The nine officers comprising the patrol staff of the Brookfield Zoo Police Department are now union members. The police officers joined their groundskeeper and zookeeper colleagues as members of Teamsters Local 727, the union announced on April 7. Previously, the zoo’s police officers were not members of a union.

According to a press release issued by the Teamsters on Friday, Local 727 had requested that zoo management voluntarily accept the police officers into the bargaining unit. On March 25, the union got that recognition and officers voted to join the union.

Sondra Katzen, spokeswoman for the Chicago Zoological Society, which operates Brookfield Zoo, said that zoo management and the union are negotiating the terms of a contract.

“Just like that, these patrol officers have gone from having zero work protections to having the backing of a healthy contract that has existed for more than 30 years,” said John Coli Jr., president of Local 727.