How do kangaroos jump, slide, or swim?

The familiar hopping gait of kangaroos probably evolved from the hopping gait that has been preserved by the diminutive primitive musk-rat-kangaroo. The hind legs became larger and larger than the forelegs, and the hindfoot became longer, providing a very effective means of accelerating. hopping locomotion. At an equivalent speed, and allowing for differences in weight, the jumping kangaroo uses less energy than a running dog or horse.

But such specialization comes at a cost: a the typical kangaroo cannot walk. When moving slowly, it raises the hindquarters on a tripod formed by the forelegs and tail pressed against the ground, then swings both hindquarters forward and always together. Ground kangaroos cannot move each hind leg independently while supporting the body, although they can alternately kick them when swimming.

Tree-kangaroos, which have undergone secondary shortening of the hind legs, can also alternately move their hind legs when walking along a branch. In typical kangaroos, the tail is not very flexible, but it does move up and down to help with balance during movement. jumping march and acts as a fifth limb to support the body when it moves slowly. In more primitive rat-kangaroos, the tail is moderately prehensile in the vertical plane and is used to carry bundles of nesting material.

The ability to glide has arisen independently in three families of marsupials: the Pseudocheiridae, Petauridaeand acrobats. In each case, this involves a skin membrane between the forelimbs and hindlimbs, which, when the legs are extended, expands into a rectangular kite-like airfoil.

jumping from a tall tree, a glider can fly quite long distances, steering by altering membrane tension to either side, balancing with its tail extended, and finally orienting its body vertically to land on another tree trunk with all four legs. No other gliding mammal has anything comparable to the tail of the feather-tailed glider: each side has a thin row of tight, stiff hairs, all the same length, that form a structure very similar to a feather’s vane.

Although it seems that most marsupials are capable of swimming when necessary, only the yapok can be considered truly aquatic. With alternating movements of its webbed hind feet, this Central American species swims to the bottom of a pond or stream with its eyes closed, feeling with its long fingers and spatulas for live prey, which it seizes in its mouth and brings to shore to be eaten. The rear-opening pouch of a female yapok is closed by a strong sphincter muscle and sealed with water-repellent secretions when the animal is swimming.

The most extreme locomotor specialization of any marsupial is seen in the little sausage-shaped mole marsupial. It is blind, lacks external ears, and has a horny shield over its snout and around its nostrils. The limbs are short, with very strong bones and powerful musculature, and the spade-shaped forelegs have two huge triangular claws on the third and fourth fingers, with smaller claws on the other fingers.

The forefoot is used to dig up the ground in front of the animal and push it forward. The hindfoot, which has four short claws and, uniquely among marsupials, a claw-like structure on the great toe, is used to kick sand behind the body. The marsupial mole does not build a tunnel but rather “swims” through the sand, usually to a depth of 10–20 centimeters (4–8 in), but sometimes descends to a meter (62 ft) or more.

The feather-tailed glider, honey possum, and pygmy possums, genus Cercartetus, are very small marsupials that climb by grasping on the expanded tips of their fingers and toes. Except on the conjoined second and third toes of the hindfoot, the claws are reduced and nail-like, and lie on the tips of the toes. The pads of the feather-tail glider’s fingers and toes have microscopic grooves, like those of geckos, allowing them to adhere to a smooth surface, such as a vertical pane of glass, and even hold on, however briefly, at the bottom of a horizontal. sheet.