How do you know when a guinea pig is sad?

You Know when a guinea pig is scared when you see it start to kind of curl and make his/her self shorter. They also tend to pee or poo where they get scared. If the Guinea pig is in a cage when he or she is scared it will most likely hide in a tunnel,Pigaloo,Igloo,Ect.!! Just make sure that if he or she is out or in a cage ALWAYS avoid hovering over them..Slowly walk totheir cage or where they are in a calm fashion.Hope I helped.Hope your piggie(s) won't be as scared.It takes a while to get them used to you.Enjoy!:)