Hairs Help Flight Maneuverability

a light brown hairy bat with dark brown wings on a tree

Biological Strategy

Big brown bat

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Sense Motion

Perceiving motion is important for a living system to sense where it is in relation to a moving environment, which is critical in locating resources or wayfinding. This applies whether the environment itself is in motion (such as water movement coming from a nearby fish) or the living system is moving within a stationary environment (such as a bird flying through the air). Because motion dampens over distance and the cost of missing those motion signals is high, living systems must be quite sensitive to these signals. For example, fast-flying big brown bats have microscopic, stiff, domed hairs on their wing membranes that act as a sensor array to monitor flight speed and airflow conditions.

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Sense Balance/Orientation

Living systems must maneuver, remain in position, detect differences in weight, and find direction. This often requires more than visual cues, and so living systems have strategies for sensing balance and orientation from both internal and external cues. Once balance or orientation is detected, living systems must make the adjustments necessary to maintain position and direction. For example, sea slugs use neural mechanisms to detect and align themselves at an angle to the earth’s north-south magnetic axis.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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Tactile hairs in wing membranes of bats serve as flight control organs by providing immediate sensorimotor feedback.

“Bats are the only mammals capable of powered flight, and they perform
impressive aerial maneuvers like tight turns, hovering,
and perching upside down. The bat wing contains
five digits, and its specialized membrane is covered with stiff,
microscopically
small, domed hairs. We provide here unique
empirical evidence that the tactile receptors associated with these
hairs are involved
in sensorimotor flight control by providing
aerodynamic feedback. We found that neurons in bat primary somatosensory
cortex
respond with directional sensitivity to stimulation
of the wing hairs with low-speed airflow…the hairs act as an array of sensors to
monitor flight speed and/or airflow conditions that indicate stall.
Depilation
of different functional regions of the bats’ wing
membrane altered the flight behavior in obstacle avoidance tasks by
reducing
aerial maneuverability, as indicated by decreased
turning angles and increased flight speed.” (Sterbing-D’Angelo et al. 2011:11291)

Last Updated August 18, 2016

References

Journal article

Bat wing sensors support flight control

Proceedings of the National Academy of Sciences | 21/06/2011 | S. Sterbing-D'Angelo, M. Chadha, C. Chiu, B. Falk, W. Xian, J. Barcelo, J. M. Zook, C. F. Moss

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