Conserving Missouri's Hellbenders
Ettling, Jeff, Endangered Species Bulletin
The hellbender (Cryptobranchus alleganiensis) is the largest species of salamander native to North America. It is represented by two subspecies, the eastern hellbender (C. a. alleganiensis), which ranges from southern New York state south to northern Georgia and west to Missouri, and the Ozark hellbender (C. a. bishopi), which occurs only in south-central Missouri and adjacent north-central Arkansas. (For more on the Ozark subspecies, see the following article.) Missouri is the only state where both subspecies occur. These salamanders are perfectly adapted for spring-fed stream and river habitats with their flattened head and body, short stout legs, long rudder-like tail, and tiny eyes.
Over the last 30 years, biologists have collected extensive data on the Missouri populations of both the eastern and Ozark hellbenders. These studies indicate that there has been an approximately 80 percent decline in the hellbender population, with a major shift in the age structure to one composed of larger, older animals. The lack of young in these populations indicates either reproductive failure or high mortality of juvenile hellbenders. In addition, researchers have been finding increasing numbers of adult hellbenders with missing toes, limbs, and eyes as well as open lesions and tumors. At present, we know of no single cause for the observed decline, although habitat alteration resulting from dams, gravel mining, and increased recreational use appears to play a significant role. In addition, chemical contamination, other types of water quality problems, disease, and illegal collection have contributed to the decline.
In 2006, at the request of the Saint Louis Zoo, the Conservation Breeding Specialist Group (part of the Species Survival Commission of the World Conservation Union (IUCN), facilitated a workshop that produced a population and habitat viability assessment for the Ozark and eastern hellbenders. The workshop was hosted by the Saint Louis Zoo and attended by 30 invited individuals. The participants worked to explore threats to hellbender populations and develop management actions to halt the hellbender's precipitous decline. Workshop participants developed recommendations addressing biological and human-induced threats, land use issues, and captive reproduction. Their final report was published in early 2007.
The aging population of hellbenders in Missouri and the strong shift in age structure over the years highlight the need for more information on the general health of adult hellbenders and the lack of young age classes. With funding from the Saint Louis Zoo's Field Research for Conservation program, Dr. Yue-Wern Huang and colleagues at the University of Missouri--Rolla have provided preliminary information on hematology and serum chemistry, reproductive hormones, and chemical and nutrient assessments. Their research produced insight as to the next steps needed to help recover hellbenders in Missouri. Investigating and understanding health conditions, reproductive hormones, and heavy metals in hellbenders is important in assessing if this aging population can successfully reproduce in the wild, and in determining the feasibility of capturing wild specimens for long-term propagation efforts. …