The recently completed 2024 California monarch butterfly count showed just over 9,000 of the winged critters returning to the state, which is a big concern, considering there were more than 200,000 of them in the previous year’s count.

Every year, biologists perform winter statewide counts of California’s monarch butterflies, as the butterflies complete their migrations from the Rocky Mountains or Mexico. And the count has varied wildly in recent years. After less than 2,000 of them were observed in 2020, the monarch butterfly population exploded to nearly 250,000 by 2021, and burst up to more than 300,000 for 2022, before declining somewhat to 230,000 in 2023.

But the bottom has dropped out again for the 2024 count. The just-released results are still considered a 2024 count, as it is conducted between Thanksgiving through the end of December. And the Associated Press reports that the counting agency Xerces Society for Invertebrate Conservation found only about 9,100 monarch butterflies in California during that period, the lowest total since that 2020 lowpoint.

“We know small populations are especially vulnerable to environmental fluctuations, and we think that’s what happened this year,” Xerces Society endangered species biologist Emma Pelton told the AP. “The record high late summer temperatures and drought in the West likely contributed to the significant drop-off we saw in the third and fourth breeding generations.”

Yes, there are different breeding generations in the annual trek from Mexico to California locales like Santa Cruz and Monterey. That means the butterflies returning are actually the grandchildren and great-grandchildren of the butterflies who started the migration, as their life span is only about six weeks.

Despite the population booms and busts, the US Fish and Wildlife Service moved to classify monarch butterflies as a threatened species, which would prohibit people from killing them, transporting them, or making property changes that would render their properties unusable for the butterflies.

Related: Second Consecutive Monarch Butterfly Population Rebound Has Butterfly Fans Just Thrilled [SFist]

Image: Chris Chow via Unsplash