"I have an animal, it is a mouse."
Translation:Eu tenho um animal, é um camundongo.
I see my Brazilian English students love using commas instead of periods when writing English... Seems to be a common mistake.
In Portugal a mouse is a "rato (pequeno)". In Brazil apparently it's a "camundongo". (I have just noticed that I had a comma in my comment, which is incorrect, and have changed it to a period. Duo's sentence has the same mistake, which is very common, but still is wrong.)
I wish duolingo offered Portuguese Portuguese as well as Brazilian Portuguese.
o Camundongo is a little mouse (probably a species, not just a size issue).
o Rato is any kind of mouses and rats.
a Ratazana is a big one, scary thing.
I usually made the distinction between a mouse and rat with ratinho e ratao.