Only after the Spanish conquest did the Otomi of the valley become more settled, although to this day there are some fringe groups which still maintain much of the hunter-gatherer traditions. The Tula area was initially ruled for the Spanish by Pedro Miahuazochil in Tula and Pedro Rodríguez de Escobar in Ixmiquilpan. The ecology of the valley began to change dramatically in the colonial period, mostly due to logging and the introduction of grazing animals, especially sheep, causing erosion and other damage.