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Eptesicus serotinusserotine

By Madison Elliott

Geographic Range

Serotine bats (Eptesicus serotinus) are native to the palearctic region. They live as far north as southern Sweden and all of Denmark. Serotine bats' range extends westward to Spain, Portugal, France, and Great Britain. Their range includes the entirety of Germany, Poland, and Ukraine and as far south as Greece, Turkey, and eastern Syria. Serotine bats have a disjunct population in central Iran. Their range extends east to Tajikistan, Kyrgyzstan, and northern Nepal. Serotine bats can migrate a short distance, about 300km. (Godlevska, et al., 2020)

Habitat

Serotine bats roost on and in buildings all year round but not in the same location all year round. They will roost close to where they forage for insects such as farmland, open grassy meadows, on the edge of forests, and around streetlights. If there are no buildings nearby, serotine bats will roost in trees. Their maternity colonies establish roosts in buildings, and no males are present in those roosts. Serotine bats inhabit located at elevations as high as 1500 meters and as low as 5 meters. (Catto, et al., 1996; Hayrapetyan and Harutyunyan, 2015; Kervyn and Libois, 2008; Martinoli, et al., 2020; Tink, et al., 2014)

  • Range elevation
    5 to 1500 m
    16.40 to 4921.26 ft

Physical Description

Serotine bats have dark brown pelage on the dorsal and ventral sides and a black unfurred muzzle. Their wings and uropatagium also are unfurred. The range of reported lengths is about 62mm to 80mm, and range in wingspan is 320mm to 380mm.

Typically, adult females are larger than adult males, although clear ranges across the species have not been reported in a scientific manner. Weights and lengths are derived from studies of maternity colonies and summer males. In these studies, adult weights average about 23 grams for males, and range from 22 to 26 grams for females. In adult males, total-tail-hind foot-ear measures are reported as 70mm-50mm-13.7mm-19mm, respectively. Forearm lengths are reportedly 49mm. In adult females, forearm length ranges from 44.8mm to 55.8mm and body weight is 15g to 35g, depending on stage (or lack) of pregnancy.

At birth, young weights range from 4 grams to 6 grams (typically 4.5 g) and they are born hairless. (Martinoli, et al., 2020; Robinson and Stebbings, 2016; "Serotine bat", 1990)

  • Sexual Dimorphism
  • female larger
  • Range mass
    22 to 26 g
    0.78 to 0.92 oz
  • Range length
    62 to 80 mm
    2.44 to 3.15 in
  • Range wingspan
    320 to 380 mm
    12.60 to 14.96 in

Reproduction

Serotine bats use social calls at a frequency of 22 kHz to 27 kHz to attract a mate. They are polygynandrous and mate in the fall season typically September and October. Female serotine bats store sperm throughout the winter months when they are hibernating (ca. October to March). After hibernation, serotine bats will start their pregnancy. Serotine females come together in the spring to create a maternity roost. (Pfalzer and Kusch, 2003; "Serotine bat", 1990)

Serotine females form maternity colonies once they have become pregnant. They breed once a year and mate in September through October. Serotine females only have one offspring per year, rarely have two offspring. The gestation period is approximately 52 days. They give birth at end of June and early July. The young are volant about 36 days after birth. The young's birth mass is about 4.5 grams (range 4 to 6 grams). The mothers wean the young after three to four weeks after birth. When the mothers leave to forage for food, the young are left alone to stretch their wings and try to fly. Serotine males and females reach age of sexual maturity about one year after their birth. Serotine females are iteroparous and viviparous. They employ delayed fertilization, storing sperm for months, and have internal fertilization. (Harbusch and Raccey, 2006; "Serotine bat", 1990)

  • Breeding interval
    Serotine bats breed once a year.
  • Breeding season
    September through October
  • Range number of offspring
    1 to 2
  • Average number of offspring
    1
  • Average gestation period
    52 days
  • Range weaning age
    3 to 4 weeks
  • Range time to independence
    4 to 5 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Serotine males provide no parental investment beyond the act of mating. Serotine females do not need to prep a nest, but other females do come together to form a maternity colony until their young can take care of themselves. Serotine females look after the young until they have learned how to forage on their own. Once they young are weaned, the mothers show the young foraging areas. After 4-5 weeks, the young are independent from their mother, and they no longer depend on her for food or shelter. In captivity, after the mothers gave birth and the young were old enough to fend for themselves, they would be released into the wild. When they were released, they young would be independent and would start a new roost location. Those born in the wild typically return to the roost in which they were born. (Baranauskas, 1999; Kleiman, 1969; "Serotine bat", 1990)

  • Parental Investment
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Based on the banding data, the longest-lived serotine bat in the wild was 21 years at the time of capture. These bats have with an expected age lifespan in the wild of 5 years. They are not likely kept in captivity. Big brown bats (Eptesicus fuscus) are well-studied members of the same genus; researchers consider them "elderly" at 14 years or greater. In general, bats have lifespans approximately 3-10 times longer than non-bat mammals of comparable size. (Gaisler, et al., 2003)

  • Range lifespan
    Status: wild
    21 (high) years
  • Average lifespan
    Status: wild
    5 years

Behavior

Serotine bats are volant, but are also capable of climbing. They live and hibernate in buildings. Months of hibernation typically are October to March. Serotine bats are typically nocturnal, but they can be crepuscular, as most of the insects on which they forage are active in these time blocks. These bats use echolocation to find and capture their prey. They can feed mid-air, or they can feed on the ground-dwelling insects.

Serotine females create a maternity roost in spring months, focusing on anthropogenic sites, like buildings. Females exhibit roost fidelity, meaning they often return to the same roost year after year to raise their pups. Females all exhibit one bout of activity per night early in the season, during pregnancy. They switched to a bimodal activity pattern (two bouts of activity per night) later into their pregnancies, and the bouts were shorter in duration than those in early pregnancy. Finally, after giving birth, these adult females practiced multiple bouts of feeding and activity. Typically, males can form bachelor colonies, but it is unclear where these are located on the landscape. During summer months, breeding females form maternity colonies and roost in groups of 60-300 individuals. Males do not share roosts, and it's unknown how far away they choose to roost or if they roost-switch.

Serotine females use social calls to attract a mate during September to October. They can migrate a short distance about 300km. (Godlevska, et al., 2020; Robinson and Stebbings, 1997; "Serotine bat", 1990)

Home Range

Serotine bats do not forage too far away from their roost locations. They will fly up to 7km, but they will most likely fly about 2km away. For serotine females in maternity roosts, Robinson and Stebbings (1997) report home ranges for the entire colony to encompass 24 to 77 square km with a core range of 13 to 33 square km. One serotine individual will range in an area of 120 ha. They travel up to 10 feeding sites in a single night. They do not need to defend a territory. (Catto, 1993; Godlevska, et al., 2020; Robinson and Stebbings, 1997)

Communication and Perception

Serotine bats can see well during the day, like humans, but are nearsighted. They can navigate well at night using echolocation. Their frequency ranges from 15kHz to 65kHz with the mean frequency concentrated from 25kHz to 30kHz. When this frequency is graphed over time, their pulses appear like curved vertical line that looks like a "J."

Serotine bats use tactile senses to communicate to mate and to raise their young. They use vocalizations in roosts to communicate at frequencies that are lower than echolocation. The adult females use pheromones, so young and mother can recognize each other. (Jensen and Miller, 1999; Obrist and Fluckiger, 2004)

Food Habits

Serotine bats are insectivores. They eat a variety of flies, moths, chafers, and beetles. According to a study by Kervyn and Libois (2008), their diet in southern Belgium consists of 55.4% beetles (Order Coleoptera), 14.5% flies (Order Diptera), 10.8% moths (Order Lepidoptera), 7.2% true bugs (Order Hemiptera), 6.4% wasps (Order Hymenoptera), 5.6% caddisflies (Order Trichoptera), and 0.1% spiders (Class Arachnida). They eat a wide variety of beetles by opportunity across the range. Serotine bats eat on the fly and flying low to where they sometimes hit the ground to get to some of these insects. The young serotine bats drink monthers' milk until three or four weeks after birth then they eat what the mother regurgitates to them. (Catto, et al., 1996; Kervyn and Libois, 2008; Martinoli, et al., 2020; Tiede, et al., 2020)

  • Animal Foods
  • insects

Predation

Serotine bats are opportunistically preyed on by other aves and some snakes if the opportunity presents itself. Some snakes such as the horseshoe whip snake (Hemorrhis hippocrepis) may prey on them when they are roosting in buildings. Barn owls (Tyto alba), tawny owls (Strix aluco), and common kestrels (Falco tinnuculus) are some of the birds that eat serotine bats as part of their diet. The presence of the barn owls make serotine females group together more frequently in maternity roosts. Humans (Homo spaiens) also kill serotine bats because they hit windshields on vehicles. These bats avoid predation by grouping together and sometimes changing when they would leave the roost to forage. (Garrido-Garcia, et al., 2013; Godlevska, et al., 2020; Zukal and Petrzelkova, 2001)

  • Known Predators

Ecosystem Roles

Serotine bats eat flies, moths, true bugs, beetles, and occasionally spider. Avian predators and some snakes eat serotine bats. Some of the parasites of serotine bats are trematodes (Plagiorchis vespertillionis, Ophiosacculus eptesicus) and tapeworms (Hymenolepis acuta). They have bat fleas (Ischnopsylla). Serotine bats are also infected with Trypanosoma, which belong to the clade Excavata. They can be parasitized by nematodes (Spirocera lupi, Physocephalus sexalatus). (Alveraz, et al., 1991; Gardner, et al., 1987; Guerrero and Bain, 2011; "Serotine bat", 1990; Tiede, et al., 2020)

Commensal/Parasitic Species
  • Trematode (Plagiorchis vespertillionis)
  • Trematode (Ophiosacculus eptesicus)
  • Tapeworms (Hymenolepis acuta)
  • Bat fleas (Ischnopsylla)
  • Nematodes (Spirocera lupi)
  • Nematodes (Physocephalus sexalatus)

Economic Importance for Humans: Positive

Serotine bats help control the pests on farmlands. They eat craneflies (family Tipulidae) and tortrix moths (family Tortricidae), which are crop pests on farmlands. Pikula et al. (2009) examined internal organs for heavy metal toxins such as lead, cadmium and zinc when few serotine bats were discovered dead. They did bioaccumulate lead. (Alveraz, et al., 1991; Pikula, et al., 2009; Riccucci and Lanza, 2014)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Serotine bats can transmit rabies to humans. Living in human structures, there is always a risk of bites. They are infected with lyssavirus 1-type (EBLV-1), which is a type of rabies that frequently infects serotine bats. They are the primary species in Europe that transmits rabies to humans. (Moussy, et al., 2015)

Conservation Status

Serotine bats are listed as a species of "Least Concern" on the IUCN Red list. They have no special status on the US Federal list, CITES, and State of Michigan list, and their population is considered stable.

Threats in loss of habitat and tearing down buildings in which they possible roost or hibernate. They are threatened by changes in agriculture, e.g., farmers planting energy corps, and the farmland getting deprived of insect-rich soil that serotine bats need. Serotine bats are threatened by railroads, roads, and colliding with vehicles.

Serotine bats are protected by the national legislation in most of their European range except Russia and Kazakhstan, and it is unknown what their protection status is in China. They are protected through Convention on Migratory Species and EUROBATS agreement. In Appendix II of the Council of Europe's Convention on the Conservation of European Wildlife and Natural Habitats, serotine bats are protected from capturing and keeping, killing, destroying maternity roosts, disturbing during breeding season and hibernation, and trading them alive or dead. In Annex IV of EU Habitats and Species Directive, it states the same information as Appendix II, but adds that serotine bats need a management plan. ("Bern Convention on the Conservation of European Wildlife and Natural Habitats", 1979; Godlevska, et al., 2020)

Contributors

Madison Elliott (author), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

crepuscular

active at dawn and dusk

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

European Treaty Series. Bern Convention on the Conservation of European Wildlife and Natural Habitats. 104. Bern, Switzerland: Council of Europe. 1979.

Bat Conservation Trust. Serotine bat. None. London, England: Bat Conservation Trust. 1990.

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Baranauskas, K. 1999. Serotine bat eptesicus serotinus breeding under enclosure conditions. Acta Zoologica Lituanica, 9/1: 209-210.

Baydemir, N., I. Albayrak. 2006. A study on the breeding biology of some bat species in Turkey. Turkish Journal of Zoology, 30: 103-110.

Boshamer, J., J. Bekker. 2006. Summer observation of serotine (Eptesicus serotinus Schreber 1774) at 1481m altitude in the Republic of Macedonia. Lutra, 49/2: 111-114.

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Kleiman, D. 1969. Maternal care, growth rate, and development in the noctule (Nyctalus noctula), pipistrelle (Pipistrellus pipistrellus), and serotine (Eptesicus serotinus) bats. Journal of Zoology, 157/2: 187-211.

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Obrist, M., P. Fluckiger. 2004. Variability in echolocation call design of 26 swiss bat species: Consequences, limits and options for automated field identification with a synergetic pattern recognition approach. Mammalia, 68/4: 307-322.

Petrželková, K., J. Zukal. 2003. Does a live barn owl (Tyto alba) affect emergence behavior of serotine bats (Eptesicus serotinus)?. Acta Chiropterologica, 5/2: 177-184.

Pfalzer, G., J. Kusch. 2003. Structure and variability of bat social calls: Implications of specificity and individual recognition. Journal of Zoology, 26/1: 21-33.

Pikula, J., J. Zukal, V. Adam, P. Bandouchova, M. Beklova, P. Hajkova, J. Horakova, R. Kizek, L. Valentikova. 2009. Heavy metals and metallothionein in vespertilionid bats foraging over aquatic habitats in the Czech Republic. Environmental Toxicology and Chemistry, 29/3: 501-506.

Riccucci, M., B. Lanza. 2014. Bats and pest control: A review. Vespertilio, 17: 161-169.

Robinson, M., R. Stebbings. 1997. Home range and habitat use by the serotine, Eptesicus serotinus, in England. Journal of Zoology, 243/1: 117-136.

Robinson, M., R. Stebbings. 2016. Activity of the serotine bat, Eptesicus serotinus, in England. Myotis, 35: 5-16.

Tiede, J., M. Diepenbruck, J. Gadau, B. Wemheuer, R. Daniel, C. Scherber. 2020. Seasonal variation in the diet of the serotine bat (Eptesicus serotinus): A high resolution analysis using DNA. Basic and Applied Ecology, 49: 1-12.

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