“What we’re seeing is this insane level of aggressiveness,” Frederich told the Associated Press.
According to the research, even though the green crabs from both locations are related, genetic differences set them apart from one another. While the angry green crabs from Nova Scotia originate from northern Europe and are used to cold water, the green crabs in Maine came from southern Europe. According to the Washington Department of Fish and Wildlife, green crabs arrived to the U.S. in the 1800s and moved into Maine in the 1950s, feeding on the soft shell clam population there and causing it to start declining. From there, the creatures began slowly migrating to Nova Scotia.
“The green crab is most often confused with native helmet crabs or hairy shore crab,” the agency wrote on its website. “The most distinctive feature is not its color – which can vary from reddish to a dark mottled green – but the five spines or teeth on each side of the shell. There are three rounded lobes between the eyes, and the last pair of legs are somewhat flattened. The carapace is broader than it is long, and seldom exceeds 3.5 to 4 inches across.”
University of New England graduate student Louis Logan experienced some difficulties with the crabs when he had to label those captured in Nova Scotia’s waters during his research. The crabs attacked him at a distance of five feet and grabbed onto him — with no apparent intention of letting him go.
“Any time I went down to grab one they went to grab me instead,” he wrote in an email to The Associated Press.
As part of his research, he released both populations of green crabs on a space of eel grass. The angry green crabs from Canada destroyed their milder relatives from Maine. Frederich compared the damage done to that done by the fictional character Edward Scissorhands.
Green crabs were already known to be quite dangerous to existing ecosystems. The University of Washington has provided tips on what to do if you come across one.
Frederich said there will be more studies focusing on these crabs’ behavior to learn whether certain genes are responsible for their overly aggressive nature.
The angry green crabs migrating down from Nova Scotia take out only about 2% to 3% of the green crabs living on the ocean floor in Maine. However, those numbers will undoubtedly grow.
“It will be an entirely different ball game,” Frederich said. “It’s just a question of when more of the crabs come and out-compete the Maine green crabs. We can’t do anything about it. The only thing that we can do is learn how to live with it.”