Forum:Gladiator Beast Effect

Does a Gladiator Beast have to remain on the field until the end of the battle phase in which it attacks/is attacked in order for its effect to be activated? I know it doesn't specify that it has to be sent from the field to the deck, and that there are monster effects that activate when the card isn't on the field, but at the same time, I wanted to be sure, since the effect activating either way seems a bit too easy.

Also, on an entirely different note, do spell cards go to the graveyard when they are activated, or when their effect is resolved?