A seemingly strange demise has befallen five cattle on the Silvies Valley Ranch in remote eastern Oregon. Reports from NPR and the Associated Press paint a bewildering scene, free from tracks, predator activity, poison, shot wounds and even blood. But it might just be the latest instalment in a long line of 'mysterious cattle death' stories that appear as early as the 17th century.

According to reports, the five purebred bulls were found dead at various locations on the ranch.They apparently had their tongues cut out, their genitals sliced off, and their bodies drained of blood.

"To lose a completely healthy animal would be an oddity," vice president of the ranch Colby Marshall told AP. "To lose five young, very healthy, in great shape, perfect bulls that are all basically the same age … that is so outside the bounds of normal activity."

It sounds like the beginning of an eerie alien fiction novel, except it's not the beginning at all. Mystifying cattle death reports are an entire genre; so far, nothing supernatural has ever been discovered as the source.

Last year in Arizona, a cow and bull were found mutilated in what was reported to be the same fashion. In the decades before that, thousands of seemingly similar cases have popped up across the US mid-west.

In fact, the FBI even got involved in the mid-1970s, having been asked to investigate these "reports of scattered animal mutilations".

Not all of these cases had the same features however, and many of the seemingly bizarre 'mutilations' most likely occurred due to natural causes.

For example, it's unlikely the cattle had all of their blood drained. When a cow drops dead, gravity pulls the blood down to the bottom of the carcass, and when the skin here dries out, it can split open in surgical-like slices. If the blood then seeps into the ground and is consumed by insects, there's a chance it will appear the body was 'drained'.

Similarly, it's possible the missing genitals and other body parts shrink away as part of the natural decomposition process; scavengers, like birds or carrion bugs, are also known to feed on the soft external tissue, such as the udders and the genitals, the eyes and the mouth.

That said, reports of the bizarre appearance of the cattle remains have stoked the imaginations of many.

"A lot of people lean toward the aliens," the county's Sheriff Dan Jenkins told NPR.

"One caller had told us to look for basically a depression under the carcass. 'Cause he said that the alien ships will kinda beam the cow up and do whatever they are going to do with it. Then they just drop them from a great height."

Jenkins is still investigating the mysterious deaths, but with little evidence to work with and no leads to speak of, it's doubtful that he'll be any more successful than those who came before him.

According to NPR, the FBI won't confirm or deny whether an investigation is being launched, but the last time its agents looked into such a matter, they found no reason to suspect anything other than natural predators.