Great game...for the first few days

I got this game a few days ago. The first 2 days, it was great. I was rescuing all kinds of animals and adding them to my zoo. Yesterday and today, though, I have been in the Mesozoic era, savannah, and jungle for hours without being able to find a single animal to rescue. I have driven in all directions and released all my animals that can be and have still not found any in the wild. I dont understand why a game like this would be amazing for 2 days and then not let you do anything.

Peacegrl3399 about Wonder Zoo - Animal Rescue!, v2.1.2