Each year, bar-headed geese migrate over the Himalayas from India, at sea level, to the Tibetan highlands in China and Mongolia. This journey includes an elevation change of more than 26,000 feet in eight to 12 hours.
“They’re the astronauts of the bird world,” said Julia York, a graduate student at the University of Texas at Austin who has been studying bar-headed geese since she was an undergraduate at the University of British Columbia.
Humans who climb the Himalayas have to acclimatize or use an oxygen mask. The bar-headed goose, however, uses oxygen more efficiently. Scientists have known for decades that these geese have an enhanced ability to bind oxygen in their hemoglobin, a process that moves large quantities of oxygen to individual cells.
In the past, experiments have been done on bar-headed geese that were resting or walking on a treadmill. Studies have demonstrated that bar-headed geese have more capillaries around individual cells in their pectoral muscles than barnacle geese and other related species that don’t fly at such high altitudes. Those cells are also dense with mitochondria, which use oxygen to supply energy to the cell.
Additionally, bar-headed geese hug the terrain as they fly over the Himalayas, taking advantage of the relatively more oxygen-rich air over valleys.
A study published Tuesday at eLife highlights the work of Jessica Meir, an astronaut and physiologist, and her colleagues, including Ms. York. They obtained 19 bar-headed goose eggs from Sylvan Heights Bird Park in Scotland Neck, N.C. (a dozen in 2010 and seven more in 2011).
Dr. Meir and Ms. York were present with the goslings for several weeks after they hatched, allowing the geese to view them as caretakers. The geese were then taken to the University of British Columbia. When the geese reached adulthood, the researchers took measurements of how they flew in reduced oxygen conditions in a wind tunnel, closely mimicking their migration conditions.
Dr. Meir and her team found that the geese slowed their metabolism in oxygen-limited conditions, decreasing the amount of oxygen they needed to fly. They also employed more efficient flight strategies, changing the biomechanics of their upstroke and downstroke to conserve oxygen.
Dr. Meir’s team also showed that the temperature of the blood in the birds’ veins decreased as they flew in conditions with less oxygen. Hemoglobin, the protein that binds oxygen in the blood, has a thermal sensitivity. When blood is cold, it can carry more oxygen than when it is warm. As the temperature in the veins near their lungs drops, bar-headed geese could theoretically circulate more oxygen to the chest muscles that enable them to fly.
“If you can get by with using less, then if you’re in an environment that has less, you’re going to be more successful,” Dr. Meir said.
If we can understand more about how bar-headed geese are able to thrive in oxygen-deprived conditions, there might eventually be applications for the medical treatment of people who have been deprived of oxygen, for example after having a heart attack or stroke. And while human organs can be damaged in low-oxygen conditions, the geese are able to fly for hours.
“I think geese get a bad rap sometimes,” Ms. York said. “They’re amazing athletes.”
She marveled at their capacity to migrate long distances at high altitudes, in continuous flight.
“The bar-heads have done that migration for millions of years before the Himalayas were as tall as they are now,” Ms. York said, “and the birds have been pushed as the mountains have moved up to go higher and higher.”