The Collaborative International Dictionary of English v.0.48:

Mara \Ma"ra\, n. (Zool.)
   The Patagonian cavy, a hare-like rodent (Dolichotis
   patagonum or Dolichotis Patagonicus) of the pampas of
   Argentina.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Dolichotis patagonum
    n 1: hare-like rodent of the pampas of Argentina [syn: mara,
         Dolichotis patagonum]