On Nov. 14, 2023, Yellowstone National Park and the Wyoming Game and Fish Department (WGFD) confirmed the presence of chronic wasting disease (CWD) in the carcass of an adult mule deer buck found near Yellowstone Lake in the southeastern section of the park. This was the first confirmed positive detection of the disease in Yellowstone National Park.

The mule deer buck was originally captured by WGFD staff near Cody, Wyoming, in March 2023 as part of a population dynamics study and fitted with a GPS collar. The collar signaled the animal died mid-October 2023. The samples tested positive for CWD based on multiple diagnostic tests performed at WGFDﾒs Wildlife Health Laboratory.