Average lifespan
Status: captivity: 25.0 years.
Average lifespan
Status: captivity: 6.0 years.
The hellbender is a large totally aquatic salamander characterized by loose highly folded skin along the lower sides of the body. The folds of skin are used in respiration as the hellbender has no gills and the lungs are only used for buoyancy control (Danch 1996). The hellbender's body is dorsoventrally compressed and the head is extremely flattened. The hellbender undergoes incomplete metamorphosis so that adults lack eyelids and retain one pair of gill slits that are seen as circular openings on the neck. All adults have four digits on each forelimb and five digits on each hind limb (Cogger and Zweifel 1998). The hellbender is sexually dimorphic in size, with females being larger than males. The length in adults varies from 11-29 inches, with most being in the range of 11-20 inches. The other dimorphic characteristic for the hellbender is only seen in the breeding season when the male develops a swollen ring around the opening of the cloaca (Behler and King 1979). The body color varies from yellowish brown to almost black with very faint scattered dark or light spots in the adults. The young, once they lose their external gills at about 4 to 5 inches, have numerous irregular dark spots that are easily seen on a light body color (Conant and Collins 1998).
Other Physical Features: ectothermic ; bilateral symmetry
Average mass: 358.1 g.
Average basal metabolic rate: 0.0253 W.
The hellbender prefers clear fast-flowing larger streams and rivers with rocky bottoms and plenty of cover in the form of logs and debris (Behler and King 1979).
Aquatic Biomes: rivers and streams
The hellbender, Cryptobranchus alleganiesis, occupies the Susquehanna River drainage in southern New York and Pennsylvania, and large portions of the Missouri, Ohio, and Mississippi River drainage from western Pennsylvania, southern Ohio, extreme southern Indiana, most of West Virginia, Kentucky, and Tennessee, northern Alabama and Georgia, western North Carolina and Virginia. The subspecies Cryptobranchus alleganiensis bishopi, or Ozark hellbender, is only found in the Black River and White River systems of Missouri and Arkansas (Danch 1996).
Biogeographic Regions: nearctic (Native )
The hellbender is strictly carnivorous. The diet consists primarily of crayfish but insects, fish, and worms will also be eaten (Behler and King 1979). The hellbender has a very unique mechanism for capturing and consuming its prey. It exhibits a highly unusual mode of asymmetrical suction feeding in which the bilateral elements of the mandibles and hyoid move independently. Typically the hellbender only depresses one side of the mandible, dropping the jaw 10 to 40 degrees from the resting position and the prey is drawn in with a jet of water (Pough et al. 1998).
The hellbender does not have a direct positive economic importance. However, the hellbender belongs to the suborder Cryptobranchoidea which is the most primitive of the living salamanders and may hold clues for scientists to use when studying the evolution of other salamanders (Cogger and Zweifel 1998).
Development - Life Cycle: metamorphosis
Although the hellbender has no special status given to it there are still a number of factors which may in the near future change it's status. Agricultural runoff and the acidic runoff from large scale mining operations threaten much of the hellbenders habitat. The most serious threat to the future of the hellbender is the impoudment of rivers and streams for the formation of recreational lakes and hydroelectric facilities. Another threat to the hellbender comes in the form of indiscrimante collecting, for both the pet trade and scientific research (Danch 1996).
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: near threatened
There are two subspecies of hellbender Cryptobranchus alleganiensis alleganiensis, Eastern hellbender, and C. a. bishopi, Ozark hellbender. The Ozark hellbender is smaller and often has more numerous and larger dark blotches on it's back, but the best way to tell them apart is solely based on geographic location (Danch 1996).
There is a wealth of folklore that surrounds the hellbender. It has been said that a hellbender will smear a fisherman's line with slime in an attempt to drive them out of the area. The hellbender has also been reported to chase off game fish and if disturbed they will inflict a poisonous bite. For these reasons the hellbender has been nicknamed Allegheny Alligator and Devil Dog. The problem is that the hellbender is completely harmless and avoids game fish altogether, or it risks being eaten, so this folklore leads to unwarranted persecution (Behler and King 1979).
Unusual among salamanders is the fact that the hellbender exhibits external fertilization. The breeding season shows a degree of geographic variability. With those in the eastern populations demonstrating breeding activity in late August through early September. While the western and southern populations begin breeding activity in early September to early November. At the onset of the breeding season the male will excavate a nest site that he will defend from other males. The nest site is usually beneath flat rocks or other debris. Males will persuade females to enter the nest site and lay their eggs. The eggs are between 5 and 7 millimeters in diameter and are spherical in shape. The eggs are always laid in paired rosary-like strings that form an egg mass that contains anywhere from 270 to 450 eggs. The male will float over the female and will undulate his lower body in order to disperse his milt throughout the nest cavity. Often times the male will attract more than one female to the nest site in a season so there could be as many as 1,000 or more eggs per nest site. The male will remain with the eggs until hatching to provide protection from predators. The eggs usually hatch 68 to 84 days after fertilization, with larvae ranging in size from 23 to 26 millimeters in length. The larvae retain their external gills for approximately one and a half years or until they reach about 4 inches in length. At this stage the larvae resemble the larvae of other salamanders and lack the pronounced flattening of the body and the dermal folds. The hellbender grows very slowly at a rate of about 2 centimeters per year, and may continue for five or six years before sexual maturity is reached, at which point the individual will be approximately 14 inches in length. The hellbender is long lived and captive individuals have been recorded to survive for 29 years (Danch 1996).
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)
Average time to hatching: 72 days.
Average number of offspring: 275.
Average age at sexual or reproductive maturity (male)
Sex: male: 1825 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1825 days.
The Ozark hellbender (Cryptobranchus alleganiensis bishopi) is a subspecies of the hellbender (Cryptobranchus alleganiensis), strictly native to the mountain streams of the Ozark Plateau in southern Missouri and northern Arkansas.[1] Their nicknames include lasagna lizard and snot otter.[2] These large salamanders grow to average from 29-57 centimeters in length over a lifespan of 30 years.[3] Ozark hellbenders are nocturnal predators that reside under large flat rocks and primarily consume crayfish and small fish. As of 2011, the U.S. Fish and Wildlife Service (USFWS) has listed the subspecies as endangered under the Endangered Species Act of 1973.[4] The species population decline is caused by habitat destruction and modification, overutilization, disease and predation, and low reproductive rates.[5] Conservation programs have been put in place to help protect the species.[6][5]
Two distinct members of the family Cryptobranchidae, also known as "giant salamanders," are found in the United States, the eastern hellbender (Cryptobranchus a. alleganiensis), and the Ozark hellbender (Cryptobranchus a. bishopi).[7]
Hellbenders are known for their primitive body design and their large size. They have small eyes, a keeled tail, and a flat body to assist the Ozark hellbender in movement in rivers and streams.[8] They have folds along their sides that assist them in respiration, as oxygen is able to diffuse across the skin.[3] It is a strictly aquatic species, even though it technically lacks gills.[9] On average, they are about 29-57 centimeters in length.[3]
Ozark hellbenders are endemic to the White River drainage in northern Arkansas and southern Missouri. Historically they have been found in portions of Spring, White, Black, Eleven Point, and Current Rivers and their tributaries. Hellbenders are now considered extirpated in the mainstem White, Black, and Spring Rivers and Jacks Fork, and with their range being considerably reduced in the remaining rivers and tributaries.[10]
The Ozark hellbender is declining throughout its range with no population appearing to be stable throughout its range.[11] It is unknown whether a viable population exists in the mainstem of the White River, where few individuals have been found. Much of the potential habitat along this river has been destroyed by a series of dams constructed on the upper portion of the river in the 1940s and 1950s.[12] The North Fork White River has historically contained a high population of Ozark hellbenders and was considered the strong point for the species with a mark and recapture study in 1973 marking 1,150 individuals within a 1.7-mile reach of the river.[13] In recent years, this population is now beginning to experience a decline similar to those in populations in other rivers.[12] Though the overall population of the Ozark hellbender is known to be in decline, there is no data available on current population sizes, likely due to their small numbers and reclusive life history.[14]
There is currently no critical habitat designated for the Ozark hellbender.[4]
Ozark hellbenders are frequently found underneath large flat rocks in rocky, fast flowing streams in the Ozark Plateau at depths from less than 1 meter to 3 meters.[8] They are primarily nocturnal, remaining undercover until nightfall. Hellbenders are habitat specialists that are dependent on consistent levels of dissolved oxygen, temperature, and water flow.[15] Warmer stagnant waters with a low dissolved oxygen content do not meet the Ozark hellbenders respiratory needs.[15] It has been observed that Ozark hellbenders in warm stagnant waters sway or rock in order to increase oxygen exposure.[15]
Ozark hellbenders are nocturnal predators, remaining beneath rock cover during the day and emerging to forage at night, primarily on crayfish.[16] They become diurnal during the breeding season, searching for mates.[3] They are highly sedentary, moving very little throughout their entire lifespan.[16] Ozark hellbenders are territorial and will defend their cover from other hellbenders.
They have been recorded living 25 to 30 years in the wild and grow slowly over time.[17] Wild Ozark hellbender populations are dominated by these older and larger individuals. Female Ozark hellbenders have been found to mature at 6 to 8 years old, while males tend to mature at around 5 years of age.[1][17][18] Some of the issues that Ozark hellbenders have in reproduction come from their late sexual maturity.[5]
Typically, Ozark hellbenders breed in mid-October, although certain populations that live in the Spring River area tend to procreate in the winter. Paternal care is present in this subspecies, even though it is rare to see this in tetrapods.[19] The males are responsible for preparing the nests and ultimately guarding the eggs. They build nests under submerged logs, flat rocks, or within bedrocks. Hellbenders mate via external fertilization.[1] Usually, around 138 to 450 eggs are present per nest,[3] and they hatch after approximately 80 days.[20] Once the eggs hatch, the larvae and juveniles hide under small and large rocks in gravel beds.[1][21] Ozark hellbenders are highly sedentary creatures, meaning that neither males nor females have long distance dispersal rates.[8]
The Ozark hellbender became a candidate for listing under the Endangered Species Act in 2001. It was assigned a priority level of 6 for threats due to habitat loss and fragmentation because of human activity and pollution.[22] In 2005 the Fish and Wildlife Service increased its listing priority number to a 3 because of increased pressures on the species from recreation activity in their habitat including gigging and boat traffic, and increases in the contamination of their waters.[23] The USFWS put forth the proposed rule to list the Ozark hellbender as endangered under the ESA in September 2010, and the listing of the species as endangered became effective November 7, 2011.[4][24] In April 2017, a five-year review of the subspecies’ status was initiated.[25]
The subspecies of C. a. bishopi does not currently have its own IUCN listing, but the species C. alleganiensis was listed as near threatened in April 2004.[14]
The construction of reservoirs in the White River has destroyed Ozark hellbender habitats and separated their populations.[5] These reservoirs also increase predation and the deposition of silt upstream from the reservoir, both of which threaten hellbenders.[5] Siltation endangers the larval salamanders because it fills in the gravel stream beds where they live, reducing their ability to find food and hide from predators. Silt can also destroy their eggs.[5] Agricultural and construction runoff, waste disposal, and mining activity within the hellbender’s range pollute and degrade their habitat and threaten hellbender survival.[5][23] Mining is especially detrimental as it increases zinc and leads hellbender habitats to dangerously high levels for aquatic life.[8] Human and livestock waste from the areas surrounding hellbender habitats have further decreased water quality.[23] Pollution is readily taken up by hellbenders due to the absorptive properties of their skin and decreases in water quality can make rivers and streams unlivable for this subspecies.[8][15]
Recreation in Ozark hellbender habitats also harms populations. Boat traffic, including canoes, kayaks, and motor boats may injure or kill hellbenders and further degrade their habitat.[8][23]
Additionally, direct removal from the environment has contributed to the decline of the Ozark hellbender. While Missouri and Arkansas have decreased or stopped issuing permits for scientific collection since the 1990s, illegal harvesting for the pet trade has continued.[5][8] The Ozark hellbender also experiences predation from non-native rainbow and brown trout stocked in river for sport fishing.[5][8]
Like most amphibians globally, the Ozark hellbender is at risk of chytridiomycosis, a very infectious amphibian fungal disease. It has been detected in all but two rivers C. a. bishopi is currently found in. Additionally, unusual physical abnormalities have been observed in Ozark hellbenders in recent years, such as missing limbs or eyes and epidermal lesions, with increasing frequency, although the cause of these deformities is currently unknown.[5][8]
The small size of Ozark hellbender populations combined with their isolation from each other puts them at greater risk of extinction, as does the documented loss of genetic diversity within those populations.[5][8] They also suffer from very low reproductive rates as a result of their late sexual maturity and long lifespans. Their late sexual maturity makes them more likely to die before reproducing and the time between generations is extended when reproduction does occur. Very low numbers of juvenile Ozark hellbenders in most populations confirm these problems.[8] These threats are further worsened when combined with the other threats to this subspecies.[5][8]
The decline of the Ozark hellbender was first recognized in the 1990s. Since then, the Arkansas Game and Fish Commission (AGFC) and Missouri Department of Conservation (MDC) have begun to track the health and wellbeing of the creatures. They also study trends in their size and overall presence in their natural habitat. From this information, they are able to predict population trends. Since this species is now considered endangered, there is more effort to protect the habitat and populations of the Ozark hellbender. Both USFWS and State agencies have enacted laws and policies to aid in hellbender protection.[5]
The most popular conservation strategy for the Ozark hellbender is captive breeding and reintroduction back into their natural habitats. There is currently only one successful example of successful captive breeding, which is taking place in the Saint Louis Zoo.[6] In regards to hellbender release after captive breeding, planning should include data on genetic information and the presence of chytrid fungus and other pathogens. Since there is little gene flow or genetic variation in the subspecies, it is hard to continue to build their numbers due to negative consequences from inbreeding. Some scientists suggest research into their genetic delineations for answers. Not much is known about their genetic history. Many scientists also suggest that translocation should not be a part of Ozark hellbender conservation plans, since they are habitat specialists and haven’t had translocation success in the past.[26] Other current conservation plans include population monitoring, protecting populations and habitat, and disease assessment and treatment [5]
Due to the impact of disease on the Ozark hellbender populations, there is more effort to study the physical deformities of the hellbenders affected by disease, as well as understanding how diseases cause the deformities. Research is also exploring the effects of the amphibian chytrid fungus. Heat treatment has seen some success as a method of treating chytrid cases.[5]
Other than captive release programs, the recommended way to meet the recovery needs of Ozark hellbenders is to protect and clean their habitat. It is necessary to decrease sedimentation and to protect areas where Ozark hellbenders reproduce.[5]
The Ozark hellbender (Cryptobranchus alleganiensis bishopi) is a subspecies of the hellbender (Cryptobranchus alleganiensis), strictly native to the mountain streams of the Ozark Plateau in southern Missouri and northern Arkansas. Their nicknames include lasagna lizard and snot otter. These large salamanders grow to average from 29-57 centimeters in length over a lifespan of 30 years. Ozark hellbenders are nocturnal predators that reside under large flat rocks and primarily consume crayfish and small fish. As of 2011, the U.S. Fish and Wildlife Service (USFWS) has listed the subspecies as endangered under the Endangered Species Act of 1973. The species population decline is caused by habitat destruction and modification, overutilization, disease and predation, and low reproductive rates. Conservation programs have been put in place to help protect the species.
