New data suggests the number of monarch butterflies in California has grown this year. That's good news since the population of this near-threatened species has been thin in recent years.
“We are really pleased to see that the number of butterflies we’re overwintering are a little higher than they were last year,” said Sarina Jepsen of the Xerces Society for Invertebrate Conservation.
The Western Monarch Count Resource Center collects monarch butterfly data. Since 1997, volunteers have flocked to assist the center in an annual Western Monarch Thanksgiving Count of monarch butterflies along the California coast. To estimate the size of the species population, these citizen scientists visit 200 coastal sites over the course of three weeks where butterflies spend their winters.
Jepsen said the monarch population in Marin County in Northern California had an especially big turnaround relative to last year's numbers. In 2014, there was only one butterfly counted at each site in Marin. This year, volunteers counted an average of 4,000 per site in the county.
"We’re not ready to say that’s true across the whole overwintering range," said Jepson. "We’re really waiting for the rest of the information to come in and look at the data more holistically.” The center will release that official count in January.
Jepsen said some researchers have found the monarch will reach its peak at the end of the year. The Western Monarch Count Resource Center is looking for more volunteers to help with a New Year's count.