I'll tell you about my urban fox squirrels. They aren't afraid of ANYTHING. They're used to skittering around people, cars, lawnmowers, bicycles, screaming kids, dogs, and cats. In fact, they won't run away unless you chase them. Then they come right back. They are totally immune to spices (hot pepper sprinkles, etc.) and threatening smells (feline urine, for example). They just ignore all that. Their world is filled with natural and unnatural smells. I've seen these guys climbing over a fabric and wood owl. I can't imagine that a fake stationary animal or person is going to bother them in the least. Maybe if you can arrange for the thing to move suddenly, it might get their attention.

There are people who swear by these repellants, though. They just don't have street-wise or gangsta squirrels.

they keep fake pests away

i have no problem with fake snakes, so whatever i'm doing seems to be working.