Jerboas look somewhat like miniature
kangaroos, and have some external similarities. Both have long hind legs, short forelegs, and long tails. Jerboas move around in a similar manner to kangaroos, which is by hopping, or
saltation. However, their anatomy is more attuned towards erratic hopping locomotion, making use of sharp turns and great vertical leaps to confuse and escape predators, rather than for sustained hopping over long periods of time. Researchers have found that, when jerboas execute their vertical leaps, the primary tendons in the hindlimbs only recovered and reused on average 4.4% of energy contributed to the jump; this is lower than many hopping animals. Unlike other hopping mammals which are
facultative bipeds, jerboas do not use their forelimbs to walk at slower speeds; instead, unlike nearly any other
mammal apart from
humans, they almost exclusively move on two legs, making them
obligate bipeds. Jerboas have
metatarsal bones that are fused into one long bone, called the cannon bone. Their cannon bone is more distinct and defined than in other rodents. The tail of a jerboa can be longer than its head and body, and a white cluster of hair is commonly seen at the tip of the tail. Jerboas use their tails to balance when hopping and as a prop when sitting upright. Jerboa fur is fine and usually the colour of
sand. This colour usually matches the jerboa's
habitat (an example of
cryptic colouration). Some species of the jerboa family have long
ears like a
rabbit, whilst others have ears that are short like those of a
mouse or
rat. In addition to the jerboa's large ears, they also have large feet which are a result of multiple genes overlapping each other in their DNA. Researchers found a gene called the
shox2 gene that is
expressed in jerboa feet. This gene has the ability to turn other genes on and off and has been seen to cause mutant limbs. ==Behavior==