I have a friend who annoys me so much by saying that animals are not intelligent.
Look at this video, there is a whole string of intelligent actions orangutan did:
1.) he unfolded side handles on glasses, because he understood their purpose,
2.) then he correctly imitated humans and without hesitation put glasses in a correct fashion, without fumbling, and tried them on,
3.) He even concluded he gets no benefit from them and returned them to the owner. Which essentially encompasses lots of abstract thinking, like: future utility and even moral judgement and empathy in predicting that owner would want them returned.
How this animal can not be a sentient being?