Termites are remarkable engineers, capable of building mounds standing more than 10 metres high and 15 metres wide at their base. Their mounds regulate heat and the condition of the air inside, and are used to home and raise generations of the tiny social insects. But a new discovery reveals how even more astounding these structures are. In the Miombo woodland area of central Africa, scientists have found an abandoned termite mound that is more than 2200 years old. That makes the mound the oldest termite structure ever dated, notwithstanding those that have become preserved as fossils. Another mound studied is at least 750 years old, confirming the ancient mound wasn’t an anomaly. The discovery suggests that termites used the same structures for millennia. The mounds were built by the termite species Macrotermes falciger, in an area of the Miombo woods in the Lubumbashi region of Upper Katanga in the Democratic Republic of Congo. “The sheer size of the mounds suggests that their age surpasses the lifespan of a single termite queen, which rarely exceeds 20 years,” write scientists in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. Led by Hans Erens, a team of researchers from Ghent University in Belgium and the University of Lubumbashi in DR Congo dated four large termite mounds using a technique called Carbon 14 dating. This samples the ratio of the radioactive Carbon 14 isotope in the soil the termites used to build the mounds. The ratio of the isotope present relative to normal carbon accurately reflects the age of the structure. The researchers took samples down the vertical axis of each mound. Of the four mounds tested, two were active, with termites residing in the top part of the structure. Two were abandoned, and in each category the researchers sampled a smaller mound standing less than 3.5 metres tall, and a larger one more than 6 metres tall. In the larger abandoned mound, the age of the earth used to create the structure increased towards the ground, with the base of the mound dating between 2335–2119 years before present. The smaller abandoned mound showed a similar profile, its base being 796 to 684 years old. The active nests were more modern, but the larger nest was built upon an ancient mound that was 766 to 675 years old, confirming that termites continue to build on the same mounds for centuries. The 2200-year-old mound is thought to have been abandoned for decades. But the study reveals termites regularly used it 800 to 500 years ago, during an especially warm period in the region. Its use 2200 years ago, and then in the 12th to 15th Centuries, also infer termites use the same sites for millennia.
“These ages should be interpreted as minimum estimates,” say the researchers in the journal. “Nonetheless, some of the mounds are much older than previously estimated.” There have been previous claims of 4000-year-old termite mounds in South Africa, with the insects being identified as the creators of geological structures in the country known asHeuweltjies. BBC
