Onychomys leucogaster
northern grasshopper mouse

Onychomys leucogaster, the Northern grasshopper mouse, can be found from southwestern Canada throughout the western United States into northwestern Mexico. Its distribution ranges from the Pacific coast to western Minnesota and Iowa.

Onychomys leucogaster live in shortgrass prairies, sand dunes and in sage brush desert. These are primarily areas with sandy soil in which they build their burrows. Compared to other species of the same genus, northern grasshopper mice prefer higher elevations and so are also commonly found in canyon lands.

Northern grasshopper mice have white ventral fur, and dorsal fur that ranges from brown to pink. The tail is short, averaging 42 mm in length, with a white tip. This is approximately one third of total body length, which averages 164mm. The hind feet average 22mm.

Juvenile O. leucogaster have white ventral surfaces, however the dorsal fur ranges from light to dark grey. At 57 to 62 days of age, fur color changes to the cinnamon color of adult pelage. This process takes up to 20 days. Teeth are smaller than many other mice, with pointed cusps reflecting their carnivorous diet.

Northern grasshopper mice are primarily solitary. Dominance hierarchies are established when contact is made with other grasshopper mice. If grasshopper mice of the same sex are put together in a closed environment, the socially dominant individual will kill the other within 72 hours of initial contact. Although this is typically only true of same sex encounters, some females have been known to kill their mates.

Onychomys leucogaster are nocturnal and hide in an intricate burrow system during the day. Three main types of burrows are built. The first is a nest burrow in which these mice spend the majority of their time resting and escaping from the heat of the sun. They also build emergency burrows for escaping predators and storage burrows in which to hide seeds and other preservable food items for when live prey is not available.

Since grasshopper mice are active year round and nocturnal, their activity is influenced by lunar phases, photoperiod, and daily weather. On clearer nights, when the moon is full, they are more active.

The shrill cry of the northern grasshopper mouse is thought to be both a hunting call, as stated above, as well as a mating call.

O. leucogaster are unique among mice in that the majority (almost 90%) of the diet is other animals. They feed primarily on insects, including grasshoppers, scorpions, beetles, crickets, and moths. They have been known to eat rodents as well, including other O. leucogaster.

Northern grasshopper mice stalk their prey in an almost feline manner letting out a shrill cry before attacking.

In the stomach of these creatures, two of the glands are enclosed in a 'pocket' of tissue. This is thought to protect them from damage by the chitin from their insect prey.

In shortgrass prairies northern grasshopper mice add prairie birds to their diet. This may result in the loss of a variety of birds because of predation by this species and other mammalian predators.

Since the diet of this species consists of mainly insects and very few plants (such as commercially produced grains), it has been suggested that O. leucogaster may be able to serve as a natural predator against pests that commonly disturb agriculture.

They also make interesting pets, and become tame in captivity.

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Northern grasshopper mice have suprisingly few predators. Other than humans, their primary predators are owls and other nocturnal birds of prey.