Number Two Squared: A Wombat Mystery
Wednesday, February 24th, 2021The common wombat, a humble, thick-bodied digging mammal of Australia, is not the kind of animal that often attracts the attention of scientists. Common wombats, also known as bare-nosed wombats, live in the coastal forests of Australia and feed mostly on grass, small bushes, and roots. They have thick brown fur and a stocky build. But, common wombats are number one in a category all their own among mammals, and it has to do with their number two!
Animal scientists have long observed that wombats produce cube-shaped feces (solid bodily wastes), something that has never been observed in any other mammal. Exactly how wombats make these cubic poos has been a mystery. That is, until a team of scientists in Australia examined the remains of several wombats that had been killed in road accidents. Through careful examination of the wombat’s digestive system, the researchers were able to crack the case of the squared nuggets.
The scientists found that the distinctive wombat deuces are made as the digestive system processes undigested waste just before it leaves the body. In the large intestine and colon, water is absorbed from the undigested waste as it passes. Muscular contractions that help to move the manure through the colon also squeeze the scat into a uniform lump. The scientists found that wombats have regions of varying thickness and stiffness in the lower portion of the colon. Contractions along this final passage squeeze the dry mass into a series of squishy cubes—of equal size with soft corners—ready for deposit.
Of course, it’s one thing to know how the wombat’s distinctive cube-shaped poop is produced. But the big question is why do wombats make such square-shaped make? Scientists think communication may be the answer. Wombats usually spend the hot days in underground burrows, only coming out at night to feed. The animals have a highly developed sense of smell. To communicate with one another, they usually leave their scat in select locations, appropriately enough called latrines. An adult wombat can dump about 100 smelly cube-shaped “calling cards” each day! Other wombats passing these piles can figure out who shares their neighborhood with a sniff or two of the cuboid poo.
But why a cube? Scientists have several ideas. One thought is that square-shaped poop is less likely to roll away from where it’s deposited. This may be helpful for marking territorial boundaries in a crowded wombat community, especially on uneven ground. Another idea is that with six flat sides, a cube-shaped deuce has more surface area available to waft odors into the air. This configuration may be more effective at sending signals airborne, compared with a more rounded load.