Largest order of mammals

The largest taxonomic order of mammals is Rodentia, containing the rodents, which number 2,682 species, according to the Global Mammal Checklist as of January 2024. They therefore account for approximately 40% of all known extant mammal species – which presently number 6,642 in total. Rodents live on all continents except Antarctica.

Second in species number only to Rodentia is the taxonomic order Chiroptera, housing the bats. According to the January 2024 version of the Global Mammal Checklist, 1,465 bat species are currently recognized, which include both the megachiropterans (fruit bats and relatives) and the microchiropterans (all other bats). Their ability to fly and their predominantly nocturnal lifestyle combine to make bats very elusive and difficult to track, thereby enhancing the possibility that there are still a fair few scientifically undiscovered species in existence.