Do penguins mate for life? Pair bonds, divorce and mate fidelity

Not all penguins mate for life. Some gentoo pair bonds do last an entire lifetime, and yet the same species also breaks them up, since Animal Diversity Web puts the gentoo divorce rate at less than 20 percent, a level it calls relatively low compared with other penguin species.

A study in Ecology and Evolution on little penguins recorded a divorce rate that averaged 0.26, with figures running from 0.05 to 0.36. Animal Diversity Web also reports that king penguins pair less faithfully than smaller penguin species, and the San Diego Zoo Wildlife Alliance science blog says recent studies have shown that, given the opportunity, some South African penguins stray from their mate.

How a divorce is recorded in little penguins

In that little penguin study, divorce means the end of a breeding pair bond, after which both birds go looking for new mates. A bird counts as divorced when its partner from the breeding season right before turns up in the colony but is paired with a different bird in the season now under way.

The Summerland Peninsula study site held approximately 100 artificial nest boxes, and the data came from them across 13 breeding seasons running from August to February. The population there was given as about 28,000 to 32,000 penguins, and swapping partners again within a season, right after a breeding attempt with the replacement bird, is rare in little penguins.

What a higher divorce rate means for a colony

The little penguin paper notes that several things push divorce along, among them environmental stressors and reproductive failure, and it treats divorce rates as a dependable predictor of reproductive outcomes. That paper found a strong correlation between years of high divorce rates and low fledgling success.

The same paper adds that the whole population can see its breeding output drop for that season. Its authors go further, suggesting the divorce rate could be used as a useful, noninvasive indicator of reproductive success in seabirds generally.

Gentoos: what a lasting bond saves

A gentoo stays with one partner through a single breeding season. Staying together has a practical payoff, since mates that keep each other are spared the time and energy of finding new partners year after year.

There is a flip side when a gentoo female does change partner. In the case Animal Diversity Web describes, she picks a new partner that has already shown greater reproductive success.

Why a king penguin pair ends

Animal Diversity Web says no definitive answer is available as to why king penguins end a pair bond. It puts forward two candidates, the timing of the birds’ arrivals at the colony and how much fat a penguin carries.

When the two mates reach the colony at different times, breeding can be postponed or a new mate may be chosen.

What African penguin pairs do

The San Diego Zoo Wildlife Alliance fact sheet on African penguins describes pairs that can stay bonded into future mating seasons, though they do not always manage it. The same fact sheet describes the courtship itself, where a male courts a female with a donkey-like bray.

African penguins rely on three calls, and one of them is used by partners to find each other when one is at sea and the other on land.

African penguins become sexually mature at around four years old, and the fact sheet gives a lifespan of 18 to 22 years on average. A San Diego Zoo Wildlife Alliance science blog adds that South African penguins can store sperm from multiple donors, so DNA from several donors may appear on a single egg.