Why did the dazed Tennessee deer have fur emerging from their eyeballs?

 

Image Credit: National Deer Association

A whitetail deer was found wandering through the streets of Farragut, Tennessee, with both of its eyeballs developing thick fur.

The fur, the translucent portion of the eye covering the iris and pupil, protruded from flesh discs covering both the buck's cornea. According to Quality Whitetails magazine, the journal of the National Deer Association, the bizarre disease, called corneal dermoids, has been recorded in only one other whitetail in the state of Tennessee.

By definition, a dermoid is a type of benign tumor that consists of tissues that normally occur in other parts of the body; in this case, complete skin tissue with hair follicles cropped in the cornea of the deer.

"Maybe could tell day from dark, but I wouldn’t think it would be able to see where it was going, “Maybe the hairy-eyed deer could tell day from night. I'd compare it with a washcloth to cover your eyes. Day after night, you might say, but that's about it.

According to the Cornell Wildlife Health Lab, the same deer tested positive for epizootic hemorrhagic disease (EHD), which can trigger fever, extreme tissue swelling, and lack of fear of human beings. In late August 2020, this might explain why the disoriented animal wandered into a suburban street and seemed unaware of the nearby people, Quality Whitetails reported.

The disease, however, does not justify why tufts of hair have sprouted from the deer's eyes.

In the development of the animal, the hairy skin patches possibly developed early, when it was still in the womb, Dr. Nicole Nemeth, an associate professor in the Department of Pathology, told Quality Whitetails. Instead of forming into a clear cornea successfully, the tissue developed skin and hair follicles instead, obscuring the eyes of the growing deer.

The deer's eyes, under the thick fur, possessed all the expected anatomy.

Despite being born with corneal dermoids, Quality Whitetails confirmed that the buck had lived to be more than a year old and even grew its first set of antlers before catching EHD, which has no treatment. Nemeth said that the dermoids possibly "developed gradually," because the deer lived so long, allowing the animal to adjust over time to its diminishing field of vision.