That happened to me once, too. I finally had to re-start the challenge. :sad I discovered that by putting the camels/gazelles/other savannah animals right behind the food court (which was right inside the gate), the guests had to cross the court to see them. And when they're combined, they function fine. As I got other Savannah animals, I just kept adding them. Then I put the Tundra exhibit (musk ox, caribou) right to the left of the entrance. As soon as I could get it, I put the insect/reptile house to the right of the entrance. This keeps the guest going in a circle, stopping to buy things. As soon as I could, I added a restaurant BESIDE the Savannah exhibit, and began adding animals on that side. As I got other animals, I did the same thing on the other side. I put the Wetlands on one side and the Forest (moose/bear) on the other. WAY in the back, when I got them, I put the chimps. I also put the peafowl in a small exhibit near the food court, where I also built a sandy 'play' area with the bouncy ride, adding other 'toys' as they became available.
It worked for me, so hope the hints help you! :happy