After the animal has very long legs it will have a very good chance of survival but there is a chance that there will start being overproduction and there will be too much polar fomentin's. They will adapt again and develop longer legs because the previous adaption is no longer enough. This is because they have to be the best to survive otherwise they will not reproduce and not pass on their traits. This is known as competition. This is an example with only one adaptation now image it with six more others all happening at the same time.