simultaneous frequencies) display. One frequency was high (the result of the supra laryngeal constriction), and the other was low (the result of normal vocal fold oscillations). Yelping Yelping also known as "grunting" is usually only made by herd bulls when they are excited. They are made more often while interacting with cows than with other bulls. "Yelping commonly was accompanied by contractions of the penile region with simultaneous emission of short spurts of urine." Phases The rut has six phases: the pre-rut, the first breeding phase, the first rest phase, the second breeding phase, the second rest phase, and the third breeding phase. The pre-rut takes place from mid-August through the beginning of September. During the pre-rut bulls begin bugling and gathering their herds. Bulls will bugle to attract cows as well as to express dominance over other bulls. A "herd" bull is the dominant bull in a herd. Younger, smaller bulls are known as satellite bulls, as they tend to cling to the edges of a herd trying to pick up any cows willing to leave the herd. Larger satellite bulls will challenge the herd bull to try and take control of the herd. These challenges include a good deal of bugling as well as fighting. The first breeding phase of the rut takes place between the beginning and the middle of September. This is when the three year and older cows come into estrus. During this time herd bulls bugle to keep their cows close by, they also answer the bugles of satellite bulls to let them know they are still dominant. A herd bull will also bugle while approaching a cow in estrus so the cows become familiar with his bugles. The first rest phase of the rut occurs between the middle and the end of September. At this time the older cows are predominantly out of estrus and the younger cows have not yet come into estrus. During the rest period, satellite bulls will try to join the herd while the herd bull is resting. The second breeding phase of the rut takes place three to four weeks after the first breeding phase. This is due to younger cows coming into estrus, as well as older cows that were not bred on their first estrus cycle coming back into estrus. Herd bulls are less aggressive towards satellite bulls at this phase in the rut due to