In this Wednesday, May 15, 2019 photo, a young giraffe, right, looks out at her keeper in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)

BARCELONA, Spain (AP) — Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild.

Barcelona's town council voted on May 3 to modify the zoo's bylaws to include a rule to eventually halt breeding programs unless there is a plan to release the offspring into nature at some point.

Activist Leonardo Anselmi, who coordinates ZOO XXI, the animal rights group that successfully pushed for the new mandate, said the group wanted to stop zoo breeding programs "that do not respond to an environmental strategy."

But some zookeepers are worried that reproduction restrictions could do more harm than good, and held a strike early this month to voice their concern.

In this Wednesday, May 15, 2019 photo, a giraffe examines an African spurred tortoise at the zoo in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)
In this Wednesday, May 15, 2019 photo, amphibian expert Viqui Mercedes points at a Montseny brook newt inside a breeding and research laboratory in the zoo in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)
In this Wednesday, May 15, 2019 photo, a male Saharan Dorcas gazelle looks outside from the indoor area of her enclosure at the zoo in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)
In this Wednesday, May 15, 2019 photo, a little girl points at a family of Bornean orangutans at the zoo in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)
In this Wednesday, May 15, 2019 photo, a giraffe looks at the camera from inside its enclosure at the zoo in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)
In this Friday, May 10, 2019 photo, an elderly female former circus elephant stands at the edge of her enclosure at the zoo in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)
In this Friday, May 10, 2019 photo, Pedro, a 45-year-old white rhinoceros eats a baguette for breakfast together with a peacock and pigeons in his enclosure at the zoo in Barcelona, Spain. Animal rights activists in Barcelona are celebrating a victory after the Spanish city ordered its municipal zoo to restrict the breeding of captive animals unless their young are destined to be reintroduced into the wild. (AP Photo/Renata Brito)