Musth is a period of time during a bull elephant's life when they start hitting their stride and reach sexual maturity. Just like their male human counterparts, it usually occurs when they reach the age of somewhere between fifteen and twenty.
Now, the last thing I think I'd ever want to run into is a horny elephant and apparently male elephants that are in musth become pretty gosh darn aggressive. Their temporal gland becomes quite swollen and a strong smelling fluid is secreted that is chock full of testosterone and runs down their cheeks. As a matter of fact, testosterone levels can climb up to 60 times higher than normal when an elephant is in the midst of musth. Apparently, they find this very annoying and become aggressive towards other males and anything else that might happen to get in their way.
Actually, the musth phase occurs in three distinct stages. The first is what is known as a pre-musth phase and lasts about three weeks. It's during that time that the temporal glands began to swell and the fluid begins to build up. The elephant might display some acts of aggression towards other members of the herd or his handlers but is usually able to calm himself down and make nice.
The next phase is when the poor fella hits what is known as a "musth high" and it lasts about a month. Any females that happen to be in heat and are not protected by more dominant members of the herd are fair game. Bull elephants have even been known to go after females that are not in cycle, a rarity in the animal kingdom.
The third phase is known as "post-musth". I'd like to think about it as something along the lines of when elephants cuddle and have long bouts of pillow talk but it's more of a calming down period. You never know when round two might start but the odds are against it.
Some scientists think that reason mother nature has thrust musth upon the elephant is to prevent excessive inbreeding among members of the same herd. Studies have shown that the timing of elephants entering musth often varies and the likelihood of two or more males entering musth at the same time is usually slim.
We've all probably seen video footage on Fox or The Nature Channel about "When good elephants go bad!". Circus handlers and trainers are mauled and entire villages are trampled by these so-called "rogue elephants" who one day just seem to go nuts. Well, for the vast majority of the time, most of that occurs when an elephant is "musthing" and can't control himself.
Usually, an elephant will musth up until he hits the age of fifty or so and then, like most of us, he starts to slow down. Some studies also indicate that their tusk size may have something to do with how long a bull will musth. Another study indicates that elephants who are held in captivity may be subject to longer period of musth that actually can last up to a year. Poor fella. I find that hard to imagine.
All in all, I guess not all that much is known about what an elephant really goes through when in musth. I imagine it would be hard to approach them in order to examine their feelings but if you happen to see a bull elephant with what looks like tears coming down his eyes and they stink to high heaven, my advice would be to stay very far, far away.
Source(s) http://www.elephant.se/musth.php