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," unaware that "buffalo" in this case was in reference to the sauce. (DW: Voyage of the Damned)