Penguins are fascinating creatures. Between their inability to fly and their unique vocalisations, is it any wonder that scientists find them a compelling subject of study?

More specifically, one group of scientists sought to understand how African penguins (Spheniscus demersus) recognised their partners among all the other penguins who lived nearby. These penguins are one of 18 species found globally and the only one to inhabit southern Africa.

Penguins have a sophisticated identification process based on vocalisations. In other words, they are able to recognise each other based on the sound of their calls—an impressive ability when you consider how loud and crowded penguin colonies can be. In addition to auditory cues, their sharp eyesight may also be important for recognising individuals. However, we still didn’t know much about how they use visual cues to identify other members of their species.

This was the question that scientists hoped to answer. Before continuing with our story, there are a few things to know about African penguins. First of all, they have monogamous, life-long partners, meaning that they will only nest with one other penguin throughout their lives. It is, therefore, essential for them to be able to quickly and accurately recognise their mate within the colony. Second, African penguins have a pattern of little dots on their bellies. Each penguin has a different pattern, making them unique to the individual. These are very useful to zookeepers and other humans who need to identify individual penguins.

Our scientists came up with a hypothesis: perhaps African penguins use these ventral dots to recognise their mates. If zookeepers can use these markings to tell penguins apart, isn’t it likely that the penguins might do the same?

Using a captive colony of African penguins in Rome, the researchers set up a range of tests. Each adult penguin, who already had a partner, was shown a pair of life-size pictures of two different individuals. Numerous variations of these pictures were presented to the test penguins, but the key variations were as follows:

Test 1 showed full-body pictures of their partner and a non-partner.

Test 2 had full-body pictures of their partner, and their partner but with the little dots removed.

Test 3 had full-body pictures of their partner and a non-partner, both without the dots.

Test 4 showed only the heads of their partner and a non-partner.

Test 5 showed only the bodies of their partner and a non-partner.

The penguins were shown these life-size pictures side by side, and the scientists measured the time they spent looking at each picture. The idea was that they would look at their partner longer than at a non partner, because their partner would be more interesting to them than a neighbour with whom they had no particular attachment. The scientists also hypothesised that if the little belly dots were missing, the penguins wouldn’t be able to distinguish their partner from a non-partner, and would pay equal attention to both pictures.

And that’s pretty much what ended up happening—when given the choice between their partner and a non-partner, they spent more time looking at their partner. But when the dots were removed, they didn’t exhibit any preference towards either of the pictures.

While this experiment doesn’t show that penguins depend exclusively on the dots to recognise their partners, it does demonstrate that these dots are an important visual cue and a feature that African penguins use to recognise each other.

This may seem like a small and insignificant conclusion, but in fact it is very useful for conservation biology.African penguins are unfortunately endangered, and anything we learn about them can inform conservation efforts. The possibility of understanding individual recognition—which is important for their breeding strategy—is essential for us. By connecting the dots between various studies, we can piece together a broader picture that will hopefully lead us to reversing the endangered status of African penguins.

Further Reading

Baciadonna, L., C. Solvi, F. Terranova, C. Godi, C. Pilenga and L. Favaro. 2024. African penguins utilise their ventral dot patterns for individual recognition. Animal Behaviour 207: 13–21. doi.org/10.1016/j.anbehav.2023.10.005.