Elephants Carry Babies for Two Years, and More Amazing Animal Pregnancies
During this state of suspended growth, mom returns to the water for food. “They actually eat for three for most of their adult lives, and it’s just amazing that they have the resources to be able to get through this.”
All four species of kangaroos have two separate uteri, an adaptation that allows them to carry a “spare” embryo. After giving birth to their candy-sized hairless joey, females often quickly become pregnant again in the other uterus.
As this little one matures in mom’s pouch, she keeps the other fertilized embryo in arrested development until the brother is weaned and can fit into the pouch. A kangaroo doe can produce milk with different nutritional values for two joeys of different ages, and she has four teats from which both joeys can suckle.
If a female loses a joey, “then the embryo that’s in diapause resumes its development, so it can reproduce better and have more offspring without having to wait an entire year,” Travis explains.
A March 2020 study showed that the swamp wallaby can also have two embryos at different stages of development in its wombs. Using high-resolution ultrasound, researchers learned that females ovulate, mate, and form a new embryo while carrying a full-term fetus in the other uterus. This means that the swamp wallaby is the only known species that is essentially always pregnant.
Peeking inside the womb
Although much is known about reproduction and mating in the animal world, what happens inside the womb is more of a mystery.
That’s why more and more scientists are increasingly turning to cutting-edge technology to see what happens when an animal develops in utero. Using 4D imaging on a pregnant captive African lioness, for example, Hildebrandt discovered a protective hammock-like structure in which the cubs lie inside the lioness’ belly.
When a lioness hunts prey like a zebra, she is likely to be kicked in the abdomen. “These challenges would normally kill the baby, but that’s not the case because nature has designed a way, a suspension system to lessen the impact of these challenges,” he says.
For the new National Geographic documentary series, growing animal, which airs August 18 on Disney+, sculptors have handcrafted and hand painted lifelike 3D baby animals with detailed precision, even down to the blood capillaries and hair follicles. For the first time ever, viewers can see baby chimpanzees, Steller sea lions, African wild dogs and others in the womb.