Buffalo were cow-like creatures that lived on Earth. Because Roz Forrester's family name translated as "buffalo", she wasn't allowed to eat a buffalo. (NA: The Also People)
The Seventh Doctor and Ace saw buffalo living in the Ngorogoro Crater in 1926. (DWM: Prelude: Birthright)
The password used by Mickey Smith to access the UNIT website was buffalo. (DW: World War Three)
On the Cruiseliner Titanic, buffalo "wings" were served to guests as food. Foon Van Hoff commented that "These buffalo must have lots of wings". (DW: Voyage of the Damned)