Inside the efforts to save Mexican wolves

Karin Brulliard got a rare up-close view of the mission to reintroduce critically endangered Mexican wolf pups to the wild this spring

Wild- and captive-born pups doze before being placed in the den (Washington Post photo by Matt McClain)

In a private plane soaring 26,000ft over pine-swathed mountains, three tawny Mexican wolf pups sleep. Their weight is less than 3lbs each, their 10-day-old eyes still screwed shut. Their worth, as some of the newest members of a critically endangered species, is immeasurable.

The pups are protected by a soft pet-carrier and kept toasty – 25C, an attached thermometer indicated – by hand-warmers wrapped in a towel. They are flanked by a veterinarian and a zookeeper, chaperones for this leg of a precisely choreographed operation.

The pups were whisked from their birthplace, El Paso Zoo, two hours earlier. Their destination is the den of a wild wolf pack in the New Mexico mountains, where it is hoped the pups will be adopted into the pack, their genes bolstering an inbred population and helping to restore an apex predator and perhaps eventually providing a link in a chain of wolf populations stretching from Canada to Mexico.