The disease devastating deer herds may also threaten human health

But the mountain lions know that something is wrong. A number of years ago, Swanson and her colleagues studied which deer mountain lions prefer to attack. “The mountain lions were definitely preferentially selecting deer that had chronic wasting disease over those that were negative,” she says. “And for most of the ones that they had killed, we had not detected any chronic wasting disease symptoms yet. So certainly the lions were able to key in on far more subtle cues than we were.”