communication in the wolf, making up 60–80% of all scent marks observed. Reproduction Wolves are monogamous, mated pairs usually remaining together for life. Should one of the pair die, another mate is found quickly. With wolves in the wild, inbreeding does not occur where outbreeding is possible. Wolves become mature at the age of two years and sexually mature from the age of three years. The age of first breeding in wolves depends largely on environmental factors: when food is plentiful, or when wolf populations are heavily managed, wolves can rear pups at younger ages to better exploit abundant resources. Females are capable of producing pups every year, one litter annually being the average. Oestrus and rut begin in the second half of winter and lasts for two weeks. Dens are usually constructed for pups during the summer period. When building dens, females make use of natural shelters like fissures in rocks, cliffs overhanging riverbanks and holes thickly covered by vegetation. Sometimes, the den is the appropriated burrow of smaller animals such as foxes, badgers or marmots. An appropriated den is often widened and partly remade. On rare occasions, female wolves dig burrows themselves, which are usually small and short with one to three openings. The den is usually constructed not more than away from a water source. It typically faces southwards where it can be better warmed by sunlight exposure, and the snow can thaw more quickly. Resting places, play areas for the pups, and food remains are commonly found around wolf dens. The odor of urine and rotting food emanating from the denning area often attracts scavenging birds like magpies and ravens. Though they mostly avoid areas within human sight, wolves have been known to nest near domiciles, paved roads and railways. During pregnancy, female wolves remain in a den located away from the peripheral zone of their territories, where violent encounters with other packs are less likely to occur. The gestation period lasts 62–75 days with pups usually being born in the spring months or early summer in very cold places such as on the tundra. Young females give birth to four to five young, and older females from six to eight young and up to 14. Their mortality rate is 60–80%. Newborn wolf pups look similar to German Shepherd Dog pups. They are born blind and deaf and are covered in short soft grayish-brown fur. They