un hamster
a female hamster is 'un hamster femelle' in French.
j'ai un hamster
A hamster is called "un hamster" (masc.) in French. Its prounounced like amstere rather than hamster.
If you could spell it in English, you would have the French - un HAMSTER.
J'ai un poisson (un poisson rouge if a goldfish) et un hamster.
J'aimerais (avoir) un hamster.
J'ai un hamster, j'ai un hamster apprivoisé
Yes, we do (see http://fr.wikipedia.org/wiki/Hamster).
Je n'ai pas un hamster
un hamster is masculine. To indicate a female, you say 'un hamster femelle', but the piece of sentence is still masculine.
J'ai un hamster à la maison : I have a hamster (guinea pig) at home