"Those poachers -- they kill even the small baby, this is -- may not be more then 2, 4 years. Small baby," he said while showing us one tiny horn.
The Nepali government is now starting to have some success in its anti-poaching crackdown. The most recent rhino census found 36 more rhinos than last year, which is terrific news. But no one is popping any champagne corks yet. These animals are still extremely endangered because the poachers are still active.
The World Wildlife Fund has also set up a network of informants in the local community, providing rewards to undercover agents. One agent we met, whose identity we had to protect because his work could get him killed, said he helped to catch 70 poachers.
The chief warden then took us to meet an arrested poacher in one jungle prison, where he is serving a 15-year jail term.
He claims he was just a middleman who was paid about $300 to transport a rhino horn from one area to another. Like most people who live here, he says, he was ignorant about how endangered the rhinos are. And what's more, he needed the money.
"That's the saddest part," Williams said, "The … guys who actually set the traps or shoot it, they will live in poverty for their entire life. They will die in poverty. They will never see the profits for this trade."
Nepal is one of the poorest countries in the world. It doesn't take much for the Mafias that trade in rhino horns to bribe the locals into becoming poachers. Many of these people are more worried about feeding their kids than protecting the rhinos.
Perhaps one of the most important things I learned on this trip was this: When you start trying to save wildlife, you quickly get into complex human issues of culture, sociology and economics. Williams says he spends more time thinking about human behavior than rhinos.
"One person told me: Listen, conservation is 99 percent man management and 1 percent actually doing something in the field," he said.
Williams says the only way to protect these animals in the long term is to mobilize public opinion. He'd like to see everyone who has a "Save the Whales" bumper sticker add one that says "Save the Rhinos."
As he points out, rhinos have a public relations problem. Elephants have Dumbo, lions have the "Lion King," but there isn't a cuddly rhino character in popular culture. As a consequence, humans haven't created the same sort of emotional bond with rhinos.
In the middle of interviewing Williams, we heard a snort. We scrambled and caught a glimpse of two rhinos running away. The male was chasing the female as part of a mating ritual.
Even after years of studying these creatures, Williams was exhilarated.
What a shame it would be if these creatures that have been around since the time of dinosaurs disappeared and their awkward majesty erased, because of us.