Researchers at the University of Georgia have studied what are believed to be the first conjoined twin deer fawns to have reached full term and be delivered by their mother.

The two deer fawns that share one body were discovered in May 2016 near Freeburg, Minnesota, according to the University of Georgia. A man said he was foraging for wild mushrooms when he stumbled across the fawns about a mile away from the Mississippi River.

The mushroom enthusiast called the Minnesota Department of Natural Resources about his discovery. Researchers said the female fawns were clean, dry and appeared to be recently deceased. They were frozen until a necropsy could be performed.

Gino D’Angelo, the University of Georgia researcher who studied the deer, said that the only other examples of conjoined twin fawns have been found still in utero. D’Angelo and other researchers published a paper describing the deformity in the April edition of American Midland Naturalist.

“It’s amazing and extremely rare,” D’Angelo said. “We can’t even estimate the rarity of this. Of the tens of millions of fawns born annually in the U.S., there are probably abnormalities happening in the wild we don’t even know about.”

A CT scan of the conjoined fawns reveals separate heads sharing the same body. (The University of Georgia)

Lab tests on the lungs revealed the fawns never breathed outside air and were delivered stillborn. A necropsy revealed they shared a liver that was malformed, and had extra spleens and intestinal tracts. The fawns also had two separate hearts that shared one pericardial sac, which is the tissue that surrounds the heart.

“Their anatomy indicates the fawns would never have been viable,” D’Angelo said. “Yet, they were found groomed and in a natural position, suggesting that the doe tried to care for them after delivery. The maternal instinct is very strong.”

The discovery is incredibly rare, according to researchers. Though highly unlikely, conjoined twins are not unheard of in domestic animals or humans. Researchers said they are very unusual in the wild and rarely make it all the way to delivery.

Researchers found only 19 cases of conjoined twins in wildlife between 1671 and 2006, five of which were in the deer family. Only two cases were found in white-tailed deer, but both were undelivered fetuses.

As for what caused the abnormality, D'Angelo said, "Even in humans we don’t know. We think it’s an unnatural splitting of cells during early embryo development."

The Minnesota Department of Natural Resources will have the fawns stuffed and on display at their headquarters in St. Paul, researchers said. The University of Minnesota Veterinary Anatomy Museum will have a skeletal display.