When wildlife biologist Maria Leung was pregnant with her first child, she decided to spend the early years of motherhood studying creatures that were more readily accessible than her usual subjects. With her baby tucked in a backpack, Leung returned to forests, fields and marshes to follow the fortunes of butterflies.
Eighteen years and two children later, she has become a local go-to person for those of us who have come to marvel at and wonder about Yukon’s butterflies. The world she has opened up for her children, and the rest of her fellow Yukoners, sometimes sounds as if it’s composed of science fiction scenarios plucked from distant exoplanets.
Currently, Leung is continuing a project she started at Tarfu Lake off the Atlin Road four years ago. Every 10 days, from the second half of May until mid-July, she heads to Tarfu and counts butterflies along set transects.
Over the past four years, she has watched numbers fluctuate, depending on species. She correlates those numbers with other factors, such as climate and habitat health.
“The butterflies were out much earlier this year,” she says. If this trend continues how much impact will it have on species’ health? Could butterflies appear before the plants they feed on?
Most of us have heard that butterflies overwinter in the Yukon. They infuse their tissues with a sort of anti-freeze, then go to sleep… and, depending on species, they may doze the winter away under the snow as fully-grown winged insects, or in the other three stages of butterfly life – as an egg, chrysalis or caterpillar.
“But what happens now that we have those bizarre thaw events in winter?” Leung asks. The insulating snow cover melts in a thaw and then the cold returns with a vengeance. Leung has been planting “temperature buttons” (about the size of watch batteries) on small posts on the ground to record the temperatures, the highs and lows, the sleeping butterflies have been coping with … or not.
And there are other issues, says Leung. “Like two years ago we had this crazy, crazy late spring … at the beginning of April there was actually less snow than at the end of April.”
Habitat change is a big concern. While butterflies can usually feed on a variety of plants, their caterpillars are very specific. “For example,” she says, “Milbert’s Tortoiseshell: the caterpillars can only grow if they have access to stinging nettle. Nothing else. If you destroy habitat and that plant disappears there’s no way for that particular butterfly to continue.”
Leung pauses a moment, as if on retreat from that gloomy scenario, then her eyes light back up. “It still astounds me that a stinging nettle plant can transform into a butterfly. That’s amazing!” Not just the creature, but the whole complex transformation process is beautiful.
“In the Yukon we have a really rich diversity when you get above tree line and in the tundra,” she says. But ecosystem changes that can follow climate change are a major issue in the North. For instance, “they’re saying the tundra is going to get more willow,” says Leung. “I wonder if that will displace some species. A lot of alpine species need sedges and grasses.”
There are some species that will do well in that willow habitat, like the ubiquitous Mourning Cloak, but for true tundra species, what will happen with climate change?
Species rarely face one challenge to their wellbeing at a time. Temperatures can shift and food plants disappear even as landscapes are modified and developed. New predators can follow the warming trend north and stalk the butterfly tundra.
And there are some other, seemingly more-gruesome, threats. “Last year I took about 40 Mourning Cloaks into captivity, raised them as caterpillars,” says Leung. Two of them did not become Mourning Cloak adults. “One of them pupated like the rest of them, but it just hung there for five days and instead of breaking open the way that a butterfly comes out, a little cap came off of it and out came a big black parasitic wasp.”
Recently Leung’s daughter collected a caterpillar “and when it opened a bunch of maggots came out.”
Fortunately for butterflies, many taste terrible. The bright colours we enjoy are not dinner invitations for birds and other creatures but warnings. And butterflies have evolved phenomenal camouflage. Some non-toxic species even share colour patterns with toxic species.
Many butterflies display the markings of bark or fallen leaves against which they appear to vanish. Some display wing spots that look like the wide-open eyes of larger creatures – making would-be predators think twice when considering supper.
In its early caterpillar stage a swallowtail larva looks just like a smear of bird poop on a leaf … not too dignified, perhaps, but what the heck? The ruse looks effective and is certainly better than becoming someone’s lunch.
Perhaps the most impressive self-defence mechanism of any butterfly is displayed by Milbert’s Tortoiseshell caterpillars. “They are very gregarious,” says Leung. They clump together. If they hear a threatening noise they all twitch synchronously – as if they were one, larger creature.
Despite their parasites and predators and the sorrows of habitat loss, a life spent among butterflies presents many pleasurable experiences and memories, says Leung. The research favours basic watchfulness and ever-more-complex, invasive technology. “There’s nothing that can replace the experience of interacting with your study species,” she says.
Asked about amateur butterfly collectors, Leung says there have been issues because some Yukon species are very uncommon elsewhere and can fetch as much as $100 overseas. But she doesn’t believe citizen-scientist Yukoners participate in that trade. And non-residents require permits to collect in the territory. Some areas, such as Tombstone Park, are off-limits to all collectors.
Fortunately, butterflies are very photogenic. (Leung’s own photos prove that.) “There is a shift in the way people document things because of digital cameras,” she says.
Enthusiasts can upload their photographs to sites like e-butterfly.org, where experts will help with identification.
Cameras allow folks to get intimate without becoming destructive. That seems only fair, especially considering that butterflies, armed with flexible “straw” rather than stingers or jaws, can’t bite.
“Yes, people ask me sometimes, ‘Do they bite?’” says Leung.
This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at http://www.yukoncollege.yk.ca/research/publications/your-yukon