Gorilla

The gorilla is a synthetic creature found in the Bioscience division of the Institute contained in terrariums. With the Wasteland Workshop add-on, they can be captured in cages and domesticated in a player character's settlements.

Background
The gorillas are a pet project by Clayton Holdren in an attempt to recreate pre-War gorillas and hopefully other species. There are two specimens, and both are actually synths designed in the form of the Silverback gorilla. This is revealed upon talking to Clayton, who brings up the gorillas while introducing the Sole Survivor to Bioscience during Institutionalized.

Biology
They are synthetic gorillas, natural in appearance and realistic in behavior, but robotic at base level.

Gameplay attributes
The gorillas are largely passive to the player character and wander around their terrarium. However, during A House Divided, their enclosure can be opened, where they will be hostile to everything, including the player character. This same occurrence can happen if the The Nuclear Option quests are carried out against the Institute. Also, placing an Institute beacon during Airship Down may spawn a couple of them to the player character's side. Upon breaking into the Bioscience division, the cage will then be opened and the gorillas will attempt to assist the synths in combating the Sole Survivor and whatever faction they chose to side with.

Ghoulrilla
In Nuka-World, the player can find that the pre-War Gorrillas in the Safari Adventure attraction have undergone ghoulification.

Appearances
Gorillas appear only in Fallout 4.