Evening bat

The evening bat (''Nycticeius humeralis'') is a species of bat in the vesper bat family that is native to North America. 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 and eastern United States. 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, 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. Evening bats can be mistaken for juvenile big brown bats, 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 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, 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 beetles, including the 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 beetles and scarab beetles. Moths are also a significant dietary component. Bugs, winged ants, and flies are prey items of less significance. Evening bats partition resources with other insectivorous bats in their range, such as the eastern red bat and Seminole bat.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, 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 zones, and open fields. Evening bats have home ranges of approximately 300 hectare (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 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, 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

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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