The Ozark hellbender (Cryptobranchus alleganiensis bishopi) is a subspecies of the hellbender (Cryptobranchus alleganiensis). The subspecies is strictly native to the mountain streams of the Ozark Plateau in southern Missouri and northern Arkansas.Nickerson, M.A., and C.E. Mays. 1973. The hellbenders: North American giant salamanders. Milwaukee Public Museum Publications in Biology and Geology 1:1−106. Its nicknames include lasagna lizard and snot otter. This large salamander grows to a total length (including tail) of over a lifespan of 30 years.Dundee, H.A., and D.S. Dundee. 1965. Observations on the systematics and ecology of Cryptobranchus from the Ozark plateaus of Missouri and Arkansas. Copeia 1965:369−370. The Ozark hellbender is a nocturnal predator that hides under large flat rocks and primarily consumes 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 population decline of the subspecies is caused by habitat destruction and modification, overutilization, disease and predation, and low reproductive rates.U.S. Fish and Wildlife Service. 2012. Recovery Outline for the Ozark Hellbender. Columbia, Missouri. 13 pp. Conservation programs have been put in place to help protect the subspecies.A., Rachel, et al. “Quantitative Behavioral Analysis of First Successful Captive Breeding of Endangered Ozark Hellbenders.” Frontiers, Frontiers, 14 Nov. 2018, www.frontiersin.org/articles/10.3389/fevo.2018.00205/full.
Taxonomy 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).Hayes, Thomas. "Cryptobranchid update: eastern hellbender/Ozark hellbender 'North America's Largest Salamander'." Endangered Species Update, vol. 24, no. 2, 2007, p. 42+. Accessed 1 Apr. 2020.
Description The Ozark hellbender is known for its primitive body design and its large size. It has small eyes, a keeled tail, and a flat body to assist in movement in rivers and streams. It has folds along its sides that assist in respiration, as oxygen is able to diffuse across the skin. It is a strictly aquatic subspecies, even though it technically lacks gills.Guimond, Robert W.; Hutchison, Victor H. (1973). "Aquatic Respiration: An Unusual Strategy in the Hellbender Cryptobranchus alleganiensis alleganiensis (Daudin)". Science, American Association for the Advancement of Science, 21 Dec. 1973. It grows to a total length (including tail) of about .
Distribution and habitat The Ozark hellbender is endemic to the White River drainage in northern Arkansas and southern Missouri. Historically it has been found in portions of the Spring, White, Black, Eleven Point, and Current rivers and their tributaries. The Ozark hellbender is now considered extirpated in the mainstem White, Black, and Spring rivers and Jacks Fork, and with its range being considerably reduced in the remaining rivers and tributaries.Johnson, T. R. (2000): The amphibians and reptiles of Missouri. Jefferson, MO: Missouri Department of Conservation.
The Ozark hellbender is declining throughout its range with no population appearing to be stable throughout its range.Wheeler, B. A., E. Prosen, A. Mathis, and R. F. Wilkinson. 2003. Population declines of a long-lived salamander: a 20+-year study of hellbenders, Cryptobranchus alleganiensis. Biological Conservation 109:151–156. 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.Irwin, K. 2008. Ozark hellbender long-term monitoring SWG project. Final Report. Arkansas Game and Fish Commission, Benton, Arkansas. The North Fork White River has historically contained a high population of the Ozark hellbender and was considered the strong point for the subspecies, with a mark and recapture study in 1973 marking 1,150 individuals within a 1.7-mile (2.7-kilometer) reach of the river.Peterson, C. L., R. F. Wilkinson, Jr., M. S. Topping, and D. E. Metter. 1983. Age and growth of the Ozark hellbender (Cryptobranchus alleganiensis bishopi). Copeia 1983(1):225–231. In recent years, this population is now beginning to experience a decline similar to those populations in other rivers. 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 its small numbers and reclusive life history.
There is currently no critical habitat designated for the Ozark hellbender.
The Ozark hellbender is frequently found underneath large flat rocks in rocky, fast flowing streams in the Ozark Plateau at depths from less than to . It is primarily nocturnal, remaining undercover until nightfall. Hellbenders are habitat specialists that are dependent on consistent levels of dissolved oxygen, temperature, and water flow.Williams, R. D., J. E. Gates, and C. H. Hocutt. 1981. An evaluation of known potential sampling techniques for hellbender, Cryptobranchus alleganiensis. Journal of Herpetology 15(1):23–27. Warmer stagnant waters with a low dissolved oxygen content do not meet the Ozark hellbender's respiratory needs. It has been observed that Ozark hellbenders in warm stagnant waters sway or rock in order to increase oxygen exposure.
Ecology and behavior Ozark hellbenders are nocturnal predators, remaining beneath rock cover during the day and emerging to forage at night, primarily on crayfish.Dierenfeld, E. S., K. J. McGraw, K. Fritsche, J. T. Briggler, and J. Ettling. 2009. Nutrient composition of whole crayfish (Orconectes and Procambarus species) consumed by hellbender (Cryptobranchus alleganiensis). Herpetological Review 40(3):324–330. They become diurnal during the breeding season, searching for mates. They are highly sedentary, moving very little throughout their entire lifespan. 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.Peterson, C.L., Ingersol, C.A., and R.F. Wilkinson. 1989. Winter breeding of Cryptobranchus alleganiensis bishopi in Arkansas. Copeia 1989:1031–1035. 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.Taber, C.A., R.F. Wilkinson, Jr., and M.S. Topping. 1975. Age and growth of hellbenders in the Niangua River, Missouri. Copeia 1975:633−639. Some of the issues that Ozark hellbenders have in reproduction come from their late sexual maturity.
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.Bishop, et al. “A Quantitative Field Study of Paternal Care in Ozark Hellbenders, North America's Giant Salamanders.” Journal of Ethology, Springer Japan, 1 Jan. 1970, link.springer.com/article/10.1007/s10164-018-0553-0. 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. Usually, around 138 to 450 eggs are present per nest, and they hatch after approximately 80 days.Bishop, S.C. 1941. Salamanders of New York. New York State Museum Bulletin 324:1−365. Once the eggs hatch, the larvae and juveniles hide under small and large rocks in gravel beds.LaClaire, L. V. 1993. Status review of Ozark hellbender (Cryptobranchus bishopi). U.S. Fish and Wildlife Service status review. Jackson, Mississippi. Ozark hellbenders are highly sedentary creatures, meaning that neither males nor females have long distance dispersal rates.
Conservation status
The Endangered Species Act of 1973 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.Endangered and Threatened Wildlife and Plants; Review of Plant and Animal Species That Are Candidates or Proposed for Listing as Endangered or Threatened, Annual Notice of Findings on Recycled Petitions, and Annual Description of Progress on Listing Actions, 66 Fed. Reg. 54811 (Oct. 30, 2001). 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.Endangered and Threatened Wildlife and Plants; Review of Native Species That Are Candidates or Proposed for Listing as Endangered or Threatened; Annual Notice of Findings on Resubmitted Petitions; Annual Description of Progress on Listing Actions, 70 Fed. Reg. 24877 (May 11, 2005). 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.Endangered and Threatened Wildlife and Plants; Proposed Rule To List the Ozark Hellbender Salamander as Endangered, 75 Fed. Reg. 54561 (Sep. 8, 2010). In April 2017, a five-year review of the subspecies’ status was initiated.Endangered and Threatened Wildlife and Plants; Initiation of 5-Year Status Reviews of Eight Endangered Animal Species, 82 Fed. Reg. 18156 (Apr. 17, 2017).
IUCN 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.
Threats
Human impact The construction of reservoirs in the White River has destroyed Ozark hellbender habitats and separated their populations. These reservoirs also increase predation and the deposition of silt upstream from the reservoir, both of which threaten hellbenders. 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. Agricultural and construction runoff, waste disposal, and mining activity within the hellbender’s range pollute and degrade their habitat and threaten hellbender survival. Mining is especially detrimental as it increases zinc and leads hellbender habitats to dangerously high levels for aquatic life. Human and livestock waste from the areas surrounding hellbender habitats have further decreased water quality. 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.
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.
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. The Ozark hellbender also experiences predation from non-native rainbow and brown trout stocked in river for sport fishing.
Other threats