Lange's Metalmark Butterflies Released on Antioch Dunes National Wildlife Refuge

A daring attempt to help a nearly-extinct butterfly that began last August has been successful beyond the most optimistic hopes, and now biologists are about to re-populate one of the species’ few remaining habitats. 

On August 29 of 2008, U.S. Fish and Wildlife Service Biologists were joined by Moorpark College and the Urban Wildlands Group from Southern California to release 30 endangered Lange’s metalmark butterflies in the Antioch Dunes National Wildlife Refuge.  Thirty larvae were also released in hopes that they would survive to metamorphosis in their natural environment and mate on the refuge.

Unlike some butterflies that can travel hundreds of miles, the Lange’s metalmark is a homebody that never ventures beyond the sand dunes along the southern bank of river at the western edge of the Sacramento-San Joaquin Delta.  Now, with most of those dunes destroyed, the butterfly’s only remaining habitat is on and near the 55-acre Antioch Dunes National Wildlife Refuge.

A few remnant sand dunes along the San Joaquin River in Antioch is the only home left to the Lange’s metalmark butterfly.  After a one-day peak count of 2,342 butterflies in 1999, the number of butterlies plummeted to just 45 in another one-day count in 2006.  In a desperate attempt to save the species, biologists carefully collected nine females from the remaining Lange’s metalmark in 2007 and placed them in two experienced breeding facilities.  Moorpark College, operated in conjunction with Urban Wildlands Group, produced 129 adults from that initial stock.  Butterflies that were not released back onto the refuge in 2008 will be bred to increase the breeding population for release next year.

The captive breeding program is just one component of the restoration efforts.  The other key component is the rejuvenation of naked-stemmed buckwheat, a wispy plant that is the butterfly’s host plant.  The task facing the refuge is how to save dune-dependent naked-stemmed buckwheat when the dynamic movement of sand dunes had dramatically diminished.  The native plants need the shifting sand, steep banks and clear ground of naturally functioning dunes.

Refuge managers are currently using different techniques to control the weeds that crowd out the buckwheat.  Using controlled cattle grazing to eat the weeds last spring, refuge biologists cleared major areas of exotic plants, allowing a good growth of buckwheat in some areas.  Sand had been recently purchased and trucked into the refuge to re-create the dunes that used to exist prior to the 1906 earthquake in San Francisco.  The sand was used to make bricks for the buildings in San Francisco.  The new sand will smother the non-native vegetation for a few years, giving the native plants a chance to survive.