Do female dogs become more aggressive toward male dogs?

Yes, female dogs can become more aggressive toward male dogs when in heat. This is because when a female dog is in heat, she is releasing pheromones that attract male dogs. These pheromones can cause male dogs to become aroused and aggressive, and in some cases, to attack the female dog. In addition, if a female dog is spayed and not in heat, she may still experience aggression toward male dogs due to territorial instincts.