Wolf reintroduction involves the artificial reestablishment

Reintroduction

Reintroduction is the deliberate release of a species into the wild in zones formerly inhabited by said species but where it has disappeared from for a number of reasons, from captivity or relocated from other areas where the species still survives in...

 of a population of wolves

Gray Wolf

The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...

 in areas where they have been extirpated

Local extinction

Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...

. Wolf reintroduction is only considered where large tracts of suitable wilderness still exist and where certain prey species are abundant enough to support a predetermined wolf population.
The five last known wild Mexican grey wolves

Mexican Wolf

The Mexican Wolf is a subspecies of the Gray Wolf. It is native to North America, where it is the rarest and most genetically distinct subspecies.- Physical features :...

 were captured in 1980 in accordance with an agreement between the United States and Mexico intended to save the critically endangered subspecies.