Eastern pipistrelles, Pipistrellus subflavus are found throughout the eastern United States, and the far eastern edge of Mexico and Central America. These bats are found as far north as the southern edge of Canada and the southern edge of their range ends in northern Honduras (Fugita and Kunz, 1984).

Biogeographic Regions: nearctic (Native ); neotropical (Native )

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

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Nova Scotia, southern Quebec, Michigan (Kurta and Teramino 1994), and Minnesota south to Honduras, Texas, Gulf Coast, and Florida.

Eastern pipistrelles are small bats with yellowish-brown pelage. The individual hairs of P. subflavus are tricolored; the base is dark, the middle is yellowish brown, and the tips are dark. This trait may be used to distinguish them from similar species such as Pipistrellus hesparus.

The tragus of P. subflavus is long, straight, and bluntly rounded. The calcar lacks a keel, the membrane is blackish, and the dorsal base of the interfemoral membrane is furred (Schmidly, 1991). Eastern pipistrelles have a dental formula of I 2/3, C 1/1, P 2/3, M 3/3 = 36 (Whitaker and Hamilton, 1998).

Eastern pipstrelles are sexually dimorphic: Females are larger than males. In the fall, the mean weights of females and males are 7.9 g and 7.5 g, respectively. In the spring, females average 5.8 g, and males average 4.6 g.

The measurements for P. subflavus are as follows: length 77 mm to 89 mm; tail 34 mm to 41 mm; hind foot 7.3 mm to 9.9 mm; ear 12.4 mm to 14.1mm; forearm 31.4 mm to 34.1 mm; and wingspan 220 mm to 250 mm (Fugita, and Kunz, 1984; Farney and Fleharty 1969).

Range mass: 4.6 to 7.9 g.

Range length: 77 to 89 mm.

Range wingspan: 220 to 250 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: female larger

Length: 9 cm

Weight: 6 grams

• Terrestrial

Eastern pipistrelles can be found in open woods near the edges of water, as well as over water. They are not usually found in open fields or deep forests (Schmidly, 1991; Nowak, 1991). They roost in rock crevices, caves, buildings, and tree foliage in the summer. During the winter, caves, mines, and deep crevices serve as hibernacula (Briggler and Prather, 2003; Sandel et al., 2001).

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest

Wetlands: marsh

Other Habitat Features: caves

Comments: Prefers partly open country with large trees and woodland edges. Avoids deep woods and open fields. Probably roosts in the summer in tree foliage and occasionally in buildings; may use cave as night roost between foraging forays. Usually hibernates in caves and mines with high humidity. Generally, maternity colonies utilize manmade structures or tree cavities; often in open sites that would not be tolerated by most other bats (Schmidly 1991). However, in Indiana, pregnant and lactating females roosted exclusively in foliage, typically in clusters of dead leaves and less often in live foliage or squirrel nests (Veilleux et al. 2003).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

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: No. No populations of this species make annual migrations of over 200 km.

Eastern pipistrelles are insectivores and are considered generalists. Stomach content and fecal analysis show that eastern pipistrelles consume a variety of insects including Coleoptera, Homoptera, Diptera, Hymenoptera, Lepidoptera, Neuroptera, Ephemoptera, Hemiptera, Psocoptera and Trichoptera. The diet of pipistrelles varies geographically (Griffith and Gates, 1985; Carter et al., 2003).

Because of their effective use of harmonics during echolocation, P. subflavus is an efficient hunter (MacDonald et al., 1994). Eastern pipistrelles are able to consume 25% (1.4 g to 1.7 g) of their body weight (5.3 g to 6.7 g) within half an hour (Gould, 1955).

Animal Foods: insects

Primary Diet: carnivore (Insectivore )

Comments: Solitary feeder on various flying insects. Forages at treetop level, often over water.

Eastern pipistrelles are insectivores and help control the populations of the insects they consume.

At this time there is no information regarding the natural predators of P. subflavus. Eastern pipistrelles are often killed by humans. Generally, bats are most vulnerable to predators during the day, while they are in their roosts.

Known Predators:

• Homo sapiens

Probably feeds within a 5-mile radius of its roosting site. In spring and summer in Indiana, the maximum distance traveled by 19 radio-tagged reproductive females was 4.3 km (Veilleux et al. 2003). Probably occurs in low densities. Relatively uncommon. Generally solitary or in small groups.

Eastern pipistrelles are effective echolocators. Their echolocation calls are a combination of fundamental and second ary harmonics, which helps to distinguish their calls from those of similar species which share their geographic range. The use of harmonics allows eastern pipistrelles to increase their target resolution and aids in their ability to efficiently capture prey (MacDonald et. al., 1994).

The young are able to call to their mothers (Fugita and Kunz, 1984). These calls are a type of social call that signals female-infant interactions. These calls allow mutual recognition (Pfalzer and Kusch, 2003).

Although not specifically mentioned in any references, some communication must occur between a mother and her young through touch. Tactile communication may also occur between mates.

Communication Channels: tactile ; acoustic ; chemical

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

Comments: Feeds after dark until dawn. Has intermittent feeding periods to midnight and another period of feeding activity toward dawn. Rarely may fly outside hibernation site in winter (Whitaker and Rissler 1992).

Eastern pipistrelles have a lifespan of 4 to 8 years in the wild (Nowak, 1991). The known record for the oldest P. subflavus is 14.8 years.

Range lifespan

Status: wild: 14.8 (high) years.

Typical lifespan

Status: wild: 4 to 8 years.

Eastern pipistrelles copulate between August and October while “swarming” in front of cave openings. This is the only time the sexes of this species are together- during this time females mate with multiple males (Whitaker and Hamilton, 1998).

Mating System: polygynandrous (promiscuous)

After copulation, female eastern pipistrelles store sperm over hibernation until they ovulate in the spring. Insemination occurs in the spring with ovulation (Nowak, 1991). Up to seven ova may be fertilized, but only two will implant. This results in twins (Wimsatt, 1945). Newborn twins weigh up to 52% of the weight of the mother. It has been suggested that having twins is a response to the high mortality rate of the young, however having twins is rare among bats (Hill and Smith, 1984).

Gestation lasts 44 days from the time of implantation to parturition. Birth occurs from the end of May to early June depending on the latitude of the population (Whitaker, 1998). The young are altricial, however they are able to make a clicking sound to signal their mothers (Fujigta and Kunz, 1984).

Breeding interval: Eastern pipistrelles breed twice a year.

Breeding season: Copulation occurs between August and October and again in the spring.

Range number of offspring: 2 to 2.

Range gestation period: 44 (high) days.

Average gestation period: 44 days.

Range weaning age: 28 (high) days.

Average weaning age: 28 days.

Range time to independence: 5 (high) weeks.

Range age at sexual or reproductive maturity (female): 3 to 11 months.

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

Average birth mass: 0.94 g.

Average number of offspring: 2.

Female P. subflavus carry their babies to different roosts. Males do not help rear the young (Whitaker, 1998). Within one week the young are covered in fur. At 3 weeks they are able to fly (Nowak, 1991). The young are weaned at 4 weeks and begin to forage with their mothers. At 5 weeks the young are independent (Whitaker, 1998). Juveniles reach sexual maturity within 3 to 11 months (Fujigta and Kunz, 1984).

Female eastern pipistrelles carry their babies to different roosts. Males do not help rear the young. Within one week the young are covered in fur. At 3 weeks they are able to fly. The young are weaned at 4 weeks and begin to forage with their mothers. At 5 weeks the young are independent from their mothers. Juveniles reach sexual maturity within 3 to 11 months.

Parental Investment: altricial ; pre-hatching/birth (Provisioning: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

Mates in October/November. Litter size usually is 2, born June to mid-July in north, May in south. Probably sexually mature 1st summer. Young able to fly within a month. Maternity colonies are small.

The Vitali organ in the middle ear of the Eastern pipistrelle bat helps it hunt by sensing changes in barometric pressure that influence the number of insects flying at a given time.

This species is not considered threatened at the global or national levels, but it is a species of special concern in the state of Michigan.

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%.

US Federal List: no special status

CITES: no special status

State of Michigan List: special concern

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N2 - Imperiled

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Eastern pipistrelles sometimes inhabit human dwellings and may be considered un-welcomed guests.

Negative Impacts: household pest

Eastern pipistrelles eat many insects that may be harmful to humans.

Positive Impacts: controls pest population

Comments: See Davis (1959) for information on geographic variation and subspecies.

The relationships of the genera Eptesicus and Pipistrellus are unclear; for several Old World species there is some uncertainty as to which is the appropriate genus (see Morales et al. 1991 and Hilton and Harrison 1978).

Menu (1984) transferred P. subflavus to a new genus (Perimyotis), "but comparisons are clearly inadequate" (Koopman, in Wilson and Reeder 1993), and Koopman, Jones et al. (1992), and Simmons (in Wilson and Reeder 2005) retained this species in the genus Pipistrellus. Hoofer et al. (2006) revised the generic status of American pipistrelles and transferred Pipistrellus hesperus to the genus Parastrellus and Pipistrellus subflavus to the genus Perimyotis.