Quantcast
Environmental News for a Healthier Planet and Life

Study: Monarch Caterpillars Get Angry When They’re Hungry

Animals
Study: Monarch Caterpillars Get Angry When They’re Hungry
A monarch butterfly caterpillar munches on a milkweed plant. AttaBoyLuther / Getty Images

Humans aren't the only animals that get "hangry" when deprived of a meal.


A new study published in iScience Thursday found that monarch butterfly caterpillars (Danaus plexippus) will aggressively push each other out of the way when food gets scarce.

"The less food that is present, the higher their level of aggression," study coauthor Elizabeth Brown of Florida Atlantic University told New Scientist.

The idea for the study was born when the wife of fellow Florida Atlantic University researcher Alex Keene saw two monarch caterpillars fighting over a milkweed plant in the couple's garden, The New York Times reported.

"I decided to investigate monarch caterpillars because I was intrigued by their combative behavior, which I observed first-hand in my own garden," Keene explained in a Florida Atlantic University press release. "They are large and easily recognizable compared to many other insects. These are charismatic animals that everyone loves, and there's a growing appreciation for their potential to tell us about how the brain controls behavior."

The researchers gave the caterpillars three different amounts of food, New Scientist reported. The less milkweed the caterpillars received, the more aggressive they became. The caterpillars who were larger and closer to metamorphosis were the most aggressive, probably because they required more energy, Brown said.

Caterpillar aggression looked like a "combination of boxing and 'bumper' cars," the press release detailed, with caterpillars head butting or knocking other caterpillars away from the food.

"I went to grad school with a guy who played rugby in college," Keene told The New York Times. "A flying head butt is a fair assessment."

The attacked caterpillar would then shuffle away from the food, defeated. This is a big problem for the losing caterpillar, since monarch caterpillars essentially eat non-stop from hatching to forming a cocoon.

The researchers hope to build on this study to learn more about the genetic drivers of aggressive behavior.

"There's a lot we could learn about more complex animals from this ecologically relevant insect model," Keene told New Scientist.

The research could also have conservation implications. Monarch caterpillars mainly dine on milkweed: They can strip an entire plant in two weeks and, when they are at their largest, consume a leaf in less than five minutes, the press release noted. But this dependence on milkweed has made the species vulnerable. The number of monarch butterflies has decreased in the U.S. over the last 20 years, according to the U.S. Fish and Wildlife Service, and one factor is the use of pesticides that harm milkweed.

"It's interesting to think about how this would potentially impact the survival of these caterpillars, when they're crowded onto plants," University of Michigan monarch biologist D. André Green, who was not part of the study, told The New York Times. "The amount of milkweed is decreasing. This may become a bigger issue."

Eat Just's cell-based chicken nugget is now served at Singapore restaurant 1880. Eat Just, Inc.

At a time of impending global food scarcity, cell-based meats and seafood have been heralded as the future of food.

Read More Show Less

EcoWatch Daily Newsletter

New Zealand sea lions are an endangered species and one of the rarest species of sea lions in the world. Art Wolfe / Photodisc / Getty Images

One city in New Zealand knows what its priorities are.

Dunedin, the second largest city on New Zealand's South Island, has closed a popular road to protect a mother sea lion and her pup, The Guardian reported.

Read More Show Less

Trending


piyaset / iStock / Getty Images Plus

In an alarming new study, scientists found that climate change is already harming children's diets.

Read More Show Less
Wildfires within the Arctic Circle in Alaska on June 4, 2020. Contains modified Copernicus Sentinel data processed by Pierre Markuse. CC BY 2.0

By Jeff Masters, Ph.D.

Earth had its second-warmest year on record in 2020, just 0.02 degrees Celsius (0.04°F) behind the record set in 2016, and 0.98 degrees Celsius (1.76°F) above the 20th-century average, NOAA reported January 14.

Read More Show Less

In December of 1924, the heads of all the major lightbulb manufacturers across the world met in Geneva to concoct a sinister plan. Their talks outlined limits on how long all of their lightbulbs would last. The idea is that if their bulbs failed quickly customers would have to buy more of their product. In this video, we're going to unpack this idea of purposefully creating inferior products to drive sales, a symptom of late-stage capitalism that has since been coined planned obsolescence. And as we'll see, this obsolescence can have drastic consequences on our wallets, waste streams, and even our climate.

Read More Show Less