The Mallers have two things they are doing besides raiding. First, they were taking fuel trucks. We already know that early on they were collecting fuel trucks for an attack on the arena (This does mean that they already knew about the Arena.). Second, The Mallers are/ were creating zombies for recreational purposes. Those are two majorly weird things. We know that the Mallers had been to Locked and Loaded prior to Angel and Saul. They took over a freaking MALL, meaning that they have plenty of food from shops/restaurants. It doesn't give them a lot of time, food wise, but enough for about a day or two. Also, we already know that the ZOMBIES eat anything edible, including dog food.