Pouch
The pouch is a distinguishing feature of female marsupials (and rarely in the males as in the water opossum and the extinct thylacine); the name marsupial is derived from the Latin marsupium, meaning "pouch". Marsupials give birth to a live but relatively undeveloped fetus called a joey. When the joey is born it crawls from inside the mother to the pouch. The pouch is a fold of skin with a single opening that covers the nipples to protect the joey as it continues to develop.
Pouches are different amongst the different marsupials: for example for quolls and Tasmanian Devils, the pouch opens to the rear and the joey only has to travel a short distance to get to the opening (resting place) of the pouch. While in the pouch they are permanently attached to the nipple and once the young have developed they leave the pouch and do not return. The kangaroo's pouch opens horizontally on the front of the body, and the joey must climb a relatively long way to reach it. Kangaroos and wallabies allow their young to live in the pouch well after they are physically capable of leaving, often keeping two different joeys in the pouch, one tiny and one fully developed.
Kangaroo pouches are sticky to support their young joey.
An early birth removes a developing marsupial from its parent's body much sooner than in placental mammals, and thus marsupials have not developed a complex placenta to protect the embryo from its mother's immune system. Though early birth places the tiny newborn marsupial at a greater environmental risk, it significantly reduces the dangers associated with long pregnancies, as there is no need to carry a large fetus to full-term in bad seasons.
Because newborn marsupials must climb up to their mother's nipples, their front limbs are much more developed than the rest of the body at the time of birth. It is possible that this requirement has resulted in the limited range of locomotor adaptations in marsupials compared to placentals. Marsupials must develop a grasping forepaw during their early youth, making the transition from this limb into a hoof, wing, or flipper, as some groups of placental mammals have done, far more difficult.
An infant marsupial is known as a joey. Marsupials have an extremely short gestation period (about 4–5 weeks), and the joey is 'born' essentially in a fetal state. The blind, furless, miniature newborn, the size of a jelly bean, crawls across its mother's fur to make its way into the pouch, where it latches onto a teat for food. It will not re-emerge for several months, during which time it develops fully. After this period, the joey begins to spend increasing lengths of time out of the pouch, feeding and learning survival skills. However, it returns to the pouch to sleep, and if danger threatens it will seek refuge in its mother's pouch for safety.
Joeys stay in the pouch for up to a year in some species, or until the next joey is born. A marsupial joey is unable to regulate its own body temperature, and thus relies upon an external heat source. Until the joey is well-furred and old enough to leave the pouch, a pouch temperature between 30–32 °C (86–90 °F) must be constantly maintained.
| Stub icon | This article about a marsupial is a stub. You can help Wikipedia by expanding it. |
.png){kind=link}