Moreover, the detection threshold of any object (including large obstacles) would be much higher. Because of the extremely narrow tuning of their hearing system, without Doppler shift compensation, CF bats would have real difficulties to detect the Doppler shifts created by insects’ wing beat, allowing them to detect prey. Bats that use constant frequency echolocation signals (henceforth CF bats) adjust their emission frequency according to their speed in order to maintain the frequency of the returning echoes at the most sensitive range of their auditory system. Doppler shift compensation in bats is a prime example of a sensory adjustment. Some examples include the following: pupils dilate and contract in response to changing illumination, the middle ear muscles contract to reduce the received level of loud noises, and the olfactory system habituates to long lasting odors. ![]() How they do so have mostly been studied in the context of external input. Sensory systems must constantly adjust according to the information they receive to improve sensory acquisition. Our results illustrate the robustness of one particular sensory behavior however, we suggest this ability to rely on different streams of information (i.e., internal or external) is probably relevant for many sensory behaviors. We thus show an ecological need for using internal cues as well as an ability to do so. Moreover, using on-board GPS tags on free-flying bats in the wild, we demonstrate that the ability to perform Doppler shift compensation response based on internal cues might be essential in real-life when echo feedback is not available. Bats experiencing accelerations in an echo-free environment exhibited an intact compensation response. We show that the Doppler compensation system works even without external feedback. Previous studies documented the importance of external echoes for this response. Constant frequency echolocating bats are renowned for their Doppler shift compensation response used to adjust their emission frequency in order to optimize sensing. Here, we take advantage of the rapid sensory adjustments exhibited by bats in order to study how animals rely on internal cues in the absence of external input. When external input is not available, idiothetic-internal-cues become crucial for guiding behavior. Adjustments based on external input are much better documented and understood than internal-based sensory adaptations. Their whole body has evolved to interpret their environment, giving them remarkable skills.Sensory systems acquire both external and internal information to guide behavior. ![]() It’s not “hearing” as we would understand it, but like elephants who hear through their feet, bats hear through their ears and wings combined. As the bat flies, they can pick up approaching objects and relay this information to the brain. ![]() These wings are covered with what are known as “Merkel hairs”, which are ultra-sensitive to air movements. Their hearing systems seem to extend to the hairs on their wings. Recently, scientists have found another amazing thing about bats. Even though their brains are tiny, these amazing creatures use the echoes to create a map of their environment, enabling them to fly flawlessly through the dark. They do so by creating high frequency noises, which bounce off anything they hit, then return to the bat’s ears. But, no matter how sensitive human hearing becomes, it never approaches the amazing abilities of bats.īats famously use something called “echolocation” to locate their prey and get around the nocturnal world. When humans go blind, their hearing becomes doubly important, allowing them to get around more easily and detect obstacles. For bats, echolocation makes darkness irrelevant
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