Ants can be annoying, but if they didn’t exist, the world would be very different. Insects live on every continent except Antarctica, and everywhere they are deeply entangled in the networks of nature. They are therefore important for the survival of other animals and plants. Among other things, they distribute seeds, keep pests in check and ensure that the soil is constantly mixed.
Their disappearance, but even their decimation would have serious consequences. The result of a small study carried out by a team of American biologists Journal of Animal Ecology published is worrying against this background: Ants can therefore probably adapt only poorly or not at all to climate change and the associated rise in temperatures.
Like all living beings, ants have a comfortable temperature at which their metabolism and their whole body work best. If it gets warmer, their fitness drops rapidly, and the animals quickly reach a point where nothing works, where they can neither eat nor move, let alone reproduce. If it gets any hotter, they die.
Ants are willing to expose themselves to uncomfortable temperatures
Unlike most other animals, the insects do not seem to avoid temperatures that are actually too high for them, write the authors of the current study. And not even if they theoretically had the opportunity to do so.
The team led by Elsa Youngsteadt from North Carolina State University studied the behavior of five different ant species at sixteen locations near Raleigh, the state capital of North Carolina, during the summer months of June to August. At each location, they placed 14 baits with treats irresistible to ants: tuna, strawberry jam, and cookie crumbs. Half of the bait was located in a place that heated up significantly over the course of the day, while the researchers placed the other half in cooler places.
As soon as ants spotted one of the baits, the biologists observed for five minutes how many and which species appeared there. They also measured the temperature of the bait and caught some of the insects to take to the lab. There they placed the animals in a chamber with a temperature gradient and documented where they crawled to and stayed. In this way, they determined the comfort temperature of the animals, which varied somewhat from species to species.
When evaluating the data, the researchers discovered to their surprise that most of the ants they had observed in nature had visited baits in locations where the temperature was well above the insects’ comfort temperature determined in the laboratory. Even if there were bait in cooler spots nearby. “It’s interesting that the workers we observed were willing to put themselves in uncomfortable situations when foraging,” says Sara Prado, who was involved in the study, in a university press release.
Why the animals behave this way remains a mystery. Don’t they realize it’s too hot for them? Don’t you care? Or are they unable to react adequately to excessive temperatures for some other reason?
Ants cannot regulate their own body temperature
According to the authors of the study, the self-injurious behavior of workers when foraging is an indication that ants are ill-prepared for the challenges of climate change. While many birds and mammals are already shifting their distribution ranges towards the poles or to higher altitudes to avoid rising temperatures, ants appear to be doing: nothing.
As so-called ectothermic animals, which cannot regulate their body temperature themselves, insects are particularly vulnerable to the temperature in their environment. “Warmer times and places make warmer ants,” says Elsa Youngsteadt in the press release. “Nevertheless, they don’t adjust their activity in a way that makes them feel good.”
Perhaps it is not even necessary for the survival of ants in times of climate change that individual workers change their foraging behavior. Many ant species function as a kind of superorganism in which different animals take on different functions: the queen is responsible for reproduction, others for brood care, defense or even foraging. The survival of the individual animal is not so important in these superorganisms – what matters is the survival of the colony.
And together, the animals may well be able to respond to rising temperatures. For example, it is known from the winter ant Prenolepis imparis that the colony reacts to excessive temperatures in the nest: When it gets too hot, all the animals work together and move the nest further down the ground. To where it’s cooler.