On one side of a path in the idyllic hills of Santa Barbara, a dense clump of dried out mustard rises more than six feet. Meanwhile, just across the way, the invasive plant is thinned to wisps.

Carolyn Chaney, 77, pointed out the difference in vegetation and also provided the reason: sheep.

“This is where they’ve been,” she said, pointing to the cleared patch of land.

Chaney would know. She’s a regular sheep docent at the 300-acre San Marcos Foothills Preserve, owned by Santa Barbara County and located between Santa Barbara and Goleta.