The outside air intake is within the cowl assembly that runs along the firewall at the back of the engine compartment.

I understand a small mouse can enter through a 1/4" hole. If you keep the cabin air recirculation door closed when your HiHy is parked, MAYBE that will prevent mice from getting in.

I just noticed your animated avatar which is very funny! Since you own two hybrids I don't imagine you have much need for gearshifting...

Patrick Wong