Seven Mexican wolf puppies were born at Brookfield Zoo in Chicago on 27 April 2023, but only one of the males will emerge from their den as the other six puppies have gone on a remarkable journey back into the wild. On 6 May the other pups —four males and two females—were flown to Arizona and placed in wild Mexican wolf dens as part of the U.S. Fish and Wildlife Services' Mexican Wolf Recovery Program. At just nine days old, the six puppies, accompanied by veterinary and animal care staff from the Zoo, went on their plane trip. From there, the Mexican Wolf Interagency Field Team placed three of the puppies in a wild pack in southeast Arizona and three into a wild pack in southwest New Mexico. This process of cross-fostering puppies with different packs, then the ones they were born into, is done to help enhance the genetic diversity of the overall Mexican wolf population. The objective of the breeding and rewilding programme is to re-establish the Mexican wolf population in its native habitat of the southwestern United States and Mexico. Over the years, the Chicago Zoological Society has had puppies from several litters cross-fostered with wild packs and even had an adult from the Zoo released to the wild and successfully raise puppies. The 2022 population estimate represents a 23 percent increase from the minimum of 196 wolves in 2021. This marks the seventh consecutive year of population growth and a more than doubling in size since 2017. From the 1980s until 1998, when reintroduction efforts began, Mexican wolves were considered extinct in the wild.