Isabelle Robertson and Madison Thomson, of East Taieri School, asks :-

How do mother Emperor penguins know if their chick is a boy or a girl?

Kerry Barton, a penguin expert with Landcare Research, Nelson, responded.

I don’t think anyone knows for sure (it hasn’t been tested scientifically) how a mother Emperor penguin knows if her chick is a boy or a girl. Most animals use visual (size, shape, colour), smell, and calls to identify and sex other animals. In penguins where they all look the same I don’t think that a mother penguin would be able to tell if a chick was a boy or girl by looking at it. We know smell is important for identifying the sex of mammals, and some seabirds may find food by smell but there is no work that shows that smell is used by penguin parents to identify the sex of their chicks.

We do know that penguins can identify their mates/parents/chicks by their call. Each bird has a unique call (known as a display call); a mother penguin can pick her own chick’s call out of a crèche (a huddle) of chicks, some of these crèches can contain hundreds of chicks. She can also recognise her mate in the same way.

Calls have a really important role in building a strong bond between parents and chicks and this starts at the egg stage. Remember a penguin can hear its chick pepping even when it’s in the egg.

We think that a call tells a listening bird more than just its identity. For example Adelie females are more likely to choose mates with deep calls. A deep call means a male is in good condition and therefore likely to be a better father – their call proves that they are well feed and therefore good at catching fish and krill which means their future chicks will get more food. So it is also likely that a chick call will provide a mother penguin with information on their condition (e.g., if they are hungry) and may be also if they are a boy or a girl.

Most penguin species have nests. When a mother penguin returns from sea she will go straight to her nest and vocalise, reconnecting with her mate and chick. If her chick is old enough it will not be at the nest but in a nearby crèche but still the mother’s call will be heard by her chick. The chick will call back and then rush to the nest for food.

Emperor penguins don’t have a nest site, father penguins and their chicks huddle with other birds to stay warm and move around on the sea ice. There is no one spot (like the nest of other penguin species) that a mother penguin can return to to find her mate and chick. When she returns to the colony from the sea she has to find her mate and chick by calling to them and listening for their response as she moves through the colony. And all this happens in a noisy colony where thousands of other birds may also be calling and under extreme Antarctic conditions.

Emperor penguins are probably only able to hear and identify their mates in this environment (no landmarks to navigate by, lots of noise, thousands of birds all looking the same) because unlike us, they are able to produce two voices (harmonically related sounds) at the same time (like a 2-person choir) from their syrinx, the avian vocal organ. This means they are able to convey a lot of information in their calls and their calls travel further so they increase their chance of finding mates and chicks