the day, with no clear preference for sunlight or night time. They make runways through the surface growth, connecting feeding grounds to burrow entrances, although these are not as clear as those made by some other vole species. They also sometimes forage in low bushes. The burrows consist of a number of chambers, many of them used to store food for the winter, connected by very narrow passages. These passages, typically around wide, make it difficult for any animal larger than a vole to pass through, and thus help protect against predators such as weasels. The burrows run horizontally, no more than below ground level, and can extend for as far as from the tunnel entrance. Unusually among voles, in addition to storing food, such as roots and rhizomes, underground, singing voles also often leave stacks of grasses out on rocks to dry. Often, these stacks are instead constructed on low-lying branches, or on exposed tree roots, helping to keep them dry. The stacks of grasses slowly dry out, producing hay, and may include other food materials, such as horsetails or lupines. The voles begin to construct the stacks around August, and by the winter, they may have reached considerable size, with piles of up to in height having been reported. The piles are a source of nutritious food through the winter, although they are liable to be raided by other animals. This species gets its common name from its warning call, a high-pitched trill, usually given from the entrance of its burrow. Reproduction Singing voles breed from May to September, and each female can give birth to up to three litters in a breeding season. Gestation lasts 21 days, and typically results in the birth of eight young, although litters of between 6 and 14 young have been reported. Since, like other voles, the female has only eight teats, litters of more than eight young are unlikely to survive. The young weigh at birth, and grow rapidly during the first three weeks of life. They are weaned at around four weeks, by which time the mother is often ready to produce a new litter. Although females generally do not reproduce until their second year, males may be sexually active within as little as a month of birth. In the wild, many singing voles do not survive even their first winter. In captivity, they have been reported to live for