While the number of species is under constant review, and any estimate at any given time is probably inaccurate, there are between 4500 and 5000 species of mammals. The latest available list from the Mammal Species of the World lists 4629 unique species.
These range from the smallest (shrews, pikas, and voles) to the largest (whales, rhinoceroses, elephants, and hippos).
Humans are a species of mammal.
About forty percent of mammal species are rodents. Since there are about 5,400 mammal species, there are over 2,000 species of rodents.
4,500
I would guess rats are the most common mammal in the world.
Weddel seal
Humans, at over six billion.
In the Simpson desert there is 180 species of bird,44 species of mammal and 92 species of reptile.
A bat (many species) are the only truly flying mammal.
450
There are around 15,000 known species of mammals.
I would guess rats are the most common mammal in the world.
The biggest mammal in the world is the blue whale and is and endangered species. The second biggest mammal in the world is the hump-back whale which is also an endangered species. Hope this helps