Maryland Bat Identification Dichotomous Key

How do scientists tell one type of bat species from another?

Biologists use a dichotomous key to identify both plants and animals. Such keys include minute details about shapes and sizes of the parts of organisms that are being keyed out. Most bats that are found in the Maryland are not difficult to sort and identify into basic types.

To identify a specific Maryland bat, it is necessary to recognize the features that distinguish one species from another. Before you can give a bat a name, you must first sort features of the organism into groups of similar and dissimilar types.

Once you are able to assign a name to a bat, you can begin to see the variation among the different species and distinguish one from another. Learning to use a Dichotomous Key is the first step in understanding the diversity of life. Following the dichotomous key for bat identification step-by-step, compare features of the bat you have chosen with the descriptions given, narrowing your choices until you determine identification.

To understand the terminology see the online
Guide to Bat Anatomy.

Maryland Bat Identification
Dichotomous Key

Dichotomous means having two equal parts. A key is a tool used to identify organisms.  A dichotomous key will give you a series of choices between two related characteristics.  Choices based on these two characteristics that best fit the organism in question will take you on different paths to ultimately find the name of the organism. Choices typically begin with broad characteristics and become narrower as more choices are required. Begin with number 1 (a).

1(a). If dorsal (upper) surface of tail membrane furred Go to 2
1(b). If dorsal (upper) surface of tail membrane naked or sparsely furred Go to 4
2 (a). If fur black, many hairs silver-tipped Silver-haired Bat
(Lasionycteris noctivagans)
2(b). If fur never uniformly black, hairs silver-tipped or not Go to 3
3(a). If ears conspicuously black edged with patches of yellowish hair scattered inside; fur yellowish to dark brown, distinctly frosted; tan throat patch Hoary Bat
3(b). If ears not conspicuously black-edged and bare; fur red-orange (male) or yellowish-brown (female), tips of hairs often frosted Red Bat
(Lasiurus borealis)
4(a). If bats with brown fur only Go to 5
4(b). If small bat with yellowish fur and black wings; forearms 31-35mm; fur with three color bands, darkest band/base, lightest band/middle and darker tips Tricolored Bat
(aka Eastern Pipistrelle Bat)
(Perimyotis subflavus)
5(a). If muzzle naked and black, tragus rounded Go to 6
5(b). If muzzle furred; tragus pointed (Genus Myotis) Go to 7
6(a). If large bat. Forearm more than 40mm Big Brown Bat
(Eptesicus fuscus)
6(b). If small bat. Forearm less than 40mm Evening Bat
(Nycticeius humeralis)
7(a). If ears more than 16mm; when laid forward, ears extend 2mm past end of nose Northern Long-eared Bat
(Myotis septentrionalis)
7 (b). If ears less than 16mm Go to 8

illustration of bat calcar both keeled and not keeled 

8(a). If calcar keeled Go to 9
8(b). If calcar not keeled Go to 10
9(a). If foot is greater than 8.5mm long; forearm usually greater than 35mm long; hair on toes short and sparse, nose pinkish, no black face mask Indiana Bat
(Myotis sodalis)
9(b). If foot is less than 8.5mm long; forearm usually less than 35mm long; light colored fur with black face mask and lips Eastern Small-footed Bat 
(Myotis leibii)
l0(a). If a few long hairs extend to tips of claws on foot or beyond Go to 11
l0(b). If no long hairs extend to tips of claws on foot Indiana Bat 
(Myotis sodalis)
11. If fur glossy with sheen; not dense and woolly Little Brown Bat
(Myotis lucifugus)