Near Richmond Beach, Snohomish County, muskrats took up residence in a small tidal pool along Puget Sound. The nearest fresh water stream large enough to support a muskrat was two miles away. Two muskrats were trapped here. Investigation of a tidal pool a mile to the north disclosed unmistakable muskrat signs. Traps set in the culvert connecting the pool with Puget Sound at high tide took several specimens. Study showed that the muskrats were not living in the pool but among the large boulders forming the breakwater for the Great Northern Railroad, along the sound itself. They were feeding on marine mussels (_Mytilus_). These mussels lived in the salt water of the sound, not in the tidal pool. At Peavine Pass, Blakely Island, in the San Juan Islands, muskrats were living in the swift tidal current and deep, marine waters. Several were seen in late afternoon. All were swimming parallel to the shore about 50 feet out. Here also they fed on _Mytilus_, but their homes were not discovered. Certainly they were not living in the tidal pool at Flat Point, a half-mile away. In the interior of Blakely Island a colony of muskrats was discovered living in a marsh of about one acre. In the rainy season the ground of the marsh was covered with less than one inch of water. Residents said that in the dry season springs kept the ground moist. Muskrats were living in burrows whose entrances descended at a 45-degree angle and were filled with water. The ground about some occupied burrows was dry, the only water visible being in the burrow itself. A variety of marsh vegetation provided food. [Illustration: FIG. 120. Distribution of the muskrat in Washington. A. _Ondatra zibethicus osoyoosensis._ B. _Ondatra zibethicus occipitalis._] Burrows of muskrats always have entrances under water. Usually they enter a vertical bank 6 to 15 inches below water line and occasionally 3 feet below it. About half the burrows excavated near Lake Washington, King County, had a single entrance. About 40 per cent had double or triple entrances situated 2 to 3 feet apart and converging within a yard to a single burrow. About 10 per cent had double burrows more than 3 feet in length. Burrows were from 5 to 8 inches in diameter. Nest chambers were from 12 to 15 inches in diameter, spherical, and from 6 to 30 feet from the burrow entrance. The nests themselves were bulky, loose masses of cattail leaves. Embryos found in late February and early March numbered 4 to 8. Because it is abundant, widely spread and easy to trap, the muskrat is one of the most important fur bearers in the state. The fur is relatively stable in value. In recent years the average skin has brought the trapper slightly less than a dollar. Muskrat flesh is eaten and sold on the market in the eastern United States but has never been popular in Washington. The muskrat does little damage to agriculture, most complaints arising from its burrows which interfere with irrigation ditches.