Thanks to the 2006 movie Happy Feet, the role of male penguin vocalizations in attracting mates is well known. (The movie focused on Emperor penguins, but males of many penguin species use calls to get the girl.) The purpose of this film was to entertain, not to explain why females find the calls of some males more attractive than others, but a recent study explored female mate choice in Adelie penguins.
Female penguins find parenting ability desirable in mates. Females want males that will make good dads, and the calls allow females to choose males accordingly. That’s because calls reveal how much fat males have stored up, and the extreme energetic demands on penguin dads mean that males with more fat are more likely to be successful dads. Female penguins choose pudgy males over lean ones. (I know, there are plenty of men reading this and thinking, “If only . . . !”)
The more energy males have stored, the better care they can provide to their offspring, and superior care increases the likelihood that the young will survive. After laying her eggs, a female Adelie penguin returns to the ocean, leaving the male to guard and protect the eggs until she returns. For the first two weeks, males perform the majority of parental duties, so they have little opportunity to eat. While caring for their young, penguin dads can lose up to a fifth of their body weight.
Female penguins cannot tell how fat males are simply by looking at them. Males can vary their appearance by fluffing up their feathers and changing their posture. It is to males’ advantage to attempt to fool females into thinking they have more fat than they do, but for females, it’s vital to assess males’ fat stores accurately.