Editing Hellbender (section)

===Reproduction===
The hellbenders' [[breeding season]] begins in late August or early- to mid-September and can continue as late as the end of November, depending on region. They exhibit no [[sexual dimorphism]], except during the fall mating season, when males have a bulging ring around their [[cloaca]]l glands. Unlike most salamanders, the hellbender performs [[external fertilization]]. Before mating, each male excavates a brood site, a saucer-shaped depression under a rock or log, with its entrance positioned out of the direct current, usually pointing downstream. The male remains in the brood site awaiting a female. Males will combat for nest sites, often biting to defend the nest rock of their choice.<ref>{{Cite journal |last=Unger |first=Shem |last2=Catherine M. Bodinof Jachowski |last3=Diaz |first3=Lauren |last4=Williams |first4=Lori A. |date=November 2020 |title=Shelter Guarding Behavior of the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) in North Carolina Streams |url=https://bioone.org/journals/southeastern-naturalist/volume-19/issue-4/058.019.0411/Shelter-Guarding-Behavior-of-the-Eastern-Hellbender-Cryptobranchus-alleganiensis-alleganiensis/10.1656/058.019.0411.short |journal=Southeastern Naturalist |language=en |volume=19 |issue=4 |doi=10.1656/058.019.0411.short |issn=1528-7092 |archive-url=http://web.archive.org/web/20240905042428/https://bioone.org/journals/southeastern-naturalist/volume-19/issue-4/058.019.0411/Shelter-Guarding-Behavior-of-the-Eastern-Hellbender-Cryptobranchus-alleganiensis-alleganiensis/10.1656/058.019.0411.short |archive-date=2024-09-05}}</ref> When a female approaches, the male guides or drives her into his burrow and prevents her from leaving until she [[Oviposition|oviposits]].<ref name=fws1/>

Female hellbenders lay 150–200 eggs over a two- to three-day period; the eggs are {{Cvt|18-20|mm}} in diameter, connected by five to ten cords. As the female lays eggs, the male positions himself alongside or slightly above them, spraying the eggs with sperm while swaying his tail and moving his hind limbs, which disperses the sperm uniformly. The male often tempts other females to lay eggs in his nest, and as many as 1,946<ref>{{cite book|title=Encyclopedia of Reptiles and Amphibians|author=Chris Mattison|year=2005|page=23|publisher=The Brown Reference Group}}</ref> eggs have been counted in a single nest. Males also exhibit mate and shelter guarding. Mortality rate is high for hellbender eggs.<ref name="Kaunert, M. D. 2023"/> Studies have found that until the female successfully reproduces, the male hellbender will guard her in his territory until the reproduction is complete. [[Cannibalism]], however, leads to a much lower number of eggs in hellbender nests than would be predicted by egg counts.<ref name=fws1/> Adult males are more likely to cannibalize their own offspring in degraded sites with limited food availability.<ref>{{Cite journal |last1=Hopkins |first1=William A. |last2=Case |first2=Brian F. |last3=Groffen |first3=Jordy |last4=Brooks |first4=George C. |last5=Bodinof Jachowski |first5=Catherine M. |last6=Button |first6=Sky T. |last7=Hallagan |first7=John J. |last8=O’Brien |first8=Rebecca S. M. |last9=Kindsvater |first9=Holly K. |date=2023-07-01 |title=Filial Cannibalism Leads to Chronic Nest Failure of Eastern Hellbender Salamanders ( Cryptobranchus alleganiensis ) |url=https://www.journals.uchicago.edu/doi/10.1086/724819 |journal=The American Naturalist |language=en |volume=202 |issue=1 |pages=92–106 |doi=10.1086/724819 |pmid=37384763 |bibcode=2023ANat..202...92H |issn=0003-0147}}</ref>

After oviposition, the male drives the female away from the nest and guards the eggs. Incubating males rock back and forth and undulate their lateral skin folds, which circulates the water, increasing oxygen supply to both eggs and adult. Incubation lasts from 45 to 75 days, depending on region.<ref name=fws1/> Males are known to show solitary parental care for the eggs and larvae for at least 7–8 months.<ref>{{Cite journal |last1=Galligan |first1=Thomas M. |last2=Helm |first2=Richard F. |last3=Case |first3=Brian F. |last4=Bodinof Jachowski |first4=Catherine M. |last5=Frazier |first5=Clara L. |last6=Alaasam |first6=Valentina |last7=Hopkins |first7=William A. |date=2021-11-01 |title=Pre-breeding androgen and glucocorticoid profiles in the eastern hellbender salamander (Cryptobranchus alleganiensis alleganiensis) |journal=General and Comparative Endocrinology |volume=313 |pages=113899 |doi=10.1016/j.ygcen.2021.113899 |pmid=34499909 |issn=0016-6480|doi-access=free }}</ref>

Hatchling hellbenders are {{Cvt|25-33|mm}} long, have a [[yolk sac]] as a source of energy for the first few months of life, and lack functional limbs.<ref name=fws1/>