Why do sloths move so slowly?

Any ‘Zootopia’ fans out there? If you are one, then you would probably remember the hilarious and iconic scene with an office of sloths. But it is time you knew that in the real world, sloths are slow for a great number of reasons, from science to survival.

A scene from the movie “Zootopia.”
| Photo Credit:
AP

Diet and metabolism

The robin had lived in the same tree for years, and every day, she had seen her big furry neighbour, the sloth, chewing on leaves at a very slow pace. He had the same slow, green meal every day. She had once offered him a juicy berry, but he (very slowly) declined. 

Many aspects of a sloth contribute to its slow nature. One of the main factors is its diet, which largely consists of leaves that are low in nutrients and provide very few calories. This, in turn, provided the sloth with very low energy, which it works to conserve by moving extremely slowly. Because its intake of food is highly limited, the sloth has developed one of the slowest metabolic rates (slower than what is expected for a mammal of its size), with digestion taking over a month to complete! Since leaves are incredibly hard to digest, sloths have a special, multi-chambered stomach wherein they are broken down with the help of symbiotic bacteria. 

The pygmy three-toed sloth
| Photo Credit:
AP

Survival of the slowest

The jungle grass was wet, but the jaguar’s steps were silent. He was so hungry, he would pounce on the first creature that moved. As he crept, his beady eyes scanned the trees. Climbing wouldn’t be an issue. He just had to catch sight of an animal, and dinner would be served. But not a single thing moved or made a sound. The jaguar grew frustrated and stalked away. Little did he know, he had just been a few feet away from a certain tree dweller gazing at leaves.

There are times when being slow has its benefits. Despite the word ‘Sloth’ being termed as one of the seven deadly sins, which represents laziness, the mammal is often misjudged and believed to hold that quality. But that is not the case. Slowness doesn’t equate laziness. In fact, a sloth’s slow movements actually serve as a means of surviving the wild! As it turns out, in the animal kingdom, there are times when the slower an animal is, the more likely it is that their fur becomes a microcosm (small world). Sloths move so slowly to the point where fungi and algae grow and dwell on their fur, giving them a mossy appearance. This provides them with an efficient disguise, allowing them to camouflage with their surroundings. With all the algae and microorganisms clinging to its fur, and its near motionless position in the tree, the sloth may as well be a mossy forest decoration, invisible in plain sight!

Environment and evolution

Sloths are nature’s slowest arboreal (tree-dwelling) acrobats now. But similar to how our ancestors walked on all fours, unlike how we do now, the predecessors of the sloth, known as ground sloths, were large mammals that mainly scoured for food at the ground level. Far different from their descendants. It is believed that their evolution into arboreal creatures began about 35 million years ago. This change in lifestyle and habitat created development and adaptive changes in their behaviour, characteristics, and speed.