The practice of animal sacrifices dates to ancient times. A member of a herd would be slain and offered to the gods in exchange for beneficial weather or other blessings. Today, animal mutilations are sometimes linked to rituals but can also be the work of many different predators. The presumed perpetrators of these killings range from other animals to humans to the possibility that the carnage is the work of aliens and extraterrestrials.
On the cable TV program The Unexplained Files, which appeared on the Science Channel network, a rancher detailed the periodic cattle mutilations that have been occurring on his ranch for over 15 years. In each instance, parts of the animal had been removed with surgical precision. There was no blood nor parts strewn about. This would rule out death by another animal and by most humans.
Researchers have speculated that it is unlikely that aliens would travel light years to gather samples through these slayings. They propose that it is possible that the cattle mutilations are the work of an unknown agency monitoring the food chain to prevent future outbreaks of Mad Cow Disease. Also known as Bovine Spongiform Encephalopathy, the disease had decimated the beef industry in England twenty years before.