Yellow-bellied Marmot

The Monument has its share of "charismatic" wildlife—herds of mule deer, plenty of coyotes, chubby marmots, industrious beavers, fun-loving otters, and some of the most majestic elk in the West. But you might be surprised at what is the most abundant mammal here—and one of the most important.

The most abundant mammal in the shrub-steppe habitat on the Monument is the Great Basin pocket mouse. The deer mouse, western harvest mouse, northern grasshopper mouse, bushytail woodrat, and northern pocket gopher are other common small mammals. Least chipmunks can be found in the upper elevations of Rattlesnake Mountain, and sagebrush voles are relatively common above 1,000 feet (305 m) elevation in sagebrush habitat. These rodents form the prey base for much of the rest of the Monument.

Strangely, the Monument has porcupines, which are typically restricted to riparian areas where they feed on the bark of small limbs and tree branches. One of the interesting things they do is come down to the river's edge in extremely hot weather and stick their rear ends in the water to cool down.

Black-tailed jackrabbits can be found in mature sagebrush habitat. White-tailed jackrabbits are also in sagebrush/bunchgrass habitats, but generally at higher elevations than the black-tailed jackrabbits. The populations of both species are cyclical and are currently at low levels throughout the Columbia Basin.

Large mammals found on the Monument include bobcats, badgers and the occasional cougar. These species are present throughout the Hanford Site in low numbers. Coyotes, on the other hand, are the most abundant large carnivore on the Monument. The resident Rocky Mountain elk herd uses the ALE site portion of the National Monument. Many of these elk are the largest in the state and even the West. Mule deer densities on the ALE and along the Columbia River are high and are almost always seen on river trips.

The lack of sufficient roost habitat probably limits the density and diversity of bats on the Monument. Bats may be more common in areas adjacent to the Columbia River and in riparian zones around desert springs and lakes created by irrigation returns. Studies in the general Hanford vicinity have documented the presence of pallid bats, silver-haired bats, and western small-footed myotis. The extent to which these species use the Monument is not known.

Although not frequently seen, many other mammals depend on the Monument, including yellow-bellied marmots, striped skunks, mink, river otters, beavers and a host of smaller rodents, weasels and other animals.

And let's not forget ground squirrels. The Washington ground squirrel is a candidate for listing as a threatened or endangered species by both the state and federal governments. This squirrel was only documented on the Monument in 1998 just north of the crest of the Saddle Mountains. The Townsend's ground squirrel is considered a sensitive species by the state of Washington and is a candidate for listing by the state. Both species are fossorial, that is they dig burrows, and are only above ground generally from mid-February through June each year. The rest of the year, they are estivating/hibernating inside burrows underground. But while it's not likely you'll see ground squirrels, rare is the trip to the Monument that doesn't include some sort of mammal.