July 24, 2007 They may seem deceptively innocuous mixed in with other waterfowl, but bar-headed geese can do with ease what most elite high altitude athletes can’t. Now a UBC zoologist is learning how.
Native to South and Central Asia, bar-headed geese, named for the dark stripes on the backs of their heads, are often bred in captivity as domestic garden birds. In the wild, they migrate annually between India and the Tibetan plateau in China, flying over the world’s highest mountains on their way.
“They fly at altitudes up to 9,000 metres,” says Zoology PhD candidate Graham Scott. “That’s the equivalent of humans running a marathon at the altitudes commercial airlines fly.”
Even at rest, humans struggle to cope with the low oxygen environments at high altitude. Mountaineers train for years before attempting to reach the peak of Mount Everest, where less than a quarter of the oxygen at sea level is available. Even with supplemental oxygen it takes them several weeks to summit. Some members of the highest human settlement -- La Rinconada, a mining village in Peru, at 5,100 metres elevation -- still suffer from lifelong symptoms of mountain sickness including headaches, nausea and sleep disorders.
Scientists have known that the blood of bar-headed geese -- specifically their haemoglobin -- is better at holding onto oxygen than low-altitude birds. “But there’s long been suspicion that something else is contributing to their extraordinary abilities,” says Scott.
By simulating high altitude conditions in the lab, Scott has learned one of the bar-headed goose’s secrets: Unlike humans and many other mammals, which take more frequent breaths to accommodate a lack of oxygen -- think running up stairs -- bar-headed geese take much deeper breaths.
“They take in almost twice as much air per breath as low-altitude birds and thus extract a lot more oxygen,” says Scott. “That, coupled with the ability to carry more oxygen in their blood, allows bar-headed geese to send more oxygen to their flight muscles, fueling the metabolism required to fly.”
The new insight allows scientists to better understand the limitations of human physiology and potentially find ways to exceed them, says Scott.
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