Pack rats, real ones.

We had rats in one of our barns years ago. We were told for every rat you see there are 50. We finally got them with traps. Poison was no good because of other animals. Good luck!

We tries a new product this year seemed to work pretty good. Its a natural product. We also used rat traps with peanut butter as well as leaving the hood open on the truck.
http://www.earth-kind.com/

As mentioned, rats won't like to nest where there is light. My RV is outdoors and rats are a problem here so I run a cord out to the coach with a string of LED rope light attached. It consumes less than 4 watts so I leave it plugged in and draped around the engine all day and night.

It's has been working for a couple of years now. Well, that and the neighbor's cat. It's a friggin' graveyard of rats and birds underneath the coach.

Eric

In Southern Arizona, we have pack rats EVERYWHERE. They are very destructive. Give them the smallest opening, and they will try to get in. In the last week, I've trapped six of them using rat traps in the back yard right by the house.

They will get in your engine compartement and eat wires and and anything that is not metal. They bring in trash, and leave behind fleas and waste. In addition, since they are part of the food chain, they attract rattlesnakes and gila monsters.

However, they do not like to hide in places where there is light. In addition to placing rat traps around the vehicle, quite a few folks here put a mechanic's drop light or two in their engine compartment. The concept is that the rats will not want to nest in the engine compartment because of the light.

Just be careful with any traps that set so you don't hurt pets or kids. They are very powerful.

You live in the heart of farming country. There must be a farm supply store near you. Ask them how to get rid of rats. If you don't want to deal with it yourself, call an exterminator. There may be a waiting list.
You may have more than one rat if they're after nesting material.
Personally, I wouldn't want to deal with getting rid of a live rat. Or a dead one, for that matter. A really high Ewwww factor.

put some rat traps under the rv with peanut butter on the flipper.

Yep, pretty sure its a rat. He even has a food stash of acorns and small potatoes (from our storage bin). Had this happen one time when one built a nest in a combine. They will chew on wiring and cause all kinds of trouble. I'm trying traps, but no luck so far. The cats here are too lazy to hunt. Just wondered if something like the mothballs might discourage them.

Try natural peppermint oil extract, The smell keeps mice away inside the camper, should work for rats under the hood. Just put on a cotton ball, place in a baggie left open, and wait for results. Will have to repeat every 3-4 weeks.

just wondering...are you sure it is a rat?

I've found that short of having a feral cat waiting for the rat to show up for his dinner, that using mothballs placed in a leftover stocking or other kind of bag will deter the rat pretty well. Have had them tear out the sound proofing material under the hood of my pickup, and they like to chew plastic too. Don't know if one of those sound emitting devices placed under your hood would help or not, might be worth a try.