Harvester ants ( Pogonomyrmex barbatus ) of the western United States live in large mounds of sediment that they build themselves. These insects cover their mounds with a layer barely one centimeter thick made up of small rocks, thus managing to protect their habitat against the action of wind, rain and other problems that nature and humans can cause. Well, in these mounds, in addition to rocks, the ants collect small fragments of fossils and archaeological remains . This circumstance has led paleontologists to fix their gaze on these mounds and take the ants as allies to find hundreds and hundreds of tiny fossils that these tireless “paleontologists” gather.
Recent research has found more than 6,000 “mini-fossil” remains collected by these ants, including teeth and jaw parts from new species of small mammalian rodents . These tiny fossils, barely a millimeter wide, are joined by the remains of primates, ancient species close to rabbits and a type of bat that is also unknown.
From anthill to reservoir
It all started from an online forum. Marco Gulotta has a ranch in Nebraska where harvester ants accumulate mounds. In general, these ants are pests that ranchers have to deal with, since they are tireless harvesters of seeds and are capable of clearing all the land around their mounds in a radius of up to nine meters. A colony can extend activity on a mound for decades. However, Marco Gulotta is fond of paleontology and was aware of this information about these ants collecting fossils to protect their mounds.
Marco Gulotta and his sons searched for ancient remains among the pebbles for ants . They began to find small teeth. Gulotta took photos of his finds and posted them on ” The Fossil Forum ,” an online community of paleontology enthusiasts. Paleontologists Clint Boyd and Deborah Anderson saw the photos on the forum and contacted the Gulotta family to ask for some samples of these fossils so they could investigate them. The contact was not limited to this, but several researchers joined the study and in 2020 they ended up visiting the ranch to catalog the location of the anthills and continue studying these fossils. Thousands of remains found were donated by the Gulotta family to the South Dakota School of Mines and Technology, so that interested researchers can study the fossils found by ants. From that contact came a study published in the scientific journal “ Paludicola ”. In relation to this story, Boyd commented:
“Sometimes some people see, you know, a bit of antagonism between academic paleontologists and landowners when it comes to fossils. But this is a good example of how we can all work together and achieve important scientific research.”
little fossil hunters
The ability of these ants to find fossils has long been known. As early as 1896, paleontologist John Bell Hatcher advised taking a look at anthills in the western United States. Another research team already published in 2009 the results of the study of 812 anthills also in Nebraska. They found small stone flakes that could be the remains of the work of a native carving a stone to use as a tool.
The recent study led by William Korth of the Rochester Institute of Vertebrate Paleontology in New York examined 19 ant mounds from the Gulotta ranch. The collected fossil loot makes it possible to study what life was like in North America some 35 million years ago . At that time, our planet began a period of cooling that ended many species. Thanks to the work of these ants, the fossil record of such tiny materials can be located in very specific points such as anthills.
“It gives us this concentrated source of fossils that would otherwise take a lot of effort digging through the rock…or just years and years of having to crawl around on all fours, hoping to find something loose.”
Depending on your point of view, harvester ants can be a pest or the smallest paleontologists ever; their mounds can be a nuisance to eradicate or a “mini-museum” with thousands of pieces that only they are capable of finding.
References:
Greshko, M. 2022. This is how the world’s smallest fossil collector works. nationalgeographic.es.
Korth, W. et al. 2022. Fossil mammals from ant mounds situated on exposures of the Big Cottonwood Creek Member of the Chadron Formation (latest Eocene-early Oligocene), Sioux County, Nebraska. Paludicola 13, 4, 191-344. ISSN: 1091-0263.
