Among female elephants, or cows, gestation lasts 22 months, and babies are weaned after two years, so estrous cycles are spaced from four to six years apart. Because of this long interval, relatively few female elephants are ovulating in any one season. Females are thought to advertise estrus through hormones secreted in their urine as well as through the repetition of a vocalization called an estrus rumble. Musth bulls also have a particular rumble that advertises their status to estrus females.
Only a few bulls go into musth at any one time. The prevailing theory is that this staggering of bulls’ musth allows lower-ranking males to gain a temporary advantage over higher-ranking ones by becoming so agitated that dominant bulls won’t want to take them on, even in the presence of a female ready to mate. This mechanism allows more males to mate, rather than just the don, which makes the population more genetically diverse.
Although females do not go into estrus at the same time, more of them tend to become fertile at the end of the rainy season, which allows them to give birth in the middle of another rainy season, when more food is available. Long-term studies in Amboseli indicate that dominant bulls tend to come into musth when a greater number of females are in estrus, and they maintain their musth longer than younger, less dominant bulls. But this was the dry season, and Greg exhibited no signs of musth.
At the water hole, Kevin swaggered up for a drink. The other bulls backed away like a crowd avoiding a street fight. Not Greg. He marched clear around the water with his head held high, back arched, straight toward Kevin. Kevin immediately started backing up.
I had never seen an animal back up so sure-footedly. Kevin kept his same even and wide gait, only in reverse.
After a retreat of about 50 yards, Kevin squared off to face his assailant. Greg puffed himself up and kicked dust in all directions. He lifted his head even higher and made a full frontal attack.
Two mighty heads collided in a dusty clash. Tusks met in an explosive crack, with trunks tucked under bellies to stay clear of the mighty blows. Greg held his ears out to the sides, with the top and bottom portions folded backward and the middle protruding—an extremely aggressive posture. And using the full weight of his body, he raised his head again and slammed Kevin with his tusks. Dust flew, with Kevin in full retreat.
I couldn’t believe it—a high-ranking bull in musth was getting his hide kicked. A musth bull was thought to rise to the top of the hierarchy and remain there until his testosterone levels returned to normal, perhaps as long as several months. What was going on?
But just when I thought Greg had won, Kevin dug in. With their heads only inches apart, the two bulls locked eyes and squared up again, muscles taut.
There were false starts, head thrusts from inches away and all manner of insults cast through foot tosses, stiff trunks and arched backs. These two seemed equally matched, and for a half-hour the fight was a stalemate.