Abstract
The Etruscan shrew, Suncus etruscus, is not only the smallest terrestrial mammal, but also one of the fastest and most tactile hunters described to date. The shrew's skeletal muscle consists entirely of fast-twitch types and lacks slow fibres. Etruscan shrews detect, overwhelm, and kill insect prey in large numbers in darkness. The cricket prey is exquisitely mechanosensitive and fast-moving, and is as big as the shrew itself. Experiments with prey replica show that shape cues are both necessary and sufficient for evoking attacks. Shrew attacks are whisker guided by motion- and size-invariant Gestalt-like prey representations. Shrews often attack their prey prior to any signs of evasive manoeuvres. Shrews whisk at frequencies of approximately 14 Hz and can react with latencies as short as 25–30 ms to prey movement. The speed of attacks suggests that shrews identify and classify prey with a single touch. Large parts of the shrew's brain respond to vibrissal touch, which is represented in at least four cortical areas comprising collectively about a third of the cortical volume. Etruscan shrews can enter a torpid state and reduce their body temperature; we observed that cortical response latencies become two to three times longer when body temperature drops from 36°C to 24°C, suggesting that endothermy contributes to the animal's high-speed sensorimotor performance. We argue that small size, high-speed behaviour and extreme dependence on touch are not coincidental, but reflect an evolutionary strategy, in which the metabolic costs of small body size are outweighed by the advantages of being a short-range high-speed touch and kill predator.
Highlights
The Etruscan shrew, Suncus etruscus, is the smallest terrestrial mammal, and one of the fastest and most tactile hunters described to date
Comparing shrew touch to tactile sensing in other mammals, we find both similarities and striking differences
A striking difference is the speed of performance, which is slow in the human haptic system, because it relies on the serial/gradual scanning of objects with fingertips [81]. This is very different from vibrissal touch, in which global stimulus features appear to be extracted in a single whisker sweep
Summary
The Etruscan shrew, Suncus etruscus, is the smallest terrestrial mammal, and one of the fastest and most tactile hunters described to date. Shrew attacks are whisker guided by motion- and size-invariant Gestalt-like prey representations. Shrews tackle a complex task: in darkness they detect, overwhelm and kill their insect prey, a fast moving target that is almost as big as the shrew itself (figure 1a). (b) Sensory implications of small body size The Etruscan shrew, Suncus etruscus, is the smallest shrew, but presumably the smallest terrestrial mammal. It is obvious that whiskers are relatively longer in smaller mammals; i.e. small animals have a relatively larger vibrissal sensing volume [1]. Etruscan shrew whiskers sense a longer distance ahead than in the rat or mouse This may be necessary to avoid obstacles as the shrew locomotes very rapidly [8]. Body length to sample more of its direct surround, which may partly explain why shrews act so fast during prey capture
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call