Animal growth is limited by available food supply, and by predation and disease and overcrowding.

Mitosis .

The growth of an animal can be stunted if they don't get enough food rich in proteins. It can also be due to malfunction of pituitary gland which releases growth hormone. Such cases lead to dwarfism.

Its definitly animal and a mammal but I'm not sure which.

It depends on the animal/plant. For people, it is about thirty to thirty-five. Usually, the smaller the animal/plant, the earlier the growth stops.