So if a 90-pound animal living today digs a 16-inch by 20-foot borrow, what would dig one five feet wide and 250 feet long?
That sounds like a great opening line for a new adventure movie, but it’s a real question asked by geology professor Heinrich Frank as he crawled through a mysterious tunnel uncovered at a construction site in Novo Hamburgo, Brazil. After determining it was unlike any geological formation he’d ever seen, Frank speculated that it was dug out by a living thing. Whatever the strange creature was, it left claw marks across the walls and ceiling of this tunnel and others of similar size found in the area. Is it any wonder the professor slowly backed out and told the construction workers he’d be back in a few weeks? Yeah, right.
Turns out he kept his promise and Federal University of Rio Grande do Sul professor Heinrich Frank ended up finding out the name for the mysterious tunnels and identifying the animal most likely to have done the excavations, not only of the tunnels in Novo Hamburgo but thousands of others in Brazil
When I got home I looked for an explanation on the internet, but I did not find anything. Since then I have heard that the tunnels are huge anthills or that they were created by Indians, Jesuits, slaves, revolutionaries and even bears. Some even talk about a great mythological serpent, which dug the tunnels.
Five-foot-wide ants? Mythological underground serpents? Now we’re getting a movie plot!
A branching tunnel
Frank found his first tunnel in the early 2000s and learned that another scientist had coined the name “paleoburrows” for them. When his search for an explanation turned up nothing (well, nothing reasonable), he began looking for more of them in an attempt to figure it out himself. As of today, Frank and other researchers found over 1,500 tunnels in the state of Rio Grande do Sul alone and hundreds more in Santa Catarina, with many stretching for hundreds of feet and having numerous branches. The largest measured 2,000 feet long, six feet tall and up to five feet wide.
In these burrows, sometimes you get the feeling that there’s some creature waiting around the next curve – that’s how much it feels like a prehistoric animal den.
Did he find giant ant farms? Yards of shed serpent skins? No, but he did find enough evidence to convince him that the paleoburrows were probably dug by the second-largest prehistoric land mammal (next to the mammoth) – the giant sloth. That evidence is primarily those deep claw marks on the walls of the paloeoburrows that could only have been made by a giant sloth (Megatherium americanum), not smaller giant armadillos as some had suggested.
Weighing in at several tons, the giant sloths would have dug the burrows before they went extinct 10,000 years ago. So far, Frank and other researchers haven’t found fossils in the caves nor organic material or mineral deposits that could date the creation of the burrows. That evidence might also show how these giant beasts could dig for 2,000 feet .. and why.
With their size, they didn’t need to hide that much. Frank thinks the burrows were dug and shared by many giants and passed down from generation to generation. He’s also looking for reasons why the burrows are so predominant in Brazil and so rare in other South American countries. As he said in a recent interview in Discover, more research is needed.
Digging a 2,000-foot-long, five-foot-wide burrow required moving about 4,000 metric tons of dirt and rock. Don’t ever call sloths lazy again.