Then there are weird muskrats. In the Klamath Basin, in southern Oregon east of the Cascades, muskrats were not native to the landscape. They were introduced first in the 1920's, and the first introductions were of course by a couple of enterprising ranchers. The original stocks came from Minto Flats area outside of Fairbanks! They were valued for their very dark pelts. However, they were pretty small compared to their Louisiana cousins, and as such, another batch was brought in from there.
When the fur boom went bust, like so many other fur farms that went under, the rats were turned loose.
The Basin is perfect habitat for the rats and they flourished, to the chagrin of some here that rely on ditches and dikes to manipulate the water here.
Enter me, and a biologist that steered me to a fellow with an 800 acre rat problem. This is only the 2nd year I have trapped the property, and while I try to at least put a dent in his problems, he is adjacent to an even bigger, (roughly 1 mile by 12 mile), problem. A perfectly un-disturbed rat marsh heaven that is completely un-molested.
These three rats were taken the same day within 50 yards of each other.