Well I went to move my truck into the driveway and I heard a squeal.  After I moved the truck my gut said to look under the hood.  Low and behold there was a nest on one of my truck batteries.  It was made of leaves.  I moved the top layer and underneath it was a new born squirrel.  I moved in to the trees.  Here are some photos.  I only post this to remind folks that squirrels can build nest anywhere and cause havoc.  I suspect if I did not check I could have had a fire under the hood as all the leaves were very dry'

 
 A surprise indeed.  You are lucky. It could have been mice. They have a never ending appetite for wire insulation = $$$$$$.

 The worst thing I ever found was walnuts in my engine air filter assembly. No damage done, just a warning for me to be vigilant.

Squirrels and mice seem to like some kinds of silicone.

Fire up the grill. Have not had squirrel since I quit hunting years ago.

 Thinking back: There was a video on the Weather Network some months back where a red squirrel had a pickup loaded up, I mean full, of walnuts. The engine compartment, under the seats, the dash...

 There were nuts in places where the person couldn't get at to remove them. Evidently the the truck had only been parked for only a few days. 

Several years ago I started my truck one morning and heard a God awful cat noise and several lights on the dash came on.  I looked under the hood and found orange fur everywhere and the belts were off.  We had two orange cats at the time and I found the older wise one and he was fine but I couldn't find the younger one.  I had to take my wife's Jeep to wherever it was I was going and that afternoon the younger cat showed up when I rattled the feed bucket and he was missing large patches of fur.  The truck was still so new the belts were a dealer item only and of course they were trashed and expensive.  Needless to say the younger cat has avoided our vehicles ever since.

How long was it parked?  I assume this was not overnight.  We have squirrels all over the back yard.  The neighbor had one get in the garage up in the shelving and created some issues, but I have been lucky so far.

The newer vehicles use a soy based insulation on the wiring, yum yum.

How long was it parked?  I assume this was not overnight.  We have squirrels all over the back yard.  The neighbor had one get in the garage up in the shelving and created some issues, but I have been lucky so far.

Less then 48 hours however a squirrel can build a nest in a day or less

My wife gets squirrel  debris on top of her Subaru Legacy engines all the time in the winter.  I think they like the engine heat.  No signs of nesting though.  A few years back they ate through a her windshield washer line.

Wonder if mom found Jr!

Mice love engine compartments when it gets colder in Florida. I put 1/4 blocks of Irish Spring soap in a few spots that don't get hot when the engine runs so it doesn't melt. It keeps the mice away because they don't like the smell. You can also use peppermint oil on cotton balls but it does not last as long.

Nice tip!