The evening bat (''Nycticeius humeralis'') is a species of

bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...

in the

vesper bat Vespertilionidae is a family of microbats, of the order Chiroptera, flying, insect-eating mammals variously described as the common, vesper, or simple nosed bats. The vespertilionid family is the most diverse and widely distributed of bat familie ...

family that is native to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. Hunting at night, they eat beetles, moths, and other flying insects.

Description

The evening bat is a small bat weighing found throughout much of the

midwestern The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of the United States. I ...

and

eastern Eastern may refer to: Transportation *China Eastern Airlines, a current Chinese airline based in Shanghai *Eastern Air, former name of Zambia Skyways *Eastern Air Lines, a defunct American airline that operated from 1926 to 1991 *Eastern Air Li ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. Their forearms are in length. The tip of each dorsal hair is a light gray, and one to two-thirds of the basal is dark brown. Though there have been some cases of white

pelage Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily #Guard hair, guard hair on top and thick #Down hair, underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as ...

, the majority of the population is mostly brown in color.Watkins, L. C. (1972). Nycticeius humeralis. Mammalian species, (23), 1-4. They have wide, dog-like muzzles, pronounced facial glands, and disproportionately large

bacula Bacula is an open-source, enterprise-level computer backup system for heterogeneous networks. It is designed to automate backup tasks that had often required intervention from a systems administrator or computer operator. Bacula supports Lin ...

. Evening bats can be mistaken for juvenile

big brown bat The big brown bat (''Eptesicus fuscus'') is a species of vesper bat distributed widely throughout North America, the Caribbean, and the northern portion of South America. It was first described as a species in 1796. Compared to other microbat ...

s, due to their physical resemblance but smaller size.

Morphology

Evening bats have relatively robust jaws, compared to other insectivorous bats. They have an unkeeled

calcar The calcar, also known as the calcaneum, is the name given to a spur of cartilage arising from inner side of ankle and running along part of outer interfemoral membrane in bats, as well as to a similar spur on the legs of some arthropods. The cal ...

and a short, round tragus.Barbour, R., W. Davis. 1974. Mammals of Kentucky. Kentucky: The University Press of Kentucky. The curvature of the tragus helps distinguish it from bats of the genus ''Myotis'', which otherwise look very similar. Their skull has one upper incisor on each side with 4 molariform teeth.

Biology

The evening bat is a relatively short-lived, especially compared to other bats in its geographic range.Austad, S. N. (2010). Cats,"rats," and bats: the comparative biology of aging in the 21st century. Integrative and comparative biology, icq131. It has a maximum age of 6 years, though few individuals live past 4 years. Its short lifespan for a bat could be explained by its considerably higher reproductive output. Bats that only have one pup per year would need to live much longer to have the same fitness as a shorter-lived species with two or three pups per year.

Reproduction

Evening bats mate in the fall and winter; the sperm is stored until the spring, when fertilization occurs.Whitaker, J. O., Jr., J. B. Cope, D. W. Sparks, V. Brack, Jr., and S. Johnson. Bats of Indiana. Publication no. 1, ISU Center for North American Bat Research and Conservation. Indiana State University. 59 pp. Female bats form maternity colonies in May,Watkins, L. C., & Shump Jr, K. A. (1981). Behavior of the evening bat Nycticeius humeralis at a nursery roost. American Midland Naturalist, 258-268. consisting of 15-300 individuals. Of females that give birth, 90% have twins, but singletons and triplets are also possible.Kurta, A., Foster, R., Hough, E., & Winhold, L. (2005). The evening bat (Nycticeius humeralis) on the northern edge of its range—a maternity colony in Michigan. The American midland naturalist, 154(1), 264-267. Though it is more common for evening bats to nurse their own offspring, a small proportion of offspring are nursed by unrelated females. The pups are capable of flight within a month of birth. Pups are weaned within 42 days of birth. Female pups exhibit natal

philopatry Philopatry is the tendency of an organism to stay in or habitually return to a particular area. The causes of philopatry are numerous, but natal philopatry, where animals return to their birthplace to breed, may be the most common. The term derives ...

, meaning that as adults, they return to the roost where they were born to give birth.

Diet

These bats have varied diets. A majority of the bats' diet in Indiana and Illinois are

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

s, including the

spotted cucumber beetle ''Diabrotica undecimpunctata'', the spotted cucumber beetle or southern corn rootworm, is a species of cucumber beetle that is native to North America. The species can be a major agricultural pest insect in North America. Spotted cucumber beetle ...

, which is a serious agricultural pest.Whitaker Jr, J. O., & Clem, P. (1992). Food of the evening bat Nycticeius humeralis from Indiana. American Midland Naturalist, 211-214. In southern Illinois, the spotted cucumber beetle is almost 25% of the evening bats' diet.Feldhamer, G. A., Whitaker Jr, J. O., Krejca, J. K., & Taylor, S. J. (1995). Food of the evening bat (Nycticeius humeralis) and red bat (Lasiurus borealis) from southern Illinois. Transactions of the Illinois Academy of Science, 88, 139-143. Other beetles consumed include

ground beetle Ground beetles are a large, cosmopolitan distribution, cosmopolitan family (biology), family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it i ...

s and

scarab beetles The family Scarabaeidae, as currently defined, consists of over 30,000 species of beetles worldwide; they are often called scarabs or scarab beetles. The classification of this family has undergone significant change in recent years. Several sub ...

Moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...

s are also a significant dietary component. Bugs, winged ants, and

flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

are prey items of less significance. Evening bats partition resources with other insectivorous bats in their range, such as the

eastern red bat The eastern red bat (''Lasiurus borealis'') is a species of microbat in the family Vespertilionidae. Eastern red bats are widespread across eastern North America, with additional records in Bermuda. Taxonomy and etymology It was described in 1 ...

and

Seminole bat The Seminole bat (''Lasiurus seminolus'') is a species of bat in the family Vespertilionidae. Taxonomy The Seminole bat was first described in 1895 by Samuel N. Rhoads. The holotype had been collected in Tarpon Springs, Florida in 1892 by Wi ...

.Carter, T. C., Menzel, M. A., Chapman, B. R., & Miller, K. V. (2004). Partitioning of food resources by syntopic eastern red (Lasiurus borealis), Seminole (L. seminolus) and evening (Nycticeius humeralis) bats. The American midland naturalist, 151(1), 186-191. Despite foraging in the same areas at the same time, these three bat species choose different prey items at different points throughout the summer.

Distribution

At first, the evening bat was thought of as a southeastern bat species. However, breeding evening bats have been found as far north as Michigan and as far west as the 100th meridian. Evening bats roost in a variety of structures, including

Spanish moss Spanish moss (''Tillandsia usneoides'') is an epiphytic flowering plant that often grows upon large trees in tropical and subtropical climates. It is native to much of Mexico, Bermuda, the Bahamas, Central America, South America, the Southern Uni ...

, under bark, in tree cavities, and in buildings.Menzel, M. A., Carter, T. C., Ford, W. M., & Chapman, B. R. (2001). Tree-roost characteristics of subadult and female adult evening bats (Nycticeius humeralis) in the Upper Coastal Plain of South Carolina. The American Midland Naturalist, 145(1), 112-119. For foraging habitat, evening bats in Georgia prefer pine forest,

riparian zone A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks ar ...

s, and open fields. Evening bats have

home range A home range is the area in which an animal lives and moves on a periodic basis. It is related to the concept of an animal's territory which is the area that is actively defended. The concept of a home range was introduced by W. H. Burt in 1943. He ...

s of approximately 300

hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is a ...

(1.15 mi²). Because the evening bat is not found in the northernmost extent of its range in the winter, it is likely that at least some evening bats are migratory.

Conservation

While the evening bat is considered endangered in the state of Indiana, it has a

cosmopolitan distribution In biogeography, cosmopolitan distribution is the term for the range of a taxon that extends across all or most of the world in appropriate habitats. Such a taxon, usually a species, is said to exhibit cosmopolitanism or cosmopolitism. The ext ...

throughout the southeast and midwest. Because evening bats do not enter or hibernate in caves, the species is not at-risk from

white-nose syndrome White-nose syndrome (WNS) is a fungal disease in North American bats which has resulted in the dramatic decrease of the bat population in the United States and Canada, reportedly killing millions as of 2018. The condition is named for a distincti ...

, which has killed over six million bats in the United States since 2006. The evening bat's avoidance of this disease, along with die-offs of many other species, is possibly responsible for the evening bat recently expanding its range into Wisconsin in 2015 and Minnesota in 2016.

References

External links

{{Taxonbar, from=Q1832323 Nycticeius Bats of North America Bats of Mexico Bats of the United States Fauna of the Eastern United States Fauna of the Plains-Midwest (United States) Fauna of the Southeastern United States Mammals described in 1818 Taxa named by Constantine Samuel Rafinesque