The importance of captive breeding has evolved as zoos themselves have evolved. Beyond allowing captive populations to be self-sustaining, zoos can contribute to species recovery and reintroduction by improving reproductive rates and developing monitoring techniques that provide data critical to understanding reproductive processes. Several threatened canid species have recently been saved through captive-breeding efforts in partnership with reintroduction programmes. Two of those, the Mexican grey wolf Canis lupus baileyi and the Island fox Urocyon littoralis, provide case studies. For both species, data generated during monitoring revealed important basic features of their biology and also provided critical information to managers that could be used to enhance reproductive rates. Both species are also part of reintroduction programmes that exemplify successful partnerships between the United States Fish and Wildlife Service and North American zoos.