Fear, Not Climate, Most Directly Impacts Insect Growth

Researchers have found that damsels in distress are far more likely to impact insect populations than climate change alone. Observations of damselflies and other insects have led to the conclusion that fear of predation is the main driver of how fast or slow insects grow, despite claims that temperature could be a major influence.

A study detailing these findings was recently published in the journal Oecologia.

Lauren Culler, the lead author of the study and a Dartmouth researcher, is particularly excited about these findings, explaining that a better understanding of insect growth factors can help future conservation and control efforts.

"It's less about temperature and more about the overall environmental conditions that shape the growth, survival and distribution of insects," she explained in a statement.

Nature World News recently reported how climate change is leading to changing predation success, where insects like the Asian lady beetle are suddenly having much more success hunting aphids in declining winds, and where sharks are being robbed of their predatory senses thanks to ocean acidification.

Culler's latest work enforced these claims, showing how some insects are not growing as fast simply because environmental factors - the results of climate change - are favoring their predators. Fear of being eaten in particular,  known as the "flight-or-fight" response, can prompt physiological responses that stunt growth and reproductive capability, usually because less time is spent foraging and more energy is expended on defensive action. (Scroll to read on...)

According to the study, Culler and her colleagues brought several populations of damselflies into a lab and set them up in various environments. Some environments were simply ideal, but others boasted heightened temperatures or a nearby fish predator.

Predictably, the researchers found that in the absence of predator fear, the insects ate more food and grew quickly, even in warmer temperatures. Fish living near a predator, however, regardless of the temperature, grew much slower.

Culler says that this work highlights a glaring problem with some studies looking for a correlation between rising temperatures and population decline.

"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."

After all, fear is a powerful thing.