Hummingbirds by Cade Johnson

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Hummingbirds

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By Cade Johnson

In the Andes mountains in Peru, the black metal tail hummingbird chills down to 3.26° celsius at night, the coldest temperature ever recorded in a bird or non-hibernating mammal, researchers report.They go into torpor because they have to drink nectar from 500 flowers a day to warm their bodies at night, and they are not able to do that. This could allow them to cut their energy use by about 95% by not using energy to stay warm. Torpor can last from 3 to 12 hours. After a night of torpor they start warming up about a degree a minute by vibrating their muscles. Then they heat up to about 40°Celsius.

Torpor is vital to hummingbirds’ survival, as they would have had to burn large amounts of energy to maintain a body temperature of around 40°C during the cold Andean nights. Revealing that the body temperatures of hummingbirds could fall to those more characteristic of hibernating animals, it could be that the diminutive creatures were not only able to enter torpor, but to hibernate. In Peru in March 2015 they captured 26 hummingbirds of six different species and placed them in tents without food for at least one night, tracking changes in body temperature and mass. Air temperatures fell to as low as 2.4C. The team found that 24 of the 26 birds, covering all six species, entered torpor.

Some hummingbirds drink more than their own weight in nectar every day to power their energetically costly hovering flight and keep their tiny bodies warm. Astonishingly, however, hummingbirds can be found at up to 5,000 metres above sea level in the Andes Mountains of South America. The minuscule birds go into torpor — a state of reduced metabolic activity and temperature that is not unlike hibernation. Among vertebrates, hummingbirds have the highest metabolism for their size. With a metabolic rate roughly 77 times that of an average human, they need to feed nearly continuously. But when it gets too cold or dark to forage, maintaining a normal body temperature is energetically draining. Scientists traveled 3800 meters above sea level to the Peruvian Andes, where nightly temperatures dip near freezing. They captured 26 hummingbirds from six different speciesplaced each bird in a small roosting enclosure near the campsite and inserted a tiny wire into their cloaca, an all-purpose hole that birds use to excrete waste, mate, and—in females—lay eggs. This wire tracked the birds’ body temperatures overnight, letting the scientists know when the animals cooled down and warmed back up. Not only did every species of hummingbird go into torpor, but several reached surprisingly chilly temperatures. One black metaltail hummingbird’s body temperature dipped to 3.3°C,

During the day, these hummingbirds’ tiny-yet-mighty hearts can beat 1,200 times a minute to power their frenetic lifestyle. But during torpor, their heart rates plummet to as low as 40 beats a minute.
By not wasting energy trying to stay warm, these birds can thrive as high as 5,000 meters above sea level.
Some hummingbirds only entered torpor only briefly, and these lost up to 15 percent of their body weight overnight. Birds who stayed in torpor for 12 hours lost only two percent.
Hummingbirds may enter torpor for several days in a row.

I think it changes scientists thoughts of how hummingbirds live.
It could show them more how hummingbirds and other animals in the Andes mountains live.