I've never heard that rats are chewing on cables. We have a lot of trouble with martens and you can only get rid of them by a wire mesh under your motor compartment.
No, these are fully paid-up rats: I eventually found the characteristic droppings.
It's a question of which is worse: the rats or the birds. The birds poop straight acid - probably powerful enough to put into your battery. What they do to the car's paint isn't pretty, but there's nothing to be done. We also have pigeons, and can't do anything about then either. They go up on the roof and drop their droppings down the side of the building and into the various gutters, where they clog the outlets and cause flooding. We can't poison them because that's too dangerous to other wildlife; can't have them shot because it's illegal to use even an airgun in a built-up area. So the damned birds win without a battle. And then we have to pay every spring to have a couple of men go up there and clean everything up, and that doesn't take into consideration the damage that the build-up of water does to the ceiling of the staircase; I can't count the number of times that the plaster has collapsed and we've had to get the painters back in...
I did buy some fireworks once and go up into the penthouse from where I could throw lit bangers onto the roof, but in the end it was I who was the more discomfited from both the noise and the risk; not a Guy Fawkes figure at the best of times.
Though we have a hill covered in pines about a hundred yards away, and an abandoned farm on the other side of the hedge that's turning into a pine forest (the farm, not the hedge), I haven't seen any martens, nor do I know if they live on Mallorca. I did once see something at the foot of the hedge that looked like a very large and hairy brownish cat one evening, but it ran away so quickly I didn't have time to recover from the shock and take note of what the hell it really was. I hate the very idea of rabies.