alone
animal
annoyed
ape
bars
behind
cage
caged
captive
captivity
captured
chimpanzee
concept
environment
environmental
exhibit
expression
eyes
face
fence
free
freedom
gorilla
head
iron
jail
locked
lonely
look
looking
macaque
mammal
metal
monkey
natural
nature
nursery
out of focus
portrait
primate
prison
sad
sadness
solitude
tame
wild
wildlife
zoo