Canada is having trouble with what they call "very rude" green crabs that are messing up the ecosystem and get into fighting stances if they as much as see the scientists trying to study them. Some will even jump out of the water to attack.
Random fact: Apparently, there's a kind of daphnia (tiny water critter) or something that is quite common in creeks and rivers in Canada and the US -and also in one river in Denmark. Research indicated they've been in that river for about a 1000 years. Since they are strictly freshwater-only creatures, the most logical explanation is they hitched a ride in viking water barrels filled in Vinland before the vikings returned home (cleaning out their barrels of the by then pretty stale leftover water in that one Danish river).
"The scientists are researching how water temperature and salinity might alter the crabs' behavior, according to the University of New England, and even putting crabs on treadmills to test their endurance and metabolism."
For some reason the image of a crab in a treadmill in my head made me burst with laugher