
Males will stay and guard egg filled nests. It is still unclear at what point they stop defending the nests.
Length of incubation period is variable. Smith 1912 a &b give excellent accounts of the embryology of Cryptobranchus.
Little is known about neonate husbandry. Johnson 2000 raised larvae from a wild collected captive incubated eggs.
He noted that larvae had enough yolk reserves to sustain growth for three months after hatching. The author raised an
animal that was approximately 1.5-2.0 years of age at capture using conditions similar to adults.
In addition to several institutions being poised to make serious breeding attempts Philadelphia Zoo has collaborated to
describe the feeding physiology (Cundall et al 1987). Cincinnati Zoo’s CREW has be working with Cryptobranchid
reproductive biology. A large number of zoos with amphibian expertise are geographically located within driving
distance of the hellbenders range. With many hellbender populations in decline or questionable status now is an
excellent time for zoos to make contributions to its conservation beyond captive propagation.
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