There’s something tender — maybe even romantic — about penguin courtship. After spending months at sea, hunting fish and swimming in the colder waters, the female Adélie penguins (Pygoscelis adeliae) return to the same breeding grounds year after year. Wandering through a bar scene where the males are blowing trumpets and grooming themselves, they ignore advances and head for their mates from the previous season: the males who arrived before the females to tidy up the nest.
These penguins are models of long-term commitment. But are all penguins equally bonded to a single partner throughout their lives?
Turns out these penguins are the exception, not the rule. Although most penguins only mate with one partner per breeding season, they can mate with many other penguins in a breeding colony before settling on the nest. And loyalty rates vary greatly from species to species. Penguin love – it’s complicated.
“The short answer is no, penguins are not really monogamous,” said Emma Marks, a behavioral ecologist at the University of Auckland in New Zealand who studies reproductive behavior and mate choice in penguins. child. “Colonial breeders like penguins can be monogamous as they have a single mate that they nest with and raise chicks with each season,” Marks told Live Science. “But that doesn’t mean there aren’t ‘extramarital activities’ going on.”
It can be said that penguins are not sexually monogamous. Many penguins play in the field before settling down with a partner for the season. They sometimes mate with other colony members who have already been cast, resulting in soap opera-worthy drama, according to Marks.
One consequence of these messy love triangles is that by the time a female lays her egg, it’s not always clear whether the male she’ll spend the season with is raising her own young. A 2018 study published in the journal Zoo Biology described a gentoo penguin (Pygoscelis papua) in an aquarium in Utah that, due to the promiscuity of its mating mate, ended up raising two offspring that were the offspring of a different male. Scientists aren’t sure how common this phenomenon occurs in the wild because while trackers and other technologies can help researchers monitor mating behavior and pairing, there has been no concerted effort to test paternity paternity in the wild. say the study authors.
At the same time, penguins are more or less socially monogamous. It takes two committed partners to raise a chick in an environment as hostile as Antarctica, and penguins band together in pairs to effectively share the responsibilities of nesting, incubating eggs and hunting.
“Social monogamy is a prerequisite,” said Marks. “Chick rearing requires a lot of coordination between the two and if that broke down, the brood would be a failure for the season”
These social arrangements can persist over the long term, with each breeding season causing the same parents of two penguins to return to the nest for another year. How often this occurs depends in part on the species. A 2013 literature review published in the journal Comptes Rendus Biology showed that 89% of Galapagos penguins (Spheniscus mendiculus) remain faithful to their partner. In contrast, a 1999 study published in The Auk magazine showed that only 15% of emperor penguins (Aptenodytes forsteri) look for the same partner for subsequent breeding seasons. Most species return to the same mates at least somewhat consistently, with fidelity rates between 59% and 89%, according to the 2013 study.
The success of the previous season also plays a role in determining whether penguin pairs stay together long-term, says Marks. If the couple has successfully raised chicks to maturity and the male maintains a quality nest in a good location, the chances of a female returning to her former mate are usually higher. Otherwise, females are just as likely to waddle in search of greener pastures.
“For colonial species, there are many options available,” said Marks. “If breeding has previously failed, we generally expect to see more ‘divorce’ in the following season.”
Actual “divorce” rates, i.e. cases where penguins actively leave former mates in favor of new conquests, are difficult to calculate because not all penguins return to breeding grounds each season. When new pairs form, it can be difficult to determine if this is a personal decision or if the penguin only moved on after his other half did not return, for example he was devoured by an orca or a seal.
Predation isn’t the only threat to penguins’ love lives. A recent study published in the journal Ambio found that penguin populations decrease in proportion to the decrease in the amount of krill available for food. According to the study, climate change and human fishing activities are the main factors responsible for the reduction in the number of krill. Changes in sea ice due to climate also force penguins to travel to different breeding grounds, thus breaking long-term pairs and influencing migration. According to Marks, some males now arrive at breeding grounds exhausted from navigating the changing sea and ice landscape, too neglected to court females and too exhausted to properly care for the eggs.
Collectively, these factors are believed to have played a role in Halley Bay’s widely publicized failure. The breeding ground that once housed 25,000 pairs of emperor penguins each season has been barren since 2016.
“Climate change is likely lowering the success rates of breeding colonies,” said Marks. “Whenever failure rates are higher, we expect higher companion turnover rates.”