I don't doubt the dealer are correct in saying it was rats.

 

No doubt they have seen this sort of thing numerous times in the past.

11 hours ago, MJCM said:

Will follow up on your comments on how to prevent it but first priority is the closing off of the area where the car is parked so that we can put the preventive measures in place and NOT harm our dog, but that could still take a while unfortunately.

If you use the deterrent spray there's no need to close off any areas to protect pets.

In our circumstances, we find that regular sweeping and housekeeping in the yard is the primary deterrent. With this cooler weather, rodents are looking for warmer spots as well.

 

When I had my rat attack, the bro-in-law had dropped off a sack of corn for his chooks  inside the front gate, burst a corner and the rats would grab a mouthful of kernels, cross the yard and climb aboard the pickup to eat. You could see their little footprints and <deleted> in the engine compartment. One got trapped in the recirculate vent and died which we 'discovered by nose' about 4 days later. That was a four hour job to properly clean and disinfect properly; took an extra hour for all the maggots to drop out of the duct work. The rats had previously gotten into a corner between the battery and nearside headlight and chewed on a few wires but nothing major and another DIY job to fix. I have since installed a couple of 'rat guards' for the openings in the scuttle below the windshield where Ford chose to leave a couple of large openings to the recirculation system. Got them on lazada.

 

Before cleanliness became next to ratliness, a YouTube suggested mixing the napthalene mothballs with some regular tobacco in 'breathing' pouches or tubs in the engine compartment. I did that for a while but they were bit a faff to replace or replenish. Since the yardwork has improved, they've not been required. However, if we see the odd rat, I have a can of the regular deterrent and spray that around  the truck's access points and in the engine bay, just in case.