Abstract
Visual predators rely on fast-acting optokinetic responses to track and capture agile prey. Most toothed whales, however, rely on echolocation for hunting and have converged on biosonar clicking rates reaching 500/s during prey pursuits. If echoes are processed on a click-by-click basis, as assumed, neural responses 100× faster than those in vision are required to keep pace with this information flow. Using high-resolution biologging of wild predator-prey interactions, we show that toothed whales adjust clicking rates to track prey movement within 50-200 ms of prey escape responses. Hypothesising that these stereotyped biosonar adjustments are elicited by sudden prey accelerations, we measured echo-kinetic responses from trained harbour porpoises to a moving target and found similar latencies. High biosonar sampling rates are, therefore, not supported by extreme speeds of neural processing and muscular responses. Instead, the neurokinetic response times in echolocation are similar to those of tracking responses in vision, suggesting a common neural underpinning.
Highlights
Response speed critically determines the outcome of interactions between mobile prey and pursuit predators
The inter-click intervals (ICIs) used in buzzes when targeting evasive prey show dynamics that seem to correspond to changes in prey range (Figure 2A and B, Figure 2—figure supplements 1 and 2), suggesting a tight sensor-motor feedback loop
To verify that these ICI changes are linked to prey escapes, we plotted the proportion of outward depth-o f-field adjustments in time bins synchronised with the first detectable prey movement in buzzes
Summary
Response speed critically determines the outcome of interactions between mobile prey and pursuit predators. Responding to close-a pproaching predators, prey may trade accuracy for speed, relying on imprecise ballistic motor actions triggered by strong sensory cues that require little neural processing (Domenici and Batty, 1997; Turesson et al, 2009). This has led to extremely fast responses employing short efferent pathways linking sensors directly to muscles, such as the Mauthner-cell-mediated C-start response of teleost fish to fluid motion from oncoming predators (Eaton and Hackett, 1984). Predators must sacrifice speed for accuracy, typically requiring greater sensory resolution and motor-p lanning capabilities to track and successfully pursue evasive prey. The increased processing needed to locate prey in complex natural scenes, along with the typically larger body size of predators, inevitably results in slower movement responses
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