Mottled milestones: big steps for small butterflies
Posted onJune 7, 2022by|, ,
2022 is turning out to be a monumental year for the mottled duskywing reintroduction project at Pinery Provincial Park. As the return of these endangered butterflies to the Pinery was only started last year, there are many milestones that the project has yet to reach. That said, we’ve already had some major happenings this summer.
Here are some of the highlights and what they mean for the future of Pinery’s mottled duskywings.
One incredibly important sighting was made shortly after I arrived at the park in May: a mottled duskywing was found! It was photographed by a park visitor and posted to iNaturalist, and the sighting was quickly brought to our attention. Not only was it exciting to see the first mottled duskywing of the year, but it also meant that the butterflies had survived the winter – or more accurately, their caterpillars had. Most people are familiar with the monarch butterfly, and its massive yearly migration to escape the winter cold. Such journeys are not particularly common among butterflies, however. Many species, mottled duskywings included, stay in Canada year-round, and have different strategies for surviving through the winter. In the case of our duskywings, the caterpillars must eat until they are nearly ready to form a chrysalis. From there, they create a cozy nest of leaves and silk to keep them safe from the cold, and undergo a process known as diapause. This is essentially the insect equivalent to hibernation, and it allows the caterpillars to slow their metabolism enough to survive until spring.
As this was the first time mottled duskywings had spent a winter in this part of Ontario in over a decade, nobody knew for sure if any of them would survive. But sure enough, more and more mottled duskywing butterflies began to appear throughout the park.
This development led to an exciting milestone for some of my teammates and me, as well. Some of us, myself included, are new to the project, and had never had the opportunity to handle mottled duskywing before. Soon after we arrived, all of us were able to catch and mark our first mottled duskywing – or at least, for our more experienced cohorts, their first of the year. It’s always incredibly exciting getting to handle and see wild insects up close, and marking these butterflies helps us to estimate the size of the population at the park.
How do you mark a butterfly?
The butterfly team is trained to capture and mark butterflies using the utmost care and caution. Specially-designed mesh nets are used to gently capture the butterflies, and they are introduced to small jars that they fly into. We chill the captured butterflies for a few minutes, which slows them down enough that we can place a small mark on their wing with quick-drying nail polish. This doesn’t hurt them at all, and only takes around 15 minutes from capture to release. They warm up quickly in the sun, and can then go on their way. Marking duskywings allows us to better estimate the size of the population, as we can be sure that a marked individual has already been counted.
The first mottled duskywing I caught this year. The butterflies are captured, marked, and released. Photo by E. Santoni.
The most recent, and arguably most important development to happen so far this year, is the discovery of an ovipositing female. Ovipositing, the scientific term for laying eggs, is a pretty strong sign that the mottled duskywings are breeding here. This means that, among other things, the habitat restoration work done in earlier years at the Pinery has been successful. It also means that the population will eventually be able to sustain itself without the help of captive-bred butterfly releases.
The tiny egg, highlighted in red, that we saw a mottled duskywing female lay. Mottled duskywing only lay their eggs on a small species of shrub called New Jersey tea. Photo: M. Polley
Currently, the project requires releasing duskywings bred at the Cambridge Butterfly Conservatory, but if we continue to see breeding behavior at the park, this will become unnecessary in future years. The hope is that ultimately, these butterflies will someday no longer need our help. And if our efforts continue in the direction they’re going, this hope may become a reality.