Since Australia, New Guinea and South America was cut off by oceans for the last million years the pouched mammals have evolved. They exploit a separate and extraordinarily rich fauna which ranges from desert to rainforest.
Pouched mammals already existed at the time of the dinosaurs. At this time there were no continents as we know it today but one giant land mass, called Gondwanaland.
Australia, Antarctica, South America, New Guinea and the nearby islands broke apart when the tectonic plates split Gondwanaland. Over centuries the ancestral mammals of these areas evolved new pouched species.
All over the world new mammals began to grow placentas and replaced pouched species.
When South America collided with North America resulting into one continent the pouched South American opossums moved north into a land dominated by placental mammals.
The pouched mammals evolved separately from their placental cousins but they started with an identical genetic history. The result was evolution duplicate species.
MARSUPIAL BIRTH
Not having a placenta to feed the baby with nutrients efficiently from the mother's body to the embryo, pouched mammals cannot nurture their babies very long therefore marsupials are born only partly formed, The new born baby crawls up its mother's belly to the pouch. It attaches to one of her teats. It does not let go until it is capable to feed itself.
Not having a placenta to feed the baby with nutrients efficiently from the mother's body to the embryo, pouched mammals cannot nurture their babies very long therefore marsupials are born only partly formed, The new born baby crawls up its mother's belly to the pouch. It attaches to one of her teats. It does not let go until it is capable to feed itself.
Most of the babies are able to get into the pouch but some are lost. To counteract nature has formed a fascinating back-up.
Marsupial females have a double vagina and a double uterus into which the eggs are shed. The male has a two-lobed penis to be able to fertilise one egg in each uterus. The implantation and
development of the second egg can be delayed for weeks of months until the first baby stops suckling and leaves the pouch.
This enables the mother to breed immediately without a male. It also helps if the first baby died.
THE MARSUPIAL POUCH
Marsupials lead an active life, like Kangaroos. which has a single baby.
Marsupials lead an active life, like Kangaroos. which has a single baby.
Many species of American opossums and Australian carnivorous pouched mammals have eight or more babies.
Their pouch is a fold of skin around the nipples. Attached to a nipple, the young are carried around. As they gain weight the whole litter is heavier than the mother. The moment they release her teats, she leaves them in a nest.
Different species have different ways of care of their babies.
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