In the entire animal kingdom, male seahorses (and their close relatives) are the only male animals that undergo pregnancy and give birth to offspring.
Greenflies, stick insects, aphids, water fleas, scorpions, termites and honey bees are all capable of reproducing without males, using parthenogenesis.
Seahorses and their close relatives, sea dragons, are the only species in which the male gets pregnant and gives birth. Male seahorses and sea dragons get pregnant and bear young—a unique adaptation in the animal kingdom. Seahorses are members of the pipefish family.
Birds, like domesticated turkeys and chickens, have also been able to produce offspring without mating. In the 1950s, scientists discovered that unfertilized turkey eggs could develop embryos through parthenogenesis. Birds, like domesticated turkeys and chickens, have also been able to produce offspring without mating.
No doubt there is such a thing as forced copulation in the animal kingdom that is often violent, and observed in many species of insects and birds such as the mariticidal praying mantis, and among ducks and geese; drakes, more often than not, force themselves on ducks.
Ethical considerations preclude definitive research on the subject, but it's safe to say that human DNA has become so different from that of other animals that interbreeding would likely be impossible.
It happens in both animals and plants. Such encounters can affect the conservation and evolution of a species. When two different species successfully mate, the resulting offspring is called a hybrid. Hybrids are often, but not always, sterile (think of mules).
Their genomes are simply too different to come together and make something that will live. Their genomes cannot mix in any productive way.
Of course, scientifically it's not possible for a human to have sex with an animal and give birth to a hybrid creature, not matter how many demons are involved. Genetics just don't work like that.
Guinness World Records named Beatie the "World's First Married Man to Give Birth" in 2010. In a TV broadcast from Rome, Italy, Guinness World Records presented him with the title of "Unico Uomo Incinto al Mondo", translated as "World's First Pregnant Man".
When the earth was new, all living things reproduced asexually: rather than finding sexual partners, individuals begot copies of themselves to perpetuate their ilk. This was simple. It was efficient. Every member of the species was capable of reproducing and did so without help from any of their kin.
Baby mice have been made with two mums and no dad, say researchers at the Chinese Academy of Sciences. It took a substantial feat of genetic engineering to break the rules of reproduction. The scientists said the "bimaternal" (two mammas) animals were healthy and went on to have pups of their own.
Animals that mate for life: beavers
Not much is known about how beavers find their mates, but once they do, they stick with that partner for life. A genetic study by Charles University in Prague even found that beavers stay faithful to their mates. Granted, this only applies to European beavers.
Their genomes are simply too different to come together and make something that will live. Their genomes cannot mix in any productive way. Imagine you take the instructions for making an airplane and instructions for making a curling iron and mix them together.
Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus' Antechinus and bandicoots, around 1% of all bird species, such as jacanas and dunnocks, insects such as honeybees, and fish such as pipefish.
Thus, privacy, or perhaps more accurately, seclusion, allowed the male to maintain control over a sexual partner—while also allowing for continued cooperation within a group.
But creating hybrids of animals that are very genetically distinct from each other—such as a dog and a cat—is scientifically impossible, as is one species giving birth to an entirely different one.
Besides humans, few species hide sexual activity. Arabian babblers are one such species; keeping mating private may preserve the peace. Arabian babblers are one of the few known species to regularly conceal sexual activity. Researchers think the reason is to maintain cooperation within the group.
Some birds who mate for life sometimes even stop eating and die if their partner dies. This is true for geese but also for many songbirds, they have long-term bonds. Which animals do you think mourn the most strikingly?
Kalutas live fast and die young — or, at least, the males do. Male kalutas, small mouselike marsupials found in the arid regions of Northwestern Australia, are semelparous, meaning that shortly after they mate, they drop dead.
The praying mantis, black widow spider, and jumping spider are among a number of species that devour their mates. Sexual cannibalism is also found in other invertebrates, including a relative of the praying mantis, the Chinese mantis, and scorpions.