Date: 3/31/21 5:02 pm
From: John Harris <johnh...>
Subject: Re: [southbaybirds] Two Rodents on the Guadalupe River at Ulistac
Hi all,
This animal does not look like a Muskrat to me. I'm not an expert on any of
these species, but I did serve as a teaching assistant for the mammalogy
lab at UC Davis for four years, so I've seen plenty of specimens, and more
than a few wild sightings too. I would throw a third species into the mix
as far as possible identification: the Nutria, an invasive exotic.
Basically, in linear dimensions and mass, the Muskrat is close to a tree
squirrle or ground squirrel, while the Beaver and Nutria are much larger.
If you see the tail, it's an easy ID of course, as the Beaver has the
classic flat paddle-like tail, but if you don't see the tail, then other
features must suffice. One of the key features for Nutria is white
whiskers, and the pale appearance of the nose area made me wonder. Maybe if
you have some higher resolution photos that could be determined. If it's a
Nutria, it should be reported to California Department of Fish and
John Harris
Here's some basic size data on the relevant species, from the Peterson
Guide to Mammals.


Head and body length: 2-3 feet

Tail length: 1 foot

Weight: 35-70 pounds


Head and body length: 1 foot

Tail length: 1 foot

Weight: 2.5 pounds


Head and body length: about 2 feet

Tail length: about 1 foot

Weight: 10-24 pounds

Look for white whiskers

Some reference animals:

California Ground Squirrel

Head and body length: 10 inches

Tail length: 7 inches

Weight: 1-2 pounds

Western Gray Squirrel

Head and body length: about one foot

Tail length: about one foot

Weight: about 1.75 pounds

On Wed, Mar 31, 2021 at 10:37 AM Frank Vanslager via <Vanslagerf=
<> wrote:

> All:
> As Pete LaTourrette informed me, the photo I posted on 2/16/2021 of an
> almost submerged rodent could possibly have been a Beaver. Today's photos
> were taken from a spot about 150 yards north of the fencing at the pump
> spillway at Ulistac. The Muskrat/Beaver pair swam off downstream (left)
> together.
> Frank Vanslager

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