Western monarch butterflies spend winter gathered in California’s coastal groves. (Photo by Steve Corey via Wikimedia Commons under CC BY-SA 2.0)
Millions of monarch butterflies once covered the trees of California’s coastal groves each winter, but now their numbers are dwindling.
The most recent annual Western Monarch Count found that the iconic butterfly population was down 99 percent from populations 40 years ago. Now, researchers and advocates have asked the public to help fill in a missing piece of the monarch migration story by sending them photographs of the butterflies taken before Earth Day on April 22.
“We couldn’t be looking for monarchs right now without the involvement of the community. There just aren’t enough of us,” Washington State University biologist Cheryl Schultz, a lead researcher of the community science initiative, tells Amanda Heidt at the Monterey Herald. “Reaching out to the community means we might be able to learn something where there is virtually no other way to learn it.”
Monarch butterflies are usually thought of as two populations, eastern and western varieties separated by the Rocky Mountains. The populations are very similar in appearance—striking orange with black lines and white spots—but western monarchs are generally smaller and darker in color. The two also follow different migration patterns. Eastern monarchs spend winter in Mexico, while western monarchs congregate on central California coasts to wait out the cold.
In early spring, the monarchs leave their roosts and begin to travel eastward. By the time the butterflies reach the Central Valley, the butterflies breed. A butterfly can lay hundreds of eggs in a few weeks, and the new generation continues the migration. The cycle of generations and migration repeats every few weeks through the summer until the butterflies are dispersed as far as Idaho. And when the weather turns cold and the days get shorter, the insects return to California’s coast.
The overwintering population dropped from about 200,000 in 2017 to less than 29,000 individual butterflies in 2018. By the end of 2019, the count was 29,418—not worse, but not better. The missing information, Schultz says, is the time period when the butterflies leave their winter groves and begin to breed in February, March and April.
“We just don’t know what they’re doing in that middle period and how we can better support the population,” Schultz says to the Monterey Herald. Speaking to Sarah Wright at the Half Moon Bay Review, Schultz added, “Maybe it’s early flowering native milkweeds, or maybe they’re roosting up in the woods, or maybe they need more fuel along the way… Any of those things might help monarchs get from the coastal overwintering sites to breeding sites broadly in the Central Valley.”
To fill that gap, the researchers set up the Western Monarch Mystery Challenge, a ten week program asking the public to submit photographs of monarch butterflies outside of their winter range. It’s okay if the photograph is distant or blurry, they say, as long as submissions by email or iNaturalist mobile app include the date, species, and location. Submissions will be included in the Western Monarch Milkweed Mapper and earn participants an entry in a weekly raffle until the project ends on April 22, according to a statement.
Schultz is optimistic that once experts have a fuller understanding of what the butterflies are up to in early spring, they will be able to identify ways to help. Then, recovery of the historic monarch numbers could be possible.
“Butterfly populations are bouncy,” Schultz tells Karen Weintraub at the New York Times. “While we think the situation right now is very concerning, we do think there’s a lot of potential to turn it around.”
Several states, including California, have ordered residents to stay home except for essential trips to slow the spread of the COVID-19 pandemic. Luckily, people usually don’t have to travel go far to spot a monarch butterfly.
“Most importantly, stay home and stay healthy,” The Western Monarch Mystery Challenge writes on Facebook. “If you happen to sit in the backyard or walk your dog and see a monarch, take a picture and send it to us!”
About Theresa Machemer
Theresa Machemer is a freelance writer based in Washington DC. Her work has also appeared in National Geographic and SciShow. Website: tkmach.com
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