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Biodiversity – Mammals

There are more than 80 species of mammals native to Nebraska. They range in size from a bull elk, which can be 5 feet high at the shoulder and weigh more than 700 pounds, to the least shrew, which may be 2 ½ inches long and weigh 1/10 of an ounce. Nebraska mammals are adapted to a wide variety of habitats. Some, like the pronghorn, are runners adapted to escaping predators on the open prairie. The pronghorn is considered the second fastest land mammal, second only to the cheetah, which a pronghorn could outrun in distance. Others, like the river otter, are exceptional swimmers. Some, like moles and pocket gophers, spend almost their entire lives underground, while bats, the mammal counterpart of birds, are some of the most agile of all flying animals.

Selected species of conservation interest

Five mammal species are listed as endangered or threatened in Nebraska: the river otter, swift fox, southern flying squirrel, northern long-eared bat and black-footed ferret, which is considered extirpated in Nebraska.

Eight additional species of mammals are considered at high risk in Nebraska. They include the tri-colored, fringed-tailed, and little brown bats; Bailey’s eastern woodrat; Cheyenne northern and Pierre northern pocket gophers; plains pocket mouse; and big horn sheep.

Species are at risk due to a variety of factors. Big horn sheep and river otters were extirpated from the state due to overhunting and trapping before being reintroduced in the wild. Bats are threatened by disease and development such as wind farms. Species such as the northern pocket gopher are dependent on very specific soil types, and land conversion threatens populations due to direct loss of habitat and fragmentation that isolates populations and prevents them from interacting. Species of pocket mice require habitat conditions such as tall grass prairie that has specific conditions related to grass height and amount of ground cover.

Swift fox

The swift fox is the smallest of the foxes and is only slightly larger than a house cat. It has long, sandy-gray colored hair and bushy tail with a black tip. Swift fox inhabit short-grass prairies, which enables them to more readily observe predators such as badgers, eagles and coyotes. Coyotes are considered one of the main threats to swift fox, along with habitat loss due to land conversion. Historically, wolves kept coyotes in check but did not bother swift fox. The swift fox is listed as an endangered species at the state level. Swift fox utilize many dens, moving from one den to another several times during the year. Dens are usually located on high sites that provide the fox a good view of predators.

Southern flying squirrel

The southern flying squirrel is listed as threatened at the state level due to its very limited distribution in the state. The southern flying squirrel requires extensive, mature stands of woodland that contain mast (nut) producing trees such as oak and hickory. In Nebraska this habitat is limited to the southeast portion of the state on the bluffs along the Missouri River.

The flying squirrel is the smallest squirrel in the state and is only about 2/3 the size of a red squirrel. Flying squirrels are primarily nocturnal with large dark eyes, which produce a distinctive reddish-orange eye shine. They forage for acorns and nuts at night and are capable of ultrasonic communication. The most distinguishing features of flying squirrels are the folds of skin connecting its front and rear legs. When the legs are outstretched, these folds enable the squirrel to glide or “fly” from one tree to another.

Northern long-eared bat

The northern long-eared bat is listed as a threatened species at both the state and federal levels to due precipitous population declines throughout the main portion of its range in eastern North America. This decline in due to a disease called white-nose syndrome, which is caused by an introduced, non-native fungus. White-nose syndrome is attributed with reducing the number of northern long-eared bats by 95 percent. It is estimated the disease is responsible for killing nearly 6 million bats in North America.

Northern long-eared bats are a medium sized bat with a wing span of 9-10 inches. They weigh less than a third of an ounce. Northern long-eared bats hibernate in mines and caves during the winter, and the females congregate in maternity colonies of up to several dozen individuals to raise their young. These maternity colonies use trees with loose bark and cavities to roost in during the day. Unlike mice, bats do not produce multiple litters of multiple young a year. Rather, northern long-eared bats have only one pup per year.

Bailey’s eastern woodrat

Bailey’s eastern woodrat is an endemic species found only in the Niobrara River valley in north-central Nebraska. This is a relic population left from the Ice Age and is a distinct sub-species of the more widely distributed eastern woodrat. Woodrats are often referred to as pack rats due to their habitat of collecting anything they can carry to use in building their large stick houses, which can be up to two feet across and several feet tall. In the wild, houses are built in shrub thickets, under rock outcroppings or at bases of trees, but they may also be built around human structures. They get the name pack rat because they will readily incorporate many human-made objects into their houses. They are particularly fond of shiny objects such as old cans, hub caps and even coins.