The Pacific Grove Monarch Sanctuary is low on butterflies this year, and some monarch enthusiasts suspect that a late-September trimming of eucalyptus branches is to blame.

"I visited the Monarch Grove Sanctuary in Pacific Grove yesterday and was shocked to see many of the upper branches of the main eucalyptus cluster tree grove had been cut off," wrote El Dorado entomologist Paul Cherubini in a monarch listserv. "I could not hardly believe my eyes because it was obvious to me this amount of prunin will substantially degrade the suitability of the Sanctuary as a cluster site and the butterfly population is likely to be substantially lower and less stable this year and for years to come."

P.G. Public Works Director Celia Perez Martinez says the trimming was done for public health and safety. "Eucalyptus trees are very vulnerable to limb breakage," she says.

In 2004 an 85-year-old woman was killed by a falling branch while visiting the sanctuary. The city settled with her family for $1 million.

In late September, before the official Oct. 1 start of monarch season, city arborist Rick Katen directed a tree service on which branches to cut, Perez Martinez says. The city did not generate a report to document the work. “In the future we’ll do that, but we’ve never done it in the past," she says. 

The low butterfly numbers could be caused by any number of things, she adds, including the fall's heavy rains and huge windstorm. “They could have gone to Santa Cruz for all we know," she says.

Dr. Francis Villablanca of Cal Poly is tasked with reviewing the monarch count data. "At the current time we do not know if the PG Sanctuary population count is low because of something peculiar to this site (e.g.: tree trimming), or if the populations are low range-wide and across all sites," he wrote in an e-mail to Perez Martinez.

Within the next few weeks, Villablanca expects to have the data to reach some conclusions. "I would call for calm minds to prevail until we have some data," he wrote. "The story will make itself evident."