This June and July, Nashville Zoo team members waded into the waters of Middle Tennessee to successfully release a total of 29 eastern hellbenders back into the wild. These hellbenders had been raised at the Zoo for the past six years as part of a headstart program, after being collected as eggs from streams in Middle Tennessee.
This hellbender headstart program was started because researchers had observed a decline in juvenile animals in the wild and were only finding fewer and larger animals in most rivers over time. This lack of recruitment into the population indicated something was likely causing a low survival rate of eggs or larvae. With this slow decline over several decades, hellbenders had disappeared from most of their formerly extensive range in Tennessee. The Zoo collected eggs from the wild and raised the giant salamanders for six years until they were young adults and then released them back into the wild. At this size, they could be fitted with transmitters so that they could be followed to determine the success of the project. So far, all the hellbenders are doing well!
Along with Nashville Zoo, Tennessee Wildlife Resources Agency (TWRA), and Tennessee State University were involved in the project and will be documenting these hellbenders', hopefully successful, return to a Middle Tennessee river. Hellbenders are listed as a state endangered species due to the dramatic declines researchers have documented over the last few decades in the state. These declines, which appeared to have started in the 1990s, have also been seen in other states throughout the species range. There are only a few rivers and streams with healthy populations left in Tennessee where you can still find larvae, young animals, and lots of adults. These healthy populations are only located in heavily forested watersheds located in National Parks or U.S. Forest Service lands in the mountains of Tennessee.
Our hellbender conservation team has made incredible strides in past and present breeding initiatives. Nashville Zoo spearheaded the first successful captive breeding and first controlled breeding of eastern hellbenders with biotechnology in 2012, and the first successful hatching as a result of fertilization with cryopreserved sperm in 2015.
As for future plans, we hope to continue boosting this genetically distinct and highly threatened Middle Tennessee population through our established headstart program. We still have about 140 hellbenders in our Native Aquatic Conservation Center and plan to release them over the next few years as they grow up. We also plan to collect more eggs for the headstart program and further develop our breeding program.
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