Lesser long-eared bat
|Lesser long-eared bat|
It has been suggested that microbats such as the lesser long-eared bat evolved independently from megabats, and do not have a common ancestor. Their wing structure and ability to fly is an analogous feature, as they have both evolved the structure independently due to a similar habitat but not because they are closely related. There are not many other similar features between the bats — microbats mostly eat insects, are nocturnal, have poorly developed eyes and large ears, whereas megabats mostly eat fruit and nectar, are not nocturnal and have well-developed eyes. Megabats have many characteristics that suggest they are sister taxa to primates but microbats, including lesser long eared bats are more separated on the evolutionary tree. There is also some genetic evidence to support this.
The lesser long-eared bat is a medium-sized species with a forearm length ranging from 30.6–41.7 mm; it also has long ears which can vary between 17.6–25.3 mm in length. Light grey coloured fur is located on the back of the bat with noticeably lighter to white fur on its underbelly, these hairs range from dark at the base to light at the ends (bicoloured). The distinguishing feature of this species is the high nose ridge which is around 1.5 mm high, split and connected by an elastic membrane of skin, creating a Y-shaped groove.
Diet and foraging
When flying this species will point the tips of its ears forward listening for sound emitted from small openings located at the top of their snouts. The species is known to have one of the slowest flight speeds when foraging, reaching speeds of up to 4 km/h when flying into the understory and through vegetation. Despite this it has high maneuverability and while in forests 6–10 m above the ground, it can switch suddenly in directing sometimes dropping vertically to a centimeters above the ground to catch insects. In open areas they will spiral around bushes and shrubs, if they spot prey on the ground they can land capture their victim and then relaunch almost vertically. There have been observations of the species hovering as well as the ability to take flight from water. Records show that they commute around 20 km/h. Grasshoppers, crickets and moths are their most common food but have a large variety of foods including: lacewings, beetles, flies, cricket nymphs, cockroaches and spiders. It is believed that their capture in pit-traps is due to them, being attracted to previously captured insects. Their hunting techniques have notable diversity in that they use echolocation (peak power frequency 47.7 kHz; range 47–48 kHz) for capturing aerial, foliage and ground prey. Their use of sight is mostly restricted to aerial prey while they a technique that the species uses to take advantage of seasonal booms of tettigoniid crickets as well as general ground and aerial prey, known as passive listing. This method of hunting does not rely on sight or echolocation. Some moths species, like noctuids, have evolved to develop their own form of "ears" that are able to pick up the frequency of bat calls, however they are unable to sense long-eared bats as the bats use a minute whispering technique different from echolocation which bounces off the moths and is picked up by their large ears.
Habitat and distribution
This species is a highly adaptable bat and as a result is one of the most widespread bats that is endemic to Australia. It lives in deserts, tropical to alpine woodlands, mangroves, agricultural land, urban areas, wet to dry sclerophyll forests and rain forests.
These bats are usually nocturnal, living in dark caves, hollows, old trees, ceilings and hollow walls. They are fairly common throughout most of Australia their roosting habits vary greatly. Their preferred roosting places tend to be small crevices such as peeling and hanging bark, in tree hollows, caves, buildings and reportedly fairy martin nests, rolled up swags, under piles of bricks and old hung up clothes. Their sociability ranges dramatically from single bats to small groups of two bats or three bats. Some areas have found 10 to 15 bats in a maternity colony with a single mature male. There has been evidence found in the Nullarbor caves of a group of 50 deceased bats and a large living colony of found in Western Australia at the Margaret River caves. One report of around 300 bats has been found in a rundown warehouse building. Within a defined area most groups will relocate to new roost locations frequently as a distance of 6–12 km has been found from roosts to hunting areas in remnant bushland. As ambient temperature decreases below the thermoneutral zone metabolic rate increases. In Tasmania when temperatures reach 15 degrees Celsius and below they will enter torpor. A study from the Journal of Comparative Physiology found that "the first evidence that Australian long-eared bats exhibit similar thermal characteristics and patterns of torpor to their relatives from the northern hemisphere. The Tb of both Nyctophilus species fell to about 1±3 °C and torpor bouts could last for more than 1 day. TMR of the bats we measured was as low as 0.5% of that in normothermic bats at the same Taand about 3% of the BMR. As torpor was used frequently and reduced energy expenditure substantially it appears that it plays a central role in the biology of Australian microbats."
In November the commencement of spermatogenesis takes place in males which peaks in March and ends in May. The epididymides hold the sperm as the testes retreat. In April mating usually initiates, with the female then using the oviduct and the uterine lining to hold sperm over the winter. In late August to September ovulation and fertilisation takes place with gestation lasting between 72–93 days. In late October through to November (later in lower latitudes and elevations) births take place, with the mother often producing twins. The young can fly by December while early February sees the ceasing of lactation. Tasmania has reported shorted lactation periods. Mature females will not always birth every year. This species has demonstrations of sperm competition.
- Nyctophilus geoffroyi The IUCN Red List of Endangered Species
- Lesser Long-eared bat Australian Museum
- Menkhorst, Peter (2001). A Field Guide to the Mammals of Australia. Melbourne: Oxford University Press. p. 269.
- Churchill, Sue (2008). Australian Bats. Australia: Allen & Unwin. p. 255.
- Richardson, Phil (2002). Bats. London: The Natural History Museum. p. 112. ISBN 0-565-09167-0.
- Geiser á, F; R. M. Brigham (22 November 1999). "Torpor, thermal biology, and energetics". Journal of Comparative Physiology: 10.