The holes on his neck earlier were a wake-up call for Matthew to take the fight more seriously and realize the danger that the alpha monkey poses to him even though Matthew already had a lot of options in his arsenal.
Now that Matthew knew a few of the alpha monkey's abilities, Matthew was able to do some exact countermeasures for it. The first ability was the piercing scream that made his body freeze for a split second and the alpha monkey was able to do it even if Matthew was not that close to the alpha monkey. It was the least dangerous considering that the paralyzing effect on his body lasted for a split second when the ear-piercing scream entered his ears. After the voice was gone, so was the paralyzing effect on his body, with Matthew keeping his current distance from the alpha monkey, there was no way the alpha monkey would be able to capitalize on the split-second freeze without Matthew being able to retaliate to it.
