Page 36 - Mammal (DK Eyewitness)

Nine lives

A mammal whose babies develop inside the mother’s womb is known as a placental
mammal. The womb protects the babies until they are fairly well developed. A special organ
called the placenta supplies the baby with food and oxygen. Cats are placental mammals and the
babies are born with all their fur. Compare the kittens with the baby mice on page 32 (also
placental) and the baby wallaby on page 30 (a marsupial). In many species, the gestation period
(the length of time it takes for the baby to develop in the womb) is linked to body size. In shrews
it is about two weeks; in rhinos, 16 months. The birth itself is a dangerous time for mother and
babies, since they are unable to flee and
the smell of the birth fluids may give
About to be born them away. Birth is generally a
private affair, and even group-
dwelling mammals such as deer
Amniotic membrane emerging
from birth canal leave their companions for a safe
­ kitten is inside this spot in which to bear young.

THE WAITING IS OVER
1 After nine weeks’ gestation,
the time for birth has arrived. This
domestic cat is too busy to mind the
lights and camera. She has her
favorite rug and this is her second
litter so she knows exactly what to do.
In the wild most mammal mothers
hide in a den sheltered from the
wind and rain - the babies could
easily die of exposure. When it is
time for birth, the mother’s womb
contracts (becomes smaller), and the
babies are pushed down the birth
canal into the outside world. As each
kitten emerges, it is still inside the
amniotic membrane, or sac, which
enclosed it in the womb.

One kitten has already been born
The moment of birth

Amniotic membrane
FIRST BREATHS has broken
2In the womb, the developing mammal receives
oxygen and food from its mother by way of a special
organ called the placenta, which is in the inside wall
of the womb and looks like a piece of liver. In the
placenta oxygen and food pass from the mother’s
blood to the baby’s blood. The baby is attached to the
placenta by a “lifeline” called the umbilical cord. At
birth, the placenta comes away from the wall of the
womb and, still attached to the baby by the umbilical
cord, follows it along the birth canal and emerges
shortly after the baby (this is why the placenta is
sometimes called the afterbirth). The baby must then
start to breathe for itself. As soon as the amniotic
membrane is broken (by the birth, or bitten by the
mother), the fluids drain away, and the baby gulps its
first breaths of air.
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