Hostile territory? You think?

“Watch where you step,” Leandro told me. “Stay away from the caiman.”

That was the sort of warning I took seriously, even when spoken so casually. We were in water up to our thighs, deep in Brazil’s Pantanal wetlands, and it was pitch black outside, save the stars and the headlights from the jeep.

“What do you mean, the caiman?” I asked, trying to sound unconcerned about crocodile-like reptiles looming near my unprotected legs.

“Over there,” he said, pointing to a spot a few feet away. “That’s where the caiman is that we were stuck on.” I moved quickly.

Now it all made sense. We had just pushed our jeep off a dead caiman. At least I hoped it was dead.

Maybe I should have been less surprised by this development. The Pantanal, in southwestern Brazil, is the world’s largest freshwater wetland — where caiman far outnumber humans. I’d come here, along with 13 others, as an Earthwatch Institute volunteer. The coolheaded Leandro Silveira led the jaguar research project that Earthwatch co-sponsored with Conservation International.

We’d been waylaid by the reptilian roadblock going to a party at another fazenda, or farm, some miles off. In Pantanal terms, it was a 16-gate trip — meaning someone had to get off the truck to open a gate across the road 16 times.

About 13 gates into the drive, the sandy road became submerged below 3 feet of water for nearly half a mile. It wasn’t our first water crossing, but this time we got hopelessly stuck. A fellow volunteer and I hopped out to push, foolishly disregarding the likelihood of water creatures — caimans, anacondas, piranhas. Now that I knew the cause of our breakdown, the walk back to dry land seemed significantly longer.

This is no Pantanal safari

Travelers who require certain amenities — say, room service or private baths — are unlikely to find their way to the Pantanal. Although there are tours of this remote region, which borders Paraguay and Bolivia, most are safari-style outings of a few days. Earthwatch volunteers, on the other hand, spend seven or 12 days working on research or conservation projects related to jaguars, otters and other wildlife.

My group arrived by a five-seat prop plane, a one-hour flight from Campo Grande, Brazil. From the air, we watched the hills fall off into an enormous flat basin punctuated by clumps of forest and lakes or dry, circular lakebeds that would fill in the rainy season.

Waiting for the others, we walked around the 19,000-acre fazenda, out to a tributary of the Rio Negro. The river was unlike anything I’d ever seen. Scores of caimans basked on its banks. Across the river sat a family of capybara — the largest rodents in the world. Hyacinth macaws flew overhead, and kingfishers noisily dived into the water.

Reminders of the rainy season — clumps of seaweed and grasses — hung on tree branches 10 feet above the current water level. In a few months, most of Fazenda Rio Negro, including the landing strip, would be under water.

At one time, this ranch was 500,000 acres and, like most, had been used for grazing cattle. But with ranching becoming less profitable, some Pantaneiros think that ecotourism may be their future. Conservation International purchased this self-sustaining farm in 1999 and teamed up with Earthwatch to conduct wildlife research here.

There are more than 30 million caimans in the Pantanal, an area about 24 times the size of the Florida Everglades. The region is also home to jaguars, pumas, maned wolves, giant otters, peccaries, anteaters and rheas.

Researchers at the fazenda photographed four jaguars with stationary camera traps in a 1.8-square-mile area. The Cockscomb Jaguar Sanctuary in Belize, by comparison, has 8.8 jaguars per 62 square miles. It’s also much easier to spot the creatures on the Pantanal’s grassy landscape than in dense rainforest, which adds to the allure this place might hold for naturalists and tourists.

A week after our arrival, we were staring at a carcass of some sort. The manager at this nearby fazenda said the skeleton was that of a calf killed by a jaguar about two weeks earlier. Ants, vultures and other scavengers had picked its bones clean.

Leandro was unconvinced. “A jaguar would have crushed the skeleton so that it would hardly be recognizable. This is a puma kill,” he said to us, in English — and notably not to the rancher. “Look at the snout of the calf. You can clearly see where the puma made its original incision. This is something that pumas do. No way did a jaguar kill this calf.”

In the end, it wouldn’t matter.

Conservation International’s jaguar project aimed to carve out 800 square miles where ranchers voluntarily agreed not to shoot jaguars, whose numbers have been drastically reduced in Central and South America. Conservation International, in turn, compensated them for any livestock losses and included puma kills simply to promote trust. If the Pantaneiros thought Leandro might blame a puma to avoid paying out, they might not enlist in the jaguar project.

If the locals harbored suspicions about Leandro and his assistant Marian, they were doubly suspicious of the volunteers. None of us looked or acted like Pantaneiros. None of us had a rifle or carried a long knife in the small of our backs. Our machete skills were limited. Our hats came from REI or L.L. Bean.

Piranha soup

Later that night, after another dinner of beans and rice along with soup containing piranha meat from the Rio Negro, we settled in for the evening on the patio of the pousada, one of eight buildings on the fazenda. After a long day in the hot sun, we relaxed by playing cards. Without a score pad, we developed a game that was part rummy and part truth or dare. The winner of each hand chose a task for the loser.

Michael, another volunteer, was launching into his imitation of a greater rhea (which looks a lot like an ostrich but not as tall) when Leandro came by the table and asked what I was scheduled to do the following day. I was going to work on the ongoing rodent project, which was not part of our original itinerary.

“Good, because we would like you to volunteer to go with Marian and help with the fire at another fazenda.” Wading among caimans had made me wary of volunteering, but his tone left me with the impression that I already had. He drafted Aaron, another volunteer, as well. Wildfires are not unusual in the Pantanal in August, the end of the dry season.

“Make sure you pack an extra lunch,” Leandro added. “You may have to stay there tomorrow night, depending on how bad the fire is.”

When my doctor had signed my application to certify that I was physically capable of joining this team, he had no inkling that my duties might include firefighting. But we were in the Pantanal, where itineraries are rarely followed.

During our first eight days here, the temperature hadn’t dipped below 80 degrees, but the next morning there was a lingering mist and it felt like 40. I borrowed a sweatshirt from my sleeping roommate and headed out to fight the fire.

Aaron had similar trepidations about our mission. We quietly helped load the pickup truck for the 20-gate trip to the fire. As I hopped into the back, Marian sized up my lightweight nylon REI pants and said, “You can’t wear those. They’ll melt.”

Aaron said he had a pair of fatigues I could borrow, but he was 3 inches taller and 40 pounds heavier, so the pants were loose-fitting, dangerously so. At least they wouldn’t melt. Just fall off.

Unsung heroes

As we drove, the fear started to wane, and we became increasingly aware of how uncomfortable the back of a truck can be. Most of the time we weren’t even on a road, but Marian seemed to know where she was going.

“I thought we would be able to meet them here,” she said with a frustrated sigh as we stopped next to a dilapidated gazebo. “We must have missed them.” We continued to drive, spying distant clouds of smoke in three directions. There were three major wildfires burning in the Pantanal.

It took 15 more minutes before we saw flames. When the truck could go no farther through the mud, we unloaded our water packs equipped with pump hoses. After finding a large muddy puddle, we filled up our tanks and set off across the pasture.

We encountered two fires, each about 50 yards square, preying on tall, dense clumps of grass. The flames seemed to simmer when they approached the forest edge where the underlying vegetation was less dense.

Before long, all but one of the pumps jammed, and I volunteered to go back to the truck to retrieve “flappers” — long wooden poles with rubber mats on the end that suffocate flames. It was also becoming increasingly clear that I could no longer operate a water pump while constantly pulling up my pants. I simply had to put my own trousers back on and hope for the best.

With the three of us working, we quickly extinguished both fires. While Aaron and I gloated, Marian seemed less impressed and remarked that she thought this field had been “back burned” by other firefighters.

So off we went to look for the real fire. It took an hour of searching, but we found the other firefighters. They were sitting by their trucks staring at a wall of fire that raged about 100 yards in front of them. This, we learned, was “back burning.” The ground was too dry and the fire was too strong to put out, so they scorched the earth to limit how far it could spread.

There were natural firebreaks as well — a lake to our left and the sand road — and later a tanker of water arrived. We spent the day back burning and soaking the grass closest to the road. At 9 or 10 p.m., we went to the nearest fazenda, where our efforts were rewarded with pinga (also called cachaca), an extremely strong liquor made from sugar cane. After several rounds, we ate and retired, a little surprised we were allowed to sleep while the fire raged on.

The next morning, the Pantaneiros were confident that the fire was under control, so we rode for three bouncing hours back to Fazenda Rio Negro. We expected a hero’s welcome. But the place was empty, except for those few who’d stuck around to help out in the lab. Content in our own glory, though, we napped like heroes.

The next day, during the plane ride away from the fazenda, I reread our briefing book on the Pantanal projects. It described the tasks — tracking jaguars, trapping peccaries, netting birds and sampling water.

There was no mention of grass fires or dead caimans. But I would not have had it any other way.

Next time, though, I’ll pack different pants.

*

(BEGIN TEXT OF INFOBOX)

Farm country

GETTING THERE:

From LAX: United, American, Delta, Continental and Lan Chile offer connecting flights (change of plane) to São Paulo. Varig offers nonstop flights. TAM Linhas Aereas offers flights between São Paulo and Campo Grande. Restricted round-trip fares begin at $827.

TELEPHONES:

To call the numbers below from the U.S., dial 011 (the international dialing code), 55 (country code for Brazil) and the local number.

WHERE TO STAY:

Fazenda Rio Negro, Rua Parana 32; Jd. Dos Estados, Campo Grande, Mato Grasso do Sul, Brazil 79021-220; 67-326-0002, fax 67-326-8737, www .fazendarionegro.com.br. Conservation International’s farm was the location for Brazilian soap “Pantanal.” Some rooms are available to tourists.

VOLUNTEERING:

Earthwatch Institute, 3 Clock Tower Place, Suite 100, Box 75, Maynard, MA 01754; (800) 776-0188 or https://www.earthwatch.org . The group, which leads global volunteer research projects, has upcoming field dates in the Pantanal, including Nov. 1-12, 12-23 and 24-30, Dec. 1-7 and 15-21. Seven-day trips cost $1,895, 12 days $2,495, not including travel.

TO LEARN MORE:

Brazilian Consulate Trade Office, (323) 651-2664, https://www.braziltourism.org .

— Owen J. Pinkerton