Theory:

1. “How come ostriches never fly like other birds?”
The ostrich is the world's largest bird. Although ostriches are excellent runners, they are unable to fly. Their frail wings will never be strong enough to lift their heavy bodies off the ground.
  
2. “What causes the giraffe's skin to be so spotty?”
Patches (spots) on giraffes are mostly utilised for its protection. Each patch acts as a thermal window, enabling heat to escape from the body.
 
3. “How come the eyes of hippopotamuses are usually red?”:
Hippos have unique glands in their skin that emit a reddish oily fluid that is referred to as "blood sweat." Because their skin is so sensitive to dryness and sunburn, the fluid functions as a skin's natural ointment.