What is wrong with that deer?

If you have ever seen a deer walking around your neighborhood or in the woods that has odd skin “warts” and thought to yourself, “What is wrong with that deer?” Well, you wouldn’t be the only one wondering.

Idaho Fish and Game receives calls each year about deer with abnormal skin growths. Most of the time these deer have what is known as “fibromatosis”. Fibromatosis is a skin disease where deer develop large tumor-like growths known as fibromas on their skin.

Fibromas can be hairless, round, appear firm, and may be located all over the deer. Sometimes deer may just have one or there can be numerous fibromas scattered throughout the skin. They generally are less than 5 inches in diameter and may be dark in color or appear to be bleeding.

Typically, fibromas are found mostly on young bucks and it is thought the disease can be transmitted through direct contact during the rut. However, the transmission path isn’t completely known, and contact with vegetation that has been touched by a fibroma may also spread the disease. Another possible transmission path is through biting insects.

Most of the time, deer with fibromatosis are unaffected unless the growths are located in spots that impede normal activities like eating, walking, and/or seeing. The disease is not a significant cause of death for deer and fibromas disappear over time. Deer usually develop immunity for fibromatosis after having it when younger, so if exposed as an adult they are generally not affected.

Fibromatosis is species-specific and humans are not known to be affected by the disease. As unsightly as it is on the outside, meat from a deer with fibromatosis can be consumed, as fibromas are attached to the skin and not in the muscles underneath.

Idaho Fish and Game does not attempt to capture or remove deer that are reported with this condition. Fibromatosis usually does not affect the survivability of the individual deer, and does not pose a threat to the deer population.

n Kara Campbell is a regional wildlife biologist with Fish & Game in Coeur d’Alene.