12 x 12 = 144 frogs
if every player removed a frog in turn and since each move is actually two turns (one for each player) then it would take 144 / 2 = 72 moves to remove the frogs

Of course some frogs are left behind at the end of the game... and there are also multiple jumps where more than one frog is removed... Sp the present version, will most likely be finished before 50 moves...