Nature also has its own natural butt-plug. Some garter snake females are forced to defecate quickly (poo) before the male inserts the sperm since after he is done, he will insert a mating plug into the female to hinder any other males from mating. Sometimes this does not work out as he had planned and mixed paternities do occur. Snake sex is surprisingly intricate.
As I started to write this, a rather ridiculously meaty creature (Meleagris gallopavo to be precise) had been stuffed and was being slowly roasted. Eventually, it was consumed by a family of apes of genus Homo. Stripped of flesh, the skeletal remains of this creature marked it as a maniraptoran coelurosaur of clade Aves – the sole line of Dinosauria to persist after the Cretaceous-Palaeogene extinction event. Literally every example of this line is more closely related to the mighty Tyrannosaurus rex than Triceratops, Diplodocus, or Stegosaurus were to either.