Here it depends... you can't "know" what gender it will be. Usually, whatever finishes in "a" is a female. For example, "pisica" (cat).
But you can't know. "Urs" = bear, and it's masculine. "Leu" = lion, the same. So... in English it's much easier.
For "urs" you get "ursoaica" as the female bear, for "leu" you get "leoaica" as the lioness etc.