Macropodidae

The kangaroos (Macropodidae; from Greek μακρός makrós "large" and πούς poús, Gen. ποδός podós "foot") - also called true or actual kangaroos in distinction to the rat kangaroos - are a family in the marsupial order Diprotodontia. They are among the best known marsupials and are considered typical representatives of the fauna of Australia, but also live on New Guinea. Kangaroos are characterized by their clearly longer hind legs. They are herbivores and mainly crepuscular or nocturnal. The family includes about 65 recent species, of which four are extinct.

Features

General physique

Kangaroos differ significantly in their dimensions. While the largest species, the red giant kangaroo, can reach a height of up to 1.8 meters and a weight of 90 kilograms, the shaggy rabbit kangaroo weighs only 0.8 to 1.8 kilograms and has a head trunk length of 31 to 39 centimeters. In almost all species, the hind legs are significantly longer and stronger than the front legs; the exception is the tree kangaroos, which have adapted to life in the trees and no longer move about hopping, and in which hind and front legs are approximately the same length. The tail is long, muscular, and usually hairy; it is often used for support or balance, but cannot be used as a prehensile tail. In nail kangaroos, it is equipped with a bony tip. The fur is usually coloured in shades of grey or brown, there are also patterned species, for example the rock kangaroos.

The front paws are small and end in five fingers; they are used for feeding and for support. The hind foot is narrow and elongated, kangaroos are sole walkers (plantigrad). The first toe of the hind feet is absent; the second and third toes are fused, as in all Diprotodontia, but terminate in two separate nails used for grooming. The fourth toe is the longest and strongest, the fifth is medium sized.

Head and teeth

The head is elongated, but relatively small compared to the body size. The ears are large. In the upper jaw kangaroos have a total of six incisors, in the lower jaw only two. The lower incisors are enlarged, as in all Diprotodontia, and meet a hard spot in the palate behind the upper ones when biting down. The upper incisors are arranged in a U or V shape and do not lie one behind the other as in other Diprotodontia. This arrangement forms an effective tool for plucking even hard plant material and is also found in convergent form in some cloven-hoofed animals. The lower canines are absent, and the upper ones are also absent or strongly receded, so that a large gap (diastema) separates the incisors and the molars. The premolars are narrow and blade-shaped, the molars are broad and high-crowned. The molars do not come out at the same time, but one after the other; only when the front ones are worn down and fall out do the next ones come and then move forward in the mouth. Altogether the dental formula of kangaroos is I 3/1, C 0-1/0, P 2/2, M 4/4 - so in all they have 32 or 34 teeth.

Internal anatomy and reproductive tract

The stomach of kangaroos has developed in a multi-chambered manner analogous to that of ruminants. It has three sections: the first section, the forestomach sac, serves as a fermentation chamber where, similar to the rumen, plant food is processed with the help of microorganisms. Further digestion takes place in the tubular forestomach tube and in the hindstomach. The intestine is long, as in most herbivores, and the appendix is well developed. The cardiovascular system shows no peculiarities compared to other marsupials. The reproductive tract also largely corresponds to that of other marsupials. The penis of males at rest lies retracted and curved in an s-shape in a penile pouch, the testes lie in front of the penis. Females have two uteri and two vaginas and, unlike many other marsupials, a permanently attached pouch (marsupium). Its opening projects forward and it contains four teats. Juvenile kangaroos climb forward into the pouch and turn around inside. Male kangaroos do not have a pouch.

Tree-kangaroos deviate with its approximately equally long front and hind legs clearly from the construction-plan of the remaining kangaroo-types

Distribution and habitat

Kangaroos are found in Australia, including offshore islands such as Tasmania, and in New Guinea. They inhabit a variety of habitats and can be found in tropical rainforests as well as in bush or grasslands and dry steppe and desert regions. Some species such as the rock and bush kangaroos also inhabit mountainous regions and can be found at altitudes of over 3100 meters.

rock-kangaroos belong to the kangaroo-types, that inhabit rocky terrain