Earlier this year, heatwaves in parts of Gauteng caused an influx of ants into households as the insects left their nests for cooler conditions.

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Dr Tom Bishop, a lecturer at the School of Biosciences at Cardiff University, told Daily Maverick, “The main defence that ants have against extreme temperatures is to not be active. When it gets too hot, ants stay inside their nests and the colony is usually buffered from this as they are buried in the soil. However, the foraging ants won’t want to go outside their nest because of the heat.

“Their only way of getting food becomes cut off and they can only forage at dawn, dusk or cooler parts [of the day]. That’s the impact we see: the gradual starving of the colony.”

A research paper shows that extreme cold and heat cause the metabolism, development and performance of ants to decline to near zero. The same paper also found that ants do at times move their nests to cooler terrains to shield their eggs and young from delayed development caused by extreme temperatures.

Heatwaves often cause their influx into households from back gardens as they seek cooler spaces to forage and take shelter. In the long term, however, ants, like many other species, will either migrate or adapt, Bishop said.

Ants’ metabolisms, development, and performance have been shown to decline in extreme cold and heat. (Photo: iStock)

“Adaption can take on another form (besides migrating); they can tolerate the conditions where they realise they cannot forage as much any more and have to get by with foraging less. Or it could be adapting over a long period of time — years, decades, centuries. This is clearly too long a period in the context of the changes happening to our planet.

“Sometimes in certain species, it appears that adaptation can happen pretty quickly. But on the whole, no, that option is kind of off the table. Adapting by tolerating the conditions is realistic but adapting rapidly genetically is not an option. The final option would be for insects to not adapt and just die. It can be challenging to determine which of those options species will take; it’s either moving or dying.

“With ants, they’re poor dispersers from an ecological point of view as they’d have to move to a new landscape or country and that can be difficult as they’re not like larger mammals with greater migration patterns… We can drive or fly to another country, but for ants, it’s going to take years and years,” Bishop said.

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There are about 15,000 species of ants across the globe and 600-odd species in South Africa. Their collective raw biomass outweighs that of humans. They play a pivotal role in the ecosystem.

Bishop said, “If you take ants out of the picture because they’ve been killed by heatwaves then there becomes a lack of food for other creatures. Given their central position in ecosystems, lots of other insects might grow exponentially and that may cause other problems.

“Ants are scavengers and they’re constantly cleaning the ecosystem, dispersing seeds and turning over soil, which has an impact on soil activity. We know ecosystem disruption will happen.” DM