I am working on a HVAC project where lizard in going inside the electrical unit and causing wire damage and short circuit. I need to find some solution to detect or repel lizard before any catastrophic situation. Since lizard are cold blooded species, I cannot use IR head index measurement methods or PIR sensor. Also, lizard are very small creature so method need to be foolproof.
A camera with provided lighting (IR is okay) within the duct (area where no stray moving objects should appear) would be perfectly okay for detection. Lizards aren't invisible. Now, stopping the lizards might be trickier.
I think though, that the best approach would be to make the intakes/exhausts to face downwards and grease the walls - or include a T-shape section, with a service hatch on the short downwards facing segment, thoroughly greased. Detection no longer required.