Beaver dams are abundant in certain sections of Washington, notably the area between the Cascade Mountains and Puget Sound. Dams several hundred feet in length were seen in the valley of Cherry Creek, 7 miles northeast of Duvall, King County. However, in most parts of the state few dams are built. No dams are necessary in the larger streams and lakes while the smaller mountain streams possess a gradient too steep for successful damming. Spring floods and high water following rains would destroy such dams. True beaver houses, or lodges, are seldom seen in Washington. In the larger streams, rivers and lakes the beavers are "bank beavers," living in burrows with underwater entrances. In the mountain streams, log jams furnish protection. Great piles of logs and debris accumulate at bends of streams in periods of high water. These jams commonly contain large, well-anchored key logs and persist for years. Back-cutting by the stream often forms deep pools before the jams while the sloping bank opposite may support willows and alders. Thus beavers may find a home, food, and a protecting pool of deep water at a log jam. In periods of low water, and when meandering of the stream causes it to leave the log jam, canals are constructed by the beavers to connect the log jam with the stream. Where dams are built a few lodges may occur. For the most part, however, the beavers dig holes in the bank or in small islands that result from their dam-building activities. Burrows are occasionally easy to locate because of the mud and sticks laid on the ground above. At best these sticks form a layer only a few inches thick and are too loosely packed to furnish any additional protection. They probably represent a concession to the beavers' lodge-building instincts. The beaver probably breeds in January. A specimen from Cle Elum, taken on March 1, contained 4 embryos and one from the Teanaway River near Cle Elum held 2 embryos on February 28. One from Swauk Creek, Kittitas County, on the eastern slope of the Cascades, had 3 embryos on February 12. A young beaver was born to a captive animal on May 18. Its mother was taken at Soos Creek in southeastern King County. This baby weighed 884 grams. The majority of the beavers trapped are small animals, measuring from 725 to 900 mm. (total length) in February, and weighing from 10 to 20 pounds. These are kits, probably one and two years old. It is rather difficult to divide these animals into two age groups but probably the first year young (7 to 11 months old) weigh from 10 to 15 pounds and measure between 725 and 800 mm. in total length. Two-year olds (19 to 23 months) measure from 800 to 925 mm. and weigh from 15 to 25 pounds. They measure approximately 1050 mm. the third year, when they become adult, and weigh in the neighborhood of 45 pounds. Individuals occasionally weigh more than 50 pounds; these are probably old adults.