MEXICO CITY – A herd of 23 American bison – three males and 20 females – that were donated by the United States to Mexico have been released in a nature reserve in the northern state of Chihuahua, the Environment and Natural Resources Secretariat, or Semarnat, said.

The department said bison disappeared in Mexico in the 19th century and their reintroduction into El Uno nature reserve is an attempt to help conserve the ecosystem of that area.

The American Bison, the largest North American mammal, once roamed the plains of northern Mexico, the United States and Canada in large herds.

The release of the bison was witnessed by the head of Semarnat, Rafael Elvira Quesada, who said this species “plays a fundamental ecological role in regenerating grasslands.”

In addition to promoting the recovery other species, such as the prairie dog and the mountain plover, the minister said the goal is to eventually have 100 bison in Mexico within three years.

He said the bison were donated by South Dakota’s Wind Cave National Park as part of a bi-national cooperation program to conserve the North American grassland habitat.

Elvira Quesada added that Mexico will ask the United States to “halt construction of the border wall in areas where this species moves between the two countries to not disrupt its natural migration.”

Mexico has 23.8 million hectares (91,900 sq. miles) of natural protected areas, equivalent to 12.1 percent of its natural territory or roughly the size of Chihuahua state, the nation’s largest in terms of area.