Previous studies have shown that warming temperatures make insects eat more and grow faster. In fact, scientists often measure the effects of temperature on insect growth to predict how climate change will affect their distribution and abundance.
However, a new study from Dartmouth College indicates that other factors — in this case, fear — play a role as well, and some can actually decrease the rate of growth.
“In other words, it’s less about temperature and more about the overall environmental conditions that shape the growth, survival, and distribution of insects,” said Lauren Culler, lead author of the study, which was published in the journal Oecologia.
Culler and her colleagues looked at how fear, which typically lowers food consumption and growth rate, affects an insect’s response to warming temperatures. They brought damselfly nymphs into the lab and measured how much they ate and grew at different temperatures, and how that changed when a fish predator was nearby by using an experimental setup in which a damselfly was floated in a glass vial and exposed visually and chemically to a fish predator.
In the absence of fear, the damselflies ate more food and grew faster as the temperature increased. Surprisingly, however, when a fish predator was looming, the damselflies ate about the same amount of food but grew much more slowly. The researchers aren’t sure what happens to the food that doesn’t go into growth, but they think it gets lost in the anti-predator response, possibly to production of stress proteins.
“Studies that aim to predict the consequences of climate change on insect populations should consider additional factors that may ultimately limit growth and survival, such as the risk of being eaten by a predator,” Culler said.
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