A pocketful of joeys

Lt Gen Baljit Singh (retd) reveals some little-known facts about kangaroos

There are more than 50 species of kangaroos with their colours varying from reddish-brown to grey and pale brown.
There are more than 50 species of kangaroos with their colours varying from reddish-brown to grey and pale brown.

By the most common perception, all terrestrial living forms are simply called animals. And all those with a backbone and whose females breast-suckle their infants are lumped together as mammals. Further, mammals constitute the largest community of the entire living planet.

While most of these generalisations are factually not far off the mark but there is much more to the fascinating world of the mammals. For instance, all mammals get divided into three groups depending upon the different procreative processes and pregnancy triggers among the female of the species.

The largest concentration of mammal species which include the homosapien, comprise the placental group. They have disparate gestation periods, varied food sources, differing waking-sleeping cycles, exclusive-kind family bonding etc, yet have the one commonality of their mothers linking with the embryo through a placenta.

The smallest group of mammals, the monotremes, is made up of just two species. They are the only egg-laying mammals of the world who incubate and hatch their young on terra firma instead of the womb.

Even more fascinating are the 10 mammals with evolutionary oddities that constitute the entire marsupial (Latin for pouch) group. In many ways, these pouched mammals are like the Creator’s chosen few. For, how else does one explain their strange and unique procreation physiology. Their females are born with a patch of double-layered skin on the belly with an opening at the upper end. In its architecture, it resembles the patch pocket of a trendy, tweed jacket. Its length and breadth, as of course its inner texture, are governed by the number and size of the progeny it has to house within. For instance, most marsupials have only one young at a time for which two teats will suffice. But in the case of the opossum as many as 13 babies may be conceived at a time and therefore 16 teats are located within their pouches.

The gestation period varies from 12 to 40 days. At that stage, the foetus of the kangaroo is no more than half an inch long and that of the opossum the size of a mere rice grain. Once expelled, these pink fleshed and blind midges, using genetic sensors, crawl all over the mother to locate and enter the pouch. And like magnets, these joeys attach their mouths on to the teat. The teat, in turn, swells up which transfixes the mouth on it, lest the hapless creature may fall out. Incredible biological engineering indeed.

In the case of the opossum alone, there is a chance of the foetus-infant falling out because the pouch opening is at the lower end. But then, it is provided with an anatomical door which only the mother knows how to operate. The pouch, in essence, is a baby cradle with automated feeding and temperature control. And structurally robust to provide occupancy up to at least five months at a time.

But who all are these pouched creatures? Perhaps the best known is the kangaroo, Australia’s national emblem and the largest of the group. Though of somewhat awkward gait, it can clear a 25-foot-wide ditch with ease and can out-distance the hunting dogs. When unable to do so, he enters a water body, swims across and waits for his pursuers. As the leading dog emerges, the kangaroo grabs his head and pushes it in the water till the dog drowns. There is an instance on record when, seven dogs were done to death, one after the other.

The other familiar marsupial is the koala which because of its looks is also called the koala bear. Now here is a mammal which is totally arboreal. Once the young outgrows the pouch, for the next three to five months the mother carries him on her back. They live and feed almost exclusively on the eucalyptus leaves and buds.

There were two unfortunate marsupials who inhabited Tasmania. The first of these, the Tasmanian wolf was hunted to extinction by 1936. And the Tasmanian devil, the size of a tomcat, has similarly been pushed close to extinction.

It is a strange fact of evolution of life that eight of the 10 marsupial species are confined to Australia or its breakaway segments — Tasmania and New Guinea. But the wombat, the bandicoot and the mole are both inconspicuous looking and too wary of humans so that the world seems not to notice their existence. The same is the case with the cuscus, a lovable bundle of silver grey pelt with white dabs, who much like the koala, remain hidden among tree canopies. They inhabit New Guinea and eastern fringes of Australia.

Difficult to rationalise how, but nevertheless just two species of marsupial, the opossum and his closely related flying opossum are in South America. If not for his looks, the opossum is certainly known by the adjective "lying opossum". He simply feigns dead when confronted by an adversary.