DESPITE their tiny brains, fiddler crabs excel at trigonometry. Fiddlers constantly watch for other crabs that might steal their burrow, and when one nears, they can accurately triangulate the distance between that crab and their burrow, even if they have wandered so far they have lost sight of home.
Fiddlers鈥� eyes are adapted to their mudflat habitat, so an intruder鈥檚 position relative to the guarding fiddler is determined by its distance below the horizon. The intruder鈥檚 proximity to the burrow is then estimated by combining this with the fiddler鈥檚 inbuilt 鈥渨alking odometer鈥�, which tells it how far it has wandered from home. 鈥淭hese are very accurate but very simple short cuts,鈥� says Jan Hemmi of Australia National University in Canberra, who publishes his findings in Nature (vol 421, p 160).