Virginia opossum, Didelphis virginiana

Mammals are adapted to a multitude of ecosystems and are found in the seas, the oceans, on all the continents, on the ground and in the soil, in the air or in the water. Their common features include carrying their offspring in the womb, suckling them, maintaining a constant temperature, having hair, or sometimes spines or scales, mammary glands and pinna, or earflaps. The list of their characteristics is a long one, but there is no doubt that Homo sapiens are indeed one amongst the 5,400 living species of mammals.