That's the title of a four-part PBS series about animal mating and reproduction, each episode concentrating on a different species of mammal:Sex in the Wild
The episodes feature elephants, kangaroos (with glances at koalas), orangutans, and dolphins (with some material on whales).
They include lots of intriguing facts that could be applied to the creation of aliens. Male elephants in the grip of mating frenzy (which can last up to five months) have been observed attempting to mate with hippopotamuses. Male dolphins (like many other species) are known to engage in homosexual activity; an example appears in the video. Because they're mating in water, or in midair while leaping out of the water, dolphins complete an act of copulation in seconds. Orangutans, on the other hand, may stay coupled for thirty or forty minutes. Alpha male orangutans, each of whom controls a large territory also inhabited by females and low-ranking males, grow large and muscular ("like the Incredible Hulk," as mentioned on the show) and sport cheek adornments called phlanges. A phlanged male seems to emit pheromones that prevent any lesser males in his territory from developing into alphas. Once the "king" is gone, another male undergoes transformation into an alpha. A female kangaroo has the ability to suspend development of a fetus until environmental conditions become favorable for pregnancy and birth. Thus, she may have three babies in different stages of development—an infant in the pouch, a young joey hopping alongside, and an embryo "in reserve."
Elephants have the longest pregnancies of any mammal, twenty-two months. (Aargh.) Kangaroos—and all marsupials—have three vaginas (connecting to a single outlet, through which the baby emerges)! The kangaroo gives birth after only thirty days of gestation, but that's because marsupial babies are born still in a fetal stage. They complete their development in the pouch instead of the womb, a pattern that sounds much more comfortable and convenient than our way. One of the hosts of the show pointed out that if our babies stayed in utero long enough to match the developmental level of newborn elephants, our pregnancies would last almost as long as theirs. Human infants emerge into the world about nine months sooner than our overall lifespan would predict, as a byproduct of the compromise between the newborn's large brain and the limitations of the mother's pelvic structure. So we undergo extensive development after birth that would normally occur in the womb. Just one of our species' many anomalous features (like our lack of body hair).
Margaret L. CarterCarter's Crypt