However, a good estimate is around 6,400 species of mammals.
Here's why it's so difficult to give a precise number:
* New discoveries: New mammal species are being discovered regularly, especially in remote areas like rainforests.
* Taxonomic changes: Scientists are constantly refining the classification of mammals, sometimes merging or splitting existing species based on new genetic and morphological evidence.
* Difficult to access areas: Some parts of the world remain poorly explored, making it challenging to assess the full diversity of mammals.
The International Union for Conservation of Nature (IUCN) is a leading authority on species classification and conservation. Their Red List provides a comprehensive overview of the status of known mammal species, but it's always subject to change.