Nature Notes

Mount Rainier National Park

Vol. III July 15th, 1925 No. 3

Issued weekly during the summer season, monthly during the winter by the Nature Guide Service.
F. W. Schmoe,
Park Naturalist.
O. A. Tomlinson,

By Charles Landes, Nature Guide.

What is the animal that makes all the burrows along the trail? This is a question asked often by the visitors who travel the mountain trails. When told that the animal is the mountain beaver, the usual reply is, what a strange life for a beaver.

As a matter of fact the animals making these burrows are not beaver at all and have no characteristics in common with the beaver except that both are gnawing animals and the mountain beaver sometimes makes its burrow in rather wet places. It has several other names. The Indians called it the "Sewellel" and it is also called mountain boomer, Chehalis and other local names.

In structure this animal is an oddity. The genus Aplodontia contains but a single species, (rufa). Today this single species is divided into nine subspecies. The mountain-beaver appears to be a solo survivor from some former age. While a rodent he has no relatives among the Rodentia. He is sometimes likened to a squirrel probably his nearest relative. He is a stout-bodied rodent, head broad, flat and blunt; neck short and thick; ears inconspicous; eyes small, tail rudimentary; legs short; well developed claws for digging; hair coarse and brown above, white or chestnut brown below; weight up to four pounds.

The Mountain-beaver is found only on the North Pacific Coast west of the Cascades. While originally he was probably more strictly a mountain animal he finds many of the cultivated plants very desirable as food and so in many places has moved into the valleys, and is a pest to the settlers and one very difficult to combat.

The Mountain-beaver is largely nocturnal in his habits and so is seldom seen by the Park visitor. Occassionally he comes out to feed in the early morning or late afternoon or he may be observed as he is busily engaged removing dirt at the mouth of some burrow. He is a hay-maker like the Cony and often piles of partly cured plants are found near the entrance. He is purely vegetarian and selects a large number of varieties of plants, including skunk cabbage in his bill of fare. After cutting off the plants he desires he drags them to the mouth of the burrow and neatly arranges them, butt ends all one way, over some logs or some rocks as a drying rack.

The Mountain-beaver is a great digger and makes a perfect labrynith of burrows. Although mostly solitary in habits they sometimes colonize and have burrows in common in addition to those used by each individual.

On some trails as the Bear Prairie trail those numerous shallow burrows make travelling difficult especially for horses as they frequently break through into the tunnel below. The burrows are clean and often lined with a hard layer of earth. Separate burrows are used to get rid of the refuse.

They seem to spend much time digging. The writer observed one make a number of trips to the mouth of a burrow each time sending out a shower of earth. They push the earth ahead of them in the burrow with their nose and when the earth is about the fall out turn about and send it out into space by kicking the piles with the soles of the hind feet. The force is so great that the animal is carried out with the earth and is compelled to scramble back. In the woods he often makes use of logs, running his broows just under the surface or even using hollow logs for concealment.

The Mountain-beaver lives a menotonous existence and lacks the intelligence and cunning of many of the other rodents.

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