14 DAY TRIAL // During the summer mating season, female penguins choose their mate. To attract them, males fluff up their feathers and emit mating calls. These calls show females how fat the male is, and the fatter the male penguin, the more successful it is.
Researchers noticed for a while now that female penguins have certain preferences for big mates. This is quite logic if we think that the companions split “childcare” equally, and the egg must be kept warm even for two weeks continuously. The extra fat only means that the male can babysit without needing to look for food. What the researchers found out is how does the females recognizes the “fatness” in the voice.
The subjects chosen for this research were Adelie penguins, a species of Antarctic penguins that comes to shore once a year, on Ross Island. After analyzing dozens of males for three months, scientists found a link between the penguins' voice and body mass. Although the sounds emitted were not very melodic and sounded rather like “a cross between a donkey and a stalled car,” according to study researcher Emma Marks of the University of Auckland, New Zealand, females chose some over others. The key to this mystery appears to be the stability of the frequency in the male's voice. Researchers do not know yet if body fat is what stabilizes this frequency but they admit this is a possibility.
According to study researcher Dianne Brunton of Massey University in New Zealand, “a fat male is a good choice for a female, because males do so much of the offspring care. They're able to incubate the eggs for longer and use up their fat stores, while skinny males aren't able to do that.”
Each summer, Adelie penguins spend a few months on land, to breed and raise their chicks. After the egg is laid, the female returns to sea for two weeks, leaving the babysitting to the males. After sitting on the egg to keep it warm and not eating for 14 days, the male penguin is relayed by its mate. Over the breeding season, fat penguins can lose up to 20 percent of their body weight.
Having observed the male's voice before and after the summer season, scientists said that it changes radically. Therefore, they added that even for the smartest penguin it would be impossible to fake its voice and trick a female.