Local residents described the rabbits as having “black quills or black toothpicks” growing out of their faces.

As weird and concerning as they appear, the virus that causes the dark, wart-like horns or tentacles to grow on cottontail rabbits is relatively common and usually not anything to worry about, CPW

According to Colorado Parks and Wildlife's (CPW) website, the black growths on the rabbits' heads are due to a grimmer, more reality-based reason — a viral infection called the cottontail rabbit papillomavirus.