The Butterfly Effect...
In chaos theory, the “butterfly effect” is the sensitive dependence on things as insignificant as the movement of a butterfly’s wing. Meteorologist Edward Lorenz coined the phrase, suggesting that something as insignificant as the movement of a butterfly might create a wind disturbance that could become sufficiently amplified to cause a thunderstorm in a distant place. Lorenz wanted to highlight the immense number of tiny variables affecting long-term weather trends. The term "butterfly effect" refers to the fact that small, imperceptible things can have larger consequences.
I thought of this expression when I read about a Recovery Plan for the Half-moon Hairstreak butterfly. This drab butterfly spends its life in a few dry grassland habitats in Alberta and the south Okanagan. In this mid-winter period, Hairstreak butterfly eggs lie protected under a few inches of snow. The female butterfly would have laid her eggs on not just any plant, but under the blue and yellow lupines which dot dry sage habitat at White Lake, Osoyoos, and Keremeos. The larvae will emerge in the spring and begin life feeding on the emerging leaves of the lupine. The larvae feed until late spring before forming a pupa and emerging about two weeks later in early summer as a small, grey and black butterfly.
The adult butterfly will live for a week or two, visiting nectar-producing yarrow, buckwheat and horsebrush plants that grow amongst the sage. As the lupine plants fade, this signals the end for the adult butterfly and eggs are laid on or under a lupine which will be the host plant needed by next year’s young larvae. So ends the quiet life of a small, insignificant butterfly which few of us will ever see.
But dig a little deeper and the picture is more complex. Seven out of eight Canadian locations for this butterfly are from White Lake south to near Keremeos and Osoyoos. The largest group ever found of this rare butterfly was 250 sighted near the Keremeos columns. Willowbrook resident Dennis St. John has spent years studying local butterflies. Many aspects of the Half-moon Hairstreak’s life puzzle him and the more he learns, the more multifaceted the picture is. Why are there so few of this species when other similar butterflies are dispersed over large areas? How do these scarce butterflies find each other?
Observation of their habitat and behavior suggests that a microhabitat with bare patches of soil and not much leaf litter is needed for reproductive success. After watching males and female behavior, St. John suspects that females may perch near the top of sagebrush on cool summer mornings to use the breeze to send out a plume of chemical pheromones to attract males. This is unlike many other butterflies who rely on visual cues to find a mate.
More of a mystery is the Hairstreak’s relationship with ants. It has been observed that lupines attract ants and related butterfly larvae that feed on lupines often have ants all around them. Rather than eating the butterfly eggs or larvae, the ants appear to protect them. The butterfly larvae produce a sugar substance which the ants collect while also protecting the larvae from other predators (similar to the way ants look after aphids). The presence of ant colonies is thought to be a critical aspect of Half-moon Hairstreak habitat with a mutualistic relationship between the two species.
St. John believes that we are just beginning to learn about how the butterflies of our region live and interact with other plants and animals. The Half-Moon Hairstreak reveals a tiny piece of the puzzle that is part of the web of life and interdependence of small creatures living in any one of hundreds of microhabitats that make up our region.
The Half-Moon Hairstreak is the subject of a Recovery Strategy by the BC Ministry of Environment. A recovery strategy summarizes the best available knowledge about a species or ecosystem to identify approaches for its recovery. In the case of many species including the Hairstreak, many small changes have a “butterfly effect” and can gradually lessen the ability of a local butterfly to survive. Land development cuts up habitat and isolates wildlife populations, introduced weeds and non-native animals change habitats, climate warming affects soil moisture, the flow of streams, and regeneration of wetlands. Each of these incremental changes is a challenge to native flora and fauna and reduces species richness and biodiversity.
The goal for Half-moon Hairstreak recovery is to ensure the persistence of populations of this extremely rare butterfly at all the known locations in Canada. Taking steps to maintain natural grassland environments and connectivity is important not only for this butterfly but for all the interrelated plants and animals that call this habitat home. The hairstreak is only one part of “the butterfly effect”. Change one part of the environment, lose one or two “insignificant” species and face unknown consequences later in time.
Article by Margaret Holm, OSCA
Photograph of Half-moon Hairstreak courtesy of Denis Knopp.