Bat Walk in the City Park: Whose Wings Are Related?

Dusk at Riverside Park

1On summer evenings, Riverside Park in the city holds a bat walk led by park ranger Dominic Ishikawa. Eighth grader Zuri Pellegrino joined one in July. At dusk, little brown bats streamed out of a bat house near the pond and swooped low over the water, catching insects. A bat detector in the ranger's hand clicked as the bats called to find their prey. High above them, chimney swifts circled the old brick tower by the boathouse, also snapping up insects in flight. Gray squirrels, done with a day of gathering food, climbed into their leaf nests in the oaks.

2Ranger Ishikawa explained that the park changes with the seasons. In the fall, the swifts fly south for the winter, and many of the little brown bats move to nearby caves, where they hibernate. The squirrels stay active in the park all winter, eating nuts they buried in the fall. By late spring, the bats and swifts are back.

3After the walk, the ranger showed the group skeletons of a little brown bat, a chimney swift and a gray squirrel, along with casts of two fossils. One is an early bat, about 52 million years old, found in Wyoming. Its wings were shorter for its body size than a modern bat's wings. The other is a pterosaur, a flying reptile about 150 million years old. Pterosaurs lived at the same time as many dinosaurs, but they were not dinosaurs. The early bat's skeleton is complete enough that its finger bones and teeth can be studied in detail. Zuri recorded the features of all five animals in a table.

4Bats and squirrels are covered in fur and feed their young milk. Swifts are covered in feathers and lay eggs. Fur is rarely preserved in fossils, so Zuri left it out of her table. She also noticed that a bat's clawed thumb sticks out from the top edge of the wing, and the ranger said little brown bats use these claws to grip the walls of the bat house. The ranger added that two animals can look alike because they do the same job, such as flying, even when their bodies are built in different ways.