The extinct Shasta ground sloth was a bizarre looking, cow-sized herbivore, which inhabited the south-western parts of ice age North America.

Statistics
Length: 2.75m (9ft), Weight: up to 250kg (550lb).

Physical description
The Shasta ground sloth is like no animal alive today. It was about the size of a cow and had shaggy reddish brown fur. It had a long neck and relatively small head. A very large stout tail and powerful hind legs enabled it to rear up and reach leaves on shrubs and trees. Its legs were built in such a way that it would have walked with a waddling motion using the outer sides of its hind feet and the knuckles on its front feet.

Distribution
Southern parts of North America, especially in the canyons of the southwest.

Habitat
Shasta ground sloths inhabited the dry canyons, open woodlands and scrublands of south-western North America.

Diet
Shasta ground sloths were herbivores and their diet included shrubs, cacti, yuccas and numerous flowering plants.

Behaviour
With no similar modern animals to enable comparison, very little is known about the behaviour of this species. Its build suggests it was a slow-moving animal that relied on its size and sharp claws for defense against potential predators like sabre-tooth cats. From fossilised remains and preserved dung deposits, it is known that the Shasta ground sloth made regular use of caves in places such as the Grand Canyon. Perhaps these caves provided shelter at night, or during the heat of the day. They may even have been used as denning sites.

Reproduction
It seems likely that the Shasta ground sloths were solitary animals, except at breeding times when they would have had to come together to mate. What little evidence there is suggests that ground sloths produced just a single young. This is based on the fossilised find of a similar species in Brazil in which the foetus was still preserved in the body cavity. As with the tree sloths, a young ground sloth was probably carried by its mother, possibly clinging on to her back. The youngster would have stayed with its mother for several months until it was large and experienced enough to fend for itself.

Conservation status
Extinct from approximately 12,500 years ago.

History
Ground sloths evolved on the South American continent over 30 million years ago. Not until the Panamanian land bridge connected South America to North America around three million years ago did ground sloths move to North America. By the end of the ice age, around 13,000 years ago there were four species living in North America.

Closest relative
The tree sloths of South America.