Welcome to ZooChat SylviaS. We are largely a community of zoo enthusiasts as opposed to zoo professionals, although there are definitely a few of them here too.
Your question isn't entirely clear, are you asking what societies/associations/organisations/groups small zoos should be members of? Or something to do with memberships offered by zoos?![]()
If its the former, talking to small zoos directly would probably be beneficial. In Australasia, ZAA is the main (only?) zoo association, but I can't tell you anything other than that. This is their website: Zoo and Aquarium Association