The first kangaroos collected by Europeans from the east coast of Australia were taken near what is now Cooktown, Qld, when Cook's expedition spent seven weeks there in 1770. Early descriptions of these kangaroos appear to be composites based on three specimens brought back to Europe and, as convention dictates that the first-used scientific name takes precedence, it has been essential to establish their identity. Unfortunately, little survives of the three animals other than the date of collection and their weights, but diagnostic characters of the skull and teeth, together with the recorded weight, have been used to identify one animal from an original wash drawing of its (lost) skull as an Eastern Wallaroo. Another has been identified from a photograph of a skull (which was subsequently destroyed during World War II) as a Grey Kangaroo. A new specimen specially collected near Cooktown, and lodged in the Queensland Museum, is now recognised as the type (neotype) of the latter species.

Grey kangaroos have a wide and almost continuous distribution between the inland plains and the coast where annual rainfall is more than 250mm, in habitats ranging from semi-arid mallee scrub through woodland to forest. Throughout this vast range grey kangaroos were 'discovered' more than once by various explorers, and it is not surprising that taxonomists dealing with widely separated localities interpreted the considerable range of colour and form to represent as many as five different species. For many years there was much controversyover the status of grey kangaroos but it is now clear that there are only two species; the Eastern and Western Grey Kangaroo.

Distributed throughout most of the eastern states, including Tasmania, the Eastern Grey Kangaroo is predominantly a grazing animal with specific food preferences, restricted to grasses and forbs, which are retained even when the number of available plant species is depleted during drought. Its favoured food is grass and, on this diet, it has a lower nitrogen requirement and intake of dry matter than sheep of equivalent weight.

During the hours of daylight, the Eastern Grey Kangaroo usually rests in the shade or shelter of treess and shrubs, moving out to graze from late afternoon to early morning, when animals tend to aggregate in more open country.

Communication between mother and young and between males and oestrus females involves a series of clucking sounds. Aggressive males and alarmed individuals of both sexes give vent to a guttural cough.

Breeding occurs throughout the year but there is a peak of births in summer. Males, which are notably larger than females, display an increasing interest in a female by remaining near and making occasional close inspections for about four days as she approaches oestrus. Competition between males for a female's attention may occasionally lead to fights. Courtship involves the male sniffing the region of the female's cloaca and pouch opening, together with frequent pawing at her head and clutching at the base of her tail with his forepaws. Attempts to mount are made over a period of several days before successful copulation occurs. This may last up to 50 minutes.

At parturition, the female adopts a crouching posture with the tail behind in its normal position and hindlegs thrust forward with toes in the air, the weight of the body apparently being taken on the heels. The newborn animal climbs from the urogenital opening to the pouch in a few minutess and shortly afterwards attaches to one of the four teast. Twin you habe been recorded, but usually only one young weighing just over 800mg is produced. The oestrus cycle has an average length of about 46 days, considerably longer tan the 36 days required for gestation. Females do not normally come into oestrus immediately after giving birth, as in the Red Kangaroo and some other macropods, but return to oestrus about 11 days after loss of pouch young. Perhaps a response to a sudden improvement in nutrition, a female carrying a pouch young more than 4 months olde may occasionally mate again. The fertilised egg from this mating developss to the stage of blastocyst but ceases further development until the incumbent young vacates the pouch at the age of about 11 months. A young animal begins to leave the pouch for short periods at the age of 9 months but continues to be suckled, from the same teat which it used when in the pouch, until it is about 18 months old. At this stage, the mother may also have a pouch young about 8 months old.

In areas of low and variable rainfall, populations of kangaroos may vary considerably in response to the availability of food and water. Aerial surveys in 1975-76 indicated that the plains of New South Wales supported between 1,500,000 and 1,600,000 Eastern and Western Grey Kangaroos but further counts in 1977 indicated that, over the intervening two years, the population had increased by an annual rate of 13%, despite a legal annual harvesting rate of 4%. A return to drier conditions, leading to increased juvenile mortality, reduced reproductive success, and eventual death of adults, would reverse this trend.

For many thousand years, Aborigines killed kangaroos for food and skins and, although they may have been the only significant predator on these animals, they could not have had much effect upon the large populations. Early European settlers valued kangaroos as a source of meat and hides but, as land was cleared, native pastures were changed by the impact of domestic stock and improved by human intervention and, with the provision of many more watering points, these large native grazing animals came to be regarded as agricultural pests. It is indeed likely that development of the pastoral industry led to a marked increase in kangaroo populations. Local reductions in numbers were achieved by a variety of methods: initially bounties were paid on their scalps, then skins were taken for leather manufacture, and later both skins and meat were used.

Both species of grey kangaroos are protected by law and are extremely common throughout their extensive range on the mainland but at risk in Tasmania, where active conservation measures are now in train. Management of these populations is under the control of the State faunal authoritiess which may grant licences to shoot excess kangaroos where these are deemed to be causing damage to fences, crops, or pastures. Export of kangaroo products taken under such licences is subject to the approval of federal government authorities.

Author: W. E. Poole, The Australian Museum Complete Book of Australian Mammals, published Angus & Robertson Publishers, 1983.