World’s fastest ants found racing across the Sahara

The silver ants can run their body length in less than a hundredth of a second—the equivalent of a human running 400 miles an hour.Thursday, 17 October 2019

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Like a tiny, glinting missile, the Saharan silver ant blazes across the searing sand in search of dead animals that have succumbed to the heat. Now, new research reveals these fleet-footed foragers are not only the fastest ants alive, but among some of the fastest insects on the planet.

In a recent experiment on the sun-baked dunes of Douz, Tunisia, the insects clocked in at about 2.8 feet per second—or about 108 times their body length. If that were scaled up to humans, we’d zoom along at over 400 miles per hour.

The ants are outpaced only by a few invertebrates, including a mite from California, Paratarsotomus macropalpis, and an Australian tiger beetle, Cicindela hudsoni, which can move at speeds of 377 and 171 body lengths per second, respectively.

The ants’ super speed is likely one of their adaptations to life in the harsh desert, allowing them to go about their business quickly before getting roasted in temperatures as high as 140 degrees Fahrenheit. Saharan silver ants are also relatively spindly, a body shape that helps them dispel heat more easily, and their special, triangular hairs reflect heat and give them their metallic hue. (Read about the Dracula ant, which has the fastest bite on Earth.)

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"From an evolutionary perspective, low food density and a hot climate in the North African deserts exert selective pressures that make fast and efficient foraging a crucial feat for the scavenging silver ants,” write Sarah Pfeffer, a biologist at the University of Ulm, Germany, and colleagues in the Journal of Experimental Biology.

Overall, the research provides a new window into the impressive lengths animals will go to thrive in hostile places, the study says.

Fancy feet

In the Sahara, Pfeffer and her team first located several of the ants’ subterranean nests, then set up small, aluminium channels—with floors lightly covered with sand—on the front steps of the nests. The channels funnelled the foraging ants into a more manageable space, so the researchers could film them with high-speed cameras from above as they raced by.

By analysing the high-speed video, the scientists could calculate the ants’ blistering pace. When the team compared these numbers with speeds of a closely related, slightly larger desert ant, Cataglyphis fortis, the silver ants were twice as fast—despite having proportionally shorter limbs. (Read about a technique allows scientists to accurately guess the speed of any animal.)

Looking closer at footage of the Saharan silver ants’ legwork, the team discovered why: The silver ants were simply moving their shorter legs blindingly fast, taking nearly 50 strides per second. They did this partially by barely ever letting their feet touch the ground, with each contact lasting as little as seven milliseconds.

The ants also had remarkable coordination, even on shifting, loose sand—seamlessly churning between the two sets of three legs that work in unison when running. At higher speeds, the ants would even gallop, lifting all of their feet simultaneously off the ground at certain points.

“I am surprised that the silver ants are smaller and shorter, yet compensate with stride frequency,” says Alyssa Stark, a biologist at Villanova University in Pennsylvania who was not involved with this study. It’s especially surprising, she adds, considering having longer legs would be another way for the ants to reduce overheating.

Amir Ayali, a zoologist at Tel-Aviv University in Israel, was impressed by the study’s approach comparing the closely related ants. (Watch "monster" ants attack faster than the blink of an eye.)

“It would be extremely interesting to try and see if the reported differences between the species can be also traced down—or up—to the level of muscle physiology and even neural control,” says Ayali.

Hell’s kitchen

So why go so fast? Pfeffer and her team suggest thei ants' speed allows them to find and scavenge its meals quickly and efficiently. When the ant comes across a corpse, it carves up the body and takes some of the parts back to its underground nest to eat in peace. 

The fast strides and limited contact with the sand may also prevent them from sliding or sinking into dunes as they look for food, the study says. 

It’s possible further investigation will reveal precisely why there’s such a pep in the ants’ step, but for now, the Sahara’s silver ants are just concerned with what they do best: running.

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