Brown bears in Bulgaria can weigh up to 350 kilograms - about the same as five large adult humans. They have thick fur that can range from almost black to pale honey-coloured, and enormous curved claws that are perfect for digging up roots, turning over rocks to find insects, and climbing trees when they are young.
Despite their size, brown bears eat mostly plants. In summer they feast on berries, wild honey, roots and insects. In autumn they gorge on beechnuts and acorns to build up fat for winter. When the cold comes, they find a cosy den - sometimes a cave, sometimes a hollow tree - and sleep for several months without eating or drinking.
Bear cubs are born in the den during winter, usually in litters of two or three. The cubs are tiny when born - smaller than a guinea pig - and they snuggle into their mother's warm fur until spring. By the time they emerge from the den in March or April they have grown into fluffy, bouncy little bears ready to explore the world.
Bulgaria has set up special sanctuaries for bears that need extra care. The Dancing Bears Park near Belitsa - in the Rila Mountains - is a nature reserve where rescued bears live freely in a large forested space, watched over by conservationists who make sure they are healthy and happy.