Bison, Lupine & Karner Blue

Karner Blue

Karner Blue
Photo: FWS

Bison once roamed North America in large numbers. Bison, because of their large size and density, had profound effects on the prairie ecosytem. Bison grazed and trampled young trees, creating disturbed areas that favored grasslands. Bison left wallows, areas where Bison would roll in the mud, compact the soil and deposit hair, body secretions and buffalo chips. At one time, large herds of Bison were abundant, but they were hunted to low numbers in the 1800s. Development and agricultural improvements have maintained Bison populations in low numbers.

The Sandhill Wildlife Area in central Wisconsin contains a small herd of American Bison in order to maintain the oak savanna ecosystem. It also contains protected populations of the endangered Karner Blue Butterfly. Its larval host is wild blue lupine. The butterfly is found in a few open areas such as oak savannas or barrens. Both the lupine and the Karner Blue are species of “disturbed” areas. Much of the habitat has been developed and has shrunk to a handful of areas in Great Lakes and northeastern US.

A team of scientists* studied the Sandhill Wildlife Area and butterfly species found in different habitats. They were especially interested in the habitat preferences of the Karner Blue. Female Karner Blues were most abundant in areas that contained bison wallows. This suggests that the disturbances caused by the bison are important to the Karner Blue and that loss of Bison has led to loss of disturbed areas and reduction of habitat. As a management strategy, it may be possible to enhance Karner Blue populations by creating artificial wallows.

*Anna N. Hess, Robert J. Hess, Joy L. M. Hess, Beverly Paulan, Julie A. M. Hess. 2014. American bison influences on lepidopteran and wild blue lupine distribution in an oak savanna landscape. Journal of Insect Conservation. 18:327-338.

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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