The northern limit of Nycticeius humeralis is the Great Lakes Basin. There has been one record of evening bats in Ontario and three from southern Michigan (Kurta, 2001). The eastern end of its range is in Virginia and North Carolina. It is found as far west as eastern Texas and as far south as Florida.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Throughout the eastern U.S., north to Nebraska, Iowa, southern Michigan, Pennsylvania, New Jersey, west to Kansas, eastern Texas, south to northern Veracruz, Mexico. Cuba population was regarded as a distinct species (N. cubanus) by Simmons (in Wilson and Reeder 2005).

Nycticeius humeralis is dark brown except for its black ears. Its snout, wings, and tail membranes are hairless (Kurta, 2001). It has a non-keeled calcar, a short tragus that is curved and round, and a skull that is broad, especially in the anterior (Barbour and Davis, 1974). The dental formula of N. humeralis is 1/3, 1/1, 1/2, 3/3 = 30. Measurements of this bat are as follows: Weight ranges from 6 to 14 g; the body is 86 to 105 mm long; the tail is 33 to 42 mm long; wingspan ranges from 260 to 280 mm; the hind foot is 8 to 10 mm in length; ear height is 11 to 15 mm; forearm length is 34 to 38 mm.

Evening bats can be easily confused with Myotis species, even though the curved tragus can differentiate the two genera. These bats can also be confused with Eptesicus fuscus, although E. fuscus is larger (39 to 54 mm forearm) and lacks a keel on the calcar (Barbour and Davis, 1974).

Range mass: 6 to 14 g.

Range length: 86 to 105 mm.

Range wingspan: 260 to 280 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes alike

Length: 9 cm

Weight: 9 grams

• Terrestrial

Evening bats prefer the forest and open habitats such as river corridors and wetlands. These are forest bats and are never found in caves. Instead N. humeralis roosts in hollows of trees, under loose bark, or in buildings. (Kurta, 2001)

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest

Comments: Prefers deciduous and mixed forest interspersed with cultivated areas. Commonly found along waterways (Schmidly 1991). Summer roosts include attics of buildings, tree cavities, and spaces behind loose tree bark. May also use Spanish moss for summer roosting, and cave mouths in fall. Hibernation site not known. Maternity colonies may be found under loose bark, in tree cavities, in Spanish-moss, or in buildings.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Northern breeding populations move southward for winter; usually has vacated northern roosts by mid-October (Watkins 1972). Present all year in Texas, but only occasionally recorded in winter (Schmidly 1991).

Evening bats feed on beetles, moths, flies, and leafhoppers that they are able to catch in midair during slow, steady flight. If a solitary bat is unsuccessful, it will follow a group of bats to the food source. A colony of 100 bats can consume over 1.25 million insects a season (Kurta, 2001). Evening bats find food using echolocation.

Animal Foods: insects

Primary Diet: carnivore (Insectivore )

Comments: Preys on flying insects. In Clay County, Indiana, major foods were beetles (60% of volume), moths (20%), and leafhoppers (7%); the species eaten in greatest quantity (14% of volume) was the pest Diabrotica undecimpunctata (spotted cucumber beetle/southern corn rootworm) (Whitaker and Clem, Am. Midl. Nat. 127:211-214).

Because colonies of evening bats can consume so many insects, it is likely that they play an important role in regulating insect populations. As a result, they have an indirect positive effect on the vegetational community that the insects feed upon.

This species may fall prey to snakes, racoons, owls, and hawks. Specific anti-predator adaptations in have not been described.

Known Predators:

• snakes (Serpentes)
• raccoons (Procyon lotor)
• owls (Strigiformes)
• hawks (Accipitridae)

Usually congregates in summer and disperses in small groups for winter.

Little information is available on the communication of these animals. Mothers use the voice of the pup and its scent to locate it, indicating that both sound and scents are used in communication. Tactile communication is also likely to be important in the roost (where animals may come into physical contact), between mates, and between mothers and their young. Like other members of the family Vespertilionidae, these bats use echolocation to find prey. Visual signals are probably not used extensively by these nocturnal animals.

Communication Channels: tactile ; acoustic ; chemical

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

Comments: May be found searching for insects before sunset. Most active during the first hour after sunset and the first hour before sunrise.

Most evening bats are expected to live about 2 years in the wild, although some have been known to live as long as 5 years (Nowak, 1999).

Range lifespan

Status: wild: 5 (high) years.

Average lifespan

Status: wild: 2 years.

Average lifespan

Status: captivity: 5.0 years.

One male mates with up to 20 females. Males and females then go their separate ways. Females give birth in colonies with other females, but no adult males are present (Nowak, 1999).

Mating System: polygynous

Mating takes place in the late summer and early fall. Sperm is stored in the reproductive tract of the female until spring, when ovulation and fertilization occur. Evening bats have a harem-like association of one male with around twenty females. The young are born in nursery colonies, usually in hollow trees, behind loose bark, and sometimes in buildings and attics. The female usually gives birth to twins, but some females have been known to produce triplets and successfully raise them. At birth the pups weigh 2 g, and represent 50% of the mothers’ postpartum body mass. This is the largest litter in relation to maternal size of all bats, and one of the largest for any mammal (Kurta, 2001).

When born, the pups are pink and hairless but are able to squeak. They open their eyes within 24 to 30 hours of birth. The bats don't fly until they are about three weeks old. At the end of three weeks they are able to negotiate turns and land on walls and ceilings (Barbour and Davis, 1974). The pups are weaned 6 to 9 weeks after birth. The male pups leave the roost after six weeks, but the females remain in the colony. Bats breed in the year following their birth (Kurta, 2001).

Breeding interval: These bats breed once per year.

Breeding season: Breeding occurs in late autumn.

Range number of offspring: 1 to 4.

Average number of offspring: 2.

Average weaning age: 42 days.

Average time to independence: 6 weeks.

Average age at sexual or reproductive maturity (female): 10 months.

Average age at sexual or reproductive maturity (male): 10 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous ; sperm-storing ; delayed fertilization

Average birth mass: 1.75 g.

Average number of offspring: 2.

Young are born naked and blind. Within 24 hours, their eyes have opened. Development is rapid, and pups are able to fly by the end of three weeks. Females nurse their pups for about six weeks. All parental care is supplied by the female, although there are reports of communal nursing. A mother recognizes her pups within the colonly by scent and by auditory cues, and will retreive them if they fall before they are able to fly. Male offspring disperse at 6 weeks of age, but female offspring remain in their natal colony (Barbour and Davis, 1974; Kurta, 2001).

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); inherits maternal/paternal territory

Mating occurs late summer-fall. Parturition occurs late May to mid- June in south, mainly mid-June in North. Litter size usually is 2. Young can fly by third week but continue to nurse until 6-9 weeks old. Young are not carried during mother's feeding flights. Reported maternity colony size range is 25-950, or up to thousands (Caire et al. 1989); adult males are not present in these colonies.

It is likely that the conversion of forested wetlands to agricultural and logging uses has resulted in prime foraging and roosting habitat.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Nycticeius humeralis mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Some bats roost in buildings and attics and are a nuisance to people. They can carry rabies, which can be transmitted to humans that are bitten by an infected bat.

Negative Impacts: injures humans (bites or stings); causes or carries domestic animal disease ; household pest

Evening bats feed on the adult form of a chrysomelid beetle, better known to farmers in its larval stage as the corn rootworm, which is an agricultural pest. By reducing the numbers of these pests, evening bats may increase the yield of the harvest.

Positive Impacts: controls pest population

Comments: Nycticeius cubanus was included in N. humeralis by Koopman (in Wilson and Reeder 1993) but was regarded as a distinct species by Simmons (in Wilson and Reeder 2005).