December 2020 Edition | Volume 74, Issue 12
Published since 1946
First Natural Breeding of Eastern Hellbender in Captivity
A nest full of eastern hellbender eggs was discovered at the Mesker Park Zoo and Botanic Garden marking the first time that this species has bred naturally in captivity. The discovery signifies the culmination of a long and collaborative effort to breed the species and restore this endangered species to its native environment. The historic breeding occurred October 7, 2020 and has produced 68 fertile eggs. It will take an estimated 72 days for those eggs to hatch into larvae. The hatched larvae, typically between one and two inches long, will retain their yolk sacks for nutrients for another several months. The larvae will develop legs over time and eventually lose their external gills by age two. Hellbenders have a lifespan of more than 30 years.
The Mesker Park Zoo and Botanic Garden, located in Evansville Indiana, partnered with Purdue University Forestry and Natural Resources to construct an artificial stream, or raceway, which was meant to simulate the habitat of Indiana’s Blue River and serve as a breeding ground for the hellbenders in captivity. In 2017, the first adults were put into the artificial stream, which measures 22- feet 1-inch long, 4 feet wide and 2.5 feet deep. Over the next four breeding seasons, alterations were made annually to create favorable conditions for breeding. This included changing the male:female ratio in the stream and also adjusting water quality parameters.
Purdue Forestry and Natural Resources’ Rod Williams and his lab captured five of the six hellbenders involved in breeding at Mesker Park Zoo (three males and two females, all of which were captured in the Blue River between 2015 and 2018) and were instrumental in coordinating the procurement of the third female from West Virginia in 2019.
Hellbender populations are declining across their range, from Missouri to New York. This decline, which affects the hellbender population in Indiana's Blue River, is likely caused by human influences such as habitat degradation and destruction. The stream-bottom habitat of hellbenders can be degraded by sediment from eroded banks and fields and destroyed when streams are dammed or dredged.
The captive breeding efforts were made possible by long-term support from the Evansville Zoological Society. Grant funds that helped construct the hellbender facilities were received from Aquarium and Zoo Facilities Association’s Clark Waldram Conservation Fund, Pittsburgh Zoo & PPG Aquarium’s PPG Conservation and Sustainability Fund, and Association of Zoos and Aquariums Amphibian Taxon Advisory Group’s Small Grant Fund.
There are two subspecies of Hellbender, the eastern hellbender (Cryptobranchus alleganiensis alleganiensis) and the Ozark hellbender (Cryptobranchus alleganiensis bishopi). The eastern hellbender is a large, fully aquatic salamander, nicknamed the snot otter, water dog, devil dog, Allegheny alligator and water eel among other things. At maturity, the species can measure approximately two feet long.
The Saint Louis Zoo was the first to breed Ozark hellbenders, the other subspecies of hellbender, doing so back in 2011. The Nashville Zoo was the first to successfully hatch eastern hellbender eggs using artificial insemination in 2012. They repeated the feat in 2015 using cryopreserved sperm (another first).