This 2017 video says about itself:
Langur monkeys grieve over fake monkey | Spy in the Wild – BBC
Langur monkeys mistake the motionless robotic spy monkey that was accidentally dropped as a lifeless baby langur and begin to grieve.
Documentary in which animatronic spy creatures infiltrate the animal world to explore their complex emotions.
From the Society for Neuroscience:
Monkeys appreciate lifelike animation
Monkeys experience the uncanny valley effect, just like humans, but a new realistic avatar can overcome it
June 8, 2020
Monkeys can overcome their aversion to animated monkeys through a more realistic avatar, according to research recently published in eNeuro.
Humans feel more comfortable toward life-like humanoid robots, but if a robot gets too life-like, it can become creepy. This “uncanny valley” effect plagues monkeys, too, which becomes a problem when scientists use animated monkey faces to study social behavior. However, monkeys overcome the uncanny valley when presented with a sufficiently realistic monkey avatar created using movie industry animation technology.
Siebert et al. compared how Rhesus monkeys reacted toward five types of monkey faces: video footage from real monkeys, a natural-looking avatar with fur and facial details, a furless avatar, a greyscale avatar, and a wireframe face. The monkeys looked at the wireframe face but avoided looking at the furless and greyscale avatars, showing the uncanny valley effect at work. However, the natural-looking avatar with fur overcame this effect. The monkeys looked at the model and made social facial expressions, comparable to how they would act around real monkeys. Using this type of avatar will make social cognition studies more standardized and replicable.