Sheepdogs can display aggression under certain circumstances, but it's not a common trait among them. Sheepdogs are generally bred and trained to be gentle, intelligent, and obedient animals that work well with other animals and people. However, certain factors can trigger aggression in sheepdogs, such as lack of socialization, fear, insecurity, or territorial behavior. Aggressive behavior in sheepdogs can be directed towards other dogs, livestock, or even humans, and it can range from growling and barking to biting and attacking. Aggressive behavior in sheepdogs is not a desirable trait, and responsible breeding and training can help prevent it. Proper socialization, early training, and positive reinforcement can also help reduce the risk of aggressive behavior in sheepdogs.