Red-haired vespers speed up their hearts one hundred and fifty times.
Several years ago, employees of the University of Konstanz and the Institute of Ornithology Max Planck Society discovered that bats called bat-bearers slow down their hearts when they rest. While in flight, the bat’s heart beats at a rate of 791 to 1066 beats per minute, but at rest it only beats 300 beats per minute; moreover, from time to time the rate drops to 200 beats per minute. Each period of slow heartbeat lasts about six minutes, and there are several such periods during an hour of rest. Most likely, bats save energy in this way: they feed on fruits, of which there is not always enough, and sometimes bats have to save every calorie. According to calculations, regular “cardiac braking” allows bats to save 10% of their daily energy reserves.
In a new article in Proceedings of the Royal Society B The same researchers write about other bats – the noctule bat. In flight, their heart rate reaches approximately 900 beats per minute. But the lower limit of their heart rate is surprisingly low, only 6 beats per minute. Before these six beats, the heart slows down in torpor – this is the name of a special physiological state when the metabolism slows down, the heart rate slows down and the body temperature drops sharply. Noctule bats fall into torpor during daytime rest and only in spring, when there is again little food. After waking up, noctule bats literally in a few minutes speed up their heart from six beats to nine hundred, that is, one hundred and fifty times.
Red noctule. (Photo: ognevit / iNaturalist)
In summer, these bats do not fall into torpor, and their energy consumption increases by 42%. They hunt twice as long on summer nights as on spring nights, and in one June night they can eat 33 beetles or more than 2,500 mosquitoes. However, the researchers only worked with male noctule bats, and all the figures obtained, accordingly, concern only males; in females, they may differ in one direction or another. The heart rate of the bats was measured in natural conditions: a 0.8 gram sensor was hung on the animals and they were released into the wild. However, in order to get readings from the sensor, the receiver had to be no further than a few hundred meters away from it. During the day, while the mice are sleeping, you can listen to their heart without any problems, but at night they can fly several kilometers from their overnight place. So at night, a small Cessna plane flew over the bats’ hunting grounds, receiving signals from the bats’ heart sensors.
Torpor is also experienced by other living creatures that spend a lot of energy and are constantly faced with the fact that they do not have enough energy. For example, hummingbirds that live in the mountains and have to endure rather cold nights practice torpor. Two years ago, we wrote that Andean hummingbirds cool down to 10°C and below, and their heart rate drops from 1200 to 40 beats per minute. The upper limit of hummingbirds is higher than that of noctules, but the heart of noctules still accelerates more. And, of course, a separate question here is what features of the heart muscle of hummingbirds and bats allow it to withstand such a range of frequencies.
Source: www.nkj.ru
