As a species, we have evolved drastically over the course of a million years and a billion years for some animals. Our mating habits and other biological evolution allowed us to survive and live through the present day.
Some animals we have today may face some mating difficulties at some point. Although rare, interbreeding with closely related species, or at the extreme, interbreeding with the distant ones may happen.
This is evident in a video footage of a macaque riding a deer. It may look like one of those cute, animal friendly videos - but there is more to the scene than meets the eye.
While there wasn't any sexual penetration, the macaque ejaculated on top of the deer's back after its gentle humping and thumping. The deer licked the sperm off after the macaque dismounted.
The two animals may have formed a platonic bond as observed prior to doing the sexual act. They were seen to have been regularly interacting with each other. In some instances, the researchers witnessed the macaque dropping food on the ground for the deer to eat.
The researchers believed that the sexually active macaque may have been a "peripheral male" in his group. It means there aren't enough female available for him to have sex with. According to them, there are no available females in the macaque's troop.
For the deer, what she got out of it was a small amount of nutrition.
"The licking behaviour shown by the deer seems to indicate that the sperm could be a good source of protein," the authors added in their report.
The report is published in Primates journal