Hummingbirds have made another record: they are not only small, but can reach the body temperature of any non-hibernating mammal and any other bird.
Hummingbirds are one of several small organisms, including some bats, that can enter a state known as the diurnal torper, a phenomenon where they lower their metabolism and body temperature to conserve energy.
Unlike hibernation, it does not last long: after one night in torpor, the metabolic rate of sparrows increases again, reaching a body temperature of about 40C.
Now researchers studying six species of luminous birds in the Andes, about 3,800 meters above sea level, have found that black metal sparrows can have body temperatures as low as 3.3C.
The study’s co-author, Professor Andrew McKenney of the University of Pretoria, South Africa, said that the tarmuff was important for the survival of the humming, as they had to burn large amounts of energy to maintain body temperature during 40C. cool night. “They will not be able to store enough fat at the end of the day to provide them with enough fuel for the entire night”, he said.
McKenney said with the new study that sparrows’ body temperatures could drop to those more characteristic of hibernating animals, it could be that dim creatures were not only able to enter tortures, but to hibernate. “It would be big news if they did,” McKenney said. “Only one avian hibernator has been reported.”
McKenney stated that the mechanisms behind the torum were of interest for biomedical applications. “At one stage NASA was asking quite seriously whether it would be possible to create a torper-like condition in humans, or hibernation-like conditions, to get out of the area around Earth.”
Writing in the journal Biology Letters, McKechnie and colleagues described how they captured 26 hummingbirds of six different species in Peru in March 2015 and kept them in tents without food for at least one night, in the body. Tracked changes in temperature and mass. The air temperature dropped to 2.4C.
The team found that 24 birds out of 26, covering all six species, entered the taurum; However their lowest body temperature varies between individuals and species.
The body temperature of a black metal sparrows dropped to just 3.3C, which, he said, was a record for not only sparrows, and was actually lower than the record for all birds, but non-hibernating mammals. The previous record for birds was 4.3C, reported for the general poor, the only species of bird known to hibernate.
Time varied in Torper: The giant hummingbird spent an average of 5.7 hours in Torpor at night, compared to 10.6 hours for black metal. Long-term humming torpers reduce body mass loss.
McKenney said further analysis showed that the difference in torpor between different species was, at least in part, inherent in evolution. “You are different using different species [torpor] Patterns, despite all of them experiencing the same weather under the same conditions at the same site.