Jerboas are small, two-legged rodents found across North Africa and Asia’s arid and semi-arid landscapes. These creatures belong to the family Dipodidae, which also includes jumping mice and birch mice. Jerboas have developed physical and behavioral characteristics that allow them to survive in hot deserts where water is scarce.
Physical Features and Classification
The jerboa’s body plan is defined by a striking disproportion between its limbs, making its morphology unique among rodents. Their hind legs are significantly elongated, often four times the length of their small, arm-like forelimbs. The forelimbs are primarily used for digging burrows and handling food. This extreme difference in limb size is supported by the fusion of their metatarsal bones into a single, supportive structure called a cannon bone, which increases leverage for jumping.
Their small bodies typically range from about 5 to 15 centimeters (2 to 6 inches) in head and body length. A long, slender tail, often longer than the head and body combined, frequently terminates in a distinctive tuft of hair. This tail acts as a dynamic counterbalance for stabilization during their powerful leaps and serves as a prop when the animal sits upright. Jerboas also possess characteristically large ears, which vary in size depending on the species. These large ears are highly sensitive for detecting nocturnal predators and may also assist with thermoregulation by dissipating heat.
Specialized Movement and Nocturnal Habits
The most defining characteristic of the jerboa is its specialized bipedal locomotion, known as saltation. Jerboas are considered obligate bipeds, relying almost exclusively on their hind legs for movement. When moving slowly, they will walk on their two hind legs, but when pursued, they transition into a rapid, spring-loaded hopping gait.
This movement is fast, reaching speeds up to 24 kilometers per hour (15 miles per hour) when chased, and also highly unpredictable. This movement is highly unpredictable, involving rapid changes in direction and gait, which makes them difficult targets for predators. They use three different footfall patterns—hopping, skipping, and running—and can transition between these gaits mid-stride to execute acrobatic, zigzagging evasive maneuvers. When alarmed, they can launch themselves upward into vertical leaps of up to 3 meters (10 feet), a distance far greater than their body length.
To avoid the extreme temperatures of their desert habitat, jerboas are strictly nocturnal, confining their activity to the dark, cooler hours of the night. They spend the entire day sheltering in complex burrow systems, which act as a thermal refuge.
Adaptations for Arid Environments
Jerboas possess several physiological and behavioral mechanisms that enable them to thrive in environments with minimal water availability. A primary adaptation is their ability to obtain virtually all necessary moisture from their diet of seeds, roots, and insects, making drinking water unnecessary for survival.
The kidneys of the jerboa are specially adapted to retain water by producing a very low volume of highly concentrated urine. This ability is linked to a higher concentration of the hormone arginine vasopressin (AVP) and a kidney morphology that includes an increased relative medulla thickness. Behaviorally, they utilize their burrows to regulate body temperature and minimize water loss through respiration. Many species will plug the entrance of their burrows with soil during the day to seal in moisture and maintain a cooler, more constant temperature inside.