Sewellel (Mountain Beaver)

Part of Hall of North American Mammals.

NAM Sewellel Hero

August Morning
Mount Rainier, Washington

Neither a beaver nor a high-mountain dweller, the sewellel is a rather singular animal. It’s the last living member of a once-successful family of rodents called the Aplodontiidae. The sewellel is a “living fossil,” showing primitive skeletal features that other rodents have lost. Its kidneys are also unusual: they are inefficient at maintaining the body’s water balance. Thus the sewellel needs to live close to water so it can drink a lot—a third of its weight in water per day. 

Mount Rainier, Southern Slope
Mount Rainier National Park, Washington

An August morning brings ample sunshine to the high meadows of Mount Rainier, the tallest peak in the Cascade Range. Rainy or snowy weather is much more typical, though, especially on Rainier’s western and southern slopes. The prevailing winds come from the west, dumping moisture picked up over the Pacific Ocean along the way. Once the winds reach the Cascades’ eastern slope, the air is mostly dry.