Evolution is all about exploiting niches where other animals fear to tread – or just can’t. Ground too hot to touch deters many an animal, but not the valiant silver ant of the Sahara, which has now been proven to be the fastest ant in the world.
How does the Saharan silver ant survive the burning dunes, the surface of which can reach 70 degrees Celsius (158 Fahrenheit)? For one thing, it has a heat shield. Its silver coat and the uniquely shaped triangular hairs on its coat reflect the sun’s rays.
For another, the ants come out to scavenge at the hottest time of day, when other ants are hiding from the burning sun – but they don’t remain exposed for long. This is where their extraordinary speed comes into play, as described by Harald Wolf, of Germany’s University of Ulm, and his colleagues in the Journal of Experimental Biology.
Saharan silver ants, or Cataglyphis bombycina, by their scientific name, scoot like little silver bullets along the sand as they seek corpses to eat. They rocket along at 855 millimeters per second, which is equivalent to 3 kilometers per hour (almost 2 miles per hour).
Humans, by comparison, traverse crosswalks at about 5 kilometers per hour on average. And we have long legs. They don’t, even by ant standards. The silver ant achieves its zippy pace by swinging its legs at speeds of up to 1,300 millimeters per second.
Their 855 millimeter per second velocity is 108 times their body length per second. You try to achieve that. And the ants do that during the hottest part of the desert day.
To be clear, we are talking about the fastest ant in the world, not the fastest insect. Although the Saharan silver ant is the speediest ant, Paratarsotomus macropalpis, a leggy southern California mite the size of a sesame seed can sprint at 377 body lengths per second. Cheetahs run about 16 body lengths per second.
Even put in proper perspective, silver ants rock. But finding the inconspicuous silver ant nests to film their speed was far from easy, Sarah Pfeffer, who coauthored the journal article on the subject, said. “We had to look for digging ants or follow a foraging ant back home,” she explains.
Having achieved that in Douz, Tunisia, all that remained was to lay bait and wait. “They love mealworms,” Pfeffer noted.
Further study with a nest that was extracted and taken to the lab revealed that at 10 degrees Celsius (50 Fahrenheit), the ants slowed to a mere 57 millimeters per second. That’s only 7 times their body lengths – not that we could achieve that either.
Cousin ant Cataglyphis fortis can only achieve 620 millimeters per second, which is 50 times its body length per second. Lame.
Tapping their inner gearbox
One might assume the silver ant has extraordinarily long legs. It doesn’t. It has stumpy legs, almost 20% shorter than those of their leggier cousins the Cataglyphis fortis.
The trick is that the silver ants swing their legs at speeds of up to 1,300 millimeters per second, taking up to 47 strides per second, Wolf and his team wrote.
Crucially, the team’s film footage has shown that silver ants “gear up” when running on the baking ground, as much as quadrupling their stride length from 4.7 to 20.8 millimeters. In other words, they’re not running – they’re galloping, the team said. At top speed, all six feet are off the ground simultaneously.
Wolf suspects that not only do the ants barely touch the sand. They may be capable of muscle contraction speeds close to physiological limits. That will take further study. Stay tuned.