Categorized | Imperiled Wildlife

Lake Erie watersnake recovery is a success for the ESA – and for invasive species?

Photo courtesy of Richard King. Lake Erie watersnake (bottom), with two closely related specimens. The Lake Erie watersnake has fully recovered from the threat extinction thanks to the ESA, and will soon be delisted.

This past Tuesday, the U.S. Fish and Wildlife Service announced that the Lake Erie watersnake, Nerodia sipedon insularum is now fully recovered and will be removed from the federal endangered species list (76 Fed. Reg. 50680). With a population of just under 10,000 snakes in 2010 (almost two times the recovery target), the Lake Erie watersnake joins the ranks of the bald eagle, the Aleutian Canada goose, the American alligator, and 18 other species that have come back from the brink of extinction, thanks to the regulatory protections and conservation measures of the Endangered Species Act (ESA). This event comes as a welcome victory after furious debates over a rider-ridden House Interior Appropriations bill in July and early August. The watersnake’s delisting is a success that proves the ESA is not broken, as critics are wont to declare, and instead reinforces the Act’s long record of success.

Listed as ‘threatened’ only 12 years ago, the Lake Erie watersnake’s recovery story has a twist to it: its remarkable resurgence was, in part, made possible by an “invasive” species, the round goby. Since the round goby first appeared in Lake Erie in the early 1990s, the watersnake’s diet has changed from being based on native fishes and amphibians to a diet composed of more than 90% round goby, with remarkable consequences – increased watersnake growth rates, increased body size, and increase in fecundity, with female watersnakes producing on average 25% more offspring post-invasion (Richard B. King Laboratory, Northern Illinois University). Increase in benthic fish biomass in Lake Erie increased prey availability, effectively dismissing the issue of low watersnake fecundity; the round goby’s success in the ecosystem means that the watersnake has a significant and secure prey source for years to come.

The narrative of the Lake Erie watersnake’s recovery adds an interesting dimension to discourse on invasive species and how we evaluate their impacts on ecosystems. While the majority of the literature focuses on the detrimental effects invasives have on the adopted environment (Byers 2002, Fritts and Leasman-Tanner 2001, Rhymer and Simberloff 1996, etc.), the potential benefits to ecosystems deserves the scientific community’s attention, and calls for an honest appraisal of the current stigma against invasive species.

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Katherine Eshel is the Endangered Species Policy Intern for Defenders of Wildlife. Katherine works on research and writing projects for various endangered species policy issues, including current regulatory reform.

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