You might have heard that penguins mate for life, but for little penguins, the grass is often greener. These tiny birds, found in Australia and New Zealand, divorce their mate if they’re not happy with how many chicks they’re producing.
“Divorce and nookie in the local hotel is a really important part of [a penguin’s] life,” says Rory Wilson, a penguin expert at Swansea University, Wales.
Now, researchers have discovered the surprising impact of penguin break-ups. The number of divorces impact the colony’s reproductive success more than factors like sea temperature and foraging efforts.
This connection gives researchers a handy clue for predicting the future health of the colony and protecting it from harm, as penguin habitats get warmer with climate change.
What we know about little blue penguins
Little blue penguins (Eudyptula minor)—also known as little penguins or fairy penguins—are the world’s smallest species of penguin, growing to an average of just 12 inches high.
Phillip Island, southwest of Melbourne, is home to around 30,000 of these tiny birds. “It has the world’s largest colony of little penguins,” says Richard Reina, a biologist at Monash University and coauthor of the new study published in Ecology and Evolution exploring the surprising repercussions of penguin divorce.
After a day foraging at sea, the tiny birds return to their burrows in the hillside. Some of the colony live in special nesting boxes and are microchipped, just like a pet cat or dog, so scientists can easily scan them to collect data on any of the birds in the box.
“You can just put a reader and go ‘blip’ and it tells you who’s at home,” says Wilson, who wasn’t involved in the study.
During the breeding season—September to February—researchers record which birds are paired in nesting boxes or “married”, when they lay eggs and when the eggs hatch as well as the chicks’ growth and survival rates. They also note if any pairs separate or “divorce”.
How penguin ‘divorce’ works
Although it might feel “a bit unfair,” a penguin with a subpar partner might think, “I’m going to go and find someone else, and then things will be better,” says Wilson. Splits often happen when pairs fail to reproduce.
But this tactic is risky. “That new partner may not actually be better. They potentially could be worse,” says Reina.
It also takes time and “faffing” to find and bond with a new partner, says Wilson. This means penguins “might skip a breeding season because they haven’t got their act together.”
Reina his colleagues examined penguin divorce rates over 13 breeding seasons. On average, around one in four pairs found new partners each year but the divorce rate in one year could be as low as one in 20 or as high as one in three. This high variability of divorce rates was “fairly unexpected,” says Reina.
And the complex love lives of these little birds could have unexpected ripple effects for the whole colony. Years with a higher divorce rate were strongly correlated with lower fledgling success and vice versa.
The divorce rate was also more reliable for predicting future breeding success than environmental or behavioral factors, like sea surface temperature or foraging habits.
Other species—including King (Aptenodytes patagonicus), Emperor (Aptenodytes forsteri), and Adélie penguins (Pygoscelis adeliae)—are also known to divorce, but whether their divorce rates impact the the health of their colonies remains to be studied.
Protecting little penguins
Currently, the Phillip Island population is doing well. “Little penguins are very good at buffering themselves against environmental disturbance,” says Reina because they can adapt where they forage and for how long.
Another survival strategy is abandoning their chicks when food is lacking. “It’s heartbreaking to see because there will be all these chicks in the colony starving to death,” says Reina.
But this seemingly heartless move protects the adult, so they can reproduce again in future. “If it abandons the chick, there’s always next year and the year after that,” he says.
“Understanding the factors that influence breeding is essential for assessing their long-term survival,” says Diane Colombelli-Négrel, a behavioral ecologist at Flinders University in Australia, also not involved in the study.
Experts could potentially predict how successful upcoming breeding seasons will be based on penguin divorce rates. This is particularly important as human activities continue to impact the ocean.
“The Bass Strait, where these penguins feed, is warming much faster than the global average,” says Reina. Scientists worry penguins can only withstand their changing environment for so long before they reach a tipping point.
“The bottom line is, of course, the environment plays God in this,” says Wilson. “If there are no fish, that’s it. You can forget it.”
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