The Saharan silver ant is able to survive in temperatures that would kill most other animals. They live in one of the hottest environments on Earth, where the surface temperature regularly reaches a sweltering 70°C (158°F) in the midday sun. Despite this, the little insects are able to keep their body temperatures down, and researchers have finally worked out how.
The trick to the ant’s success is their space-age metallic look. The ants are covered in microscopic silver hairs that have been found to reflect the sun’s rays while at the same time radiating the insect's own body heat, keeping them below the magic 53.6°C (128.48°F), above which they perish. The researchers plan on using the same technique to help inspire new ways to create cooling surfaces.
“This is a telling example of how evolution has triggered the adaptation of physical attributes to accomplish a physiological task and ensure survival, in this case to prevent Sahara silver ants from getting overheated,” explains Nanfang Yu, who co-authored the paper published in Science.
One of the most heat tolerant animals in the world, the ants live such a unique life that one of their behaviors even has its own specialized term known as “thermal savaging.” They wait in their nest until the sun is at its highest and the environment is at its hottest. Then, during a 10-minute window, the ants leave their nest and start foraging for all the dead insects that have died in the heat. And since their predators are avoiding the intense midday sun, this has the added benefit of reducing their risk of predation.
The silver hairs coating the ants, and their cross section. Credit: Norman Nan Shi and Nanfang Yu/Columbia Engineering
The team of researchers from Columbia University focused on the ants' silver coat to understand how they managed this. They used electron microscopy to take a detailed look at their body hairs and found that they had a triangular cross section that worked to cool the body in two ways. Firstly, they were highly reflective of visible and near-infrared light — the wavelengths of the sun that are hottest. Secondly, they are also highly emissive of mid-infrared light, the excess heat produced by the body, a process known as “black body radiation” or thermal radiation.
“To appreciate the effect of thermal radiation, think of the chilly feeling when you get out of bed in the morning,” says Yu. “Half of the energy loss at that moment is due to thermal radiation since your skin temperature is temporarily much higher than that of the surrounding environment.”
These amazing creatures have many other adaptations to help them cope with the crippling temperature. They have long legs that hold their bodies above the searing sand, produce heat shock proteins that help them tolerate stress, and regularly pause on top of pieces of wood and plants to get themselves out of the worst of the surface heat. They also have an incredible ability to pinpoint their exact location by looking at the sun, allowing them to calculate the most direct route back to the nest when their time is up.
