 The pygmy three @-@ toed sloth , like others in its genus , is an arboreal ( tree @-@ living ) animal . This sloth can spend as many as 15 to 20 hours on trees . It moves at an extremely slow speed of 0 @.@ 24 kilometres per hour ( 0 @.@ 15 mph ) , making it one of the slowest animals . The pygmy three @-@ toed sloth is symbiotically related to green algae ; a 2010 study investigated this in detail . Different sloths harbour different types of algae – only Tricophilus species were found on the brown @-@ throated and pygmy three @-@ toed sloths . These algae discolor the fur of the sloth , giving it a greenish hue – this serves as an efficient camouflage . Some of these algae might be transferred to offspring through the mother , others may be picked up from the surroundings over time . The smaller size of pygmy sloths reduces their energy requirements for survival and reproduction , making them an apparent example of insular dwarfism . A BBC documentary , in which English naturalist Chris Packham recognizes the pygmy three @-@ toed sloth as the first in his list of the top ten discoveries in the 2000s , shows a rare clip of a swimming pygmy three @-@ toed sloth . 
