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Ants are not properly adapting to warming temperatures

A new study led by North Carolina State University has found that ants do not adjust their behavior in response to warmer temperatures and tend to persist in sub-optimal microhabitats even when optimal ones are available. These findings suggest that ants may not be able to adjust their behavior in response to climate change.

Ants are ectotherms – animals whose body temperature depends upon the environment. Although such animals experience a variety of temperatures in their lives, most of them prefer habitats that are slightly cooler than the optimal functioning temperature in which an ectothermic animal is able to best perform its life functions. Usually, if an ectotherm encounters an environment warmer than the optimal point, it risks approaching the lethal end of its physiology’s spectrum.

Until recently, little has been known about how – and if – insect ectotherms will adjust their behavior to avoid warmer yet sublethal temperatures in which functioning is possible but not optimal. Now, experts have counted and collected specimens from five different species of ants common in North Carolina and measured air temperatures at the collection sites, as well as the body temperature of the ants themselves. To determine each species’ preferred temperature, they collected some ants and placed them in a rectangular chamber with a controlled temperature gradient.

The analysis revealed that, while ants in the laboratory did have distinct thermal preferences, those in the wild were active in their preferred climates only slightly more often than expected by chance. In fact, most species were collected from warmer than optimal sites, thus suggesting a lack of awareness or some type of limitation in their capacity to adjust to rising temperatures.

“It’s interesting that the worker ants we observed were willing to put themselves in uncomfortable situations while foraging,” said study co-author Sara Prado, a research associate in Zoology at NC State. “I wonder if the food was ‘profitable’ enough for the ants to stretch their comfort levels, or if they are simply willing to sacrifice their well-being for the sake of the colony.”

“Warmer times and places make warmer ants, and they’re not adjusting their activity to match their preferred conditions,” added co-author Elsa Youngsteadt, a professor of Applied Ecology at the same university. “For now, this may be a tradeoff that works out fine for them. But if you think of the huge biomass of ants underfoot, their metabolic rates are all creeping upward as the climate changes. Even if it doesn’t kill them outright, what does that amped-up metabolism mean for their life cycle and even the whole forest ecosystem?”  

In future research, the scientists aim to address these questions in the case of urban ants, which are currently living in even warmer temperatures.

The study is published in the Journal of Animal Ecology.

By Andrei Ionescu, Staff Writer

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