The Basics — Order: Chiroptera. Eight species are likely to live around the Key Peninsula: big brown bat (Eptesicus fuscus), California myotis (Myotis californicus), hoary bat (Lasiurus cinereus), little brown bat (Myotis lucifugus), long-legged myotis (Myotis volans), silver-haired bat (Lasionycteris noctivagans), western long-eared myotis (Myotis evotis), Yuma myotis (Myotis yumanensis).

Identification —Bats are nearly impossible to identify visually in flight. But new technology can analyze recordings of a bat’s echolocation calls to identify the species, even though many calls are beyond the range of human hearing.

Seasonal Habits — Bats are most active in late spring, summer and fall, when insects are abundant. Most of our species migrate elsewhere for the winter. A few, such as the long-legged myotis, hibernate within 100 miles of their summering grounds. Recently, however, naturalists have discovered that others actually emerge to forage on calm winter evenings, including the silver-haired bat and California myotis. Observations of bats in winter should be noted.

Bat Vocabulary —Patagium: the wing membrane, stretched between arm and finger bones. Hibernaculum: a roost where bats hibernate during the winter. Magnetoreception: bats’ ability to use Earth’s magnetic field to tell north from south. Flittermouse: an old English word for bat.

Fossil Record —Bats are rare in the fossil record. One of the oldest examples is from the Green River Formation in Wyoming, dating to the Eocene about 50 million years ago. This early bat had short wings, long hind limbs and a claw on every digit, suggesting it was just as adept at scrambling around trees as flying. Its small ear suggests that early bats developed flight before they developed echolocation.