When it becomes furious, its blood circulation becomes more robust, and its muscles are made stronger. But it also becomes much less intelligent.
(From Bulbapedia) Primeape is a bipedal Pokémon with a round body covered in whitish, shaggy fur. There is usually has a stress mark on the left side of its forehead, and it has triangular ears with pink insides and a pink, snout-like nose. Its arms and legs are brown and have metal shackles on the wrists and ankles. This is probably indicative of a method of training with weights. The hands have no visible fingers, instead resembling mittens or boxing gloves, and the feet have two toes.
Primeape is easily angered; even the slightest glance of eye contact will make it furious. When Primeape is furious, its blood circulation is boosted. This makes its muscles stronger, but at the cost of some of its intelligence. It will chase anyone who upsets it and will not stop until it has caught its quarry. Even if it is awoken from sleep, it will groggily chase whatever woke it.
Very short-tempered and prone to going berserk when enraged. Signs that it is angry include shaking and rough breathing. However, at this stage it is already too late to flee. It is not very intelligent however, and gets even less intelligent when it flies into one of its signature berserk rages.
Primeape can be found in vibrant forests or on mountains.