By Jody Bourton
Earth News reporter
Dying for the toilet?
Researchers in Panama have found the first evidence of a sloth that has been killed by an owl.
They found the body of a radio-collared three-toed sloth with lethal wounds that suggest it was hunted by a spectacled owl, which ate its organs.
Three-toed sloths are much larger than spectacled owls, a bird of prey standing around 45cm tall.
That adds to the impression that sloths are helpless on the ground, and camouflage is their main defence.
Details of the extraordinary kill are published in the journal Edentata.
The problem with sloths is that when they do move, and are detected, they are an easy kill
Max Planck Institute of Ornithology, Radolfzell, Germany
A team of researchers from the US and Germany study sloths that live on Barro Colorado Island in Panama, investigating aspects of sloth behaviour including how they sleep in the wild.
Part of this process involves capturing sloths and radio-tracking their movements, including how sloths move up and down trees.
During this research one of their radio-tracked brown throated three-toed sloths climbed down a trunk, then suddenly stopped moving.
When the researchers investigated, they discovered the remains of their study subject at the foot of the tree.
An analysis of the sloth's corpse in the laboratory revealed a series of puncture wounds that correspond to the talon markings of the spectacled owl (Pulsatrix perspicillata).
Eyes too big for its belly?
The sloth's internal organs were also missing, as if pecked out by a bird of prey. Other predators such as ocelots usually take their prey and hide it, say the scientists.
Spectacled owls are much smaller and lighter than sloths, standing 45cm tall and weighing up to 1.25kg, compared to a sloth which has a body length twice as long and may weigh four times as much.
The identity of the sloth hunter surprised the scientists who discovered it.
"These animals are relatively large, so one would expect their predators to be limited to harpy eagles and ocelots," says Mr Bryson Voirin of the Max Planck Institute of Ornithology, Radolfzell, Germany, who undertook the study.
They are also surprisingly adapted to life in the canopy.
Brown throated three-toed sloths (Bradypus variegatus) are among the world's slowest mammals, occurring in many forested habitats in Central and South America.
But this slow motion helps it avoid detection by predators.
Sloths also have fur that has green algae growing amongst it, providing camouflage against the canopy.
But "the problem with sloths is that when they do move, and are detected, they are an easy kill," Mr Voirin explains.
Sloths are particularly vulnerable as every eight days or so, they make a perilous journey to the foot of the tree in which they reside.
The venture there to go to toilet, though no one knows why.
But out of the branches, they are much more exposed, and their slow movements become a liability.
The scientists believe that it was during one of the trips that the sloth was killed.
"In this case, the prey was a defenceless three-toed sloth, an animal that has evolved this strange slow behaviour so they can remain undetected in the canopy," says Mr Voirin.
Why sloths behave this way remains a mystery.
But their lifestyle appears even more risky than previously thought.
"We think the evolutionary strategy of this cryptic lifestyle has opened them up to a wider range of predators."