One of the easiest ways for us as humans to tell a loved one from a stranger is by looking at an individual’s face. However, this is not the case for African Penguins. These penguins live in large groups called colonies, where remembering all of the other members can get confusing. One colony member that a penguin definitely needs to be able to recognize is their mate. However, this can be difficult because mated pairs do not spend a lot of time together so they do not have the benefit of being familiar with one another. The lack of time spent together is the result of one partner going off to find food and bring it back during the time when they breed. This is why penguins require a way to identify their mate.
So how do these penguins recognize each other? Luigi Baciadonna and fellow researchers believe that these birds recognize each other using the dots on their bellies! To test their hypothesis, the researchers looked at 6 pairs (12 penguins in total) of mates and whether or not they could recognize each other in different situations. For each test, one of the 12 penguins was left in a separate room alone with two life size images of penguins, one that was their mate and the other of a penguin they lived with. The two images were separated by a triangular wall and a stick placed on the ground. The stick was used so that the researchers could tell which image the penguin was standing closer to (see figure).
To see if the 12 penguins could tell which image was their mate, the researchers used two cameras to record the penguin’s behavior. In these videos they observed how long the penguin looked at each picture and how long they stood near each of the images. They looked at these two actions because penguins consider their partners worth noticing and paying attention to, meaning that if a penguin looks longer at and stands closer to the picture of their mate, they likely recognize them.
In one test, the penguins saw pictures of their mate and a fellow colony member, both without their dots. The researchers did this because they wanted to see if the African penguins could tell which was their mate without the dots to help them. If they could, this would mean that the dots are not needed for penguins to tell each other apart.
The researchers also conducted another test where they covered the bodies of the pictures with wood so that the penguin being tested could only see the head of their mate and the head of the other penguin (see figure). This was done to determine if these penguins need to see another penguin’s entire body to know who they are looking at. It could be that the penguins are using the dots and the face of their mate to identify them and the researchers wanted to make sure that they considered situations like this.
So are these penguins able to recognize their partner based on their dot pattern? The results of this study say yes! The African Penguins did not spend more time looking at their mate when presented with a picture of their partner and of another penguin, both without their spots. They also did not tend to stand close to the picture of their mate. The penguins were unable to recognize their mate when only presented with a picture of their head as they did not stand close to or look at their mate for that much time. So if you notice an African penguin looking at another penguin’s stomach, they may just be checking to see if that penguin is their mate!
Baciadonna, L., Solvi, C., Terranova, F., Godi, C., Pilenga, C., Favaro, L. (2024). African penguins utilize their ventral dot patterns for individual recognition. Animal Behavior, 207, 13-21. https://doi.org/10.1016/j.anbehav.2023.10.005.
