Wombats' bizarre behinds are famous for their ability to produce cubic poop. These unusual square scats play an important role in wombat communication, as poop is stacked like Lego bricks to send messages like “keep out” or “let’s make a joey”. Amazingly, wombat derrieres serve many purposes beyond their primary roles of delivering dumps and sitting down, making them something of a wonder tool.
Potato-like in shape, wombats are stocky, round, and close to the ground, which is a beneficial posture for Australian outback animals that need to lay low but also hold their own in a fight. While not the most social creatures, they share burrows but will keep to their own territory within these underground systems of tunnels. Here, mating pairs will raise a joey stirring up parental instincts that see them bare their behinds as a blockade or battering ram, depending on the threat at hand.
“Wombats are generally a solitary species and quite an aggressive one at that,” Monique Spaulding of the Bonorong Wildlife Sanctuary in Tasmania told IFLScience. “[They] have a large fascia plate in their rump area. This allows them to block the entrance to their burrows if they feel threatened. The area has very little nerve endings, so even if a predator (such as a dog, fox or dingo) scratches or bites, they generally won't be harmed.”
The fur that covers the fascia plate is short to avoid being used as a means of pulling the wombat from its burrow, but when a predator is getting too close for comfort, they have another more proactive means of defense. “They will lay down at the burrow entrance, allowing the predator to slide its head into the gap between the plate and the roof of the burrow,” continued Spaulding. “The roof of the burrow is usually made of very compacted soil, tree roots, logs or rock. Once the predator's head is in the gap, the wombat will slam its rump up repeatedly, with enough force to potentially crush the skull of that predator.”
It doesn't get more badass than crushing the skulls of your enemies with your bum, but how are buns of steel useful as a means of seduction? Wombat mating is far from an affectionate ordeal and pairs will be quite rough with one another. The ritual plays out a bit like a game of kiss chase but with bottom biting, as either the male or the female chomps on the butt of the other so that they give chase. Once the object of their affections has turned tail, a few more bites and a couple of kicks later the animals leap on each other. The event often sees chunks of fur left in its wake, but the rock-hard wombat posterior prevails.
“We call our wombats 'bulldozers',” said Spaulding. “And their lifestyle truly reflects this.”