Butterfly populations soar after monsoon rains

TUCSON, Ariz. (KOLD News 13) - Pinal County just saw their first case of West Nile case in a person this week. So far, there are no reports of the virus in Pima County, human or otherwise. However, an increase in mosquitoes around town due to monsoon moisture is concerning.

“We are seeing a lot more mosquitoes now,” said Gregg Bustamante, an environmental health technician at the Pima County Health Department. “I have them at my house too, so don’t feel bad at all.”

But it’s not just mosquitoes and their bites booming around town, butterflies are too. Katy Prudic, an assistant professor at the University of Arizona, studies the tiny beauties that have sadly been on the decline every year.

“Over the past 40 years you’re looking at about a one to two percent decline across all butterfly species especially in the Western United States,” said Prudic. “Having these longer, hotter falls is a real problem for butterflies.”

More monsoon rains have increased the green landscape across Southern Arizona. This means more food for caterpillars. They can grow quicker and stronger, helping the slumping butterfly populations.

“This has been absolutely an exception week really,” said Stephen Spike, with Tohono Chul.

It’s a growth spurt Tohono Chul is seeing after an abysmal butterfly year.

“In 2017, our populations started to decline all the way to 2020, when we would only find 50 butterflies on a walk,” said Spike.

Tohono Chul counts their butterflies. This week, they broke their record, spotting more than 400 in a two-hour time frame. Populations have substantially grown since last year, but Prudic said their levels are where they normally should be. The steady decline just makes the boom more dramatic.

“From last year it looks like it’s about an 80 percent increase. It’s a lot more, but last year was miserable,” said Prudic.

The question is how long these booms will stay, or if populations will bust after another dry year.

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