Guaycuru lived in the Gran Chaco, an inhospitable region for agriculture and settlement in the eyes of the Spanish colonists. They were hunter-gatherers and nomadic, moving from place to place as dictated by seasonal resources. The governor of Paraguay, Alvar Núñez Cabeza de Vaca, said in the 1540s of the Guaycuru : The Abipón Guaycuruans acquired horses from the Spanish in the late 16th century and within 50 years developed a horse culture similar to that of the Plains Indians of North America. They and other Guaycuruans acquired horses and cattle by raiding Spanish haciendas and Guaraní settlements and Jesuit missions east of the Paraguay and Parana rivers. Between raids they traded skins, wax, honey, salt, and Guaraní slaves to the Spanish en exchange for knives, hatchets, and other products. The mobility afforded by the horse facilitated Guaycuruan control over other peoples in the Chaco and made raiding the Spaniards and their Indian allies a profitable enterprise. The Payaguá, inhabiting the shores of the Paraguay River north of the city of Asunción, were an exception to the horse culture of other Guaycuruans. The Payagua plied the river in canoes, fished and gathered edible plants, and raided their agricultural neighbors, the Guaraní, to the east. The Payaguá also became great traders, both with the Spanish and other Guaycuruans. The Payaguá menaced Spanish travel on the Paraguay river for 200 years. The bands and family groups making up the Guaycuruans were matrilocal and exogamous. The bands only united on ceremonial occasions, especially during the harvest period for wild honey and algarroba (Prosopis) pods which were used to produce a fermented alcoholic beverage. The reunions were used to designate leaders, reinforce relations among the bands, and facilitate courtships and marriages. The Guaycuruan population of the Chaco in pre-Hispanic times has been estimated to be as high as 500,000 people. Although documentation is mostly lacking, the Guaycuruans were impacted by epidemics of European diseases, but possibly less than their settled, agricultural neighbors such as the Guaraní, The Guaycuruan population in the mid 17th century is estimated at 40,000. History In 1542, Cabeza de Vaca responded to the request of the Guaraní to punish the hostile Guaycuru. He dispatched a large expedition of Spaniard and Guaraní soldiers from Asunción and attacked an encampment of Mbayas, also called Eyiguayegis. The Spanish and Guaraní killed many and took 400 prisoners. In the aftermath of the battle, however,