Wombats are surprisingly aggressive and territorial given how adorable they look. They will fight to defend their burrows and offspring, a feat especially important considering they reproduce only once every 15 months. Some species of wombats form groups (called mobs) but still remain territorial towards outsiders, and they mark their territory with their square droppings. Wombats mostly eat grass, which is fairly difficult to digest, so they have extremely long digestive tracts (up to 13 metres!) to ensure they get adequate nutrients from their food. Their cubic poop is a byproduct of their long digestive tracts. As their fecal matter travels through their intestines, it becomes so dried out that it holds whatever shape it is put into, and it just happens to be square.