Wombats are with poor eyesight, so they communicate mostly by scent. A mark only works if it stays somewhere prominent and raised, and on sloping ground anything simply rolls off. How do you solve that?
With the shape. A cube stays put on a sloping rock, where a sphere would roll down and vanish into the grass. Which turns the famous oddity into a : a solution to a communication problem rather than an anatomical curiosity. The honest part is that nobody has run the comparison directly, between a cubic mark and a round one under the same conditions.
The cube shape is the funny part, and the interesting question is why it is worth anything. The answer starts with the wombat being a nocturnal animal with poor eyesight, so nearly everything it tells its own kind runs on .
A scent message works better the higher it sits, because wind disperses further from a raised source. So a wombat looks for , a rock, a log or a small rise, and not flat ground.
And here the geometry comes in. A raised surface is almost always a sloping surface too, and a sphere rolls off it and disappears into the grass. A block with faces stays where it was put. The shape is not a strange property of the body but a solution to a problem of placement.
Worth keeping the measure right: the link between the shape and the communication benefit is an accepted and persuasive explanation, and no experiment compares a cubic mark with a round one under the same conditions. What can be taken from here is a good rule of thumb: a trait that looks random in nature is usually the solution to a problem we have not identified yet.
wat. On a sloping rock a cube stays where it was put, while a sphere would roll off and disappear into the grass.
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It is a reminder that a trait which looks random in nature is usually solving a practical problem that is hard to see at first.
How do we know?
Field observation of where wombats place their marks, combined with what is known about the anatomy of their gut and about scent-marking behavior generally.
What is still unknown
The link between the shape and the communication benefit is an accepted explanation rather than a tested one. No experiment compares a cubic mark against a round one.
Learn something?
Where to next
How do penguins decide who has to stand on the cold outside?behavior
Is handedness something only humans have?behavior
Is an octopus throwing silt at a neighbor, or just tidying up?behavior