#ISeeChange: Are there more sphinx moths in the high desert lately?
A moth seen in a Victorville yard for the first time may not signal a shift in range, but scientists say the moth’s presence may reflect drought in the high desert.
A moth that Enrique Vergara saw in his mother’s Victorville back yard for the first time ever may not signal a shift in range for the creatures due to changing climate. But scientists say the moth’s presence may be a consequence of the drought’s impacts on the surrounding high desert, those impacts in part due to climate change.
As part of our ongoing I See Change project, we’ve been asking people to tell us whether they’ve been seeing changes in their environment. Enrique Vergara did, and this is his story.
Vergara started to take pictures in his mother’s backyard, around potted flowers, because he noticed a humming sound. He saw beating wings, a few inches across, and a long nose into the plants.
At first he thought it was a hummingbird. Then he realized it was a moth. A big one.
“I had never ever seen one in my whole life. And when I asked my mother about it, she indicated that a couple of years ago they started to come in the springtime,” he said. “But it wasn't quite the number we've seen lately. This was more like a dozen even more of these hummingbird moths.”
Vergara wondered whether the moths were new to the altitude; Victorville is in the high desert, San Bernardino County, at an elevation of 2900 feet. And he wondered why they started showing up in his mother’s back yard, so many years after she started living there. “Are they supposed to be here?” he asked.
A Common Moth, with Useful Skills
The moths Enrique Vergara saw were actually White-lined Sphinx Moths (hyles lineata). They’re pretty common, and unlike some moths, they get around when it comes to what they eat.
“They eat so many plants. So even if one of their host plants was doing poorly, they could easily switch to another plant,” says Lila Higgins, who directs citizen science projects at the Natural History Museum.
Higgins looked up data on iNaturalist, and found it’s common enough to see these moths at elevation in the western United States. In fact, sphinx moths have an expansive range, from Mexico, to the Southwestern and Western United States, even to Canada.
They’re also natural pollinators on the night shift. Sphinx moths are very active after dark, hovering and unfurling a proboscis into the nectaries of plants.
“If we have this major pollinator leave this area and looking for other places to inhabit, who's going to take over the role that it's playing in the environment?” asks Heidy Contreras, a biology professor at the University of Laverne.
Contreras says sphinx moths are important to pollinating a lot of different plants, including rare California native plants, like the lemon lily.
Even if it’s not surprising they’re in Victorville, is a changing climate affecting these moths?
In a Changing Climate, Humidity May Matter
In California, climatologists have predicted longer, more intense, more humid heat waves as a result of warming. Heidy Contreras and other scientists interested in moths don’t know exactly how sphinx moths will respond to that – but they’re trying to figure out.
“That change in humidity is a really strong cue for the moths to be able to use to determine that in fact it's the season where if they emerge they'll be able to find the food that they need in order to fly and find mates.
But, confoundingly, California moths live a little differently.
“There's not really this big drastic change, humidity is not a strong enough cue to be able to determine whether in fact flowers will be present for these moths to come out and feed off of.”
Contreras says understanding what cue is most significant to moths is a huge part of her ongoing work. She’s working on more studies to nail down more answers about these and other moths.
The Hypothesis: Drought
As for why Enrique Vergara and his mother are seeing a lot of moths lately, Contreras and Higgins can only offer a guess. But they offer the same one: and it’s the drought.
“What I'm thinking is there's probably not enough flowers for all of the moths that are coming out,” Contreras says, laughing. “So yes, Enrique probably has some really delicious flowers that he's watering and keeping really nice.”
In other words, what Enrique saw is a climate-change related observation, in a way. Scientists say above average temperatures and changing atmospheric conditions are worsening California's drought, and high desert flowers around Enrique's mom's house are probably affected by those changes.
#ISeeChange is a national effort to track how climate change is affecting our daily lives.
Notice any bugs in your backyard lately? Wondering why you're seeing coyotes where you don't expect? Seen changes in your favorite tide pool? Snap a picture and tag it @KPCC and #ISeeChange on Twitter or Instagram, let us know through our Public Insight Network, or post your questions on www.iSeeChange.org. Then see what others have found and observed in their environment.