Shrews are well known for their voracious appetites (3); the common shrew has to eat every two to three hours and needs to consume 80 to 90 percent of their body weight in food in 24 hours (3). They feed on most terrestrial insects, but will also take worms, slugs and snails (2). The common shrew is more active during the night, at dusk, and at dawn, and intersperses bursts of activity with rest periods (3). Shrews do not hibernate, as they are too small to store fat reserves sufficient to see them through the winter (3). This solitary species is territorial (2), but during the breeding season males set off in search of females. His advances may stimulate scuffles and high-pitched squeaks from unreceptive females (3). Mating begins in March, and one to two (sometimes three or four) litters are produced in a year, each one consisting of six to seven young (5). By 16 days of age the young begin to emerge from the nest, they can occasionally be seen following their mother around in a 'caravan', usually after the nest has been disturbed. The young grab the tail of the shrew in front of it, so the mother takes the lead and her offspring follow in a train (3). Juveniles breed in the year after their birth, but occasionally those born early in the year can breed between July and September that year (5). Common shrews live for 14 to 19 months, and mortality rates are high; main predators include owls, birds of prey, foxes, cats and stoats and weasels (5). Shrews belonging to the genus Sorex are known to produce ultrasound, which may be used as a primitive form of echolocation (5).