What went wrong when the tortoises, snakes and lizards left the forest?

With no tortoises the jungle seemed to be rotting as the tortoises used to eat the rotting fruit and rotting animals in the river. When the snakes left the rats increased and became the biggest nuisance. When the lizards left, there was no fear to the insects and there were now millions of them growing bigger and nastier by the day. So the whole forest seemed to have gone crazy when the tortoises, snakes and lizards left it.