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.
Penguin calls are honest indicators of energy stores, according to a recent study by a team of researchers who spent three months on a remote island in Antarctica where half a million Adelie penguins spend the summer. These scientists weighed many males, recorded their calls, and noted how successful they were at attracting mates and at rearing chicks.
One part of the call was associated with high mating and reproductive success. Males who maintained a steady frequency during an extended chattering in the middle of the call were most attractive to females and were chosen first. These males were also heavier and more successful as dads. Researchers believe that the fat around the voice box stabilizes the calls. As males lose weight while caring for chicks, their calls become less consistent in pitch.
Males can’t lie about their portliness because their calls reveal the truth. That’s why the females choose mates based on their calls and are impressed by calls produced by males with larger fat stores. While the female penguins find the calls attractive, one researcher described the sound males make as a cross between a donkey and a stalled car. To each her own!
I hope dads of all sizes had a happy Father’s Day!
Karen B. London, PhD, is a Certified Applied Animal Behaviorist, Certified Professional Dog Trainer, author and an Adjunct Faculty in NAU’s Department of Biological Sciences.