26 
JOURNAL OF MAMMALOGY 
When the temperature drops below ~30“F. very few squirrels are active, and 
they become dormant at lower temperatures. Trails are worn in the snow con- 
necting the various trees visited by the squirrels, and sometimes tunnels through 
the snow are used for the same purpose. When passing from tree to tree on the 
ground the squirrels usually run hurriedly and often whimper nervously as though 
afraid. Squirrels bother trappers by springing the traps set for fur animals. This 
is perhaps done out of curiosity, as no case was observed where the squirrel had 
eaten the bait or disturbed any animal taken in the traps. A red squirrel strug- 
gling with a half-grown mink was noted July 15, 1912, on the bank of the Kus- 
kokwim a short distance above the mouth of the Takotna River. Our boat drifted 
by before the result of the struggle could be determined, but the squirrel was 
constantly screaming, and it seemed certain that the result would be a victory 
or the mink. 
Mating behavior in 1912 was first noted at the head of the North Fork of the 
Kuskokwim on March 1. A squirrel about half-changed to summer pelage was 
seen at that place June 10. One child’s parka (outer winter garment) of red 
squirrel skins was seen near Tanana, but the fur is not used to any extent by 
the Indians and is seldom purchased by traders. 
Glaucomys sabrinus yukonensis (Osgood). Yukon Flying Squirrel. — One 
was trapped October 15, 1911, and two November 2, in a white spruce and paper- 
birch forest in the hills 8 miles north of Tanana. One specimen was taken in a 
steel trap set near a stump and baited with a grouse head. This animal and 
another specimen caught at the same place in a mouse trap had bitten off and 
destroyed their tails before dying. A third specimen caught in a rat trap and 
held in such a manner that it could not reach its tail was in perfect condition. 
Castor canadensis canadensis Kuhl. Canada Beaver. — A number of workings 
were noted at the head of the North Fork of the Kuskokwim; ten skulls were 
seen on the roof of a cabin at the junction with the McKinley Fork, evidently 
taken at that place, and beavers were reported on good authority to occur rarely 
along the Takotna River. The Indians are very fond of beaver flesh, and they 
are said to kill them in spite of the closed season. 
A beaver house was located near the spring camp at the head of the North Fork 
and a number of observations were made on the members of this house. The 
house was placed on the lower end of a point of land where a slough joined the 
Kuskokwim River, here about ten yards in width. The number of individuals 
living in the house was five, as nearly as could be determined. Willow cuttings 
were extensive along the slough above the house, along the river above the 
house, along a small slough entering the river opposite the house, and for a short 
distance down the river below the house. A few poplars and small birches had 
been cut down. A small dam of sticks and mud was thrown across the mouth of 
the small slough opposite the house. 
The beavers first appeared in the spring of 1912 on April 28, when the water 
had risen in the river and the ice was going out. On that date two beavers were 
:seen about 5 p.m. in the slough near the house. By May 3 the ice had cleared out 
of this part of the river, and a number of fresh cuttings appeared in the nearby 
willows and birches. 
The beavers were to be seen only during the darker part of the night; during 
June, however, this was only a slightly modified daylight. In April they usually 
