Back to a “biodiversity hotspot”

After more than 20 years, Laguna Mountains skipper returned to historic range in Southern California

a small brown pupa on a blue cloth in a jar

A Laguna Mountains skipper pupa awaits transfer to its protective container. The temporary plastic containers were used to transport the pupae from the San Diego Zoo Wildlife Alliance's Butterfly Conservation Lab to the Cleveland National Forest. Credit: Jessica D'ambrosio/USFWS

By Jessica D'ambrosio
June 21, 2021

In a historic first, a partnership of wildlife and conservation experts recently reintroduced the federally endangered Laguna Mountains skipper (Pyrgus ruralis lagunae) to a portion of its range in San Diego County.

two women on the ground transfering pupa

Alison Anderson, left, Carlsbad Fish and Wildlife Office Entomologist, and Paige Howorth, McKinney Family Curator of Invertebrates for San Diego Zoo Wildlife Alliance, use tweezers to transfer Laguna Mountains skipper pupae into protective containers, which were then placed in the meadow. Credit: Jessica D'ambrosio/USFWS

The U.S. Fish and Wildlife Service, U.S. Forest Service, San Diego Zoo Wildlife Alliance, Osborne Biological Consulting and WildSpring Ecology released 23 pupae in the Laguna Mountains to reestablish the butterfly in its namesake habitat, where it has been absent for more than two decades.

In 2019, the Service finalized a plan to guide recovery efforts for the species. Part of the plan includes reestablishing sustainable populations in its native habitat across its range. Currently, the butterfly is only found at four sites on Palomar Mountain.

“Reintroduction of the Laguna Mountains skipper will increase the number of resilient populations, expand occupied habitat and maintain genetic diversity, which are all needed for recovery of this species,” said Scott Sobiech, field supervisor of the U.S. Fish and Wildlife Service’s Carlsbad Office.

“Southern California is a biodiversity hotspot, and numerous butterflies have been affected by habitat loss, degradation and wildfires like the Quino checkerspot, Palos Verdes blue, El Segundo blue and Hermes copper,” said Sobiech. “This effort demonstrates what can be accomplished when partners work together and offers a model for the recovery of other threatened and endangered species.”

a landscape shot of a grassy plain with threes in the background under a clear blue sky

The skipper's habitat is in meadows in the Laguna Mountains. Photo Copyright: Alexander Kunz

The exact reason for the skipper’s disappearance from the Lagunas is unclear, but was likely a combination of climate change driven-drought and human use. The tiny butterfly is not migratory and is vulnerable to disturbances like drought, fire and flood. Reintroduction to the Laguna Mountains strengthens redundancy so that no single catastrophic event on Palomar Mountain would result in extinction of the species.

a small pupa with green leaves in a small container

Multiple pupae are placed on the lid of a protective container. A few have woven together leaves as a protective layer around themselves. Credit: Jessica D'ambrosio/USFWS

The U.S. Forest Service manages these sites within the Cleveland National Forest to minimize threats to the species and its habitat while also ensuring compatible pastoral and recreational use of the land.

The reintroduction process began by collecting pregnant butterflies from Palomar Mountain and rearing their progeny at the San Diego Zoo Wildlife Alliance’s Butterfly Conservation Lab. During release, the pupae were placed in protective shelters designed to keep predators out and allow weather conditions to trigger the natural transition to adulthood.

“Since 2013, the San Diego Zoo Wildlife Alliance has worked to build a substantial program for the rearing of endangered butterfly species for recovery efforts,” said Paige Howorth, McKinney Family Curator of Invertebrates for the Alliance. “We are delighted to contribute our unique expertise to help return the Laguna Mountains skipper to its historic range.”

Additional releases of pupae in the Laguna Mountains are planned over the next few weeks, and the first butterflies are expected to emerge next spring.

white webbing in a small tube in a clear container

This pupa inside a paper straw has woven webbing around itself. Credit: Jessica D'ambrosio/USFWS

The Laguna Mountains skipper is a member of the Hesperiidae family. Its one-inch wingspan has extensive white markings, banding patterns on the hind wings and a forewing pattern resembling an “X.” This butterfly gets nectar from whatever is flowering, but prefers to deposit its eggs on the outer leaves of Cleveland’s horkelia (Horkelia clevelandii).

Skippers can be identified by a few unique characteristics. When resting, they drape their wings against their bodies or hold them flat, instead of folding them up above their backs. Their antennae are also hook-shaped at the end and they have an erratic flight pattern.

Other organizations involved in the long-term recovery of the Laguna Mountains skipper, and protection of its habitat include, The Urban Wildlands Group, Mendenhall Ranch, Moorpark College and the Disney Corporation.