Answer:
The rat population increased because of Razak's own actions.
Step-by-step explanation:
Eagles are carnivores that eat rats. When Razak made the decision to kill any eagle in his sight, he did not just protect his chickens, but also the rats. So, as time passed by, with no possible predator to take their number down, the rat population increased, also increasing the number of rats that stole the food from the chicken.
In order to prevent the rest of the chickens from dying, Razak can focus on killing the rats, instead of the hawk-eagles. He can lay traps to capture the rats. He can also keep the chickens in a safe place so that any possible hawk-eagle won't be able to get to them.