The diagram below shows a river separating grasslands X and Y.
For many years, animal P, a plant-eater, lived on grassland X. Animal Q lived in the river and would feed on animal P when it drank from the river.
In 2017, animal P moved over to grassland Y even though many of them were eaten by animal Q when they crossed the river.
Which of the following are possible reasons for animal P to move to grassland Y?
(You may select more than one answer)