*Deers* has been used that way.

From [A Popular History of Mammalia](http://books.google.com/books?id=KvI-AAAAYAAJ&pg=PA280&lpg=PA280&dq=the+subgenus+Muntjacus+is+distinguished+%22from+the+other+deers%22&source=bl&ots=hVrL-Ot8QF&sig=FFeUYSwqbsCjK5eO_EN2N0lOgXg&hl=en&sa=X&ei=fKnrU_6YG6-_sQTT74DQDQ&ved=0CB0Q6AEwAA#v=onepage&q=the%20subgenus%20Muntjacus%20is%20distinguished%20%22from%20the%20other%20deers%22&f=false), 1850:
> The subgenus Muntjacus is distinguished from the other deers by the horns being supported on elongated pedicels ...

I would say that either *deers* or *deer* would be acceptable for this type of usage. However, if you want to be indisputably correct, you could use *species of deer*.