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“Snakes! Why’d it have to be snakes?” – Indiana Jones
On August 16, 2011 the Lake Erie watersnake became only the 23rd species to ever be removed, or “de-listed,” from the U.S. Fish and Wildlife Service’s list of endangered and threatened wildlife. For the nearly 2,500 species on the list, the odds are stacked against recovery once a species starts a rapid decrease in numbers. So how did the Lake Erie watersnake, or LEWS, beat the odds? It took some scientists, a plan, and quite a bit of unexpected luck.
When the Lake Erie Islands were commercially developed for recreational water sports and vacation homes, the snakes’ shoreline habitat and much of its food source were drastically altered. Because the snakes have one of the smallest geographic ranges in the world – only found in about 100 square miles of Lake Erie in the U.S. and Canada – their survival was threatened. Their summer basking areas and winter hibernation places were disturbed, as was their food supply of bottom dwelling fishes. Add to that peoples’ general dislike of snakes, and a desire to remove them from the Lake Erie resort area, and you can see why these animals were in trouble. In the early 1990s the snakes’ population had been estimated at fewer than 2,000. They were first placed on the Federal Endangered and Threatened Species List in 1999.
Placement on the list meant that a monitoring and recovery plan had to be implemented. Kristin Stanford, a herpetologist with Northern Illinois University, became the Recovery Plan Coordinator for the LEWS. For the first several years of the recovery plan the focus was on answering several unknowns about the snake. Were the populations still decreasing? How much shoreline habitat do Lake Erie watersnakes need? Where do they hibernate in the winter? Despite the intensive efforts of the scientists assigned to the recovery project, the outlook for the LEWS was still uncertain.
And then a remarkable change took place. By monitoring the populations, the scientists began to find more and more of a relatively new non-native fish species, the Eurasian round goby (Neogobius melanstomus), in the snakes’ diet. The gobies accidentally came to Lake Erie in the ballast water of ocean-going cargo ships during the mid-1990s. To navigate the St. Lawrence Seaway and Great Lakes, cargo ships had to pump out ballast water to float higher in the shallow waters. With the ballast came the gobies. The gobies had been taken up when the ships pumped in ballast water from ports in the Caspian and Black Seas. The ballast water helped to stabilize the ships as they navigated the rougher and deeper Atlantic Ocean.
The round gobies’ diet consisted of the non-native zebra mussels, but also native fish eggs and small fry (very young fish). The Western Basin of Lake Erie, filled with yellow perch, smallmouth bass, walleye, and other native game fish, became a favorite eating stop for the gobies. Schools of gobies were capable of devouring entire nests of unprotected eggs in less than a half-hour, and the future of the native sport fish was being threatened by this new invader. In just 5 years, the Lake Erie water snakes were able to adapt to the changing conditions in the lake and they put the gobies on their dinner table! In fact, more than 90% of the Lake Erie watersnakes diet is now made up of round gobies!
Since 2004, the Lake Erie water snakes have thrived because of their protected status and the abundant food source that the gobies provided. They increased their survivorship rate, their reproduction rate, their physical growth rate, and their population numbers – now estimated at 12,000 – 15,000.
So what next for the LEWS? They will be monitored for at least five more years under a “post de-listing” monitoring plan. More than 300 miles of Lake Erie shoreline has been marked as protected nature preserve. And their new neighbors – humans – are learning to ‘Respect the Snake’ after they came back from the brink of extinction.