Millions of Butterflies Migrate to the Sierra

This summer, butterflies have taken over the Sierra skies by the millions. The migration of the California Tortoiseshell occurs annually, however, this year we’ve seen an unusual amount of fluttery friends throughout the region. The reason? Scientists are perplexed and are working hard to figure out why this year has brought such an influx.

Traditionally butterflies migrate North in the spring to mate and lay their eggs. The butterflies traditionally lay their eggs on Ceanothus, also known as the California Lilacs, but also use other native plants, including Mountain Whitethorn, Mahala Mat, Tobacco Brush, and at lower elevations, Deerbrush.

Once the eggs hatch, the larvae munch on the host plants until they are ready to form a chrysalis, in which they transform from a caterpillar into a beautiful butterfly. But this still doesn’t explain why there are so many more butterflies than previous years.

Typically, the butterflies only lay eggs according to how many healthy host plants are available. Due to the significant amount of snowfall last winter, these healthy host plants are thriving, leading to a significant increase in eggs being laid and ultimately a sharp increase in butterflies hatching in the Sierra.

The butterfly phenomenon and life cycle is very complex and still not completely understood by scientist. But it sure has been fun to see these beauties fluttering around the lake the last few months.

If you haven’t had a chance to see for yourself, you still have some time. After hatching, the butterflies find a place to mature for a few weeks before heading back South during the cooler months.

The California Tortoiseshells usually hang out near sources of water and food. If you are looking for them, some of the best places to find the butterflies are around beaches and ponds, where butterflies can extract salt from the water. Or seek them out on hiking trails abundant with wild lilac, such as Relay Peak or Mount Rose.