Sleeping 15-20 Hours a Day, Sloths Aren't Lazy but Energy-Saving Masters

Sloths are known as lazy animals due to their extremely slow movements, diet of leaves, and spending most of their day sleeping. Their English name, "sloth," even means "laziness." However, this slow lifestyle is not due to a lack of willingness to be active, but rather an evolutionary strategy for survival with very limited energy, as suggested by recent research. Sloths are arboreal mammals living in the trees of tropical rainforests in Central and South America, particularly in Brazil, Panama, and Costa Rica. They are distinct from lorises, which are nocturnal primates living in Southeast Asia, including Indonesia. Despite both moving slowly and having similar names, they belong to different taxonomic groups. Sloths are part of the Order Pilosa and are related to scaly anteaters and armadillos. This group of mammals has inhabited Earth for approximately 65.5 million years. Sloths are capable of sleeping for 15–20 hours a day. Recent research suggests that the secret to their lifestyle may lie within their DNA. The genome of the two-toed sloth (Choloepus didactylus) is filled with transposons, which are DNA segments that can copy themselves and move to other parts of the genome. Geneticists refer to these as "jumping genes." Transposons are also found in other mammals, including humans, but most are inactive. In sloths, these genes are still active, rearranging the genome. Many of them are linked to mitochondria (the energy-producing part of cells) and metabolic pathways that regulate the body's energy use and storage. These jumping genes are estimated to have emerged around 30 million years ago, shortly after sloths diverged from the evolutionary path of anteaters and armadillos. Since then, transposons have become part of the sloth's genetic identity. Researchers hypothesize that these genes function as a sort of backup system that helps minimize energy expenditure.