Jumping Mice Birch Mice and Jerboas: Dipodidae

Birch mice are able to mate after their first hibernation, and usually have one litter per year containing three to eleven pups. Their gestation period is two to five weeks, and parents care for the young for one month, which is quite long by rodent standards. In jumping mice, which (with a few exceptions) are also ready to mate after hibernation, mating pairs sometimes produce two or three litters. The gestation period is seventeen to twenty-three days and the litter size is usually two to nine pups. Among jerboas, some species breed only once a year during the spring and summer and produce litters of two to nine pups. Others breed in the spring and fall and can produce up to three litters a year, although their litter size is smaller (one to eight pups). In the majority of jerboa species, pups stay in the burrow for five to six weeks before emerging, probably because it takes extra time for them to develop the coordination required for bipedal movement.

Birch mice and jumping mice, while quadrupeds (animals that move about on all fours), also hop and use their tails to hang onto twigs and grasses. Jumping mice can hop up to 6 feet (1.8 meters) long and 3.3 feet (1 meter) high. Both types of mice are strong swimmers as well, and hop straight up when startled. Jerboas move on their hind feet exclusively and are very fast runners. The five-toed jerboa, for instance, can maintain speeds of 25 miles per hour (40 kilometers per hour).

Jumping mice and birch mice seldom dig, finding shelter under logs, in other animals' abandoned burrows, among roots, or under boards. Jerboas, on the other hand, typically dig and live in complex burrows with multiple chambers that they plug during the day to seal out heat and keep in moisture. Sometimes they have different burrows for daytime shelter and for nighttime escape from predators.

Most members of the Dipodidae family hibernate, but for how long and when varies widely based on geography and species. Birch mice hibernate for six or seven months of the year, and can lose up to half of their body weight. Species that breed in the spring and fall hibernate for shorter periods, while those that live in tropical regions experience only a few days of lethargy.

Species of this family are typically solitary and every individual has its own burrow for sleeping and hibernating. In general, these mammals seem tolerant of other individuals' presence, although females are reportedly more aggressive in defending their areas. Neighboring birch mice and jumping mice species even share shelter burrows, but jerboas actively avoid contact with other jerboas in overlapping areas. This is problematic in places where the abundance of jerboas results in population densities of forty to fifty individuals per 2.5 acres (1 hectare). Some jerboas mark their territories by rolling in sand, while others rub their genital areas on the ground.

None of the species in this family store food. Many of them, however, have specialized ways of finding prey, such as highly developed inner ears that help them hear tiny vibrations in the earth and powerful hind legs that allow them to jump extremely quickly into the air to catch passing insects.