Many animals, from the very large to the odd, lived during the most recent ice age. Harlan’s Ground Sloth is one of the most bizarre animals from that era. A mix of large and odd, these tall, furry animals are related to modern sloths, armadillos, and anteaters. Unlike its smaller modern cousin, Harlan’s ground sloths could be as tall as modern elephants and as heavy as a small car.
Sheer size was not the only odd part of a Harlan’s ground sloth. These giants were bulky, with short necks, powerful chests, and massive jaws. The sloth also had three claws per hand for digging, grabbing, or defending themselves. Just like armored armadillos today, the sloth had a protective coat of rough, brown fur, with nickel-sized bone plates underneath their skin. Scientists call these plates dermal ossicles, or "bone skin".
Ground sloths migrated to North America during the most recent ice age. They spent their lives wandering open-grasslands with water sources like rivers and lakes. Using its stubby snout and sense of smell, the sloth ate grasses, shrubs, and plants with flowers. The need for water sources may have brought Harlan’s Ground Sloths to this area during the ice age. Before the sand dunes existed, a giant lake called Lake Otero filled the area. It provided a water source that attracted many ice age animals, including Harlan’s Ground Sloths.
Today on Alkali Flat, the old dried lakebed of Lake Otero, Harlan’s ground sloths left clues that they were here in the form of crescent-shaped fossilized footprints. Their back feet twisted inward when they walked, which made them walk slowly, almost like waddling. These strong, slow moving animals became easy targets for daring predators such as ancient human hunters.
The giant ground sloth did not survive to the present day. Around 10,000 years ago, the large ice age animals died out. Scientists still debate why the larger animals disappeared. The Harlan ground sloth is reminder of a time long past.
References
Lange, Ian M. ice age Mammals of North America: A Guide to the Big, the Hairy, and the Bizarre. Missoula, Montana: Mountain Press Publishing Company, 2002.
Bustos et al., Sci. Adv. 2018; 4: eaar7621 25 April 2018, Footprints preserve terminal Pleistocene hunt?: Human-sloth interactions in North America
