Sensitive rat

Question
When I first adopted my baby boy (He was 3 weeks old at the time)he got out. He got out during the night and was trapped in my house for two days before I finally found him. He's 3 months old now. What I'm curious about is, the night he got out there was a huge thunderstorm. I have a big window in my upper level room so the thunder was loud, and the lightning was very bright. Could the storm have been what spurred him to escape? Can rats be scared of thunder or lightning?

Answer
Oh absolutely they can!  Like humans, some rats are more sensitive to noise and sudden movement than others.  I've had rats who sleep through any loud noises in my house, including my vacuuming right by their cage, and some others who get startled even just by my walking in the room and run to hide in a hammock when I start vacuuming.  

You didn't say how your rat escaped...was the cage door open or did he gnaw his way through it?  It's not certain that he escaped BECAUSE of the storm, but it's likely that he stayed hidden because of the storm's sights and sounds.  However, he was a tiny baby then and not being used to his new environment, he may just have been plain scared in the huge house so therefore stayed hidden for comfort, regardless of the storm.

If your boys has a tendency to be afraid of sights and sounds, the next time there's a storm, I suggest either shutting the drapes/shutters on the window, or covering his cage with a dark cloth/towel (be sure to leave openings for fresh air to circulate).  To muffle the sounds, you can try leaving a radio on with music during the storms, or run an appliance that makes white noise like a fan or humidifier.

I was wondering if you have a companion for your boy.  If not, you should consider getting him a male friend as rats are very social creatures and can become quite lonely and depressed or withdrawn, despite spending time with you, especially during the night when they are most active and you are asleep.

I hope this was helpful and feel free to ask if you have any other questions.