Monarch butterflies return in surprising numbers
By: Mary Flaherty, The San Francisco Chronicle
Tuesday, November 22, 2011
Monarch butterfly naturalist Adrienne De Ponte had a surprise waiting for her this fall when she arrived in the San Leandro grove where she’s been leading tours for 11 years.
After witnessing fewer and fewer butterflies appearing each autumn to overwinter in the grove, this year she found 5,000 of the orange-and-black butterflies clustered in the eucalyptus trees – up from 3,000 at their peak last year.
“It was the largest population of monarchs I’ve ever seen so early in the season,” said De Ponte. By Nov. 14 the number had grown to at least 8,000, she said. “This is such an exciting year.”
Same story at Point Pinole, where no clusters had been seen for about five years, said Park Supervisor John Hitchens.
“We had almost kind of given up,” Hitchens said. Around Nov. 1, a cluster appeared and is now several hundred strong, he estimated.
It’s happening all over California.
“We are getting reports of higher monarch numbers from almost everyone,” said Scott Black, executive director of the Xerces Society, which monitors 80 to 90 monarch winter sites in California. But this is coming after a 90 percent drop in the Western monarch population between 1997 and 2010, he said.
Although the annual Western monarch count doesn’t take place until Thanksgiving weekend, the preliminary numbers are causing, well, quite a flutter. In many locations, counters are reporting two to four times more monarchs than last year. At Albany Hill, where no one has seen more than 100 in five years, there were 1,400 Nov. 12 – and numbers everywhere aren’t due to peak until early December.
Monarch butterflies are one of only two insects in the world that make a true, annual migration. The population east of the Rockies migrates by the millions to Mexico. (The Eastern population, which has also decreased, is not seeing an increase so far this year.)
The smaller Western population funnels from west of the Rockies and as far north as Canada to the California coast. The monarchs cluster in trees that provide shelter from winter storms. On sunny days they flit from their roosts with a shower of orange wings.
The monarchs start arriving in October. Those that survive winter weather scatter around late January to repopulate inland regions. Three to four generations of egg laying, caterpillar hatching and metamorphosis occur during the year, with each generation spreading farther from the coast before returning the next winter.
Fluctuations in insect populations are normal, but the enormous decrease in monarchs indicated problems somewhere in the life cycle. Theories include loss of milkweed – the only plant on which monarchs lay their eggs – development, agriculture and drought. Other reasons could be loss and deterioration of winter sites, and use of pesticides, both on farms and in gardens.
It’s hard to know what changed this year, say experts. One hypothesis, Black and others say, is more rain last year. More rain means more and healthier milkweed, and therefore, more habitat.
Temperature, combined with the rain, may also be a factor, says Laurie Davies Adams, executive director of the Pollinator Partnership, in San Francisco. This summer’s lower temperatures were closer to those of decades past, when monarch populations were higher, she said.
“But all these things are as speculative as the stock market,” she added.
Another factor could be an increase in milkweed planting. The Xerces Society facilitated planting 11,000 acres of pollinator plants – including milkweed – in California over the past decade, Black said. “I don’t think there’s evidence that we can take credit” for the monarch increase, Black said. “But we hope that’s been part of it.”
Also, home gardeners seem more interested in cultivating what was once seen as an eyesore, said Bobby Gendron, who has operated Butterfly Encounters, an online seed business, for 15 years.
“Last year was our best year as far as milkweed seed sales – and this year we’re on track to do about the same in sales,” Gendron said.
Black agrees that gardeners seem more open to milkweed, and adds, “The neat thing about protecting monarchs is anybody can do it. You can provide flowering plants, as well as pollinators, and avoid pesticides. You can do something to help.”
Experts recommend planting native varieties of milkweed. For more on that issue see www.xerces.org. To find milkweed vendors, see www.plantnative.org/nd_ca.htm. An app for finding pollinator plants in your area, BeeSmart, is available at www.pollinator.org.
Where to see the butterflies
If you go, be sure to bring along binoculars. Monarchs cluster 20 feet or more off the ground.
Monarch Bay Golf Club, San Leandro: Naturalist-led walks at 1 p.m. Sat. ($12 adults; $5 children) and Dec. 18 ($12 adults only). 13800 Monarch Bay Drive. Register at www.sanleandrorec.org. (510) 577-3462 ; for group tours, e-mail firstname.lastname@example.org.
Ardenwood Historic Farm, Fremont: Naturalist-led walks starting at 1:30 p.m. weekends beginning Dec. 10. Entry fee: $2 adults; $1 children. 34600 Ardenwood Blvd., Fremont. (510) 544-2797 . www.ebparks.org/parks/ardenwood.
Point Pinole, Richmond: No tours, but the butterfly location is marked. 5551 Giant Highway, Richmond. For directions see www.ebparks.org/parks/ptpinole. (510) 237-6896 .
Natural Bridges State Beach, Santa Cruz. Public walks weekends. $10 vehicle fee. 2531 West Cliff Drive. (831) 423-4609 . www.thatsmypark.org/cp-parks-beaches/natural-bridges-state-park.
For more sites, see www.xerces.org/where-to-see-monarchs-in-california.
E-mail Mary Flaherty at email@example.com.
This article appeared on page E – 1 of the San Francisco Chronicle