Fighting for the San Emigdio Blue

Earlier this month, Los Padres ForestWatch submitted a formal request to the U.S. Forest Service to place a critically threatened butterfly – the San Emigdio Blue – on the forest’s list of sensitive species. If our request is granted, it would be only the second butterfly species to appear on the list of sensitive species in the Los Padres National Forest, and would ensure that its habitat is protected from a variety of threats.

The San Emigdio Blue butterfly (Plebejus emigdionis) is a unique species found only in Southern California. It is unique in that females will only lay their eggs on three different species of saltbush when a particular species of ant (Fomica pilicornis) is present. The ant protects the caterpillars from being eaten by other ants and wasps, and in return, the caterpillar secretes sugar and amino acids for the ant to eat.

But even with these personal bodyguards, the species is struggling. Activities threatening its survival include water diversion, off-road vehicle trespass, livestock grazing, vegetation clearing, land development, road work, and spread of invasive species. As a result, San Emigdio butterfly populations are predicted to decrease 50-70% in the long-term.

Bouton_SEB 004

Image courtesy Bill Bouton.

While the San Emigdio Blue butterfly appears on sensitive species lists for two other forests in California, the Forest Service did not acknowledge its occurrence in the Los Padres. However, based on historical accounts and suitable habitat, we suspected that the San Emigdio Blue may occur in the Los Padres National Forest. We researched historic records and habitat models, finding that San Emigdio Blues did indeed occur in the Los Padres National Forest. However, without inclusion on the Forest Service’s list of sensitive species, the butterfly and its habitat would remain unprotected.

Plebejus emigdionis

Image courtesy David Horner, SolarDarkroom Photography.

Consequently, ForestWatch recently submitted a petition to list the San Emigdio Blue butterfly as a sensitive species in the Los Padres National Forest. The addition of the San Emigdio Blue butterfly to the Los Padres National Forest sensitive species list will help protect San Emigidio Blue populations by confirming that any potential impacts to the butterflies or their habitat are evaluated and mitigated. It will also ensure the utilization of the best and most current information to inform land management decisions throughout the region.

As we await a response from the Forest Service, the status of San Emigdio Blues in the Los Padres National Forest remains at risk. It is critical to provide the San Emigdio Blue with protections afforded by prompt placement on the sensitive species list to avoid further population declines. The continued survival of San Emigdio Blues in our region depends on it.

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