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We all know what it is like feel a little hungry. You haven’t eaten in hours, your stomach starts rumbling and you start getting a little nervous. Maybe you answer a co-worker or unexpectedly raise your voice in a conversation with loved ones.
It can be a consolation to know that humans aren’t the only ones experiencing this unique blend of hunger and anger.
In a study published Thursday in the journal iScience, scientists reveal that late-stage monarch butterfly caterpillars display aggressive tendencies when faced with a limited food supply.
Chow Time – One of the unique traits of the monarch butterfly (Danaus plexippus) caterpillars is that the caterpillars feed on the milkweed plant. It is the main food source of the monarch caterpillar.
In the latter stages of their development, monarch caterpillars break down as if there is no tomorrow, quickly passing through their food supplies and leading to competition for scarce resources.
“Monarchs feed mainly on milkweed, and we have seen late-stage caterpillars remove leaves from the entire plant,” said Alex Keene, lead author of the study and professor of biological sciences at Florida Atlantic University. Reverse.
In nature, researchers have noticed that caterpillars become aggressive in their final days before becoming a pupa, the stage where they are in a cocoon before transforming into adult butterflies.
“We decided to systematically test the relationship between food availability and aggression in a controlled laboratory environment,” says Keene.
The link between aggression and food – or aggressive behavior – in caterpillars has never been scientifically documented before, according to the researchers.
Keene’s team built a milkweed garden behind their laboratory in Boca Raton, Florida, allowing monarchs to come to them. The scientists then placed the caterpillars near the milkweed leaves in their laboratory.
The results were clear: the caterpillars began significantly more attacks on their fellow creatures when the milkweed supply was low and they were looking for food.
In most cases, the attached caterpillar was feeding at the time of the violent encounter, suggesting that the attacking caterpillar was trying to eliminate the competition so they could eat the milkweed leaf on their own.
Future implications – The study is a fascinating examination of how caterpillars start out Hunger Games-style brawl over scarce resources. It is also timely research.
In recent years, scientists have lamented the decline in monarch butterfly species, in part due to decreasing amounts of milkweed.
This could mean even more competition among caterpillars for increasingly scarce food resources. Surviving caterpillars may be more aggressive as a rule.
“One could imagine that further competition for food sources increases aggression,” says Keene.
“I guess this means we are more likely to see this behavior in the wild, but it could also increase selection for aggressive caterpillars over time.”
Abstract: Food represents a limiting resource for the growth and progression of development of many animal species. Consequently, competition for food, space or other resources can trigger territoriality and aggressive behavior. In the monarch butterfly, Danaus plexippus, caterpillars feed predominantly on milkweed, increasing the possibility that access to milkweed is critical for growth and survival. Here, we characterize the role of food availability on aggression in monarch caterpillars and find that monarch caterpillars exhibit stereotyped aggressive lunges that increase during development, peaking during the 4th and 5th stages. The number of lunges towards a conspecific caterpillar was significantly increased in conditions of scarce food availability, suggesting that resource defense can trigger aggression. These findings establish monarch caterpillars as a model for investigating the interactions between resource availability and aggressive behavior under ecologically relevant conditions and pave the way for future investigations into the neuroethology of aggression in this system.
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