A Way Through the Backyard Fence

The Fence and the Toads

Toads in Amira's backyard often rested in a damp, shady space beneath a shrub during the day. In the evening, they traveled to a grassy patch where they ate insects. An open strip of ground connected these two places. Amira watched from a distance without touching or feeding the toads.

The family added a wooden fence for privacy beside the patio. The fence crossed the toads' route, and its bottom reached the ground. A gate could open between the two areas. The shrub and grassy patch stayed in place. During three evenings before the fence was built, Amira recorded 10 crossings along the route. During three evenings afterward, with the gate shut, she recorded 1 crossing. She also saw several toads reach the fence and turn back.

The family wanted at least 8 crossings during another three-evening check while keeping the gate shut. They planned three trials. For the dish plan, they placed a shallow water dish beside the shrub and kept the gate shut. For the low-opening plan, an adult made a smooth opening at ground level, large enough for a toad, and shut the gate. For the open-gate plan, they left the gate open.

The family tried one plan at a time at the same fence. Each trial lasted three evenings with similar weather. Amira watched for the same amount of time each evening and counted completed crossings between the two areas. The dish was removed before the other trials, and the low opening was covered during the open-gate trial. The graph shows her trial records.