Contrary to popular belief, penguins are not paragons of marital fidelity. While scientists consider many species of penguins to be monogamous, the notion that these marine birds choose a lifelong partner and never stray is a misconception. A team of researchers from Monash University in Australia studied a mega-colony of little penguins (Eudyptula minor) on Phillip Island and found that their divorce rate is significantly higher than that of humans. It’s true that little penguins often mate with the same partner for years, but experts assert that around 50 percent of pairs end up separating.
What did the scientists discover? Although most penguin species form pairs with the same partners as the previous year during the breeding season, these bonds do not always last a lifetime. The mega-colony of little penguins on Phillip Island boasts over 37,000 individuals, providing a substantial sample for studying the dynamics among these birds. Over 12 breeding seasons, the university team identified about 250 divorces within a cohort of around a thousand paired individuals. In comparison, the annual divorce rate in the U.S. is approximately 2.4 per thousand marriages, which the researchers calculated to be nearly ten times lower than that of the studied seabird species.
“Penguins generally remain loyal to their partners, although they often have flings on the side,” noted ecophysiologist Richard Reina, who has studied the island colony for 20 years. “After an unsuccessful breeding season, they may seek a new partner for the next season to improve their chances of reproductive success,” he added. Thus, it turns out that little penguins are not particularly devoted. And they are not the only species that defy the human illusion of eternal love among penguins, as reported by Science Alert. For instance, emperor penguins (Aptenodytes forsteri) and Adélie penguins (Pygoscelis adeliae), which typically mate in pairs, often stray as well. This indicates that they are not truly sexually monogamous. One previous study found that only 15 percent of emperor penguins stay with a single partner over multiple breeding seasons.
Penguin divorces as a positive factor for species reproduction Last year, marine biologist Andrea Chiariadia from Monash University told ABC that due to climate change, little penguins on Phillip Island have started breeding earlier, giving them more time for infidelity. Moreover, according to the scientist, “they could have four to five partners in one night.” He believes that the divorce rate among little penguins is the most consistent factor that can predict the reproductive success of the colony. The authors of the new study noted, “In little penguins and other seabirds that pair for several seasons, reproductive success tends to increase over time. However, divorce can also be an adaptive strategy to enhance long-term reproductive success, especially when previous reproductive success has been low.”
According to the researchers, during such times, a “higher quality” partner may emerge, displacing a lower-quality individual. The findings of the study were published in the journal Ecology and Evolution.