Also, we need a moat because we don't want to be keeping the gators in cages, nor should we be splitting up gator pods. They deserve to be accommodated and a moat seems like the best way to do this.
Finally, a moat is naturally sanitary and self-cleansing once it reaches those sizes. Maintenance costs = almost zero. We don't want a San Francisco (or whatever other liberal stronghold city) situation on our hands.