Why does one of my rats bite the other 2 and pull them back in when they try to leave the cage?

Question

i have 3 rats the older one i got first and then 2 smaller ones, it the smaller of the 2 new ones, that bites the other 2 when they leave the cage

Answer 1

That's pretty much the only way a rat has of trying to keep another rat from moving away so for whatever reason it doesn't want the other two to leave the cage.  It could feel insecure about leaving the cage itself and doesn't want to be left alone.  The solution in this case would be to put extra emphasis on hand-taming it, and especially getting it used to being handled by itself outside of the cage.  You could also try feeding it by hand near the door so that it starts to regard that area as a good place.