Success by Learning - Smallest Predator Recognizes Prey by its Shape (5/16/2008)

Etruscan Shrew

The Etruscan shrew (Suncus etruscus) is one of the world's smallest mammals. It is about four centimetres long and weighs merely two grams. Being a nocturnal animal, it hunts predominantly with its sense of touch. Professor Michael Brecht (Bernstein Center for Computional Neuroscience, Berlin) now reported on the particularities of its hunting behaviour at the international conference "Development and function of somatosensation and pain" at the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch, Germany. "As quick as a flash, the Etruscan shrew scans its prey and adapts, when necessary, its hunting strategy," explained Brecht in his talk. "Thus, no prey escapes."

The smaller an animal is, the greater is its loss of warmth over its surface. To avoid starvation, the Etruscan shrew has to constantly compensate for this life-threatening energy loss. Thus, it consumes twice its weight every day and feeds on crickets, cockroaches, and spiders. Since the prey are nearly as big as their predator, the shrew has to attack fast and well directed.

Etruscan shrews hunt in the night and must rely on their sense of touch. With long whiskers at the snout, they can locate potential prey and recognize whom exactly they are facing. Afterwards, the shrews kill their prey using directed attacks. The researchers could observe that they track down crickets with a forceful bite in the back. To investigate whether the animals recognize their prey by its shape, they offered the Etruscan shrews a plastic cricket. Though the artificial animal neither moved nor smelled, the Etruscan shrews attacked the plastic prey up to 15 times. "The Etruscan shrews trust in their sense of touch and the tactile shape recognition in an extent we do not know from other animal species," reported Brecht at the MDC conference.

"Also, the animals can adjust quickly to new situations", Brecht pointed out. To examine this theory, the scientists exchanged the living crickets with a giant cockroach. This new animal differs clearly from the natural prey of the shrews. The back of the cockroach is protected by a heavy shield and is therefore saved from the normal attacks of the Etruscan shrews. However, the experiments showed that the shrews succeeded in adapting their natural hunting strategy to the new prey in very short time. Quickly, they realized that the belly is the cockroach's weak point. "The shrews are learning during the hunt and use the new knowledge right away," said Brecht. "Even the giant cockroach can not escape."

Note: This story has been adapted from a news release issued by the Max Delbrück Center for Molecular Medicine

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