Wombat Cubes

The Wombat is an Australian Marsupial (pouched) Mammal that produces unusual cube-shaped faeces (https://www.theguardian.com/world/2021/jan/29/box-seat-scientists-solve-the-mystery-of-why-wombats-have-cube-shaped-poo). The faeces are probably used to signal to other Wombats (they are used in other species, to mark territory or to leave information about the depositer's sex, status and/or receptivity). Cuboidal faeces have the obvious advantage that they will not (unlike rounded pellets) roll from where they are deposited. There has been much speculation about how the shape is achieved. Some people have claimed Wombats must have a square anus (they haven't) or they pat each pellet into shape (they don't). Dr Scott Carver (University of Tasmania) has now confirmed (in the journal 'Soft Matter') that the shape is achieved within the last metre of the animal's digestive tract. This organ has regions where the thickness of muscle varies. There are essentially 2 stiff and 2 more flexible regions. Their actions squeeze the faecal matter into cuboidal shapes before the pellets leave the Wombat's anus.