The Pantanal is the world's largest tropical wetland area. Brazil lays claim to most of it, though it also spills into neighboring Paraguay and Bolivia. The region is rich in biodiversity, but in Brazil the wide open floodplain is also home to some 30 million cattle, making this unique wildlife paradise cattle country.

A marsh deer and a herd of oxen in the Pantanal wetlands of Mato Grasso do Sul, Brazil. | (AP Photo/Eraldo Peres)

As stunning as it is, the terrain makes for a difficult pass for ranchers trying to get their cattle to market. With few roads and mud that rises from ankle to waist, trucks are useless.

Enter Brazil's cowboys.

(AP Photo/Eraldo Peres)

In the Brazilian wetlands, herding cattle is still a vibrant and lucrative way to make a living — one requiring years of experience and an intimate understanding of the peculiarities of the wetlands. Most grazable pastures, for example, are underwater, so cattle must be transported across great stretches of deep, murky waters to find food. And though the rainy season can obstruct passage, the blistering heat of the dry season can be even worse for the animals.

Market runs can take up to several months, depending on the weather and time of year. In May, Associated Press photographer Eraldo Peres followed a group of six professional cowboys, capturing just one grueling day of their three-week journey guiding 520 oxen through the overflowing Taquari River.

At dawn, cowboys prepare their mounts for the day's journey. | (AP Photo/Eraldo Peres)

(AP Photo/Eraldo Peres)

The men rose hours before the sun came up to rouse the herd from their slumber. They traveled 11 miles from sunrise to 3 p.m. in 90 degree heat, dressed in thick leather chaps over long clothes to protect them from the mud and brush they slogged through.

At the end of the day, they secured their charges, built camp, and cooled themselves with iced mate, a traditional South American caffeine drink. As evening closed in, they grilled meat over an open flame.

The cowboys are paid reasonably for the region. The average hand can earn about $18 a day and the pack leaders can earn as much as $285 a day. Many will do it for life.

Take a peek into the lives of Brazil's masterful wetlands cowboys:

(AP Photo/Eraldo Peres)

(AP Photo/Eraldo Peres)

(AP Photo/Eraldo Peres)

(AP Photo/Eraldo Peres)

Cowboys guide the herd across the Taquari River. | (AP Photo/Eraldo Peres)

A cowboy cooks barbeque at a ranch in the Pantanal wetlands where the cowboys break for the night. | (AP Photo/Eraldo Peres)

The team drinks a herbal mate tea called 'Terere,' served ice cold, from an ox horn. | (AP Photo/Eraldo Peres)

The Milky Way lights up the sky above the ranch. | (AP Photo/Eraldo Peres)