The sloth could be the slowest mammals on earth. The animal perches in a tree， it is famous for traveling no more than 38 m a day. Thus， people use the "slo" of the word "slow" to name it.

However， the sloth nature of laziness make it maximize the use of the resources around. Because they are herbivores， they rarely have the energy to advance rapidly. Sloth is native to the America， in the rainforest， they spend most of their time in life snuggling or hanging on the branches.

As most of the time is spent on sleeping， the sloth saves energy through decomposing food more slowly than most animal. The human body can probably fully digest a meal a day， while the sloth requires a month of time. In addition， the sloth reduces its body temperature， its metabolic rate is slower than the same size of mammals by 40% to 50%. It means that the sloths body needs less energy to work， those features will facilitate it grow up under the condition of the rare food.