Well lets see ur born and then u die...natrual way of life, but if u want to be immortal then theres a cheat for that chickens die around 3-4 years old...Anyway the cheat is to save before ur animals death and it can give it extra time to live, but it be a pain in butt if u had to do that all the time just to keep ur animal alive, so u might want to go w/ a cheat from the game shark I think theres one there for long life or something...

what is gameshark???

They die when they get to old.I had this happen to me once.