EVANSVILLE — Conservation of an endangered Indiana salamander took a step forward in October when, for the first time, Eastern hellbenders were bred naturally in captivity.

The eggs were discovered the morning of Oct. 7 in a nest box in an artificial stream at the Mesker Park Zoo in Evansville. Zoo staff celebrated as the news spread.

“Folks were just calling over the radio, cheering,” said Susan Lindsey, animal curator at the zoo and botanic garden. “Everybody, even if they never worked with hellbenders, knew what a big deal this was.”

Eastern hellbenders are the largest North American salamander, known to grow up to 29 inches and with a lifespan of over 30 years.

They are a sentinel species. Like a canary would warn miners of dangerous gases, an absence of hellbenders warns of poor water quality.

Living their entire lives in the water, absorbing oxygen through capillaries near the surface of their skin, hellbenders need a flowing stream with a rocky bottom free of sediment.

They started to decline in Indiana in the 1960s, said Nick Burgmeier, a research biologist and extension wildlife specialist at Purdue University.

“By the early ‘80s they were almost gone, other than in the Blue River,” Burgmeier noted.

“They’re fully aquatic and they’re fairly sensitive, especially their eggs and their larvae. They are usually one of the first aquatic animals to decline when you start seeing water-quality changes.”


Construction of Mesker’s artificial stream, designed to mimic the Blue River, began in 2016. The first hellbenders were placed in the stream in 2017.

Hellbenders breed in the fall, and each year changes were made to the water in the stream and the ratio of males and females.

The male, Knick, guarded the clutch of 68 eggs for the first two weeks before they were moved to a specialized tank where their development could be monitored.

Mesker officials are uncertain which of the three female hellbenders — Tiamat, X-23 and Matilda — in the stream mated with Knick.

On a trip to Eastern Kentucky to collect eggs with the Kentucky Department of Fish and Wildlife, Burgmeier found cooler stream temperatures, and the Mesker artificial stream was changed accordingly.

“We had just taken the temperature about three or four days before in Indiana, and the temperatures over there were about 3 to 4 degrees Celsius cooler. ... It was much cooler,” Burgmeier explained.

While researchers aren’t sure whether the temperature modification prompted the hellbenders to mate, Mesker plans to use the same variables next year.

“Whether or not it was just our time, whether or not it was lowering the temperature, whether it was some of the other things that we did in terms of phosphate values, we’re not sure which one. But I tell you we’ll be doing the same thing next year,” Lindsey said.

The successful hellbender breeding collaboration was years in the making. Purdue University has been involved in the effort since 2007.

“We have an adaptive management model where we take research, learn from it, ask new research questions,” explained Rod Williams, professor of wildlife science and extension wildlife specialist with Purdue. “Once we get those answers, we try to pivot based on what the research is telling us.”

When the research showed captive breeding as the way forward, Purdue started seeking partners.

“This is very much a project that couldn’t be done without partners,” Lindsey said. “We were very lucky to get some funding to help us. We’re not the biggest zoo in Indiana, by any means, or the ones with the deepest pockets. But this is something that’s right in our backyard, and we wanted to help and make a difference.”

In 2011 the St. Louis Zoo bred Ozark hellbenders, the other of the two subspecies.

The following year, Nashville Zoo hatched two Eastern hellbenders using artificial insemination. In 2015, they did it again using frozen sperm.

Mesker was the first to breed the Eastern hellbender naturally.


Hellbenders hatched from eggs collected in the wild at Purdue’s lab are raised for four years before being reintroduced to the wild. They start in tanks before being moved to two artificial streams designed to acclimate them to their native environment.

Williams and Burgmeier are optimistic about restoring wild populations in Indiana with captive-reared animals.

“I think it was 119 hellbenders that we had transmitters in for the first couple of years, and they did pretty well. We got between roughly 50% and 75% survival,” Burgmeier said.

Thanks to better soil conservation practices, such as no-till farming and cover crops, along with the removal of dams, Purdue is releasing hellbenders into improved habitat, according to Williams.

The Natural Resources Conservation Service and the Soil and Water Conservation Districts “folks have been fantastic in working with those farmers and utilizing those conservation practices to improve soil health and minimize erosion,” Williams said.

“We’re really hopeful in the next two years we start finding eggs from (hellbenders) that we’ve released, and that’s what is really going to indicate to us that we’ve turned the corner.”

Follow Don Knight on Twitter @donwknight, or call 765-622-1212 ext. 204567.

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