Endangered Butterflies: The Karner Blue

Karner Blue Butterfly
Karner Blue Butterfly. shene/Moment Open/Getty Images

Due to its very specific habitat requirements, a small, delicate butterfly has been a concern for wildlife managers and conservation biologists for decades now. The Karner blue butterfly (​Lycaeides melissa samuelis) was classified as endangered in 1992 under the United States Endangered Species Act.

Ecology of the Karner Blue

To complete its life cycle, the Karner blue is completely tied to the wild blue lupine, a plant associated with dry, acidic soils. The caterpillars feed exclusively on the leaves of the lupine, while the adults feed on a wider variety of nectar and pollinate many flowering plant species. Two generations emerge every summer, and the eggs of the second generation of adults ride through the winter to hatch the following spring.

Where Are Karner Blues Found?

In the past, Karner blues occupied a continuous narrow band overlapping with the northern edge of the blue lupine range, from southern Maine all the way to eastern Minnesota. Karner blues are now found in appreciable numbers only in some areas of western Michigan and in managed savannas in central and western Wisconsin. Elsewhere, only small disconnected populations remain in southwestern New Hampshire, the Albany area in New York, and isolated locations in Ohio, Indiana, and Minnesota. Many of these small isolated populations were reintroduced using adults from captive breeding programs.

A Disturbance-Dependent Species

Karner blues only do well on sites that have been disrupted by some kind of disturbance, knocking back vegetation and leaving room for the wild blue lupines to grow amidst other early-successional species. They spread abundantly in areas kept open by wildfires or by grazers, for example. Human activities like logging can also produce lupine habitat. We have long changed the disturbance processes on land, especially by preventing wildfires from spreading. As a result, once regularly disturbed habitats have grown back to forest, squeezing out the lupine and its companion butterfly. In addition, the flat, well drained soils once hosting lupine colonies are prime areas to build housing developments, conduct agricultural activities, or mine for fracking sand.

Intensive Restoration Efforts

  • Fort McCoy, an Army installation in central Wisconsin, is the site of successful management efforts to maintain both the butterfly and military readiness. After years of collaborative research between the Army and the U.S. Fish & Wildlife Service, officials are coordinating habitat disturbances from military activities to maintain a balance of Karner blue habitat.
  • Captive breeding programs have been established at several facilities, including the Toledo Zoo and the Detroit Zoo. Eggs are hatched in captivity where the caterpillars are then reared. After they metamorphose, adults are released into the wild where appropriate high-quality habitat has been protected or restored.
  •  Management for Karner blues at Indiana Dunes National Lakeshore has been challenging. After years of providing what appeared to be plenty of high-quality habitat, the butterfly essentially vanished over a handful of weeks in 2012. Thanks to global climate change, that year was unusually hot (hotter years have since been recorded), and many caterpillars hatched before the lupines appeared, so they starved to death. Those who hatched at the right time saw their newly emerged host plants wither and die before they could finish their larval stage. The population declined by 99%.
  • The Albany Pine Bush Preserve, in New York, increased Karner blue habitat from 13 acres in 1991 to over 200 acres today. Following decades of fire suppression, the sandy pine and scrub oak barren was overrun by invasive species. Since then, a regime of disturbances was created to open up the forest canopy and favor lupine growth. Shrub thickets were mowed down with heavy equipment and regular prescribed burns were done.

The recovery goal established by the U.S. Fish & Wildlife Service calls for an eventual network of at least 28 metapopulations (groups of smaller populations) containing each at least 3,000 butterflies. These metapopulations need to be distributed throughout the species’ range. At that point, the Fish & Wildlife Service will consider reclassifying the butterfly’s status to Threatened.