Croatian wildlife is not very diverse, but still a few interesting species can be found (and seen if you are lucky..!). I am particularly fond of these two FDCs which show deer and white-tailed eagle (issue from 1993) and loggerhead sea turtle and bottlenose dolphin (1995). These stamps, as from the 90´s, are not valid for current use. Grr. xD
Many many great stamps on this topic, check here!