The ability to sense the environment is vital to all living things, and is a key characteristic that separates life from non-life. The senses are not limited to the five we learn as children – sight, hearing, touch, taste, and smell. In the animal kingdom there are more. Some of them repurpose existing organs; some detect other information from the world not detectable with the normal sense organs. In mammals, two very different animals – bats and dolphins – have expanded our understanding of sensation.
Two papers in Science this week added to our understanding of echolocation in bats. One paper explored how bats are able to separate target information from background clutter. Bates, Simmons and Zorikov, writing in Science,1 experimented with “big brown bats” and found that they “exploit harmonics to distinguish clutter echoes from target echoes, sacrificing delay acuity to suppress masking.” That ability would be amazing enough for a stationary target, but bats do this while flying rapidly through complex aural surroundings. One would think from the researchers’ description that they are sophisticated audio engineers: “The key to how the bat recognizes weaker FM2 from lowpass filtering is an interaction between the amplitude of an echo and the timing, or latency, of the neural responses it evokes—an effect called amplitude-latency trading.”
In the other paper in Science,2 Simon, Holderied, Koch and von Helversen discovered a neat cooperation between a nectar-eating bat and its host plant. Targeting of the plant is enhanced by a specialized leaf that reflects the bat’s echoes like a satellite dish. Science Daily showed a picture of the flower with the sonar dish right over the flowers. This host plant lives in low abundance in the tropics, so it relies on the bat’s wide foraging range and excellent spatial memory. By providing the bat with an echolocating enhancer, the plant has a 50% higher chance of being found. The bat gets its energy drink, and the flower benefits from the pollination that occurs. The shape of the leaf, therefore, serves a similar purpose to an echolocating bat that beautiful colors in flowers serve for daytime pollinators. “Because of their peculiar shape and presentation, we hypothesize that these special leaves evolved as echo beacons that attract pollinating bats,” the authors said….
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