To spot a fit partridge, check its fractal necklace
- 24 January 2013
- Magazine issue 2901.
HOW do you spot a fit partridge? Check out the fractals round its neck.
Fractal geometry is used when a pattern is too complex to be described by Euclidean geometry. It has been applied to coastlines, plant structures and animals' foraging patterns. Lorenzo Pérez-Rodríguez at the National Museum of Natural Sciences in Madrid, Spain, and colleagues wanted to see if it could also be helpful when analysing the complex plumage patterns of birds.
Using images fed into software, the team found that red-legged partridges with a more gradual transition between the plain and spotted areas of their bib have a higher fractal dimension (FD) - a measure of a pattern's complexity.
To see if this was linked to the bird's fitness, they compared the bibs of 68 birds of both sexes, half of which were on a restricted diet. After six months, the bibs of undernourished birds had a lower FD than before their food was reduced. Low FD also predicted poorer immune responsiveness.
Pérez-Rodríguez thinks that a fractal-rich bib could be used to advertise the health of the bird to potential mates. "Birds have quite a different visual system to ours," says Thanh-Lan Gluckman at the University of Cambridge, so the work could also help us understand what one bird sees in another.
Fractal bling (Image: Ernie Janes/naturepl.com)
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