During the birthing process, kangaroos have a total of three vaginas. (Photo credit: Mark Anderson via Alamy)
Kangaroos have some pretty unusual external characteristics: they're the largest marsupials on the planet, they hop and use their tails as a fifth limb. But their internal structure is also quite unique: female kangaroos have two vaginas – or three, if they've given birth. Why is that?
The most likely explanation is an adaptation to Australia's harsh conditions. Having multiple vaginas – and wombs, of which they have two – gives female kangaroos and all marsupials the ability to have multiple young at different stages of development at the same time. This greatly increases the chances of at least one surviving to adulthood.
“They may have a baby that no longer needs the pouch but still depends on them,” Dr. Marcy Logsdon, an associate professor at Washington State University's College of Veterinary Medicine, told Live Science. “They may also have a baby in the pouch and another one in reserve, waiting for its time to develop.”
A newborn kangaroo is very underdeveloped and must spend a long time in its mother's pouch, being cared for and developing before it is ready to go out into the world.
“In the first 10 months, they go from these pinkish, skinny little things to these little furry little cute creatures that you see in pictures,” said Kelly Forrester, a doctoral student at the University of Alberta who co-authored the kangaroo reproduction study. “And then in the last eight months, they’re what’s called ‘young feet,’ where they’re constantly moving in and out of the pouch and learning to hop, but they’re still pretty clumsy and can’t thermoregulate … so they’re completely dependent on their mother for 18 months of their life.”
All that feeding in the pouch takes a huge amount of energy from the mother kangaroo. “Lactation is a very expensive process,” Logsdon said. “Often, lactation is more expensive than the pregnancy itself.”
When kangaroos face drought, they often cannot get enough food to continue lactating, and the baby in their pouch may die. To pass on their genes to the next generation, they need to produce another baby as quickly as possible.
Baby kangaroos are born the size of marmalades.
Fortunately, pregnancy and lactation do not interrupt the kangaroo's estrous, or reproductive, cycle. At any stage of estrus, the male kangaroo's sperm can travel up one of his two lateral vaginas and fertilize an egg, which is then implanted in whichever of his two uteri is currently unoccupied. (Although many other marsupials have two
Sourse: www.livescience.com
