All domestic dogs are descended from grey wolves (Canis lupus), which began living alongside humans many thousands of years ago. Grey wolves are the largest dogs in the wild, and they live in packs of about ten individuals. A pack has a strict hierarchy, with a male and female "alpha pair" in charge. The alpha dogs bond for life and are the only members of the pack to breed. The rest of the pack is made up of the alpha pair's offspring.
In summer, pack members often hunt alone for small animals such as beavers or hares, while in winter, packs hunt together for much larger animals. Grey wolves are strong runners and can travel 200km in one night. They generally detect prey by smell and chase them down, taking turns to take a bite at the faces and flanks of their victims until they collapse from exhaustion.