Caution: A herd of bull elephants is coming to the Denver Zoo

Raw testosterone leaks from slits on either side of their broad faces, running in rivulets down the wrinkled folds of their gray skin like liquid sideburns. The smell is acrid; one elephant researcher even described it as "evil." It's a stench that, when mixed with the potent urine constantly dribbling down the backs of their thick legs, can turn stomachs from several hundred feet away.

The foul-smelling secretions are a harbinger of a very special time in a male elephant's life, a time worthy of its own young-adult novel, something with a title like Are You There, God? It's Me, Ranchipur. Known as musth, this period can last anywhere from a few days to several months and is characterized by elevated hormone levels, heightened sexual interest and aggressive activity.

Basically, it's like middle school — with 12,000-pound students.

"They're pretty much interested in two things," says Dale Leeds, the curator of large mammals at the Denver Zoo, who's worked with elephants for more than twenty years. "They both begin with F. One is fighting."

In the wild, bulls roam alone for hours on end, searching for herds of females — some of whom they hope will be up for getting down — and fending off other males who might be their competition. Their penises protrude all the time and, perhaps because of the continuous urination, grow algae — a condition known as "green weenie."

And Denver is poised to become the green weenie capital of North America.

The Denver Zoo will break ground, hopefully, this year on a new, partially publicly funded exhibit called Asian Tropics. The centerpiece will be a habitat capable of housing twelve elephants, which would make it one of the largest in the country. Up to eight of those elephants could be male, and housing them together as a bachelor herd would be a feat never before accomplished in the U.S. But it could be necessary.

Asian elephants are endangered. To help protect the species, zoos figure they should beef up their captive breeding programs. About 83 percent of the total number of Asian elephants in North America are females, but since half of the newborns will be boys — who will grow to be ten feet tall and weigh as much as two Hummers — the zoos will need bigger, stronger exhibits in which to house them.

"Somebody's got to wrestle with the issue of how you manage a group of bull elephants," says Denver Zoo President and CEO Craig Piper. "That's something we could step up to more quickly than establishing a breeding program. We could make a home for a bunch of these younger bulls and work with their social dynamics and how to manage them, and those other zoos could get back into breeding, which is critical."

But effectively starting an elephant frat house is easier said than done. Less is known about male elephants than female elephants — and the mysteries surrounding musth are many. What triggers it? Why does the duration and intensity vary from bull to bull? Do bulls affect each other's musths? What would happen if two musth males were put together? Would they fight to the death?

"You really don't know how those dynamics are going to work," Piper says. "A little bit is, it's getting your own nerve up to do it."

In other words, it takes balls. Big ones.

It's estimated that there are between 30,000 and 50,000 Asian elephants left in the wild, in countries such as Thailand, Sri Lanka and India. By comparison, it's estimated that there are up to 690,000 wild African elephants. North America is home to just under 300 Asian elephants, about half of which live in zoos. The other half belong to circuses or are in private hands. Of those that live in zoos, only 25 are male.

In early 2005, the directors of 78 North American zoos that keep Asian elephants met to review a fresh draft of a long-term plan for the species' survival. One of the plan's key goals was to increase capacity, especially for males. Most zoos don't have any, partly because females are smaller, less aggressive and easier to house. Zoos that do have males have only one or two, as that's all that's needed for breeding.

But the plan suggests that zoos interested in breeding elephants should strive to hold up to twelve animals, including two males, and that non-breeding zoos should hold up to six elephants, with the capability to house all bulls.

"There was an overwhelming feeling that zoos needed to elevate their game," says Steve Feldman, spokesman for the national Association of Zoos and Aquariums, which hosted the meeting on behalf of its Elephant Taxon Advisory Group, made up of experts who drafted the plan. "If you're going to have a self-sustaining, diverse population, you need to give the elephants the opportunity to breed, and you need room for babies."