1 Corinthians 15
21 For since by man came death, by man came also the resurrection of the dead.
22 For as in Adam all die, even so in Christ shall all be made alive.
Last I checked, animals aren't in need of a Savior -so it's an irrelevant question.
I can't imagine this, but perhaps they weren't meant to live forever? But, since the bible doesn't specifically speak to this, I don't know why you really want to know.
Jean