A scent-detecting mule from British Columbia has joined a private search for a woman missing in Arizona, bringing a new approach to terrain already searched with drones, all-terrain vehicles and cadaver dogs, CBC reports.

Sonny and his handler, Princeton Ground Search and Rescue volunteer Marion Weiskopff, are helping search for Chelsea Grimm, who disappeared during a cross-country road trip in 2023. Her vehicle was found abandoned on a forest service road in the Kaibab National Forest, south of the Grand Canyon.

The mounted search has been suspended because heavy rain and mud made conditions unsafe. Private investigator Steve Fischer, who is working on the case, told CBC he hopes to organize another large-scale search in drier weather.

Fischer learned about Sonny through search-and-rescue contacts. After discovering that Weiskopff and her husband spend several months each year in Arizona with their animals, he invited them to help search a 400-square-kilometre area of backcountry.

Weiskopff told CBC’s Daybreak South that Sonny stops when he detects a smell, draws in air and turns toward its source. He developed those abilities at training clinics in Oregon and Arizona and later won equine scenting competitions in both states, she said.

During the Arizona search, Sonny led Weiskopff to a torn-off shoe sole away from any trail. She described it as a woman’s shoe, but said investigators could not determine whether it belonged to Grimm. The discovery has not been established as evidence connected to the disappearance.

Fischer said this was his first time using scent-detecting equines. He sees their ability to reach areas difficult to search on foot as a valuable addition to the effort. Previous searches had come up empty-handed.

For Sonny and Weiskopff, the assignment is their first search specifically using his scent-detection skills, though both already have search-and-rescue experience.

Their Princeton mounted unit has five trained volunteers with their own mounts. Certification requires mastering an additional 60 tasks. Unit president Paul Fyfe told CBC that horses offer advantages in access and visibility across the region’s steep mountains and grasslands. Scent detection is not an official unit skill, but further formal training remains a possibility.

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