Kangaroos

Infraclass: Marsupialia

Order: Diprotodontia (meaning two front teeth)

Family: Macropodidae (large footed)

Kangaroos are a familiar sight around Australia particularly in the bush and semi urban areas.  Kangaroos are generally regarded as the larger of the species of macropods (meaning large footed) marsupials. They include the largest native mammal in Australia; the Red Kangaroo. The smaller species tend to be called wallabies.

Being such a common animal in Australia it is used in a variety of cultural and symbolic ways. In particular the kangaroo is part of the Australian Government Coat of Arms.

A kangaroo or wallaby is a mammal unique to Australia. image: R.Conan-Davies

Behaviours

Kangaroos generally cannot sweat to cool down. But sometimes they will lick their forearms which have blood vessels close to the skin, the saliva will then evaporate and cool the blood in the forearm.

This species of kangaroos is known as a wallaby (infraclass: marsupiala) unique to Australia. image: R.Conan-Davies

They also spend a lot of time lying under trees to avoid high temperatures. Kangaroos can be quite aggressive at times when asserting dominance and engage in Kangaroo fighting behaviour.

How kangaroos move

Kangaroos are the only large animals to use hopping as a means of locomotion. The comfortable hopping speed for a red kangaroo is about 20–25 km/, but speeds of up to 70 km/h can be attained over short distances, while it can sustain a speed of 40 km/h  for nearly 2 km

How kangaroos reproduce

 The egg inside the kangaroo which is still contained in the shell membrane, a few micrometres thick, and with only a small quantity of yolk within it descends from the ovary into the uterus. 

There it is fertilised and quickly develops into a neonate. Even in the largest kangaroo species (the red kangaroo), the neonate emerges after only 33 days. 

very early stage joey (neonate) in a pouch. image: Geoff Shaw (Zoology, University of Melbourne, Australia)

Usually, only one young is born at a time. It is blind, hairless, and only a few centimetres long; its hindlegs are mere stumps; it instead uses its more developed forelegs to climb its way through the thick fur on its mother's abdomen into the pouch, which takes about three to five minutes. 

Once in the pouch, it fastens onto one of the four teats and starts to feed. Almost immediately, the mother's sexual cycle starts again. 

Then, if she mates again a second egg is fertilised, but the development is temporarily halted. This is known as embryonic diapause, and will occur in times of drought and in areas with poor food sources.

How long does a joey stay in the pouch?

 Meanwhile, the neonate in the pouch grows rapidly. After about 190 days, the baby (joey) is sufficiently large and developed to make its full emergence out of the pouch, after sticking its head out for a few weeks until it eventually feels safe enough to fully emerge. 

From then on, it spends increasing time in the outside world and eventually, after about 235 days, it leaves the pouch for the last time.

How long do kangaroos live?

The lifespan of kangaroos averages at six years in the wild[54] to in excess of 20 years in captivity, varying by the species.[55] Most individuals, however, do not reach maturity in the wild

References:

Forelimb blood flow and saliva spreading in the thermoregulation of the red kangaroo, Megaleia rufa

http://www.sciencedirect.com/science/article/pii/0300962974905684

Source adapted from:  Wikipedia contributors. (2021, March 19). Kangaroo. In Wikipedia, The Free Encyclopedia. Retrieved 05:27, March 28, 2021, from https://en.wikipedia.org/w/index.php?title=Kangaroo&oldid=1012958185