What is Britain’s most ferocious predator? Most people might have a stab at answering this simple question, yet few would get it right . . .
Weight for weight, the shrews pack a powerful punch, regularly tackling and killing prey far larger than themselves. This is in part thanks to a venomous bite which they use to paralyse and subdue their quarry.
Shrews are extremely numerous and active. They live frenetic lives, constantly burning calories and in consequence can starve to death in as little as four hours. In the course of a day each will eat 75% of its body weight, but a lactating female needs double this. Not surprisingly, hard winters take a particularly heavy toll.
They are also fiercely territorial and very vocal (although most people mistake their high-pitched chirping for a grasshopper). Yet despite this and their 24/7 lifestyles, few people have caught more than a fleeting glimpse of one of our four species: common; pygmy; water and Scilly (or white-toothed).
Shrews hunt by scent and by picking up vibrations through their vibrissae – the whisker-like hairs that adorn their noses. Quarry ranges in size from minute insects to worms that can weigh considerably more than themselves. Prey is killed by being held down by the front feet while it is worried to death – a little like a dog killing a rat. Interestingly, while they have a
Most shrews have large scent glands on their flanks which are bigger in males than females. These secrete a rank, unpleasant, odour which may explain why many predators such as cats appear reluctant to eat the little creatures. Birds lack a sense of taste however, so their remains feature heavily in owl pellets.
Ovulation is stimulated by mating and by late April all the females are pregnant. Three weeks later about seven young are born, each weighing 0.5g (half this in a pygmy shrew). These are weaned at three weeks but may stay with their mother for up to another three weeks while she rears the next brood, during which time they may accompany her on foraging expeditions.
by their comparatively bald nose and tails.
Shrews like tunnels, partially because they are good hunting grounds and places to hide – but also because squeezing through these appears to have a grooming function. Hoels can be recognised by being oval in shape – wider than high.
Two glands on side ooze an unpleasant smelling secretion which can even matt the hair. No one absolutely sure about purpose of glands – probably not protection because it doesn’t prevent mammals such as cats, dogs and weasels killing them – merely preventing ingestion. More likely to do with marking territory – at its lowest in breeding females (ie when they might be receptive to male advances) for rest of year a warning sign for these very territorial animals.
Large numbers of dead shrews frequently found in autumn/winter: probably victims of old age and corpses shunned by most scavengers. Also, studies of captive animals shows shrews tend to come into open to die, while mice and voles prefer to do this underground.
Like their cousin, the mole, shrews have a velvety fur. This is useful in a variety of situations – both underground where it enables them to run backwards along passages as well as forwards, but – in the case of the water shrew – it allows them to swim underwater, covered with a sheen of silvery air bubbles.