After having a haunting in my own house I don't know how you can do investigations. I am strong in my own house but could not go to some of the places you visit even in the day time.
I recently had a person I met through trying to contact a group to help me with whats going on in my house get attacked severely. I don't know all the circumstance's around it but she was in very bad shape.
After watching one person get attacked and possessed, that did it for me as wanting to be and investigator.God bless you that do do it and may you be protected at all times. I really don't think some of the people that do investigations totally understand the dangers that could happen.
It's true that animals sense things we can not see. My two dogs track something in my house that I can not see at least 4-5 nights a week that I have noticed. My little Jack Russel mix is scared of nothing! When she sees something she stands at attention with her eyes fixed on what ever she is watching and I can call her and she pays no mind to me but it's like she will stay between me and what ever she sees.
But thats just my thoughts and not meant to insult are upset anyone. I am just a regular guy that happened to have a haunting and got thrust into this world of spirits. Take Care All.