Lloyd Davis, zoologist at University of Otago, New Zealand, says that penguins use a practice similar to prostitution in order to obtain stones for their nests. Davis has made nine visits to Antarctica to study penguin behaviour. "They are not nearly as faithful as we thought,' he says. "They swap partners quite frequently,' he adds. Female penguins insulate their nests with stones, and males are expected to provide these. Davis points out that males get a quick copulation for their troubles, although they are often tricked by the females. "They give all the signals that they are going to court with the male, and most often, they will simply pick up the stones and run away,' he adds.