African penguin (Spheniscus demersus) Photo by Bernard DUPONT from FRANCE, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

Dear Readers, I don’t know quite why I find penguins so endearing. Is it that they walk upright, like us? Is it the way that they bustle along with such purpose, or is it maybe their determination when faced by obstacles like finding their mate in an enormous colony of thousands of individuals? Scientists have been studying African/Cape Penguins (Spheniscus demersus) to find  out what they can about the species’ breeding behaviour – this is one of the rarest penguins in the world, with an estimated total population of less than 21,000 birds in 2019. A combination of a fall in the numbers of sardines and anchovies available for the birds to feed on, oil spills and pollution, avian flu and human persecution have led to the African penguin being on the IUCN Red List. One possible point in its favour is that it doesn’t require the very low temperatures of some other penguin species, and that it seems to breed easily in captivity – zoos are cooperating in establishing a captive breeding population in case the wild birds reach a point of no return.

Which brings us back to mate recognition. How do penguins recognise one another? African penguins form lifelong pair bonds. It’s been known for a while that they can pick out their partner’s call from all the other birds in a colony, but scientist Luigi Baciadonna, of the University of Turin, wondered if the penguins could also recognise one another visually.

If you look at the photo above, you’ll see that the penguin has a very distinctive pattern of spots on its chest. These spots remain in the same position after every moult, so Baciadonna wondered if they had a special significance. To find out, they tested 12 birds at a zoo near Rome.

First up, they made life-sized images of the penguins, showed them to the live birds, and recorded their responses. Individual birds spent more time gazing (lovingly, I’m tempted to add) at the photos of their partners than they did of any of the other familiar penguins. This was true even when the heads of the images of the penguins were obscured, so clearly our obsession with the face of our beloved isn’t replicated in the African penguin.

Then they showed the penguins two images of their partner, one with spots, one with the spots removed. The penguins preferred their ‘spotty’ partner. But when the birds were shown their partner with the spots removed and another unspotted bird, all preferences disappeared. Baciadonna and his team believe that this shows that the spots are critical to mate identification.

African Penguin at the Western Cape (Photo by Derek Keats from Johannesburg, South Africa, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons)

It’s estimated that there has been a 95% drop in the number of African penguins during the past century. Anything that helps us to understand these extraordinary birds, and to help them to survive, has to be useful information.