Monarch Mystery Confounds Biologists

Is Drought to Blame for Dwindling Numbers?

<b>BYE-BYE, BUTTERFLY:</b> Is this year’s dry weather to blame for the low number of monarchs in the Ellwood groves?
Paul Wellman

The low number of monarch butterflies to land in Goleta’s Ellwood groves this year isn’t really the story, said biologist Dan Meade. “The story is that it was an unusual weather year.” According to Meade and other officials who study the insect, the drought could be a key contributor to the small figures. With the butterfly season now behind us, data provided by Meade, who is working with the City of Goleta on its plan to keep the butterfly habitat healthy, show that the highest number to flock to Ellwood this season was just over 10,000, and only 3,800 in the popular main grove. Although similarly low counts were recorded for the main grove as recently as 2007 and 2009, the numbers were as high as 50,000 and 20,000 in 2011 and 2012, respectively.

Although he cautioned that the counts can vary year to year, Meade said that the lack of rain means a lack of milkweed, which butterflies lay their eggs on and on which caterpillars rely for food. The mild weather is also a likely culprit for the minimal Ellwood Main numbers, Meade said, because without storms to encourage the butterflies to seek the best shelter ​— ​the “dense groves and tall canopies” of the eucalyptus trees ​— ​they aren’t forced to hibernate there. At the Goleta City Council meeting on Tuesday night, city staff spoke about the city’s docent program, one of only four in California, and noted that Ellwood Main, one of the largest aggregation sites in the state, is usually the monarch’s preferred grove, but that this year the butterflies branched out.

Erica Fleishman, a research affiliate for UCSB, said that with monarchs losing their habitat around the world ​— ​a report from the World Wildlife Foundation recently found that Mexico-hibernating monarchs have reached their lowest point in more than 20 years ​— ​“their ability to take a weather-related hit is decreasing over time.” (The butterflies that travel to Mexico come from east of the Rockies, Meade said, while California’s fly from west of the Rockies.) Meade added that much of the concern over monarchs is also at the state level, as counts for bees have also been decreasing, and butterfly counts have seen “a dramatic reduction” since the 1980s and 1990s. In the meantime, preserving the migration sites is crucial, Meade said. “These are all concerns in making sure the phenomena continues,” he said.


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