A new study published in the journal Ecology and Evolution reveals that the notion of penguins as lifelong monogamous creatures is not entirely accurate. Researchers from Monash University and Phillip Island Nature Parks found that divorce among little penguins (Eudyptula minor) is linked to enhanced breeding success.
While little penguins typically have the same breeding partner for many years, they also seek chemistry with other partners. This leads to relatively high divorce rates that are not universal across all penguin species.
"In good times, they mostly stay with their partners, although sometimes an affair happens," explained Richard Reina, an ecophysiologist at Monash University who has studied the island colony for 20 years, according to Live Science. "However, after a poor reproductive season, they may try to find a new partner for the next season to increase their breeding success," Reina added.
According to Phys.org, the research, conducted over more than a decade, investigated how environmental and social factors, including divorce, influence reproductive success among Phillip Island's little penguins. The team monitored a site called Penguin Parade on the west side of Phillip Island, where visitors can watch penguins return from the ocean to their nests. Richard Reina and colleagues observed the penguins over 13 breeding seasons from 2000 to 2012.
Over the study period, the researchers documented nearly 250 divorces among about 1,000 pairs. According to Phys.org, they counted a divorce when a tagged little penguin from the previous breeding season returned with a new mate. The population of little penguins on Phillip Island is over 37,000, and the sample size provides a good indication of the situation on a larger scale.
Experts believe that the divorce rate among little penguins can fluctuate each year, sometimes reaching up to 50%, particularly during less productive breeding seasons. Researchers observed that years with lower divorce rates correlated with higher breeding success among the penguins, indicating a strong link between stable pairings and reproductive outcomes, as reported by Phys.org.
"The decision to separate and seek new partners appears to be a risky one that may reduce their next breeding attempt, especially after a failed breeding season," the researchers noted.
New couples aren't as effective at breeding and producing offspring as pairs that have spent more time together, and they may struggle with nest-building, egg incubation, and chick-rearing. The study found more divorces and new pairings in a breeding season are associated with lower overall reproductive success across the little penguin colony.
Environmental factors such as sea surface temperature had no significant effect during the study period. "Divorce rates appear to be a more reliable predictor of the reproductive success of the colony than environmental factors like habitat change or behavioral traits," stated Reina.
Matt Simpson worked with Professor Reina and Professor Chiaradia on this research as his honours project while completing a Bachelor of Science at Monash University, according to Phys.org. "I'm proud to have been able to make a significant contribution to the conservation of these fascinating birds by helping find new ways of identifying patterns that indicate the health of these bird populations," Simpson said.
The colony on Phillip Island is home to a popular Penguin Parade that attracts thousands of visitors each year to watch the little penguins waddle home from the ocean to their burrows at dusk. Little penguins are the smallest penguin species in the world and are found in Australia and New Zealand. They are also called little blue penguins or fairy penguins. They stand about 12 to 14 inches tall and weigh roughly 3 pounds, slightly bigger than a standard bowling pin.
While the study focused on little penguins, other penguin species demonstrate different levels of mate loyalty. According to Forbes, gentoo, yellow-eyed, and Magellanic penguins demonstrate high levels of mate loyalty, with over 80% of pairs reuniting annually. In contrast, emperor penguins and Adélie penguins are not known to be sexually monogamous and often partake in extracurricular activities even when they have a partner, according to Science Alert.
According to Science Alert, a study from 1999 found that only 15 percent of emperor penguins stay with the same partner for consecutive breeding seasons, while other species have shown higher rates of social monogamy, reaching nearly 90 percent.
This article was written in collaboration with generative AI company Alchemiq