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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.
“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.
Source
PLoS One citation
