White-striped free-tailed bat

White-striped free-tailed bat
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Chiroptera
Family: Molossidae
Genus: Austronomus
Species: A. australis
Binomial name
Austronomus australis
Gray, 1839
Synonyms
  • Tadarida australis Gray, 1839
  • Nyctinomus australis Gray, 1839

The white-striped free-tailed bat (Austronomus australis) is a species of bat in the family Molossidae. Its echolocation calls are audible to humans, which is a characteristic found in only a few microbat species.[2] The species was formerly classified as Tadarida australis.[1]

Taxonomy

There has been much consideration given to the seniority of what genus name to use for the white-sided free-tailed bat. The international Commission on Zoological Nomenclature (ICZN) recognises Tadarida (Rafinesque, 1814) as the senior authority before Nyctinomus, (Geoffroy, 1818). Therefore Tadarida, Rafinesque 1814 has precedence.

Subspecies and clade

Gregorin and Cirranello in their work found that Koopman[3] treated T. kuboriensis, as a subspecies of T. australis, and formed a clade with T. australis.[4] These two species display eight characteristics that make them distinctly morphologically from the other Tadarida. The most significantly characteristic beings a keel present between the nostrils, a synapomorphy combining this clade.[4] Likewise, T. kuboriensis and T. australis lack hair on the tragus and do not have thorn-like hairs on the face. The presence of hair on the tragus is a synapomorphy for non-Australian Tadarida.[4] With the relationship between T. kuboriensis and T. australis and their morphological uniqueness acknowledged when compared with other species of Tadarida, both species should be recognized under the established generic name Austronomus Troughton 1943 (type species Austronomus australis) Gray, 1834.[4]

Description

The white-tailed free-tailed bat is the largest of the eleven Australian Molossids. Individuals may have a mass of up to 40 g (1.4 oz) and a body length of 100 mm (3.9 in). The free tail extends approximately 55 mm (2.2 in) from the body and can be folded during high speed flight to reduce drag.[5][6] Its forearm length ranges from 57–63 mm (2.2–2.5 in). It has a condylobasal length of 23–24 mm (0.91–0.94 in). The skull is dorso-ventrally flattened. The baculum is trifid (divided into three lobes).[7] This species has a wingtip shaped similarly to the crescent form found on fast-flying birds and on the caudal fins of fast-swimming fish.[8] These tips have leading edges that curve around to chordwise orientation and have trailing edges with aft-sweep or zero-sweep over the outer half of the tip. This bat’s wings are considered as having low camber sections with faired humerus and radius bones, typical leading-edge flaps and surface disjunctions and protuberances. This allows this interceptor species to optimise for least drag generation at the expense of maximum lift ability at high speeds.[9] The white-striped free-tailed bat can reach speeds of up to 17 m/s.[6]

The large, forward pointed ears are approximately 25mm in length and assist in lift.[6] A short hairless tragus is present, a pointed prominence of the outer ear, and points forward. The pinnae, external part of the ear, are not joined across the top of the head.[4] The upper lip is deeply wrinkled, and this species have single incisor teeth on each of the frontal cranial bones, premaxilla, of the upper jaw. Both sexes have a throat pouch.[5] Fur colour varies with dark brown dorsally and lighter ventrally. A distinctive pattern of white fur on each side of the body progresses from the front to the back where the wings fold against the body, giving this species its common name, white-striped free-tailed bat. This species displays sexual dimorphism with the male being larger.

Echolocation

The white-striped free-tailed bat typical call has been recorded between 10-15 kHz.[6] Usually two calls per second and are audible to humans as “pink-pink-pink”.[10] Research by Herr and Klomp into the white-striped free-tailed bat’s calls showed that vocalisation changed at different stages of flight.[11] In the initial stages of flight, after release, this species used steep frequency modulated pulse, from 27 kHz to 13 kHz, changing to a low frequency modulated pulse when flying above a canopy. Once there the call structure changes to the more typical white-striped free-tailed bat call with a constant frequency with a divergence between maximum and minimum frequency of 5 kHz. All echolocating bats use a terminal phase buzz call to locate, close in and capture their prey.[12]

Distribution and habitat

An endemic species to Australia, the white-striped free-tailed bat is wide spread across the continent. Previously thought to be absent in Tasmania.[5] Recent surveys conducted in Tasmania between 2009 and 2013 indicated the species is present and that this species maybe a periodic vagrant to Tasmania.[13] In Western Australia this species is restricted south of 20°S latitude in the breeding season, spring and summer, then extending north in the winter.[14][15] This species can be found in most habitats from closed forest to open flood plain and urban areas across temperate and subtropical Australia.

Roosts

In the Greater Brisbane Region South East Queensland the white-striped free-tail bat uses over mature to dead eucalypts species with large tree diameters (>89 cm) as roost habitats.[16] These trees have developed large trunk cavities, often extending throughout the trunk and major branches.[16] The bats accesses these cavities through multiple unobstructed branch and/or trunk hollows (M. Rhodes, unpubl. data, 2003). This strategy also allows the bats a direct flight path when leaving the roost cavities which may result in energy savings for the bats and reduce the exposure to predators.[17][18]

Roosting behaviour

Although single bats spend a majority of their daytime in separate day-roosts, they spent an average of 1 day in every 11 within the communal roost.[16] The bats also visited the communal roost for periods of time during their nocturnal activity, some individuals were recorded twice as often frequenting the communal roost during the night compared with the day.[19]

Maternity roosts

This bat species is a highly colonial tree-dweller, large internal hallows are an important feature in selecting suitable maternity roost sites as population numbers increase during parturition. Therefore the quality and size of roost space is more important than the selection of specific tree species in maternity roost choice.[16][20]

Biology and ecology

Diet

This free-tailed bat is a specialized high altitude, fast flying interceptor insectivore.[21][22] Their diet consists principally of moths, beetles and bugs.[6]

Foraging habit and behaviour

In South East Queensland, white-striped free-tailed bats demonstrated a significant preference for foraging above flood plain habitat and does not prefer to feed above remnant forests.[23] In northern Australian urban areas, foraging individuals preferred and were in greater concentrations over grassland with few trees, such as golf courses, than over riparian areas, new urban developments, and suburbs that had been established for between 20–50 years.[24] White-striped free-tailed bats once they emerge from their roosts fly rapidly and directly to their foraging area, with individual bats flying up to 20 km to reach their feeding areas. However, some populations have a more localised foraging area. In the greater Brisbane area, foraging areas are usually within 2.5 km (1.6 mi) of day roost and 6.2 km (3.9 mi) of communal roosts.[23] On arrival they reduce their commuting flight speed to a lower sustainable flight speed that allows them to hunt in the foraging area for some hours.[23][7] Some researchers report that this bat will also scurry around on the ground chasing ground-dwelling insects such as beetles, bugs, grasshoppers and ants. They are able to do this by folding their wings away neatly so that their forearms are free, retracting their tail membrane and scampering around on their thumbs and hind feet.

Reproduction

Males do not have the ability to store sperm in their vesicular follicles during the winter period, therefore breeding commences late in August. Females give birth to one young between mid-December and mid-January, this indicates a gestation period of about 14 weeks.[25]

References

  1. 1 2 McKenzie, N.; Pennay, M.; Richards, G. (2008). "Austronomus australis". The IUCN Red List of Threatened Species. 2008: e.T21313A9269147. doi:10.2305/IUCN.UK.2008.RLTS.T21313A9269147.en.
  2. ↑ Regional Group, Burnett Mary. "White-striped freetail bat". All About Bats. Retrieved 7 February 2018.
  3. ↑ Koopman, K. F. (1982). "Bats from eastern Papua and the East Papuan islands". American Museum Novitates (2747).
  4. 1 2 3 4 5 Gregorin, Renato; Cirranello, Andrea (2016). "Phylogeny of Molossidae Gervais (Mammalia: Chiroptera) inferred by morphological data". Cladistics. 32: 2. doi:10.1111/cla.12117.
  5. 1 2 3 Strahan, R (1995). The Mammals of Australia: The National Photographic Index of Australian Wildlife. Reed Books. ISBN 0730104842.
  6. 1 2 3 4 5 Bullen, R; McKenzie, N. L (2001). "Bat airframe design: flight performance, stability and control in relation to foraging ecology". Australian Journal of Zoology. 49 (3): 235. doi:10.1071/ZO00037.
  7. 1 2 Clemens, W.; Richardson, B. J.; Baverstock, P. R. (1989). Fauna of Australia. 1B. Canberra: Australian Government Publishing Service. p. 17.
  8. ↑ Lazos, Barry S (2005). "Biologically Inspired Fixed-Wing Configuration Studies". Journal of Aircraft. 42 (5): 1089. doi:10.2514/1.10496.
  9. ↑ Bullen, R. D; McKenzie, N. L (2007). "Bat wing airfoil and planform structures relating to aerodynamic cleanliness". Australian Journal of Zoology. 55 (4): 237. doi:10.1071/ZO07010.
  10. ↑ Powys, V. (2010). "Recording microchiropteran bats" (PDF). Journal of the Australian Wildlife Sound Recording Group Inc. 13 (1).
  11. ↑ Herr, A.; Klomp, N.I. (1997). Reference calls of the White-striped free-tailed bat, Nyctinomus australis (Report). Australian Bat Society Newsletter. pp. 16–19.
  12. ↑ Griffiths, Stephen R (2013). "Echolocating bats emit terminal phase buzz calls while drinking on the wing". Behavioural Processes. 98: 58–60. doi:10.1016/j.beproc.2013.05.007. PMID 23701945.
  13. ↑ Cawthen, Lisa (2013). "White-striped freetail bat in Tasmania – resident, vagrant or climate change migrant?". Australian Mammalogy. 35 (2): 251. doi:10.1071/AM12052.
  14. ↑ Bullen, R. D; Dunlop, J. N (2012). "Assessment of habitat usage by bats in the rangelands of Western Australia: Comparison of echolocation call count and stable isotope analysis methods". The Rangeland Journal. 34 (3): 277. doi:10.1071/RJ12001.
  15. ↑ Bullen, R. D; McKenzie, N. L (2005). "Seasonal range variation of Tadarida australis (Chiroptera:Molossidae) in Western Australia: The impact of enthalpy". Australian Journal of Zoology. 53 (3): 145. doi:10.1071/ZO04080.
  16. 1 2 3 4 Rhodes, Monkia; Wardell-Johnson, Grant (April 2006). "Roost tree characteristics determine use by the white-striped freetail bat (Tadarida australis, Chiroptera: Molossidae) in suburban subtropical Brisbane, Australia". Austral Ecology. 31 (2): 228–239. doi:10.1111/j.1442-9993.2006.01587.x. ISSN 1442-9985.
  17. ↑ Vonhof, M. J. (1995). "Roost-site preferences of big brown bats (Eptesicus fuscus) and silver-haired bats (Lasionycteris noctivagans) in the Pend d'Oreille Valley in southern British Columbia". Bats and forest symposium. pp. 62–80.
  18. ↑ 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: 9. doi:10.1006/anbe.1994.1207.
  19. ↑ Rhodes, Monika (2007). "Roost Fidelity and Fission–Fusion Dynamics of White-striped Free-tailed Bats (Tadarida australis)". Journal of Mammalogy. 88 (5): 1252. doi:10.1644/06-MAMM-A-374R1.1.
  20. ↑ Sedgeley, Jane A; f.j. o'Donnell, Colin (1999). "Roost selection by the long-tailed bat, Chalinolobus tuberculatus , in temperate New Zealand rainforest and its implications for the conservation of bats in managed forests". Biological Conservation. 88 (2): 261. doi:10.1016/S0006-3207(98)00069-X.
  21. ↑ Churchill, S. (1998). Australian Bats. Sydney: New Holland Publishers.
  22. ↑ Vaughan, T. A (1966). "Morphology and Flight Characteristics of Molossid Bats". Journal of Mammalogy. 47 (2): 249. doi:10.2307/1378121. JSTOR 1378121.
  23. 1 2 3 Rhodes, Monika; Catterall, Carla (2008). "Spatial Foraging Behavior and Use of an Urban Landscape by a Fast-Flying Bat, the Molossid Tadarida australis". Journal of Mammalogy. 89: 34. doi:10.1644/06-MAMM-A-393.1.
  24. ↑ Hourigan, C. L; Johnson, C; Robson, S. K. A (2006). "The structure of a micro-bat community in relation to gradients of environmental variation in a tropical urban area". Urban Ecosystems. 9 (2): 67. doi:10.1007/s11252-006-7902-4.
  25. ↑ Kitchener, D. J.; Hudson, C. J. (1982). "Reproduction in the female white-striped mastiff bat, Tadarida australis (Gray)(Molossidae)". Australian Journal of Zoology. 30 (1): 1–14.
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