A drop in monarch butterfly population in the south could mean less to watch in Point Pelee

A new report says monarch butterfly populations in Mexico have decreased, but according to one expert, the number of butterflies Canada will see this year depends on what happens this month as they embark on their migrations north.

The presence of the monarch butterfly in the Mexican hibernation forests declined by 26 per cent due to a reduction of its habitat, according to the recent report by WWF-Telmex Telcel Foundation.

According to the report, the species occupied 2.1 hectares in December 2020 compared to the 2.83 hectares in December 2019.

These numbers are unsurprising to Chip Taylor, the director of Monarch Watch at the University of Kansas.

"They were about as I expected," he said. "But that tells us that we are dealing with a population that fluctuates with the weather conditions, but it's also dependent on the amount of habitat available. Had there been a lot more habitat available last year in the form of nectar plants, then it's likely we would have seen a higher population," he said.

Taylor said that monarchs need nectar plants and milkweed, which he said Canada provides a lot of.

"As we get into Canada ... we get a lot more common milkweed. And one of the things that happens in Canada is that the monarchs who have reached Canada in May and June develop a population of common milkweed and that population tends to move along the lakes and eventually move through Point Pelee in fairly large numbers," he explains.

Every fall, Point Pelee plays host to thousands of monarch butterflies on their migrations. The insects make their way across Lake Erie to the mountains of Mexico, roughly 3,000 kilometres south, for the winter.

In late spring, their offspring return to Canada, and the cycle continues. According to Parks Canada, monarchs have a life span of about a month but the ones who emerge late in the summer are born to migrate and stay alive for over six months to make the journey.

Taylor said it's hard to predict what the population of the monarch butterfly will be like this spring until he sees how conditions are like in Texas.

"The Canadian situation is highly dependent on what happens in March in Texas. So if the returning butterflies are abundant and they have good conditions in Texas, there are good conditions as they move north in May and June and they encounter good conditions in Canada, the population does well," he said.

If they get off to a bad start in Texas. It's going to be a bad year in Canada.- Chip Taylor, director of Monarch Watch

Taylor said the butterflies have already left the overwintering sites in Mexico and should reach Texas in about two weeks.

"The question is, what are they going to find when they get there?" He asks, pointing to the massive winter freeze that took place just weeks ago.

"The question I'm asking all my colleagues in Texas is that vegetation going to come back in time, so they're going to be milkweeds above ground and nectar plants for the butterflies to feed on," he said.

Taylor said he's watching the weather and monitoring plant development carefully and can better predict how things will look in two weeks.

"What we've learned in the past is that what happens in March in Texas has a big influence that that determines everything that happens, including what happens in Canada, on the rest of the year," he said.

"So it's very important for the population to get off to a good start. If they don't, if the population doesn't get off to a good start, then it's very likely that it's never going to be able to recover. There just aren't enough generations," he said.

What you can do

Taylor says people can help preserve the monarch butterfly by creating a lot of habitat for the species.

Point Pelee National Park also encourages local residents to plant a butterfly garden with native plants, milkweed for monarch butterflies and caterpillars.

"Create a habitat and they will come, they will use it," Taylor said.