I'm not sure but I believe they're called either 'vacqueros' or rancheros.
Pampas
Pampas It could also be llano
it is called the pampas
In south America plains are called Pampas.
Pampas is the name of the lowland found in Argentina and most of Uruguay. It is made up of mostly grassy plains.
The grasslands of Argentina are called the pampas.
Las Pampas
PAMPAS
latifundia
Pampas
on the huge estancias of the grassy Pampus
horsemen