THE colour of some fruits is a good indicator of their nutritional quality. Orange and yellow fruits in the Venezuelan rainforest are rich in protein, but low in carbohydrates, whereas blue fruits have the reverse profile. Trees may use colour in this way to encourage animals to eat the fruit and disperse the plant’s seeds.
Hinrich Schaefer and Veronika Schmidt at the University of Freiburg in Germany measured the nutrient content of 45 species as well as the light reflected by the fruit at various wavelengths, including UV, which birds can see (Biology Letters, DOI: 10.1098/rsbl.2004.0191).
But, around half…
