Maternity colony explained

A maternity colony refers to a temporary association of reproductive female bats for giving birth to, nursing, and weaning their pups. The colonies are initiated by pregnant bats. After giving birth, the colony consists of the lactating females and their offspring. After weaning, juveniles will leave the maternity colony, and the colony itself will break apart. The size of a maternity colony is highly variable by species, with some species forming colonies consisting of ten or fewer individuals, while the largest maternity colony in the world in Bracken Cave is estimated to have over 15 million bats.

Benefits of a maternity colony

Maternity colonies are especially prevalent in temperate regions due to the thermal benefits of roosting with other individuals.^[1] Outside of the winter months, non-reproductive females and male bats enter torpor for short periods to conserve energy when temperatures are below an optimum threshold. However, torpor is detrimental to reproductive females because it delays the development of the fetus and slows milk production.^[1] Therefore, female bats are highly incentivized to maintain a constant body temperature. Roosting in a large group allows females to share body heat, lowering the energetic costs for individuals.

Risks of a maternity colony

Roosting in large groups brings risks to the members of a maternity colony. Predators such as hawks and owls can learn to anticipate the emergence of bats from a specific roost at sunset.^[2] Smaller colonies are thought to be less risky than larger colonies, because the nightly emergence of bats would attract less attention.^[3]

Species that form maternity colonies

Incomplete list

Common name	Scientific name	Range	Maternity colony size
Family: Vespertilionidae
Little brown bat	Myotis lucifugus	U.S., Canada	107-349^[4]
Southeastern myotis	Myotis austroriparius	Southeastern U.S.	1000+^[5]
Fringed myotis	Myotis thysanodes	Canada, Western U.S., Mexico	40-200^[6]
Indiana bat	Myotis sodalis	Midwestern U.S.	30-300^[7] ^[8]
Northern long-eared bat	Myotis septentrionalis	Eastern U.S., Canada	11-65^[9]
Bechstein's bat	Myotis bechsteinii	Europe, Asia	15-40^[10]
Geoffroy's bat	Myotis emarginatus	Europe	<10-985^[11]
Gray bat	Myotis grisescens	Southeastern U.S.	100,000+^[12]
Hodgson's bat	Myotis formosus	Asia	82-200^[13]
Eastern small-footed bat	Myotis leibii	Eastern U.S., Canada	≤22^[14]
Greater mouse-eared bat	Myotis myotis	Europe	50-800^[15]
Cave myotis	Myotis velifer	Southwest U.S., Mexico	100-3,000
Yuma myotis	Myotis yumanensis	Western U.S.	100-1,000
Arizona myotis	Myotis occultus	Southwestern U.S.	67^[16]
Daubenton's bat	Myotis daubentonii	Europe, Asia	6-144^[17]
Long-eared myotis	Myotis evotis	Canada, Western U.S.	4^[18]
Tricolored bat	Perimyotis subflavus	Eastern U.S.	9-40^[19] ^[20]
Parti-coloured bat	Vespertilio murinus	Europe, Asia	>30^[21]
Big brown bat	Eptesicus fuscus	North America, Central America, the Caribbean	20-100^[22]
Serotine bat	Eptesicus serotinus	Europe, Asia	5-200^[23]
Northern bat	Eptesicus nilsonii	Europe, Asia	10-70^[24]
Silver-haired bat	Lasionycteris noctivagans	Bermuda, Canada, Mexico, U.S.	8^[25]
Townsend's big-eared bat	Corynorhinus townsendii	Canada, Mexico, U.S.	40-55^[26]
Virginia big-eared bat	Corynorhinus townsendii virginianus	Appalachian U.S.	100-6335^[27]
Ozark big-eared bat	Corynorhinus townsendii ingens	AR, OK, MO	55-309^[28]
Rafinesque's big-eared bat	Corynorhinus rafinesquii	Southeastern U.S.	≤118^[29]
Common noctule	Nyctalus noctula	Europe, Asia, North Africa	20-50^[30]
Common pipistrelle	Pipistrellus pipistrellus	Europe, North Africa, Asia	92-262^[31]
Nathusius's pipistrelle	Pipistrellus nathusii	Europe	5-150^[32]
Evening bat	Nycticeius humeralis	Eastern U.S.	≤492^[33]
Gould's wattled bat	Chalinolobus gouldii	Australia	20-30^[34]
Southern forest bat	Vespadelus regulus	Australia	<25^[35]
Lesser long-eared bat	Nyctophilus geoffroyi	Australia	3-23
Pallid bat	Antrozous pallidus	Canada, Western U.S., Mexico	10-150^[36]
Barbastelle	Barbastella barbastellus	Europe	10^[37]
Allen's big-eared bat	Plecotus phyllotis	Southwestern U.S., Mexico	18-97^[38]
Family: Rhinolophidae
Mehely's horseshoe bat	Rhinolophus mehelyi	Europe, Middle East	<60^[39]
Lesser horseshoe bat	Rhinolophus hipposideros	Europe, North Africa, Asia	2-750^[40] ^[41]
Rufous horseshoe bat	Rhinolophus rouxii	Asia, Southeast Asia	50-60^[42]
Family: Molossidae
Mexican free-tailed bat	Tadarida brasiliensis	U.S., Central America, South America	≤15 million^[43]
Big free-tailed bat	Nyctinomops macrotis	North America, Central America, South America	≤2,000^[44]
Family: Phyllostomatidae
Geoffroy's tailless bat	Anoura geoffroyi	Central America, South America	<150^[45]
Family:Miniopteridae
Common bent-wing bat	Miniopterus schreibersii	Europe, Asia, Australia	2,500-5,000^[46]
Family: Pteripodidae
Bornean large flying fox	Pteropus vampyrus	Borneo	<15,000^[47]

Notes and References

1. Dietz, M., & Kalko, E. K. (2006). Seasonal changes in daily torpor patterns of free-ranging female and male Daubenton’s bats (Myotis daubentonii). Journal of Comparative Physiology B, 176(3), 223-231.
2. Fenton, M. B., Rautenbach, I. L., Smith, S. E., Swanepoel, C. M., Grosell, J., & Van Jaarsveld, J. (1994). Raptors and bats: threats and opportunities. Animal Behaviour, 48(1), 9-18.
3. Wilkinson, G. S., & South, J. M. (2002). Life history, ecology and longevity in bats. Aging cell, 1(2), 124-131.
4. Frick, W. F., Reynolds, D. S., & Kunz, T. H. (2010). Influence of climate and reproductive timing on demography of little brown myotis Myotis lucifugus. Journal of animal ecology, 79(1), 128-136.
5. Gore . Jeffrey. Hovis. Julie . Summer 1992. The Southeastern Bat: Another Cave-roosting Species in Peril . BATS Magazine. Bat Conservation International . 2 March 2017 .
6. Web site: Species Assessment for Fringed Myotis (Myotis thysanodes) in Wyoming . Keinath . Douglas . December 2003 . Bureau of Land Management . 2 March 2017.
7. Web site: Summary of Indiana Bat Ecology . . 4 March 2008 . U.S. Fish & Wildlife Service. Department of the Interior . 2 March 2017.
8. Callahan, E. V., Drobney, R. D., & Clawson, R. L. (1997). Selection of summer roosting sites by Indiana bats (Myotis sodalis) in Missouri. Journal of Mammalogy, 818-825.
9. Menzel, M. A., Owen, S. F., Ford, W. M., Edwards, J. W., Wood, P. B., Chapman, B. R., & Miller, K. V. (2002). Roost tree selection by northern long-eared bat (Myotis septentrionalis) maternity colonies in an industrial forest of the central Appalachian mountains. Forest Ecology and Management, 155(1), 107-114.
10. Kerth, G., Safi, K., & König, B. (2002). Mean colony relatedness is a poor predictor of colony structure and female philopatry in the communally breeding Bechstein's bat (Myotis bechsteinii). Behavioral Ecology and Sociobiology, 52(3), 203-210.
11. Dekker, J. J., Regelink, J. R., Jansen, E. A., Brinkmann, R., & Limpens, H. J. (2013). Habitat use by female Geoffroy’s bats (Myotis emarginatus) at its two northernmost maternity roosts and the implications for their conservation. Visions of nature, 111.
12. Tuttle, M. D. (1979). Status, causes of decline, and management of endangered gray bats. The Journal of Wildlife Management, 1-17.
13. Shen, H. P., & Lee, L. L. (2000). Mother-young interactions in a maternity colony of Myotis formosus. Journal of Mammalogy, 81(3), 726-733.
14. O'Keefe, J. M., & LaVoie, M. (2011). Maternity colony of eastern small-footed myotis (Myotis leibii) in a historic building. Southeastern Naturalist, 10(2), 381-383.
15. Castella, V., Ruedi, M., & Excoffier, L. (2001). Contrasted patterns of mitochondrial and nuclear structure among nursery colonies of the bat Myotis myotis. Journal of Evolutionary Biology, 14(5), 708-720.
16. Hayward, B. J. (1963). A maternity colony of Myotis occultus. Journal of Mammalogy, 44(2), 279-279.
17. Encarnação, J. A., Kierdorf, U., Holweg, D., Jasnoch, U., & Wolters, V. (2005). Sex‐related differences in roost‐site selection by Daubenton's bats Myotis daubentonii during the nursery period. Mammal Review, 35(3‐4), 285-294.
18. Rancourt, S. J., Rule, M. I., & O'Connell, M. A. (2005). Maternity roost site selection of long-eared myotis, Myotis evotis. Journal of Mammalogy, 86(1), 77-84.
19. Hoying, K. M., & Kunz, T. H. (1998). Variation in size at birth and post‐natal growth in the insectivorous bat Pipistrellus subflavus (Chiroptera: Vespertilionidae). Journal of Zoology, 245(1), 15-27.
20. Winchell, J. M., & Kunz, T. H. (1996). Day-roosting activity budgets of the eastern pipistrelle bat, Pipistrellus subflavus (Chiroptera: Vespertilionidae). Canadian Journal of Zoology, 74(3), 431-441.
21. Granat, M. M. (2023). Confirmation of the presence of Vespertilio murinus maternitycolony in Warsaw. Przegląd Przyrodniczy, XXXIV, 3 (2023), 101-103.
22. Web site: Big Brown Bat (Eptesicus fuscus) Species Guidance . . 11 Sep 2013 . Wisconsin Department of Natural Resources . 2 March 2013.
23. Catto, C. M. C., Hutson, A. M., Raccey, P. A., & Stephenson, P. J. (1996). Foraging behaviour and habitat use of the serotine bat (Eptesicus serotinus) in southern England. Journal of Zoology, 238(4), 623-633.
24. Rydell, J. (1989). Site fidelity in the northern bat (Eptesicus nilssoni) during pregnancy and lactation. Journal of mammalogy, 70(3), 614-617.
25. Betts, B. J. (1998). Roosts used by maternity colonies of silver-haired bats in northeastern Oregon. Journal of Mammalogy, 79(2), 643-650.
26. Mazurek, M. J. (2004). A maternity roost of Townsend's big-eared bats (Corynorhinus townsendii) in coast redwood basal hollows in northwestern California. Northwestern Naturalist, 85(2), 60-62.
27. Web site: Virginia big-eared bat . . Center for Biological Diversity . 2 March 2017.
28. Clark, B. K., Clark, B. S., & Leslie Jr, D. M. (1997). Seasonal variation in use of caves by the endangered Ozark big-eared bat (Corynorhinus townsendii ingens) in Oklahoma. American Midland Naturalist, 388-392.
29. Hurst, T. E., & Lacki, M. J. (1999). Roost selection, population size and habitat use by a colony of Rafinesque's big-eared bats (Corynorhinus rafinesquii). The American midland naturalist, 142(2), 363-371.
30. Csorba, G. . Hutson, A.M. . 2016 . Nyctalus noctula . 2016 . e.T14920A22015682 . 10.2305/IUCN.UK.2016-2.RLTS.T14920A22015682.en . 12 November 2021.
31. Webb, P. I., Speakman, J. R., & Racey, P. A. (1996). Population dynamics of a maternity colony of the pipistrelle bat (Pipistrellus pipistrellus) in north‐east Scotland. Journal of Zoology, 240(4), 777-780.
32. Russ, J. M., O'Neill, J. K., & Montgomery, W. I. (1998). Nathusius' pipistrelle bats (Pipistrellus nathusii, Keyserling & Blasius 1839) breeding in Ireland. Journal of Zoology, 245(3), 345-349.
33. Whitaker Jr, J. O., & Clem, P. (1992). Food of the evening bat Nycticeius humeralis from Indiana. American Midland Naturalist, 211-214.
34. Dixon, J. M., & Huxley, L. (1989). Observations on a maternity colony of Gould’s wattled bat Chalinolobus gouldii (Chiroptera: Vespertilionidae). Mammalia, 53(3), 395-414.
35. Taylor, R. J., & Savva, N. M. (1988). Use of roost sites by four species of bats in state forest in south-eastern Tasmania. Wildlife Research, 15(6), 637-645.
36. Davis, R., & Cockrum, E. L. (1963). Bridges utilized as day-roosts by bats. Journal of Mammalogy, 44(3), 428-430.
37. Hillen, J., Kiefer, A., & Veith, M. (2009). Foraging site fidelity shapes the spatial organisation of a population of female western barbastelle bats. Biological Conservation, 142(4), 817-823.
38. Cockrum, E. L., & Musgrove, B. F. (1964). Additional records of the Mexican big-eared bat, Plecotus phyllotis (Allen), from Arizona. Journal of Mammalogy, 45(3), 472-474.
39. Sharifi, M. (2004). Postnatal growth and age estimation in the Mehely's horseshoe bat (Rhinolophus mehelyi). Acta Chiropterologica, 6(1), 155-161.
40. Bontadina, F., Arlettaz, R., Fankhauser, T., Lutz, M., Mühlethaler, E., Theiler, A., & Zingg, P. (2000). The lesser horseshoe bat Rhinolophus hipposideros in Switzerland: present status and research recommendations. Le Rhinolophe, 14, 69-83.
41. Knight . Tessa . Jones . Gareth . Importance of night roosts for bat conservation: roosting behaviour of the lesser horseshoe bat Rhinolophus hipposideros . Endangered Species Research . 2009 . 8 . 1-2 . 2 . 10.3354/esr00194.
42. Biswas, J., & Shrotriya, S. (2011). Dandak: a mammalian dominated cave ecosystem of India. Subterranean Biology, 8, 1.
43. Web site: Protecting a Jewel in Texas . . Bat Conservation International. 2 March 2017 .
44. Sparks, D. W., & Valdez, E. W. (2003). Food habits of Nyctinomops macrotis at a maternity roost in New Mexico, as indicated by analysis of guano. The Southwestern Naturalist, 48(1), 132-135.
45. Galindo-Galindo, C., Castro-Campillo, A., Salame-Méndez, A., & Ramírez-Pulido, J. (2000). Reproductive events and social organization in a colony of Anoura geoffroyi (Chiroptera: Phyllostomidae) from a temperate Mexican cave. Acta Zoológica Mexicana, (80), 51-68.
46. Vincent, S., Nemoz, M., & Aulagnier, S. (2010). Activity and foraging habitats of Miniopterus schreibersii (Chiroptera: Miniopteridae) in southern France: implications for its conservation. Hystrix: The Italian Journal of Mammalogy, 22(1).
47. Gumal, M. T. (2004). Diurnal home range and roosting trees of a maternity colony of Pteropus vampyrus natunae (Chiroptera: Pteropodidae) in Sedilu, Sarawak. Journal of Tropical Ecology, 20(03), 247-258.