I am minding some hens for a sick friend which I have leg-banded so I don't get confused when they need to be returned - one araucana has gone into the araucana pen; three pekins went into the pekin pen; but the two Isa Browns and one Naked Neck have been put into their own pen, after removing some of my hens from it. I was warned recently that Isa Browns can be aggressive. I have never had any of my own so I didn't know this. I breed silkies, pekins, wyandottes, araucanas and a heap of crosses and have had the occasional aggressive rooster. I assumed that as they all lived together at home that they would be fine here however yesterday we discovered one of the Isa Browns attacking the Naked Neck which was bleeding badly from the head and also from the back - the back damage covered an area the size of my fist and was red raw. We immediately removed her and have put her in an isolation pen, inside the main enclosure (40ft by 15 ft) so that she doesn't feel isolated. I had a similar incident occur (strangely - in this same pen when an Easter Egger attacked one of my pure lavender araucanas; I took her to the house and nursed her there but she died a few days later - maybe the isolation wasn't the correct thing to do?? I have treated the Naked Neck's wounds with Betadine; she is eating, drinking and enjoying some cuddles and looks okay, not at all mopey so I think ... hope ... that she will be alright. Has anyone had this type of behaviour before? They have always been together at home and as far as I know there have been no problems. They have been with me for about a month now so this struck me as odd that suddenly the IB became so vicious. I had noticed that the Naked Neck spent a lot of time on the perch so I had been hand feeding her each morning lately. Could the others have become jealous? I wonder if I need to keep her away from the IBs when she has healed. Any advice would be appreciated.