Which animals come in the category of mammals?

The number of the type of mammals in comparison to the other animal groups is not high - there are only around 4,500 species of mammal, but over 8,000 birds, 35,000 fish and millions of insects. But mammals are often fairly big, noticeable and they exist all over the earth - in the sea as whales and seals, in the ice deserts of the Arctic as polar bears and musks. On pasture lands as antelopes and lions, in the air as bats, in deserts as camels, in the tropical rainforest as monkeys and tigers. In moderate climate zones, we find deer and roe deer, in the freshwater hippopotamus, otter, bever and almost everywhere mice and rats. Even our pets dogs, cats, pigs, cows, goats and sheeps belong to mammals.

The largest mammal and the heaviest animal that ever lived is the blue whale. The water bears its weight of approximately 150 tons. Elephants, the largest land mammals, on the other hand, are at the most 7.5 tons on the scales. The etruscan tip mouse is the smallest mammal at just 2 grams.