Date: 3/31/21 5:27 pm
From: Brooke Miller via <idbirds...>
Subject: Re: [southbaybirds] Two Rodents on the Guadalupe River at Ulistac

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—Brooke Miller

> On Mar 31, 2021, at 5:02 PM, John Harris <johnh...> wrote:
> 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 Wildlife.
> John Harris
> Here's some basic size data on the relevant species, from the Peterson Guide to Mammals.
> Beaver
> Head and body length: 2-3 feet
> Tail length: 1 foot
> Weight: 35-70 pounds
> Muskrat
> Head and body length: 1 foot
> Tail length: 1 foot
> Weight: 2.5 pounds
> Nutria
> 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...> <mailto:<>> 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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