Subject: 'Possums, squirrels, and rats
Date: Jul 7 10:29:52 1995
From: Kelly Cassidy - kelly at cqs.washington.edu


Tweets,

Knowing how seldom this group ever wanders off topic :), I apologize
if anyone is offended by this post.

Dick Johnson and I are mapping the distribution of Washington mammals.
A chance mention of Columbian Ground Squirrels on tweeters produced so
much useful information that we are hoping that sharp-eyed birders
might have noticed a few of the mammals for whom the records are sparse.
If you can contribute anything about the distribution of any of these
mammals, please email me, preferably with dates, locations, and habitat
observations, especially if the observations are outside the
Seattle/Tacoma area.

First, the easy one:

Opossum: The opossum was introduced to the western US from the eastern
US. In Washington State, we have numerous records in the Puget Sound
from residential areas, farms, and along water courses. There are
many records from Seattle and Tacoma, one from Vancouver, and scattered
records throughout the Puget Trough. Along the coast, there is a
single known population from South Bend in Pacific Co. On the east
side of the state, there are records from Wenatchee and nearby Malaga
on the west side of the Columbia. We are interested in any sightings
outside of the Seattle/Tacoma area, but especially those along the
coast and on the east side. It seems odd that the opossum has not
spread beyond the Wenatchee area.

A harder one (for birders that enjoy identifying Empidonax <- note bird
reference):

Fox Squirrel (Sciurus niger): Also introduced from the eastern US.
Now in scattered cities, towns, and along some creeks in Washington.
We have records from: Seattle (at the UW and Arboretum)
Orcus Island
Walla Walla
Coppei Creek (Near border of Walla Walla and Columbia Co.)
Clarkston, Pullman, and towns between
Colfax
Okanogan River and towns along it, down to Brewster.
This squirrel seems more adaptable to 'natural vegetation in WA than
the (also introduced) Eastern Gray Squirrel. (The Eastern Gray is the
most common squirrel in the Seattle area.) Tree squirrels are not easy
to distinguish! You will have to get a good look or have the squirrel
in hand, and you will need to study the squirrel carefully against a
good field guide. You will need to supply an excellent description, or
a body, for a reliable record. (Note: please don't shoot at something
that looks like a Fox Squirrel; they look a lot like the increasingly
rare native Western Gray). We are especially interested in possible
sightings along the Methow River, where the Western Gray also occurs.

Western Gray (Sciurus griseus): A native. Hanging on in the Fort
Lewis area, Klickitat Co., and a few isolated locations up to the
Methow Valley. See squirrel ID precautions above. We are particularly
interested in any sightings north of Klickitat Co on the east side and
in Grays Harbor Co on the west side

Black Rats (Rattus rattus) and Norway rats (Rattus norvegicus). Both
introduced from Europe. The Norway rat is probably throughout WA in
cities. The Black Rat is on the west side and we have a record from
Wenatchee. The Black Rat is the biggest question mark. Some accounts
put it in natural vegetation, including old forests, at low elevations
on the West side. We are skeptical. Also, is it on the east side
outside of Wenatchee? For this species, we are interested in any
observations outside of an urban environment, or in any environment on
the east side outside of Wenatchee. For the Norway Rat, we would like
to know if they live in agricultural fields on the east side. *These
rats are very difficult to distinguish from one another.* You will
almost certainly need rat in hand. (And hand should be wearing glove;
these rats carry many diseases.) The field mark given in most field
guides as diagnostic is that the tail on the Black Rat is greater than
the length of the body and the tail on the Norway is less than the body
length. You will undoubtedly find yourself holding a rat with a tail
equal to its body length.

Oh, and any sightings of grizzly bears or gray wolves are also of
tremendous interest (and only slightly more likely than seeing a
California condor in Washington. <- Note bird reference).

Kelly Cassidy
Washington Cooperative Fish and Wildlife Research Unit
Univ of Washington
Seattle, Wa. 99185
206-685-4195