Lake Erie Watersnakes
Invasive Species, Demography, and Population Recovery of the Threatened Lake Erie Watersnake.
The Lake Erie watersnake, Nerodia sipedon insularum, has been a research subject of mine since I began graduate school. The distribution of this snake is one of the most restricted of any North American vertebrate taxon, encompassing a cluster of islands in western Lake Erie that span an area less than 40 km in diameter. Initially, my interest in this snake focused on the processes responsible for color pattern differences between Lake Erie watersnakes and the Northern watersnakes found at nearby mainland sites. In 1996, the US Fish and Wildlife Service funded my students and I to provide updated information on the distribution and abundance of this snake, information that contributed to its being listed as federally threatened and state endangered in 1999. We were then asked to participate in the conservation management of this snake by contributing to the development of the federal recovery plan and in conducting recovery-related activities, including population monitoring and public outreach. Through persistence and good fortune, I have managed to maintain continuous external funding for this work, allowing me to support Kristin Stanford as a full-time research associate. Kristin's responsibilities are divided between Lake Erie watersnake research (the basis for her PhD dissertation) and public outreach, a key element in reducing human-caused mortality of Lake Erie watersnakes, tasks for which Kristin is uniquely qualified. It has also allowed us to conduct important basic research on invasive species, watersnake demography, and population recovery. The North American Great Lakes are now home to more than 180 aquatic invasive species, many arriving in ballast water carried by trans-Atlantic ships. The round goby, a bottom dwelling fish, is one of the most recent invaders, arriving in Lake Erie in 1993 and rapidly increasing to a population of ca. 10 billion in Lake Erie's western basin. This invasion resulted in a wholesale change in Lake Erie watersnake diet with round gobies now constituting more than 90% of watersnake prey (King, Ray, and Stanford 2006; Jones et al. 2009). Furthermore, data from before and after the round goby invasion has allowed us to demonstrate both functional and numerical responses by Lake Erie watersnakes to invasive round gobies. Watersnakes now grow faster, attain larger body size, and produce more offspring than they did before the round goby invasion (King, Ray, and Stanford 2006; King, Queral-Regil, and Stanford 2006). Annual population surveys, involving NIU undergraduates, graduate students, professional herpetologists, and local residents, have generated a capture-mark-recapture dataset that now spans nearly 30 years and includes more than 16,000 capture records. This dataset is providing an unusually detailed picture of survival and population trends. Lake Erie watersnake survival exceeds that of watersnakes elsewhere and adult population size is increasing at a rate of about 6% per year. Rapid population recovery has led the USFWS to initiate delisting of the Lake Erie watersnake. This is a truly remarkable event. Of nearly 1900 species currently protected under the U.S. Endangered Species Act, just 22 have been delisted following population recovery.
Overview of Lake Erie Watersnake Biology and Conservation
King, R. B., A. Queral-Regil, and K. M. Stanford. 2006. Population size and recovery criteria of the threatened Lake Erie watersnake: Integrating multiple methods of population estimation.
Map of the Island Region (This map may be used as long as credit is given to Barbara Ball and the Department of Biological Sciences, Northern Illinois University. The map is also available in .psd format, upon request.)
Natural Selection, Gene Flow, and Color Pattern Variation
Ray, J. M., and R. B. King. 2006. The temporal and spatial scale of microevolution: fine-scale color pattern variation in the Lake Erie watersnake, Nerodia sipedon insularum. Evolutionary Ecology Research. 8:915-925.
Gorging on Gobies: Beneficial Effects of Alien Prey on a Threatened Vertebrate
King, R. B., J. M. Ray, and K. M. Stanford. 2006. Gorging on gobies: beneficial effects of alien prey on a threatened vertebrate. Canadian Journal of Zoology 84:108-115.(http://www.bios.niu.edu/rking/lab/Pubs/Can.J.Zool2006.pdf)
Jones, P. C., R. B. King, K. M. Stanford, T. D. Lawson, and M. Thomas. 2009. Frequent consumption and rapid digestion and prey by the Lake Erie watersnake with implications for an invasive prey species. Copeia. In press.
King, R. B., K. M. Stanford, and J. M. Ray. 2008. Reproductive consequences of a changing prey base in island watersnakes (reptilia: colubridae). South American Journal of Herpetology. 3:155-161.
Contaminants
Fernie, K. J., R. B. King, K. G. Drouillard, and K. M. Stanford. 2008. Temporal and spatial patterns of contaminants in Lake Erie watersnakes (Nerodia sipedon insularum) before and after the round goby (Apollonia melanostoma) invasion. Science of the Total Environment 406:344-351.
Lake Erie Watersnakes: Unique Residents of the Lake Erie Islands
Brochure (pdf format)
LINKS:
Ohio Department of Natural Resources Division of Wildlife
Ohio Ecological Services Office - U.S. Fish & Wildlife Service