Source: Discover Magazine
A possible canine distemper outbreak may have contributed to the lowest Yellowstone wolf pup survival rates since gray wolves were reintroduced nearly 30 years ago. According to the Wyoming Game and Fish Department’s 2025 wolf monitoring report, 64.3% of captured wolves tested positive for canine distemper, far exceeding the predicted infection rate of 28%. The disease appeared to hit wolf pups the hardest, with only 31 to 34 of at least 87 pups surviving in 2025.
In Yellowstone National Park specifically, only 17 of 36 pups survived, marking the lowest pup recruitment since 1996. Canine distemper affects respiratory, gastrointestinal, and nervous systems and spreads through airborne particles and shared food or water sources. While officials lack direct evidence confirming distemper inside Yellowstone, survival patterns strongly suggest disease involvement. Wildlife officials continue monitoring wolf populations and developing management strategies to support long-term wolf health and stability across Wyoming and Yellowstone ecosystems.