Quokka
Order: Marsupialia Family: Macropodidae Genus & Species: Setonix brachyurus
Now confined to swampy valleys near the city of Perth on the Australian mainland. Populations occur on islands just off the southwestern coast. Females mate the day after giving birth, to ensure that at least one offspring survives each year.
| Habitat The quokka was once widespread across southwestern Australia until its populations were decimated by shooting for sport. It now inhabits just a few sites on the mainland, but it is more abundant on two small islands lying just offshore - Rottnest Island, near Perth, and Bald Osland, near Albany. On the mainland, the quokka is concentrated in a few swampy |
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| valleys in the Darling Range, near Perth. These swamps provide not
only water but also dense cover, which the nocturnal quokka needs for shelter from the
summer sun. Additional shade is provided by areas of dry sclerophyll forest,
characterized by trees with tough or leathery leaves that resist water-loss (such as many
species of eucalypus). On the islands the quokka thrives in a wider range of habitats, including scrubby thickets and areas of dense grass. Rottnest Island loses almost all of its standing water in summer and the quokka must quench its thirst at springs or small patces of seeping water. |
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Behaviour The quokka is usually tied to a family group, dominated by adult males. Dominance is passed on from one generation to the next, so that the male offspring of top males will often become dominant males in their own right. Groups may contain up to 150 members, and the home ranges of neighbouring groups frequently overlap near prime feeding areas or reliable sources of freshwater. Home ranges are defined by the supply of food and shelter, and so become bigger or smaller according to season. They vary in size from an area equivallent to three football pitches, to one equivalent to 20 pitches. As the quokkas commute between the various sites they use regularly, for shelter, feeding and drinking, they gradually wear runways and tunnels through the grasses and other low vegetation. |
Feeding The quokka is a herbivore with a flexible diet, which allows it to survive when both food and water are scarce. It sets out from its shelter at dusk to graze with the other members of its family group, moving slowly through the group's home range in search of the best feeding sites. Winter rains lead to a rich growth of lush grasses and tender shoots, and these are the quokka's preferred diet. During this time of plenty the quokka's home range is at its smallest. |
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The summer drought reduces the food supply and forces the
quokka to look farther afield. The nature of its diet then changes; with twigs and
stems replacing the green shoots and grasses of late winter and spring. It can climb
1.5m up into vegetation to break off twigs. If food supplies are very low, the
quokka supplements its protein intake by feeding on its own urea, a urinary waste product.
Water is also scarce at this time and the quokka travels up to 2km to reach it,
although it only needs to drink very small amounts. |
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Breeding The female quokka mates in high summer. This means that her single offspring , born about a month later, will be suckling in her pouch during times of food scarcity but will emerge in late winter or early spring to feed on the flush of vegetation that follows winter rains. After mating the male plays no part in rearing the young. |
| Although born in a very underdeveloped state, the joey uses its tiny claws to haul itself over its mother's belly and into her pouch. A day after giving birth, the mother mates again. The development of her second embryo is 'put on hold': if the first-born dies within the first five months, the embryo continues its development and is born 25 days later. |