Abstract
Author SummaryMost sensory systems have an active component, i.e. driven by an animal's behavior, which contributes directly to its perception. For example, eye movements are important for visual perception, sniffs are crucial for olfactory percepts, and finger movements for touch percepts. A classic example of an active-sensing system is bat echolocation, or biosonar. Echolocating bats actively emit the energy with which they probe their surroundings, and they can control many aspects of sensory acquisition, such as the temporal or spectral resolution of their signals. A key open question in bat echolocation concerns bats' ability to actively change the area scanned by their emitted beam. Here, we used a large microphone array to study the echolocation behavior of Egyptian fruit bats. We found that these bats apply a new strategy to alter the area scanned by their beam; specifically, bats changed their acoustic field-of-view by changing the direction of consecutively emitted beams. Importantly, they did so in an environment-dependent manner, increasing the scanned area more when there were more objects in their surroundings. They also increased their field-of-view when approaching a target. These findings provide the first example for active changes in sensing volume, which occur in response to changes in environmental complexity and target-distance, and they suggest that active sensing of space is more flexible than previously thought.
Highlights
The importance of ‘‘active sensing,’’ by which an animal actively interacts with the environment to adaptively control the acquisition of sensory information, is fundamental to perception across sensory modalities [1,2,3,4,5,6,7]
We recently demonstrated that the lingual echolocator Rousettus aegyptiacus (Egyptian fruit bat) uses a sophisticated strategy for beam-steering: This bat emits sonar clicks in pairs, and it directs the maximum slope of each sonar beam towards the target, rather than directing the center of the beam, thereby optimizing stimulus localization in the horizontal plane [15]
They did so in an environment-dependent manner, increasing the scanned area more when there were more objects in their surroundings. They increased their field-of-view when approaching a target. These findings provide the first example for active changes in sensing volume, which occur in response to changes in environmental complexity and target-distance, and they suggest that active sensing of space is more flexible than previously thought
Summary
The importance of ‘‘active sensing,’’ by which an animal actively interacts with the environment to adaptively control the acquisition of sensory information, is fundamental to perception across sensory modalities [1,2,3,4,5,6,7]. Laryngeal bats control many aspects of their sensory acquisition: they determine the timing of acquisition and the information flow [8,9,10,11], they control the intensity of the emission as well as its direction [12,13,14,15,16,17], and they control the spectral and temporal resolution of the acquired data [18,19,20,21,22,23] Another acoustic parameter potentially under active control by echolocating bats is the pattern of the sonar beam. We aimed to examine a very different mechanism by which echolocating bats might control the effective space they scan, namely adjustments in the angle between sequentially emitted sonar clicks
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