I do have some anecdotes if that is enough. To me it is more efficient for a zoo or zoological society to manage the animals, memberships, maintenance, etc as that is what most of the people are trained to do and to hire others to manage food and gift services which can be very different than normal zoo management. The zoo probably saves time, money and effort because they don’t have to hire or train staff in those aspects and the deal with SSA probably works out to about the same money spent and gained without the headaches of running the operation. From what I’ve seen with these third party companies as well is they will put money down to help upgrade and build new food service areas and shops so the zoo can focus on spending money elsewhere.