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Inside JEB |
CHICKS SNOOZE TO SNIFF
kathryn{at}biologists.com
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By the time a 45-day-old blue petrel chick emerges from its burrow to embark on its maiden foraging flight, both parents have taken off, leaving the youngster to fend for itself. So how does the youngster know what to look for when hunting krill? Gabrielle Nevitt is fascinated by the way procellariiform seabirds, such as blue petrels and thin billed prions, track down food with their sense of smell, and wondered whether the youngsters recognise their prey's smell even before they have left their burrow. Working with Henri Weimerskirch and Francesco Bonadonna in France, Nevitt and her lab decided to test the chick's responses to a range of smells, some of which they'd encounter in their natural surroundings (p. 1615).
However, Nevitt suddenly had to cry off on the eve of departing for the sub-Antarctic, so Greg Cunningham stepped into the breach and headed south to join Weimerskirch's team, where they intended to record the chick's reactions using a noninvasive electrophysiological test. And when they finally arrived at the shack that would be their laboratory for the next month, the electricity supply was too unreliable to use for the sensitive tests; `it was a frustrating time' remembers Nevitt. But Cunningham had a backup plan. Just before leaving California, he had read a paper describing how sleeping chicken chicks responded to puffs of odours by `peeping' gently in their sleep. Could he get the same response from dozing petrel chicks?
He headed back out to the nesting site to retrieve chicks from their burrows, before lulling them to sleep with the warmth from a light bulb and testing out their nostrils with dimethyl sulphide (DMS). The simple approach worked spectacularly well! The blue petrels and prions stirred, and sometimes even woke up, whenever Cunningham puffed a whiff of DMS past their nostrils, while the diving petrel's slumber remained undisturbed.
Nevitt admits she was surprised by the diving petrel's lack of response to DMS, but it could be related to their hunting strategy. There is evidence that both blue petrels and prions hunt by tracking the plumes of dimethyl sulphide that mark the site of a krill swarm, while diving petrels `fly like bumble bees over the ocean, attacking waves and... diving a considerable distance' and probably rely less on their sense of smell while tracking prey. In fact, Nevitt believes that the diving petrel chicks probably can smell DMS, but `they don't respond to it in this context' she explains.
Nevitt is delighted that such a low-tech approach has proved so successful, allowing the team to reliably test large numbers of chicks in Antarctica's inhospitable conditions in the most peaceful way imaginable.
References
Cunningham, G. B., Van Buskirk, R. W., Bonadonna, F.,
Weimerskirch, H. and Nevitt, G. A. (2003). A comparison of
the olfactory abilities of three species of procellariiform chicks.
J. Exp. Biol. 206,1615
-1620.
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