Marty’s photo of the day #2637: It’s “Animals A thru Z Month.” Each day in August, I will post an animal I’ve photographed—somewhere in the world—in alphabetical order.

Z is for Zebra. When I present my show “Around the World in 90 Minutes” at colleges, the last animal photo I show is this one. I call it “Zebras at Sunset.” Coincidentally, it’s also the last photo of Animals A to Z Month.

No one knows for sure why zebras have stripes. One theory is that when zebras stand together, predators have a difficult time determining where one animal ends and the next one begins. The prevailing theory is that since each zebra has a unique stripe pattern, the stripes help herd members identify one another. Of the two theories, I personally think the first one is most logical. I could see with my own eyes how difficult it was to make out individuals when members of the herd stood together. And if zebras truly need stripes to tell one another apart, why aren’t horses perpetually confused?