Editing Hellbender (section)

==Ecology==
Hellbenders are found in clear, clean water, and their presence is an indicator that the water is of good quality.<ref name="Keitzer">Keitzer, S. C., Pauley, T. K., & Burcher, C. L. (2013). Stream characteristics associated with site occupancy by the eastern hellbender, Cryptobranchus alleganiensis alleganiensis, in southern West Virginia. ''Northeastern Naturalist'', ''20''(4), 666–677.</ref> The hellbender salamander, considered a "habitat specialist", has adapted to fill a specific niche within a very specific environment, and is labeled as such "because its success is dependent on a constancy of dissolved oxygen, temperature and flow found in swift water areas", which in turn limits it to a narrow spectrum of stream/river choices.<ref name=cryptobranchus291/> As a result of this specialization, hellbenders are generally found in areas with large, irregularly shaped, and intermittent rocks and swiftly moving water, while they tend to avoid wider, slow-moving waters with muddy banks and/or slab rock bottoms. This specialization likely contributed to the decline in their populations, as collectors could easily identify their specific habitats.<ref name=cryptobranchus291/> One collector noted, at one time, "one could find a specimen under almost every suitable rock", but after years of collecting, the population had declined significantly.<ref name=pennsylvania362>{{cite journal |last=Swanson |first=P.L. |title=Notes on the Amphibians of Venango County, Pennsylvania |journal=American Midland Naturalist |date=September 1948 |volume=40 |issue=2 |pages=362–371 |doi=10.2307/2421606|jstor=2421606 |s2cid=87410957 }}</ref> The same collector noted, he "never found two specimens under the same rock", corroborating the account given by other researchers that hellbenders are generally solitary; they are thought to gather only during the mating season.<ref name=pennsylvania362/><ref name=cryptobranchus604>{{cite journal |last1=Humphries |first1=W.J. |last2=Pauley |first2=T.K. |title=Seasonal Changes in Nocturnal Activity of the Hellbender, ''Cryptobranchus alleganiensis'', in West Virginia |journal=Journal of Herpetology |date=December 2000 |volume=34 |issue=4 |pages=604–607 |jstor=1565279 |doi=10.2307/1565279}}</ref> If rocks are lacking, hellbenders have been known to use holes in stream banks as habitat.<ref name="Keitzer" /> On average, their home range is estimated to be 198 square meters as of 2005.<ref>W. JEFFREY HUMPHRIES and THOMAS K. PAULEY "Life History of the Hellbender, Cryptobranchus alleganiensis, in a West Virginia Stream," The American Midland Naturalist 154(1), 135–142, (1 July 2005). https://doi.org/10.1674/0003-0031(2005)154[0135:LHOTHC]2.0.CO;2</ref> The ideal habitat for a hellbender has a large amount of gravel, low pH, cool water temperatures, and low specific conductivity. The large amounts of gravel enable the hellbender to hide, cool water temperatures allow for more efficient cutaneous gas exchange, and low specific conductivity may indicate an undisturbed stream. Hellbender communities may be more concentrated in undisturbed areas.<ref name="Keitzer" />

Both subspecies, ''C.&nbsp;a. alleganiensis'' and ''C.&nbsp;a. bishopi'' undergo a [[metamorphosis]] after around a year and a half of life.<ref name=cryptobranchus291/> At this point, when they are roughly {{Cvt|13.5|cm}} long, they lose the gills present during their larval stage. Until then, they are easily confused with mudpuppies, and can be differentiated often only through toe number.<ref name=fws1/> After this metamorphosis, hellbenders must be able to absorb oxygen through the folds in their skin, which is largely behind the need for fast-moving, oxygenated water. If a hellbender ends up in an area of slow-moving water, not enough of it will pass over its skin in a given time, making it difficult to garner enough oxygen to support necessary respiratory functions. A below-favorable oxygen content can make life equally difficult.<ref name=pennsylvania362/>

Hellbenders are preyed upon by diverse predators, including various fish and reptiles (including both snakes and turtles). Particularly, largemouth bass is a predator that can consume a hellbender 1–3 years old.<ref name="Kenison-2018">{{Cite journal |last1=Kenison |first1=Erin K. |last2=Williams |first2=Rod N. |date=2018 |title=Training for Translocation: Predator Conditioning Induces Behavioral Plasticity and Physiological Changes in Captive Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis) (Cryptobranchidae, Amphibia) |journal=Diversity |language=en |volume=10 |issue=1 |pages=13 |doi=10.3390/d10010013 |doi-access=free |bibcode=2018Diver..10...13K |issn=1424-2818}}</ref> [[Cannibalism (zoology)|Cannibalism]] of eggs is also considered a common occurrence.<ref name=amphibiaweb1/> One study found that in areas with increased deforestation, the likelihood of [[filial cannibalism]] increases.<ref>Hopkins, William A., et al. "Filial cannibalism leads to chronic nest failure of eastern hellbender salamanders (Cryptobranchus alleganienesis)." The American Naturalist 202.1 (2023).</ref>

In another study by Kenison & Wilson (2018), researchers found that young, captive hellbenders showed altered behavior in response to predatory fish nearby. Because of their altered behavior, it was observed and concluded that hellbenders are capable of detecting [[kairomone]]s, which are chemical cues emitted by predatory species. This suggests that hellbenders can recognize kairomones as stressful stimuli and identify potential predators.<ref name="Kenison-2018" />