A 13-year study of tiny penguins in Australia has dispelled the long-held myth that these seabirds mate for life, with the 'divorce rate' nearly 10 times that of the current statistics for US adults. And, not surprisingly, it all comes down to kids.
While not every species flap their wings at lifelong monogamy – there's evidence that Adelie (Pygoscelis adeliae), for example, will remain coupled-up as long as their partner is on time to reunite at the start of breeding season – Monash University scientists found a much higher rate of separation among the 2-lb birds found in Australia and New Zealand.
It may seem like an odd aspect of behavior to study, but through their research the scientists were able to gauge a lot more insight into what impacts and threatens penguin populations. Previously, environmental disturbances and specific behavioral traits – such as time spent foraging – have been seen as key factors in the change in colony numbers. The Monash team found that breeding seasons with low birthrates resulted in a higher number of 'divorces,' with the birds not satisfied by the lack of offspring they were able to produce with their chosen mate.
“In good times, they largely stick with their partners, although there’s often a bit of hanky-panky happening on the side,” said Richard Reina, a professor in the School of Biological Sciences at Monash. “However, after a poor reproductive season they may try to find a new partner for the next season to increase their breeding success."
From 2000 to 2012, the team peered into the secret lives of around a thousand pairs of little penguins on Phillip Island, in southern Australia – which is home to the world's largest colony of the species, numbering an estimated 37,000 birds. They found a direct correlation between low hatching success and increased separations
“Our study looked across 13 breeding seasons, tracking which individuals changed partners, or divorced, from one season to the next," said Reina, who has spent two decades studying these birds. “We recorded nearly 250 penguin divorces from about a thousand pairs throughout the study, and we found that years with a lower divorce rate resulted in higher breeding success.”
Data were gathered from around 100 artificial nest boxes, which were about 70% occupied each breeding season. Some 50-98 pairs were monitored each year, with the penguins tagged with electronic transponders for easy identification. Nest attendance and reproductive stages were recorded three times a week across the 13-season study.
Overall, the average divorce rate was 26%, but this dropped significantly when there were higher hatching and fledging successes.
So what does this mean for the little penguins? While we can't do a whole lot about nature taking its course, it does offer a rare glimpse into the social dynamics that have a direct impact on population size – independent of the factors that are usually the focus for conservation, including climate change and habitat disturbance.
“Our findings on lower divorce rates among little penguins at Phillip Island under favourable environmental conditions highlight the importance of considering social dynamics alongside environmental factors when designing strategies to protect vulnerable seabird species,” said Phillip Island Nature Parks Marine Scientist Professor Andre Chiaradia.
Of the 18 currently known and defined species of penguins, 11 are Globally Threatened according to the IUCN Red List. Despite the significant divorce rate, the little penguins are one of the seven species not yet on the threatened or endangered list.
The study was published in the journal Ecology and Evolution.
Source: Monash University
