As the altitude rises, the air becomes colder and thinner. This is obviously not an easy task for organisms trying to maintain their body temperature with less oxygen In order to understand the physiological response of the livable Calypte Anna to changes in temperature and oxygen content at an altitude of about 2800 meters (9200 feet), Austin Spence of the University of Connecticut and Morgan gingley of the University of California, Los Angeles have just published their latest research in the Journal of experimental biology.
(from: Robert mcmorran / wikipedia ) The
research During this period, they first lured a batch of hummingbirds into nets from Sacramento, California, at an altitude of 10 meters (33 feet). Along the way, Hannah lewinter, from Humboldt State University in the United States, delivered it to a bird house 1215 meters (4000 feet) in western California.
After several days of adaptation, scientists set up a small funnel to observe the oxygen consumption (metabolic rate) of hummingbirds while sipping delicious syrup (hovering in the air).
Spence and lewinter also measured the carbon dioxide exhalation of hummingbirds at night rest (another indicator of metabolism) - this small creature can turn into a "mini hibernation" state to reduce its metabolism when it becomes sluggish, so as to conserve energy during sleep.
Then they relocated the hummingbirds to a nearby research station near the bacroft peak (3800 meters /12500 feet) in California, where the air was colder (about 5 ℃) and the oxygen was thinner (about 39%).
Four days later, the researchers re measured the metabolism rate of the new town when the hummingbird was circling, and the frequency and depth of dormancy.
It was found that hummingbirds were difficult to hover in the air, their metabolic rate at this altitude decreased by 37%, and they became slow to conserve energy most of the time except at night, which meant that they were difficult to migrate to higher altitudes.
Combined with the performance of other birds migrating from low altitude to high altitude, the overall research results show that low pressure and oxygen content will pose severe challenges to their activities.
In addition to struggling more when hovering, these hummingbirds also reduced their metabolic rate and remained numb for longer periods of rest at night - more than 87.5% of the time at cold high altitude nights.
In addition, the team tried to determine through anatomical research whether birds from high altitude have larger lungs to make up for the lack of oxygen. The result is not the case - in fact, these birds have stronger hearts to provide the oxygen their bodies need.
Finally, Spence concluded, "research shows that low air pressure and oxygen content may be insurmountable challenges for hummingbirds. When climate change forces them to find a more livable environment, they may have to move north to find cooler and more comfortable climate conditions.".