How Does Flight Affect Bat Body Temperature?
Bats are the second largest mammalian order in the world, and they are widely distributed across the world. These small mammals are mainly nocturnal, and breed in the fall. Their roosts are large, and they congregate in large groups during the winter and migration periods. They often fly at dusk and at dawn. During these times, they hunt for insects and then return to their roosts. During these periods, they can also catch prey that is not readily available during the day.
While most mammals are able to maintain a body temperature of 35-39 degC during a typical activity, bats have the ability to achieve a body temperature of 24 degC. This is a much wider range than the body temperatures of most mammals, and this is one of the main reasons why bats have attracted research interest for so many years.
However, knowledge about the effects of flight on body temperature is still relatively limited. There are few reports on continuous body temperature measurements in flying bats. Moreover, determining how flight affects body temperature is complicated in the field because of the limited amount of acceleration data.
The laboratory studies of bats show that flight can increase their maximum body temperature, but this increase is not as high as reported for some species. It is possible that intermittent flights may slow the rate of the temperature increase. For example, the median increase in body temperature that accompanies flight was about 3.4 degC. That figure is comparable to the reported increase in temperature for some birds, but it is not as large as that of Phyllostomus hastatus, a species that can maintain a body temperature of 5 degC during flight.
Bats are characterized by their complex sensorimotor system. They use their vision to navigate and they can make very fast maneuvers. When they make rapid movements, they filter out ambient noise with low-pass filtering. In addition, the wing structure and membrane of the wings allow heat dissipation.
In the laboratory, bats were able to maintain their maximum body temperature below lethal levels of 44-45 degC. But when they were cooled down, their maximum temperature was lower than the ambient temperature, and the difference between Tsk and Tb was about 2 degC.
Bats also demonstrate hyperthermia and hypothermia during flight. Although their calls are very high-pitched, they cannot be heard by humans. Nevertheless, they emit ultrasonic waves with a frequency of 20-100 kilohertz, and these frequencies are reflected by objects. Therefore, a bat's flight calls are an important way to estimate the environment it is in.
Moreover, their special membrane structure on the wings allows heat to be released during wing flapping. A recent study showed that intermittent flights can also serve as thermoregulatory strategies. Despite these studies, there is still a lot of research that needs to be done. Until then, we can only speculate how bats regulate their body temperature.
To quantify the effect of flight on body temperature, bats were studied with temperature sensors placed subcutaneously and onboard temperature sensors. They were recorded during a recording session and the average Tsk increased during flight.
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