Britannica
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How many living species of mammals are there?
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mammal
Mother polar bear nursing her cubs (Ursus maritimus).
There are more than 6,800 living species of mammals currently recognized. These species are organized into approximately 125 families and between 27 and 29 orders, though these groupings can vary depending on the authority.1
The class Mammalia exhibits immense diversity in form and habit, ranging from tiny bats and shrews weighing only a few grams to the blue whale, the largest animal known to have ever lived. Among existing mammals, rodents represent the most numerous group in terms of both species count and individual population.1