I have 6 - 5 month old Marans I hatched out last Fall. 1 cockerel and 5 pullets. I just bought 2 - 14 week old Marans pullets and put them in with the 5 month old group. The next day one was dead! I didn't notice any aggression the first day...just the usual, casual chasing the newbies around but the poor thing was dead and the other one cowering in the corner when I discovered the situation. The victim only had pecking on its lower back by the base of its tail I assume from taking the usual defensive stance of head in corner to protect itself. To be honest the wound didn't look mortal but never the less the bird was dead, maybe from shock. I removed the other new pullet from the pen as I did observe their behavior for awhile and they were relentlessly chasing her around. At least one of the 5 month olders was. Now I'm wondering about integrating the 5 month old group into my main chicken coop per my plan. Will they terrorize my other chickens? Are Marans known to be aggressive? Any thoughts or ideas?