When I was younger, a friend of my mother’s (who was a scientist at the Everglades National Park) would take us on evening airboat rides to count the local alligator population. Because alligators actively hunt in the twilight hours, they can be easily spotted by shining a spotlight across the water and counting the pairs of eyes reflected back.
On one of these alligator counting trips, we ended up having no luck finding any alligators during the entire trip. However, after returning to the dock and disembarking, I decided to play with the spotlight and shine it out along the water. About thirty pairs of eyes shined back at me. Apparently, the alligators had been waiting for us.