Looks like Otters were here just before Don arrived in this World.
the modern river otter is closely related to the otters of Europe, and did not appear in North America until about 1.9 Mya.[7] The earliest known fossil of Lontra canadensis was found in the US Midwest and is from the Irvingtonian stage (the geologic timescale that spans the period 1,800,000 to 300,000 years ago).[8] The oldest fossil record of an Old World river otter comes from the late Pliocene epoch (3.6 to 1.8 Mya).[9] The New World river otters originated from the Old World river otters after a migration across the Bering Land Bridge, which existed off and on between 1.8 million to 10,000 years ago. The otters migrated to North America and southwards again across the Panamanian Land Bridge, which formed 3 Mya.[3]
http://en.wikipedia.org/wiki/North_American_River_Otter
I thinks it's a good thing they are making a come back since they belong here. They just need to be kept in check. Lets hope the Cougar's and Bears help keep the population in order. If not man will need to step in and we know how that story ends.