A new survey has found a sharp decline in desert bighorn sheep in Southern California, and biologists suspect the cause is a disease contracted from domestic animals.

The California Department of Fish and Wildlife says a survey earlier this month counted 60 bighorns in the Mount San Gorgonio region east of Los Angeles. That’s down two-thirds from a survey conducted in 2016.

Biologist Jeff Villepique says in the past, such die-offs have been triggered by an outbreak of a respiratory disease spread by contact with domestic sheep or goats.

FILE - In a 2003 file photo, a desert bighorn sheep is released in the Granite Mountains of northern Nevada near the Oregon line. (Kim Toulouse/Nevada Department of Wildlife/The Reno Gazette-Journal via AP, File)
FILE – In a 2003 file photo, a desert bighorn sheep is released in the Granite Mountains of northern Nevada near the Oregon line. (Kim Toulouse/Nevada Department of Wildlife/The Reno Gazette-Journal via AP, File)

The disease killed at least 21 bighorns whose carcasses were found in the area in December.

Southern California has about 4,800 desert bighorn sheep in 64 herds. Authorities say so far, sheep in nearby herds haven’t been affected.