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 settlements owned by the Sole Survivor . 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 synth s 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 . The ghoulrilla is a ghoulified gorilla living in Nuka - World . They are most likely offspring of the original gorillas kept in the Safari Adventure zone of the park . Years of radiation have turned them into ghoulish creatures . Characteristics . Biology . Synth gorillas are natural in appearance and realistic in behavior , much like gen - 3 synths . Ghoulrillas are very similar in appearance to synth gorillas . However , these have scabs and scratches located around the body , with scraps of fur torn out as well . Their face is very rough and worn , with many skinless patches . The eyes are very dark , either lacking pupils or being entirely pupils . They range in size from small to very large . Gameplay attributes . The gorillas largely ignore 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 can also 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 . All ghoulrillas are passive by default , however attacking them will incite them to attack . Attacking Cito will also cause any ghoulrillas in Safari Adventure to attack the player character . Similarly , attacking The Pack will cause their ghoulrilla pets to attack . Variants . Gorilla . The basic variant of the gorilla are made by the Institute and are the weakest variant in the game . Ghoulrilla . In " Nuka - World " , the player character can find that the pre - War gorillas in the Safari Adventure attraction have undergone ghoulification . The ones remaining there are trapped in a small shelter with Cito due to the gatorclaw population in the area . Some are located in the Pack headquarters , and are used as combatants in the arena , fighting against mole rats and other ghoulrillas . Ghoulrilla king . The ghoulrilla king shares the same looks as the basic ghoulrilla but the king is more powerful and rare to spawn . It first spawns when the player character has reached beyond level 50 and hasn ' t yet completed the Safari Adventure quest . The ghoulrilla king ' s affiliation is to Cito and the king acts as the leader of the ghoulrilla group . Cito has named him ' Chris ' . Pack ghoulrilla . Found in the Bradberton Amphitheater , this ghoulrilla is used by The Pack as a combatant in their little arena . Appearances . Gorillas appear only in " Fallout 4 " and its add - on " Nuka - World " .