Sloths have a reputation for being sluggish and slow, spending most of their lives dozing in trees, but a new study suggests this is one of the enduring secrets of their success.
Scientists have examined the evolutionary history of the animals, including extinct forms known only from the fossil records.
They say giant sloths walking the land were an easy target for the first human hunters.
In contrast, small sloths in the trees managed to cling on to survival.
Alberto Boscaini
The researchers say it is a reminder of the need to conserve Earth’s remaining sloths, which represent only the tip of the iceberg of 30 million years of evolutionary history.
“Some sloths are here with us today, some of them are at risk of extinction and one take home message is that we need to act now to avoid a total extinction of the group, said Dr Alberto Boscaini of the University of Buenos Aires, who led the study.
Today, sloths are small, tree-dwelling mammals, known for their cute faces and unhurried demeanour, found only in the rainforests of South and Central America.
However, back in the ancient past there were hundreds of different sloths across the Americas, of all shapes and sizes, adapted to live in every environment. Sloths lived on the ground, in caves and tunnels underground and even in water, some growing as big as elephants and standing taller than a man.