The Karner blue’s 25-millimetre wingspan isn’t the only reason these tiny butterflies are hard to spot. As of 1993, the Karner blue has disappeared from Canada. Intensive ongoing habitat restoration efforts aim to create enough suitable habitat for reintroduction. Scientists are now evaluating this habitat with the hope of eventually returning the species to Ontario.
The Karner blue is a bivoltine species, which means it has two distinct generations each year. The first generation overwinters as eggs, which were laid by the females the previous summer on the leaves of wild lupine plants. In the spring, the larvae hatch and start consuming lupine leaves, accumulating the energy reserves they need to pupate and then transform into butterflies.
Karner blue adults live an average of five days, during which they feed, mate and lay the eggs of the second generation of the year. The whole cycle repeats over the summer, with a second generation of butterflies laying the eggs that will overwinter until the following year.
Karner blue butterflies depend on a single food source for their survival: wild lupine. This wildflower grows in sandy soils, sandy pine barrens, beach dunes and oak savannahs.
Historically, the Karner blue could be found in oak savannahs and tallgrass prairies throughout the southern Great Lakes region of Canada and the United States. The population has slowly declined over the past 150 years to a point where it is now just 10 per cent of its historic size before Europeans colonized North America.
The decline of the Karner blue is largely attributed to the loss of North America’s oak savannah ecosystems, created when humans began suppressing the periodic wildfires this ecosystem depends on. As oak woodlands replace savannahs, lupines can’t get enough light to survive. Other threats include insecticides and overabundant white-tailed deer populations, which feed on wild lupine. Special attention has been given to Karner blue populations in the western-most reaches of the species’ distribution, where infections from the bacteria Wolbachia have been identified.
Recommended Recovery Actions
Recovering Karner blues in Ontario will require reintroducing this butterfly to its historic range. Before that can happen, however, the oak savannah and tallgrass prairie habitat the species depends on must be restored, managed and assessed to make sure it can support a self-sustaining population of Karner blues. A federal Recovery Strategy for Karner blue is expected to be posted in 2016/17.
What We Are Doing
Find out how Wildlife Preservation Canada helps save native pollinators, including Karner blue butterflies, and how you can make a difference.
Federal Species at Risk Profile: Karner Blue Butterfly
Karner Blue Ontario