by Sara Shipley, St. Louis Post-Dispatch
November 8, 2004
Scientists from five states met at the St. Louis Zoo last week to continue working on a plan to prevent North America's largest salamander from disappearing.
Members of the Hellbender Working Group feel they have little time left to save the animals in Missouri and Arkansas, where hellbender populations have plummeted in the past 30 years. About 35 people shared the latest research and plans for helping prevent the extinction of the 2-foot-long salamander, which lives in a few cold, spring-fed Ozark streams.
Stanley Trauth, a zoology professor at Arkansas State University, showed pictures of hellbenders with gruesome open sores, tumors and missing limbs and eyes. He said that nine out of 10 animals found in the Spring River this year had serious abnormalities, and he considered the animal extirpated from that stream.
"I'm at a loss, folks," Trauth said. "We just don't have a good explanation for what's causing this."
Max Nickerson of the University of Florida, who has worked with hellbenders for three decades, said his early research did not find nearly as many abnormalities. In 1969, out of 202 animals, he found only two with missing digits, two with head scratches and one split tail, he said.
"What you're looking at here is baffling," Nickerson told the group.
The constantly shrinking number of animals was a theme of the meeting. Researchers could easily find 100 hellbenders in a day in the 1970s and '80s; now they're lucky to find a few.
Biologists figure that many factors may have hurt the hellbender, including logging, gravel mining, sewage plant effluent, agricultural runoff, introduction of trout, disturbance from boaters, poaching, deliberate killing and scientific collection.
Ben Wheeler, a graduate student at Arkansas State University, documented habitat changes on the Spring and Eleven Point rivers, which flow from Missouri into Arkansas. "It's not that easy" to determine which factors are important, he said. He found evidence that hellbenders fare poorly in streams with lots of willows and other plants growing out of the water, perhaps because they slow down the current and capture sediment.
Other scientists are investigating water quality issues, including the possible influence of endocrine-disrupting chemicals on hellbender reproduction.
Another research project involves the impact of trout, which are not native to Missouri. Alicia Mathis, a behavioral ecology professor at Southwestern Missouri State University in Springfield, found that young Missouri hellbenders do not recognize trout as a predator. That could make them easy dinner for a fish.
To address that issue, Mathis is now working on "predator recognition training" - teaching little hellbenders to freeze when they smell trout in the water. Mathis has successfully trained newts to avoid certain fish and taught gray-bellied salamanders to avoid certain kinds of habitat. The animals learn to avoid the item associated with a negative stimulus, in this case an "alarm chemical" amphibians release when they are captured.
Mathis considered her earlier work "basic biology," geared toward understanding how animals learn in the wild. Now she hopes to apply the technique to some of the 150 young hellbenders being reared in tanks at the Zoo.
If the project works, the schooled youngsters could be released into the wild with less chance of being eaten.
"It could be a shot in the arm, for a population that really needs a shot in the arm," she said. One biologist questioned whether Mathis was getting "the cart before the horse" because no one has yet proved that trout are a problem for hellbenders. Trout fishing is a popular activity in the Ozarks, and Missouri Conservation Department trout stocking has quadrupled in the past 40 years, according to data compiled by Kellie Alsup of St. Louis University.
Mathis replied that reproductive problems appear to be a primary issue as well. "I think it's unlikely that trout are the total explanation," she said.
Republished with the permission of the St. Louis Post-Dispatch.
Copyright 2004 St. Louis Post-Dispatch
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