iSeeChange: Unusually warm temps bring bugs out in winter
Like everyone else in Delaware and the Northeastern U.S., you probably felt that we had a lot of unusually warm days last month. And along with that, you might have also noticed that humans weren’t the only species enjoying the temperate weather -- insects and other bugs that we expect to go to bed by December were out and about, as if it was summer and not the start of winter.
In our latest story for iSeeChange, our project to investigate what you’re seeing in your backyards, Delaware Public Media science reporter Eli Chen went to find out what’s behind these December critter sightings and what they mean.
Around noon on the first Saturday of December, Clayton resident LaTonya Gilliam was leaving her house to make a food run.
"And I'm walking out the door and getting to the walkway, and something jumped out at me. And I was really shocked. I didn't expect to see a grasshopper out in December," said Gilliam.
So she brought out her two sons, who love scavenging for bugs. Her youngest, who’s five, captured the grasshopper.
"I hadn't seen a grasshopper that big all summer," said Gilliam.
And it didn’t stop there. She also saw...
"...a lot of disoriented flies. They’re not afraid. They’re not trying to get away or anything," said Gilliam. "They’re just flying around...very slowly."
And after a rainstorm on Christmas Day, she and her sons collected worms from the driveway and placed them in the compost bin. This would be a normal activity in August and September -- but this was the first time she’s done it in December.
"Is it indicative that we've gotten to the tipping point with climate change or global warming, whatever people want to call it these days because this isn't the norm I grew up with," asked Gilliam. "Are we at the point where we can't fix what we've done?"
"I would not describe it that way," said Doug Tallamy, an entomology professor at University of Delaware. "It’s not going to be a single threshold where the next day everything’s different. It’s going to be long term patterns that emerge over time and sometimes these patterns emerge so slowly we don’t even recognize them.”
"That large grasshopper that she saw, it’s a common species that’s typically abundant in September," Tallamy added. "And they hang around until they’re killed by frost. It obviously wasn’t killed, even in December.”
This past December was the warmest and wettest December on record for the U.S., partly due to El Nino weather patterns. In Delaware, there were several days last month that were twenty to thirty degrees above normal, including Christmas Eve, when the high temperature in Georgetown hit a record 72 degrees.
Insects and other bugs respond to a lot of different cues in their environment. And when fall becomes winter, Tallamy says that they usually respond to a combination of temperature and “photoperiod,” or daylength, changes.
Some bugs, like LaTonya’s grasshopper, will typically die off or go dormant when it gets below freezing for a sustained amount of time -- and some will disappear as soon as the days get shorter.
“So there’s a whole bunch you’re not seeing because they respond to photoperiod,” said Tallamy.
USDA entomologist Don Weber says the bugs that go to bed as soon as the days grow dimmer might deal better with weird seasons than those that get chased out by the cold.
“If they’re responding to photoperiod when they’re going to go dormant, they’re going to be better adapted to these kind of late fall/early fall winter times," said Weber. "If they’re primarily responsive to temperatures, that might hurt them quite a bit.”
And Tallamy says there are a number of butterflies, like the white cloak and the cabbage butterfly, that live through the winter as adults. But in the wintertime, they usually hang out in a log or somewhere tucked away. That’s so they can conserve their energy until springtime, when there are things to forage again.
The unseasonably warm weather, however, could cause them to venture out, which Tallamy says isn’t good if it happens for several days in a row in the winter.
“If they’re out flying around -- they will use up their fat reserve that they need to make it through the winter," Tallamy said. "Without flowering plants to recharge, that can hurt them.”
On iSeeChange dot org, citizens reported seeing flowers in bloom and trees growing buds in December. And while the USDA’s Don Weber says that this surge in plant activity might encourage other bugs to also be active. Doug Tallamy says the flowers that have sprouted in December are too sporadic to help pollinating insects regain their fat reserves.
"If the weather conditions are such that if pollinators are active, they will overwhelm those few flowers that have popped. There’s always a few azaleas that have bloomed, and people take notice of them because it’s not supposed to happen. But I don’t think it’s nearly enough to make a big difference,” said Tallamy.
Even though there were many warm days this past December, it’s hard to say how abnormal the weather was in the insect world.
“Yeah, it’s pushing it. Record breaking temperature … that’s just within our recorded history. That’s not that long compared to what insects are adapted to,” said Tallamy.
And the lack of a long-term record on bug activity makes it hard to know what is and isn’t strange.
“It’s hard to judge if is this weird -- how weird is it in the context of long term temperature data, we have that. but in terms of when insects are sighted and where, and where plants are blooming and not, we don’t have a good database,” Weber said.
The entomologists are both confident that insects and other bugs will be able to adapt to any random temperature swings that happen in the near future -- because the bugs have done so for thousands and thousands of years. What’s less certain is how they’ll deal with long-term climate shifts and potentially permanent changes to the seasons.