01 October 2011

Smell you later, cousin

Humboldt penguins at Brookfield Zoo.
Photo credit: Jim Schulz/Chicago
Zoological SocietU
USA - They may all smell the same to us humans – stinky – but “groundbreaking” research has shown that for penguins, other penguins’ odours are a distinguishing feature, and that the birds may use smell to determine if they are related to a potential mate.

Research by the University of Chicago and the ChicagoZoological Society, which manages Brookfield Zoo, shows how related Humboldt penguins are able to recognise each other. The study, published in the journal PLoS ONE, could help conservationists design programs to help preserve endangered species. 

“Smell is likely the primary mechanism for kin recognition to avoid inbreeding within the colony,” said Heather Coffin, lead author of the paper.

Coffin conducted the research while a graduate student at the university. Co-authors of the paper are Jill Mateo, associate professor in Comparative Human Development, and Jason Watters, director of animal behaviour research for the Chicago Zoological Society.

“This is the first study to provide evidence for odour-based kin discrimination in birds,” said Mateo, who is a specialist on kin recognition.

Experts said the work offers important insights into how birds use smell to guide behaviour.

Mark E. Hauber, professor of psychology at Hunter College and a specialist on bird social recognition said that the research group’s work was “truly groundbreaking” in that it shows for the first time ever in birds how the captive penguins’ sense of smell “is both informative and functional in a behaviourally critical context: namely the recognition of friends from foes in general, and relatives from non-relatives in particular.”

Penguins are ideal subjects because they typically live in colonies made up of thousands of birds. They live in monogamous pairs, an arrangement that helps them raise their chicks, since parents frequently take turns leaving the nest to gather food. Despite the size of the community, mates are able to find each other after travelling for days foraging for food in the ocean.

Research on other sea birds has shown that smell helps guide birds to their home territory and helps them forage for food. Other research has shown that birds could use sound and sight to recognise each other, but no other studies have shown that smell might be used in connection with kin recognition, Mateo said.

In the study conducted at Brookfield Zoo, which has extensive records on which penguins are related and have been housed together, researchers first sought to determine if the penguins were able to recognise familiar individuals by smell. They constructed an experiment using a dozen penguins, from a group that included breeding pairs, their offspring and non-breeding individuals. The Humboldt penguins were from groups either on exhibit or off exhibit.

Researchers took odour samples from glands near the penguins’ tails, where an oil that the birds use for preening is secreted. They put the oil on cotton swabs and rubbed the odour inside dog kennels, similar to the enclosures penguins at a zoo use for their nests. They also put the odour on paper coffee filters and placed them under mats inside the kennels.

When the penguins were released to the area containing the kennels, the researchers found that penguins spent more time in the kennels with familiar odours. The penguins were able to distinguish between the odours of birds they spent time with and the odours of unfamiliar penguins.

“It’s important for birds that live in large groups in the wild, like penguins, to know who their neighbours are so that they can find their nesting areas and also, through experience, know how to get along with the birds nearby,” Watters said.

Because offspring usually return to the same colony for nesting, siblings have the potential of becoming mates – something that can be avoided by their smell mechanism, the new research shows.

Researchers also found that when the birds were exposed to the odours of unfamiliar relatives and unfamiliar non-relatives, they spent more time in the kennels with odours of unfamiliar non-relatives. 

This indicates they were probably able to determine by smell which animals they were related to and were more curious about the novel odours. Researchers said that being able to make the distinction may help the penguins avoid mating with kin.

The discovery also could assist zoos in managing their breeding programs – and may relieve some zoo staff of one of their duties. “It could also be true that birds do a better job determining who potential mates are than do people in zoos, who spend a great deal of time lining up the appropriate matches,” Watters said.

The ability of birds to be able to recognise familiar scents and thus be guided to their home territory also has potential value to naturalists, he added. “You could imagine that if you were trying to reintroduce birds to an area, you could first treat the area with an odour the birds were familiar with. That would make them more likely to stay.”

Bryan D. Neff, professor and associate chair of biology, University of Western Ontario and an expert on kin recognition, said, “What I found particularly notable about the study was that the authors identified the oil secreted from the penguins’ preen gland, which is rubbed on the feathers to make them water repellent, as the odour source used in recognition.

“Oils are used in kin recognition by species of other animals, most notably a variety of insect species, including bees and wasps, which when considered with the penguin data provide a wonderful example of convergent evolution.”

Convergent evolution describes the process of unrelated species having acquired the same biological trait.

Smells may help birds identify their relatives by William Harms, 21 September 2011, UChicago News

PLoS One citation
Odor-based recognition of familiar and related conspecifics: a first test conducted on captive Humboldt penguins (Spheniscus humboldti). Coffin HR, Watters JV, Mateo JM (2011) PLoS ONE 6(9): e25002. doi:10.1371/journal.pone.0025002

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