J.Halcom 1940 Ondatra Jun Club, 5 1/2 mi. N Stillwater, Churchill Co., Nevada. 3900 ft, Aug. 25 built on level of water are from 10 inches to 2 or 3 feet. They average 6-8 inches. Big ones are in sheltered places and many rats use these large "platforms". In real cold winter the rats (about 75%) of them leave the sloughs and lakes and migrate up into the sloughs and drain ditches. Rats are most active just before and after sundown. Young found in nest average about 7 to nest. Has attempted to move nest from "blinds" into a safe place but rats always desert. Often dead rats are found in early summer. One ♀ found dead on ditch bank had 6 young in radius of 6 ft. of ♂, Young were about starved but were alive and had their eyes open. Young were size of field mouse. Live rats in traps are often attacked and partly eaten by marsh hawks.