1. Your dog is spooked because of the new environment,smells,sounds. he is nervous no matter what his size. It is normal.

2. The smells that spook him come at night as the wind shifts do to nocturnal cooling of certain areas that cause smells to move thru differently at different times.
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If you think its something wild,set out bait, near the wood line.
If you think its something paranormal,get a local dog to sit outside from a near by neighbor.

If that dog goes nuts,you may have an issue.