Nashville Zoo’s ectotherm team took a monumental step toward continuing the growth of the local wild population of Eastern hellbenders.
The team produced the largest amount of healthy Eastern hellbender eggs in human care through hormonal induction and artificial fertilization. These 24 healthy Eastern hellbenders are the largest success in seven years.
The team has successfully been using a hormonal induction and artificial fertilization technique since 2012. The zoo also made a significant breakthrough in 2015 when they welcomed the hatching of the first eastern hellbender that was artificially fertilized using cryopreserved sperm.
Throughout the years, the Zoo staff have experimented with different variables to see what would produce the best results. There are a lot of things that can impact successful fertilization and development including the age of the eggs at fertilization, sperm quality, water parameters, how much movement the eggs get during development and stray voltage.
This past September when fertilizing the eggs, the team experimented with a set of three to five different techniques, which ended up producing the largest amount of viable eggs in one group.
“In previous years, and the reason why this is so important, we’ve had success from a few different groups, so it was hard to come up with good tests of what was working and not working,” said Dale McGinnity, Nashville Zoo ectotherm curator. “Now that we have a protocol that works, we can reverse engineer to see what the variables are that made it successful by removing one variable from each group.”
Once the team gains more knowledge about what variables work best to produce the most offspring, they will be able to transfer that information to successfully breed Middle Tennessee hellbenders in the bio-secure facility. This will allow the wild population found in streams and rivers in Middle Tennessee to maintain their genetic diversity and thrive in the wild.
“We would also share this knowledge with other institutions in other states, so that they can maintain genetic diversity in their populations,” said Sherri Reinsch, Nashville Zoo lead Eastern hellbender keeper. “With artificial fertilization and reproductive technologies one clutch of egg can be fertilized with multiple males’ sperm to increase the genetic diversity of animals being raised for release.”
Once common and widely distributed in the eastern U.S, hellbenders are now rare throughout most of their range and are a candidate species for endangered status listing by the USFWS. Over the last 30 years, most hellbender populations have been in rapid decline due to erosion, damming, increased pollution and disease, but Tennessee and a few other southeastern states still harbor these amphibians.
“We’re all working toward the same goal, which is to keep the hellbender species alive and off the endangered species list,” Reinsch said. “Now we’re one step closer to making that happen.”
You can see the very first Eastern Hellbenders that were bred in human care on exhibit in the Unseen New World.
Zoo staff have collaborated with a number of other researchers over the years to achieve this success. Dr. Vance Trudeau from the University of Ottowa and Dr. Robert Browne, a conservation cryobiologist, have been especially important for this project.