I wrote about ground sloth burrows a few months ago (See:https://markgelbart.wordpress.com/2012/10/10/some-giant-ground-sloths-dug-long-burrows/) At the time I was unaware of more recent studies of newly discovered paleoburrows in Brazil. Heinrich Frank and his students have published at least 54 research papers about these surprising structures, and their work is available at this website—http://www.ufrgs.br/paleotocas/
Inside one of the paleoburrows studied by Heinrich Frank and his students. This one is so large it must have been made by a ground sloth. Be sure to click on the paleotocas link above for more photos. There are some photos of the claw marks on the sides of the tunnels but they were within pdf files that I couldn’t cut and paste to my blog.
Within the last few years, Heinrich Frank has documented the discovery of 60 paleoburrow complexes of 1-25 tunnels each. The total number of paleoburrows includes 45 intact tunnels and 130 crotovines (tunnels that have become filled with sediment). Some are up to 60 yards long and many criss cross and are connected to other tunnels. Claw marks on the tunnel walls match 5 different species: giant armadillos such as Eutatus, Propraopus, and Pampatheres, and 2 giant ground sloths–Glossotherium and Scelidotherium. Scientists are still figuring out how to determine which claw marks match which species. It’s not as easy as one would assume because the nail part of the claw isn’t preserved, and the difference in size between males and females can throw off their calculations. For example the claws of a large male of 1 species may overlap in size from the claws of a small female from a larger species. Scientists must also consider 2 other large animals that could possibly dig burrows–bears and giant tortoises.
The paleoburrows found in Brazil were dug into sedimentary rock, or more rarely, volcanic rock, and are located in hillsides not far from water. Amazingly, some are dug into sandstone. This shows just how powerful diggers ground sloths and giant armadillos were. A man would need a pick axe to dig through this strata. The ceilings of these burrows have a wave-like undulating pattern, indicating the animals dug, stopped, removed the dirt, and resumed digging. The burrows were “deepened episodically” and probably used by several generations. Burrows that are 6-10 feet in diameter were undoubtedly made by ground sloths. Armadillos made narrower burrows.
Scientists working in these paleoburrows face many hazards. They can suffocate in the smaller burrows. The tunnels fill with water during rain, presenting a danger of drowing. Dust and fungi can carry lung diseases. Poisonous spiders abound here, while rabid bats and live armadillos infected with leprosy can also pass on their diseases to researchers.
Rabid bats are a hazard for researchers studying paleoburrows.
Ground sloths and giant armadillos primarily used burrows as shelters from the weather. Both belong to the primitive family of mammals known as the edentates. The edentates originated in the tropics and have poorly developed thermoregulatory systems. To survive, they had to escape from the hot midday sun and from freezing temperatures. Although no paleoburrows have been found in North America, their fossorial habit explains how one species, Jefferson’s ground sloth, was able to live as far north as Alaska. It must have dug deep burrows where it was safe from hard freezes. Heinrich Frank has asked North American cavers to be on the look out for paleoburrows, but so far, none have been found. Paleoburrows in Brazil and Argentina were dug into rock, and this is why they are so well preserved. In North America burrows were dug into soil where they likely collapsed and disappeared soon after ground sloths became extinct.