Have Nutria really spread that far North ? That's not good.

Wow - neat timing - I think its a nutria too based on the orange (more than yellow) teeth and the extensive white around the face, but it could maybe be a muskrat. How bit was it and was it moving its tail to help it swim?

Yeah, it was neat to be at Blackwater at the same time as that New York Times article: "In Maryland, nutria were released from a fur farm next to the Blackwater Reserve in the 1940s. By the 1990s, they were as many as 50,000 in the reserve. Richard Elzey, 58, recalled that he could walk across the marshes when growing up near Blackwater. Today, that same area — roughly 5,000 acres — is a vast lake clogged with silt."

I reported this sighting to Steve Kendrot, the eradication project's biologist and quoted in the article.

In terms of size and moving its tail, I didn't get a good sense of it (or more accurately, wasn't paying close enough attention). More large aquatic rodent sightings that morning: here, here, here, and here. The last one is also curious.

Thanks Steve. Happy to be wrong. Makes sense, it was pretty far off, but I guess I would expect to still see the white whiskers.