A petri dish pops open and a dime-sized fuzzy brown butterfly steps out onto a wildflower petal.
That small scene, which played out three times last Thursday in the Tall Grass Prairie Preserve near Vita, represents years of work by a team at Winnipeg’s Assiniboine Park Zoo that has pioneered a way to save the critically endangered Poweshiek skipperling.
Laura Burns and C-Jae Breiter, research and conservation specialists with the zoo, have made daily trips to the preserve over the past two weeks to release live skipperlings back into the wild.
Some are reared at the zoo, monitored daily during their year-long development from egg to caterpillar to chrysalis to winged adult.
Others, like the three males released last Thursday, are captured in the wild as adults, bred at the zoo, then returned to the preserve, which is home to the species’ entire Canadian population.
Burns and Breiter are members of the Canadian Poweshiek Recovery Team, a partnership of Canadian and American zoos, universities, conservation organizations, and government agencies that has spent the past four years trying to walk back the Poweshiek skipperling from the brink of extinction.
Once found throughout southern Manitoba and the midwestern United States in great number, there are now between 200 and 500 skipperlings left in Canada.
"I think the 500 estimate is probably generous," Burns said.
Michigan is also home to a small population.
Burns recalled reading population surveys recorded a century ago.
"They would see so many Poweshiek skipperlings that they wouldn’t even count them, because there were hundreds of them every day."
In the conservation world, when a population crashes, direct interventions like captive rearing are a last resort.
"But when you’re down to the last few individuals left in the country, sometimes these interventions are necessary," Burns said.
An international panel of experts recommended humans intervene to revive the skipperling population, whose sharp decline in Canada was detected 10 years ago.
Butterflies are to the prairies what the proverbial canary is to the coal mine: an "indicator species" that reflects the health of the environment.
At the zoo, much of Burns’ work takes place in an aerated greenhouse off limits to the public.
"The program started small because it had never really been done before—never had reared Poweshiek in human care," Burns said.
Caterpillar growth is logged weekly.
"That can be really challenging when you’re looking for a five- to 10-millimetre-long green caterpillar on the green grass," Burns said with a laugh.
Disease risk is mitigated by sanitizing equipment in between each butterfly exam.
The program started with two Poweshieks in 2017. The following year, six adults were returned to the wild. That number grew to 13 in 2019 and 19 in 2020. This year, Burns anticipated 40 live releases.
"Every year our program’s grown, just bit by bit. It’s about doubled in release size every summer."
Last Thursday, she and Breiter carried a Styrofoam cooler out to a clearing at the preserve, where they checked on skipperling chrysalises housed in breathable, grassy chambers that allow them to safely acclimate to the wild. When they are grown, they too will be released.
Next, three adult males perched on cotton balls inside plastic tubes were transferred into petri dishes and placed into a cooler.
"They’re very small and they have delicate wings, so we have to chill them in a cooler briefly so that they don’t move while we’re marking their wings," Burns explained.
Using permanent marker, they carefully made a dot on each male’s wing. Burns said the mark doesn’t harm the butterflies and ensures genetic diversity by ensuring staff don’t recapture the same adults.
While they worked, two summer students wandered around the preserve, conducting counts at other release sites. Burns said the early counts are "really promising." During one recent trip, they saw a female raised in captivity mate with a wild male.
"That was very satisfying and gratifying. It felt like the last four years of work really paid off."
The lifespan of an adult skipperling is about two weeks. The hope is that they will find a mate and lay eggs in the wild before then. One to three percent of those eggs survive to adulthood. Captive rearing at the zoo increases that winter survival rate.
Back at the preserve, Burns and Breiter gently released each adult onto a wildflower, a source of nectar for the skipperlings, so named for how they flit or skip across the landscape.
Unlike Monarchs, which migrate incredible distances, Poweshieks stay put.
"They stay in the same quarter-section that they were born in, their whole lives," Burns said.
The wildflowers—in this case, brown-eyed Susans—must be checked for spiders and other "assassin bugs" that could snuff out a year of hard work in a heartbeat.
Their work complete for the day, Burns and Breiter loaded up their SUV and headed off to monitor other release sites.
Experts debate the magic number the Poweshiek must reach to self-sustain, and the factors behind its decline.
Burns said there are a few "smoking guns," chiefly the gradual loss of undisturbed tall-grass prairie habitat.
"We think that the most recent crash possible could have been induced by climate change, because insects are very dependent on temperature for their development, so if it’s too hot or too cold, it can really throw off their whole life cycle."
U.S. researchers are also trying to determine whether pesticide use is a factor.
Burns said she is thankful for a protected preserve in which to release the butterflies that she and the team have worked hard to rear. The Nature Conservancy of Canada owns and manages the preserve.
"Without them, we wouldn’t have anywhere to put the butterflies," Burns said.
The zoo plans to continue its breeding program the until the Poweshiek population stabilizes or the species goes extinct. Lineages are being tracked to see what’s contributing to survival.
In a lab at the zoo, one of Burns’s colleagues is sequencing the Poweshiek genome to look for any "genetic bottlenecks" like inbreeding or disease risk.
Despite the pressure of trying to stave off a tiny creature’s extinction, Burns said she wouldn’t trade her job for anything.
"It’s been incredibly rewarding. It’s also very hard work. It feels very pressing at times because every decision feels very important. We have so few left."
"But there’s not many jobs in wildlife biology where you get to release an endangered species back into the wild. That feels really gratifying every time I get to do it."