At Brookfield Zoo Chicago, Regenstein Wolf Woods is home to Mexican wolves (Canis lupus baileyi) — a distinguished yet playful species that many of our guests have come to love. The rarest subspecies of gray wolves in North America, they are listed as Endangered under the U.S. Fish and Wildlife Service (USFWS) Endangered Species Act. From the 1980s until 1998, they were considered extinct in the wild due to antipredator campaigns in the U.S. and Mexico. But after several decades of decline, the Mexican wolf population is in its ninth year of growth thanks to reintroduction efforts.  

Brookfield Zoo Chicago and the wolves at Regenstein Wolf Woods have played a significant role in the recovery and growth of the population. Since 2003, we have participated in U.S. Fish and Wildlife Service’s (USFWS) Mexican Wolf Recovery Program with the goal of re-establishing a healthy and self-sustaining population of Mexican wolves within their historic range. The program brings together multiple organizations that participate in the Association of Zoos and Aquariums’ Mexican Wolf SAFE: Saving Animals From Extinction program to help raise and reintroduce wolves into the wild.

This effort starts with the wolves that live at Brookfield Zoo Chicago.

Raising Pups at Brookfield Zoo Chicago

In Regenstein Wolf Woods, one-year-old Mexican wolf sisters Molly and Sierra tumble, howl, and strike watchful, majestic poses as guests look on. We call them ambassadors for their wild counterparts, as they create powerful connection points for our guests to learn more about the species and the threats they face in the wild.  

The sisters are daughters to mother Vivilette and their late father Amigo. They were born in April of 2024, and in the year since, the siblings have reached a variety of milestones in their habitat.  

At the beginning of the summer, they explored their naturalistic habitat and began bonding with one another and playing with their parents. The public voted for Sierra’s name, paying homage to the Mexican wolves’ native range near the Sierra Madre Mountains in Mexico. In the fall, the sisters interacted more with their habitat, climbing trees and gnawing on bones as the trees turned.  

In the late fall of 2024, the wolf family and their dedicated animal care specialists, among others, were devastated by the sudden passing of 11-year-old Amigo due to a sudden stomach torsion. He was a deeply attentive father to Molly and Sierra and a uniquely dedicated mate to Vivilette. Together, he and Vivilette built a strong bond, raising three litters at Brookfield Zoo Chicago. He thrived caring for his pups, bringing them food and playing with them regularly.

But Amigo’s story is far from over. Although he is no longer at Regenstein Wolf Woods, his legacy lives on in his daughters — and in his pups that have been brought to the wild.

Reintroducing Pups Into the Wild

Just 10 days after birth, Molly and Sierra's seven siblings born in the same litter — six males and one female — flew safely with LightHawk Conservation Flying to be placed into two dens within their native range. Animal care specialists and a veterinary technician from the Zoo fed the pups and kept them warm as they traveled.  

This journey was one of the first steps in a process overseen by the Mexican Wolf Recovery Program and its partners called fostering. When pups are born to a wild mother and a mother in professional care at the same time, the pups from zoos can be raised in a wild pack.  

Pups born at the Zoo are brought to the wild and placed in dens. Once the pups are there, scientists cover them with the scent of the pups already in the den to make sure they all smell the same. Biologists watch the mother to make sure she accepts the zoo-born pups as her own.

Not only does this effort support Mexican wolf population growth, it also increases the population’s genetic diversity, which is important for the long-term health and survival of the population. A diverse gene pool helps the wolves adapt to environmental changes, resist diseases, and maintain a thriving population over time. This is especially important for endangered species like the Mexican wolf, since a limited gene pool can lead to health issues and a higher risk of extinction.

Why Reintroduction Programs Matter

Over the years of participating in the recovery program, Brookfield Zoo Chicago has established an extremely successful breeding program. Amigo and Vivilette themselves have contributed 14 puppies successfully released into wild packs in the last three years. In fact, Vivilette ranks as the #1 mom, literally, amongst other Mexican wolf matriarchs under professional care — she has the most pups in the wild of them all!

At least one of Amigo’s male pups has matured enough that he’s accepted and cared for fosters of his own. Another is believed to have recently “sired” pups, and others have likely been breeding. Each one contributes to the over 250 Mexican wolves that are now living in the protected areas of Arizona and New Mexico. This number is ahead of USFWS’ goal for their five-year evaluation published in late 2024. Populations in both the U.S. and Mexico have also surpassed the program’s projections for gene diversity.

This is a tremendous legacy for Amigo, Vivilette, their pups, and Brookfield Zoo Chicago to be a part of! The success of the effort shows us why reintroduction programs matter, and why collaboration between conservation organizations makes all the difference. Without the work of accredited facilities like zoos caring for endangered species on site, we wouldn’t be able to contribute to wild populations. And without Molly and Sierra back home at Brookfield Zoo Chicago, we wouldn’t be able to connect our guests — you! — to animals that need help in the wild.  

If Amigo was beloved, Molly and Sierra gather double the love. As guests search for the sisters between the trees, they can imagine their siblings roaming in the wild and raising their own families, with howls that echo for years to come.