The Javan rhino is one of the rarest large mammals on Earth, with only about 68 individuals left. It hasn't lived in captivity for more than a century, and because it's a solitary species that skulks through dense forests, it's rarely seen by humans.

Nonetheless, during a recent visit to Ujung Kulon National Park on the Indonesian island of Java, a team from WWF-Indonesia and Global Wildlife Conservation (GWC) abruptly found themselves in the company of this critically endangered creature.

"We heard a crashing sound, and suddenly this rhino just appeared to the right of us," says Robin Moore, the team member from GWC who took the photos. "It was a surreal, once-in-a-lifetime moment, like time had stopped, and it was all we could do not to scare the animal away in our excitement. By sharing these photos, we hope to give people an emotional connection to this rare species — an animal that even rhino biologists only dream of getting a glimpse of in the wild."

Javan rhinos have only been seen in the wild a handful of times, according to a joint statement by GWC, WWF and Ujung Kulon. This one began wallowing in mud near the elated conservationists, and thanks to lingering near-dusk daylight, they were able to capture what may be the first-ever images of a Javan rhino mud bath.

In addition to photos, the team also recorded a video of the encounter:

Javan rhinos used to be common in forests across Southeast Asia, inhabiting parts of India, Bhutan, Bangladesh, Myanmar, Thailand, Laos, Cambodia, Vietnam, Indonesia and southern China. The last Javan rhino in Vietnam was found poached in 2010, with its horn sawed off, and the Vietnamese subspecies is now recognized as extinct.

That leaves just the one population of 68 Javan rhinos on their namesake island, all living within the boundaries of Ujung Kulon, which spans nearly 500 square miles (1,300 square kilometers) at the western edge of Java.

The team was in Ujung Kulon to do "scoping work," according to Javan rhino expert and GWC director of species conservation Barney Long, to see how conservation groups could work with the park to boost Javan rhino conservation efforts.

Javan rhino wallowing in mud in Indonesia Seeing a Javan rhino was 'exhilarating,' Long says. 'You breathe with excitement when you really should be trying to think of all these scientific questions, but you're just in awe of this rare creature.' (Photo: Robin Moore/Global Wildlife Conservation)

They actually had two separate rhino sightings, Long explains. He was there for the first one, which took place the night before Moore captured these images.

"We were on a raised platform," he tells MNN. "We heard it coming, and it broke out from the forest into an area with scrubby bush. We just saw its head move through a small clearing, about 14 meters (46 feet) away. It slowly came through the low bush, and then came out of that bush very close to our platform. It was about 7 or 8 meters (23 to 26 feet) away. It actually walked up to the platform, almost directly below us. Then it smelled where we'd been on the ground and ran away."

They weren't able to photograph the rhino during that first sighting, but luckily another chance came the following day, when Moore was waiting on the platform with his camera. Almost anyone would be excited to witness a rare encounter like these, but the experience had particular significance for Long.

"I've been involved in Javan rhino conservation work for a long time, and I was part of the team that documented the extinction of the last subspecies in Vietnam," Long says. "So the feeling you get when you see something like that — when you've seen it disappear from a country, and they're literally just found in this one site now — the privilege of seeing something that rare, the mixture of emotions, it's hard to explain."

Javan rhino wallowing in mud in Indonesia Javan rhinos spend a lot of time wallowing in mud and in rivers, Long says, both to cool off and to help them remove pests like parasites and biting flies. (Photo: Robin Moore/Global Wildlife Conservation)

That mixture of emotions includes both joy and anxiety, Long explains, due to the ongoing fragility of this last population. On one hand, Javan rhinos have come a long way from the 1960s, when as few as 20 were left. This progress is due to hard work by conservationists and by Ujung Kulon National Park, which has so far managed to protect the rhinos from poachers. It's partly a good thing that all 68 survivors live in a protected park, but it also means species has all its eggs in one basket.

"Even though there's been no poaching, it could be vulnerable to poaching any day," Long says. "As we know from the poaching crisis in Africa, poachers are out there trying to kill rhinos all over the world."

The region is also home to livestock that can spread diseases to the rhinos, Long adds, whose dense concentration means a single outbreak could doom the species. And on top of that, Ujung Kulon is located just south of Krakatoa, the infamous volcano that devastated the region in 1883. Anak Krakatau, or "Son of Krakatoa," is an active volcano near the original eruption site, and if it erupts, it could easily wipe out the species in an instant. Even if the volcano didn't directly threaten the rhinos, an eruption or an earthquake could flood their habitat with a tsunami.

"So even though it's a huge conservation success story," Long says, "the species remains very vulnerable and faces an unfair number of threats against it."

Javan rhino wallowing in mud in Indonesia Although their habitat is legally protected, the last population of Javan rhinos remains highly vulnerable to threats ranging from disease to volcanic eruption. (Photo: Robin Moore/Global Wildlife Conservation)

Discussions are underway to relocate some Javan rhinos, Long adds, in an effort to buffer the species. But in the meantime, he hopes this rare glimpse will help raise public awareness of these often-overlooked rhinos.

"When people think about rhinos, they think about African rhinos. They don't think about Sumatran and Javan rhinos, which are by far the species most threatened with extinction," he says, noting the two species number fewer than 150 individuals put together, compared with thousands of white and black rhinos in Africa. "That's why we're releasing these images. The real rhino crisis is in Indonesia. We need to get attention and support to these species, but most people don't even know they exist."

Conservationists record a 'surreal' encounter with a rare forest rhino taking a mud bath
Only 68 critically endangered Javan rhinos are left on Earth.