![](https://ichef.bbci.co.uk/images/ic/640x360/p02bkb6z.jpg)
Delay tactic
The placental mammals evolved to be able to get nutrients directly to their developing young, which meant none need give birth to their babies until they were very well developed.
Baby rabbits develop within the mother for 28 days - twice as long as an opossum, which is a primitive marsupial of about the same size.
The baby rabbits don't open their eyes until several days after birth, but when necessary, a young placental mammal can be ready for action almost as soon as it leaves its mother's body.
Duration:
This clip is from
Featured in...
±«Óãtv Nature
Be captivated, informed and inspired by the world's wildlife.
More clips from The Rise of the Mammals
-
Lucky pups
Duration: 03:29
-
Egg-laying mammals? The platypus defies expectations
Duration: 03:25
More clips from Life on Earth
-
Lucky pups—The Rise of the Mammals
Duration: 03:29
-
Millennia of millipedes—The First Forests
Duration: 01:50
-
Creatures of the night—Life in the Trees
Duration: 01:16
-
Scent sense—Life in the Trees
Duration: 02:55