A big female Lake Erie water snake and a territorial male goby. Snake researcher Dr. Rich King caught the snake out of the lake with the goby in its mouth... the snake was swimming toward shore to enjoy its meal. (Photo by Rebecca Williams)
These ten threats to the Great Lakes are complicated. Researchers are finding new ways that nature reacts to them. For example, alien invasive species often compete for food and crowd out the native species. Once a foreign species takes control in an area, there’s not much anyone can do to get rid of them. But occasionally, a native species will bite back. The Great Lakes Radio Consortium’s Rebecca Williams has that story:
Transcript
Invasive species have been a real problem for native species in the Great Lakes, but some native species are turning tails on the invaders. The Great Lakes Radio Consortium’s Lester Graham is our guide in exploring the series Ten Threats to the Great Lakes:
These ten threats to the Great Lakes are complicated. Researchers are finding new ways that nature reacts to them. For example, alien invasive species often compete for food and crowd out the native species. Once a foreign species takes control in an area, there’s not much anyone can do to get rid of them. But occasionally, a native species will bite back. The GLRC’s Rebecca Williams has that story:
(waves)
These islands in Lake Erie seem like floating Gardens of Eden. They’re
popular with tourists. These islands also really appeal to a rare
snake.
“So there’s a dozen or so of them heading out into the water.”
Meet the Lake Erie water snake. It can grow up to four feet long. Snake expert
Rich King and I are watching a bunch of them swimming away, gray heads
peeking up like periscopes.
These snakes like the lake. They like hanging out in huge piles on docks
and boats, and Rich King’s discovered the snakes love to eat round gobies.
Gobies are invasive fish that are thought to have hitched a ride in the
ballast water of ocean-going ships from foreign ports. The gobies eat the
eggs of native fish such as smallmouth bass, and compete with other fish for
food and nest sites. As gobies have taken over the lake bottom, the native
fish the snakes used to eat are getting harder to find.
“What we’re seeing is that the gobies are apparently a very abundant food
source for the water snakes. Compared to the 1980’s and early 90’s when the
snakes were feeding exclusively on native fish or mudpuppies – the snakes
are now consuming over ninety percent of their prey items are round gobies.”
(Sound of walking over rocks and zebra mussels)
Today, Rich King and his students from Northern Illinois University are
prowling the beaches for snakes. They carry their catches in faded
pillowcases tied to their belt loops. This is the annual snake survey,
Nerodio. That’s Nerodia, the snake’s scientific name, and rodeo, as in
cowboy roundup.
The snake biologists don’t just look under rocks. They dive into the lake
for snakes. They sneak up on piles of snakes and then grab the whole
writhing mass.
The snakes bite. The researchers’ arms are covered in snakebites. The bites aren’t life threatening, but they’re really, really bloody. And then it comes to the job at hand. The biologists are going to force the snakes’ stomach contents out. They call it “barfing the snakes.”
“Some snakes are easier to puke versus others. The water snakes, for
example, they sometimes voluntarily just, bleagh, just puke it out when you
pick them up.”
PhD student Kristin Stanford promises me it’ll be a good show, and we’re in
luck: just down the road, Rich King makes his first prize catch of the day.
“I got a snake with a goby in it. See the bulge: that’s the head end of
the goby. I’m virtually sure it’s a goby. (laughs) So you just very gently work it
forward, and drop it into our ziplock bag. That’s a round
goby.”
King says the snakes are growing faster and getting fatter on their goby
diet. Bigger snakes are less vulnerable to predators, and bigger females
can have more babies.
The researchers are pretty happy about that. That’s because the water snakes
are listed as threatened under the Endangered Species Act. This is the
only place in the world these snakes are found. For years, people were
shooting snakes and bashing them with rocks. Their numbers were getting
dangerously low.
The snake biologists say they understand that a lot of people hate and fear
snakes, but they say now that the snakes are eating gobies, they’re
starting to get a little more popular, especially with fishermen.
(Sound of fisherman casting a spinning rod)
Mark Green fishes for smallmouth bass. Green says it seems like when he
sees more snakes, he has better luck.
“If they’re eating the gobies, that is a good thing. I mean, I’m sure they have their
place… just not at my place.” (laughs)
Green didn’t realize until today that the snakes like to hang out under the
metal rim of the pier, right by his feet. He cringes, but his curiosity
gets the better of him, and he peeks inside one of the pillowcases bulging
with snakes.
GREEN: “When they get ahold of you, do they let go pretty quick, or do they…”
STANFORD: “Typically, but every now and then you get what
I call a “chewer,” and they’ll just sit there and errr-errr-errrng.”
The people and snakes are starting to arrive at an uneasy truce, and the
snakes seem to be well on their way to recovery from all the feasting on
gobies.
The researchers are hoping to learn just how big a bite the snakes can take
out of the goby population, and if, in the long run, it’s good or bad for
water snakes to depend on a foreign fish.
For the GLRC, I’m Rebecca Williams.