Marsupials
- What is a marsupial?
- Development of pouch young under normal circumstances
- Pouches
- Immunity of young marsupials
- Milk for marsupials
What is a marsupial?
| Marsupials are commonly termed "pouched mammals". However, not all marsupials have a true permanent pouch. Many carnivorous marsupials have folds of skin that swell to act as a temporary pouch during the breeding season. Newborn marsupials are furless and have underdeveloped hind limbs and tail. Dasyurids, which include quolls, dunnarts, antechinus, planigales and phascogale, mostly prey on small mammals, birds and large insects. The omnivorous group of marsupials includes bandicoots and bilbies. These animals dig up their food, which includes insects, small vertebrates and plant material. |
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Greater glider |
The herbivorous marsupial group includes kangaroos, wallabies, possums, koalas, wombats and gliders. This group eats a variety of grasses, shrubs, fruits, eucalypt leaves and native blossom.
Development of pouch young under normal circumstances
Marsupials have a very short gestation period, ranging from 12 days to 46 days depending on the species. Marsupials are born in a very immature state, weighing between 0.1g and 1g and are about the size of a jellybean.
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When it is born, the neonate climbs from the mother's cloaca into the pouch, where it attaches itself to a teat and continues its development. Neonates rely solely on their mother for warmth. They are born with functional gastrointestinal tract, lungs and kidneys and have a special blood composition that enables them to survive the higher levels of carbon dioxide in the pouch. At this early stage, the joey is permanently attached to the teat. Joeys start to leave the pouch and either follow their mother (macropods) or stay in the den while she forages (possums, quolls and bandicoots) when they start to grow fur and open their eyes. |
| Mahogany glider pouch young |
Pouches
There are three different types of pouches:
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 Bridled nail-tail wallaby in pouch |
Immunity of young marsupials
Studies have shown that young marsupials are born without an active immune system. The immune system does not function at full capacity until they are almost ready to leave the pouch. Mothers transfer immunity to their joeys through their milk and by secreting antibodies into the lining of the pouch.
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When the supply of passive immunity stops (e.g. when a joey is orphaned), the joey becomes susceptible to disease within a few days. This makes it difficult to raise very young marsupials. Most people have found more humane to euthanase very immature orphaned marsupials because we cannot give them with immunity. |
| Rock wallaby pinkie | |
Milk for marsupials
Eutherian milk (e.g. cows' milk) and milk produced by marsupials are very different. Eutherian milk has a fairly stable composition, whereas the composition of marsupial milk can change dramatically with the different stages of the young's growth. Some species of kangaroos can produce two types of milk for suckling joeys that are at different stages of growth.
Companies such as Wombaroo and Biolac have developed formulas for the various stages of joey development. Contrary to popular belief, marsupials are not lactose intolerant. Their milk contains about 2 percent lactose, which is less than cows' milk. Joeys can suffer from a lactose-induced osmotic diarrhoea if given cows' milk in large volumes.
Last updated: 12 January 2005