California tortoiseshells are on the move! These bright orange-and-black butterflies can currently be seen in the thousands across the Santa Cruz Mountains. Sometimes mistaken for monarchs, the California tortoiseshell butterfly is native to western North America and depends on ceanothus, a shrub commonly found in California chaparral and forest ecosystems.
The species is known for dramatic boom-and-bust population cycles. Every few years, environmental conditions allow unusually high numbers of caterpillars to survive, resulting in millions of butterflies emerging as adults at roughly the same time. The butterflies then disperse across the landscape, creating sudden regional influxes even in areas where ceanothus is sparse.
The current surge is expected to be short-lived. These mass movements often last only a week or two before butterfly numbers begin dropping again. For a brief period, trails and preserves across the Santa Cruz Mountains become filled with thousands of migrating butterflies passing through the region.
Visitors to preserves including Bear Creek Redwoods Open Space Preserve, Sierra Azul Open Space Preserve, Monte Bello Open Space Preserve, Skyline Ridge Open Space Preserve, and Long Ridge Open Space Preserve are reporting seeing thousands of butterflies fluttering through forests, meadows, and along trails.
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