What I learned for the next step:

 

The spray makes a loud sound and the squirrels do not like that nor the actual spray, therefore it needs to be separated from the laser. The floor should also be in a material they know (wood for example).

 

I am also worried about traumatising the squirrels if I would use henna colour as planned, instead of just water like I've tested now. I have yet not enough knowledge to know if it would make them outcasts or feel bad about themselves (like some dogs that are coloured does). I will contact some of the experts I've gotten to know during this project and ask if I can do the experiment on some of the domesticated squirrels, also so I can track the possible behaviour changes.