Females are larger than males. Other nocturnal animals have big eyes to use the remaining light effectively. Bats generate ultrasound in their larynx and then emit it through the mouth or nostrils. Bats have big ears to collect the sounds they send out. The echos are transferred to the brain where they are analyzed and the brain makes a picture of the surrounding.
Bats use echolocation because it is a short wavelength.
So, the higher the frequency, the more detailed the sound picture the bat can. Taxonomic affiliation E. Fuscus is a member of the class Mammalia. They are the only mammals who are through fliers. E. fucus belong to the biggest family Vespertilionidae. There are 318 species in that family but just 7 species are found in Wisconsin.