Normally a shy, quiet animal, he becomes aggressive, serving notice of his territory by raking the brush with his antlers, calling to cows, challenging other bulls and building scrapes. A scrape is built by turning up the ground with his front hooves, urinating in the fresh earth and then rolling in it. The strong aroma is a call to cows and a challenge to bulls. Challenges are most often dealt with through posturing and display of antlers. Whoever looks the biggest wins.
Some injuries can be fatal.
The bull does not feed during the rut. Couple this with the stresses of keeping his harem together and defending it, the rut is very exhaustive, making him more susceptible to predators. The cow can bring big stresses onto the herd bull because she is always willing to draw in other bulls. Instinctively, her loyalty is to her species and her calf. Subsequently, she looks for the most dominant bull to breed her.