When a penguin chick begs for food, it makes its siblings鈥� hearts flutter.
Begging calls encourage a chick鈥檚 parents to regurgitate freshly collected food.
But by recognising its siblings鈥� calls, a wandering chick can home in on its
parents to get its share of the spoils, say Shinichi Nakagawa and Joe Waas of
the University of Waikato in Hamilton, New Zealand.
They measured the heart rates of penguin chicks while playing back calls from
siblings, unknown chicks and neighbours (Behavioral Ecology and
Sociobiology, vol 50, p 180). The chicks鈥� heart rates shot up an average of
10 beats per minute when they heard siblings鈥� calls rather than those of
unfamiliar chicks.
