As October is best known for the Halloween season, I’d like to dedicate this article to one of the most famous spooky symbols – bats.

These creatures are phenomenal on multiple levels. As you may already know, they are the only know flying mammals; they communicate through echolocation and – yes – they can feed on blood. At least the spookiest of them do.

Bats – classified within the order Chiroptera – are closely related to hedgehogs, shrews and moles. They are common globally, excluding the coldest, subpolar regions. That is due to energy consuming by flying, and the poles being food-scarce regions. Apart from that, the rest of the world stands wide open for bats, offering an entire spectrum of habitats corresponding to the variety of their traits. Beginning with size and ending with diet, bats differ radically across taxonomical levels. They may even collect The Smallest Known Mammal Award (if there were such a thing!) thanks to Thailand’s bumblebee bat (Craseonycteris thonglongyai) It measures only 29 -33 mm in length and weighs about 2 g in mass – roughly the weight of a sugar cube!

The largest known bats come from the tropics. Some species, called megabats or flying foxes, may weigh up to 1,45 kg and have wingspans up to 1,7 m, such as the giant golden-crowned fruit bat (Acerodon jubatus), endemic to the Philippines. As its name suggests, it feeds on fruit. Unlike the majority of birds, bats cannot perceive the reds of sweet, ripe fruits. They avoid competition with birds in tropical forests by feeding on the white and green fruits from Ficus trees. Yes, the same Ficus that may be growing in the corner of your living room.

Despite the vegetarian diet of some species, most bats prefer an insect-based menu. That includes all 11 species of bats found in Norway (Fig. 1). They belong to the family Vespertilionidae and are all legally protected.

Fig. 1. All 11 bat species that can be found in Norway.

1. Skjeggflaggermus, the whiskered bat (Myotis mystacinus); photographed by Léna Gahéry, Deed – Attribution-ShareAlike 4.0 International – Creative Commons; ↩︎
2. Nordflaggermus, the northern bat (Eptesicus nilssonii); photographed by Magne Flåten, Deed – Attribution-ShareAlike 4.0 International – Creative Commons; ↩︎
3. Skogflaggermus, Brandt’s myotis (Myotis brandtii); photographed by Manuel Ruedi, Deed – Attribution 3.0 Unported – Creative Commons; ↩︎
4. Vassflaggermus, Daubenton’s bat (Myotis daubentonii) in torpor; photographed by Lennart Lennuk, Deed – Attribution 4.0 International – Creative Commons; ↩︎
5. Børsteflaggermus, Natterer’s bat (Myotis nattereri); photographed by Gilles San Martin, Deed – Attribution-ShareAlike 2.0 Generic – Creative Commons; ↩︎
6. Storflaggermus, the common noctule (Nyctalus noctula); photographed by Mnolf, Deed – Attribution-ShareAlike 3.0 Unported – Creative Commons; ↩︎
7. Trollflaggermus, Nathusius’ pipistrelle (Pipistrellus nathusii); photographed by Mnolf, Deed – Attribution-ShareAlike 3.0 Unported – Creative Commons; ↩︎
8. Tusseflaggermus, the common pipistrelle (Pipistrellus pipistrellus);  photographed by Mnolf, Deed – Attribution-ShareAlike 3.0 Unported – Creative Commons; ↩︎
9. Dvergflaggermus, the soprano pipistrelle (Pipistrellus pygmaeus); photographed by Evgeniy Yakhontov, Deed – Attribution-ShareAlike 3.0 Unported – Creative Commons; ↩︎
10. Brunlangøre, the brown long-eared bat (Plecotus auritus); photographed by Fourrure, Deed – Attribution-ShareAlike 2.0 Generic – Creative Commons; ↩︎
11. Skimmelflaggermu, the parti-coloured bat (Vespertilio murinus); photographed by Mnolf, Deed – Attribution-ShareAlike 3.0 Unported – Creative Commons. ↩︎

Cold Norwegian winters are unfavourable for both insects and bats. As food availability decreases along with temperature, bats entera state of seasonal sleep called torpor, which differs from the hibernation as it is typical e.g. bears. During such sleep, bats wake up more often – every few hours or days rather than every few months – to warm up a little and feed. Their body temperature does not drop as much as during hibernation – only by about 1-2 °C. Hibernation is extremely demanding and requires large energy reserves stored in fat cells. Because of small size, fast metabolism and low-calorie diet, bats cannot accumulate such amounts of energy during the warmer seasons, hence the torpor was the better solution. During winter sleep, they like to hide in caves, attics or tree hollows, although little is still known about the winter habits of Norwegian bats.

To wrap up with a vampirish element as promised, there are bats specialised in hematophagy – feeding on blood – as a dietary strategy. Classified within the subfamily Desmodontinae, the common vampire bat (Desmodus rotundus), the hairy-legged vampire bat (Diphylla ecaudata), and the white-winged vampire bat (Diaemus youngi), feed solely on blood. For other species within Desmodontinae subfamily, blood is only one item of the menu. These bats are found only in the New World tropics, feeding on mammals and birds. In contrast to majority of bats, vampires are remarkably well adapted for terrestrial movement, agile in walking, jumping, and even running. That allows them to ambush prey, crawling up on it, wounding with their teeth and licking the oozing blood. Thanks to their saliva, rich in anticoagulants, the dripping blood clots more slowly, allowing for a longer meal. Not quite as monstrous nor sophisticated as pop culture would have us believe…

The photo of the skeleton of the vampire bat (Desmodus rotundus) on the cover was taken by Mokele, https://creativecommons.org/licenses/by/3.0/

References

• Bates, P.J.J., Nwe, T., Swe, K.M. and Bu, S.S.H.. 2001. Further new records of bats from Myanmar (Burma), including Craseonycteris thonglongyai Hill 1974 (Chiroptera: Craseonycteridae). Acta Chiropterologica 3(1): 33-41.
• Stier, S. C., & Mildenstein, T. L. (2005). Dietary habits of the world’s largest bats: the Philippine flying foxes, Acerodon jubatus and Pteropus vampyrus lanensis. Journal of Mammalogy, 86(4), 719-728.
• Kalko, E. K., Herre, E. A., & Handley Jr, C. O. (1996). Relation of fig fruit characteristics to fruit‐eating bats in the New and Old World tropics. Journal of Biogeography, 23(4), 565-576.
• Wojciechowski, M. (2001). Odrętwienie jako sposób na życie. O strategiach adaptacyjnych nietoperzy owadożernych. Kosmos, 50(1-2), 101-112.
• The Editors of Encyclopaedia Britannica (2025, March 12). vampire bat. Encyclopedia Britannica. https://www.britannica.com/animal/vampire-bat