Great Evening Bat (Ia io)
HB: 89-104; T: 61-83; FA: 71.5-80; E: 22-29; HF: 13-18
The largest Thai pipistrelle
with a forearm of over 70. The upperparts are a uniform sooty brown, while
the underparts are dark greyish brown with the individual hairs dark brown
at the base , becoming greyish brown at the tips. The face is relatively
hairless. The eras are rather short, not extending beyond the muzzle when laid
forward; the insides of the ears are densely haired near the tips. The tragus is
rather short, with a bluntly rounded tip. The tip of the tail extends slightly
beyond the interformeral membrane. The skull is large and robust, with a
flattened rostrum and an occuput which is distinctly elevated above the
forepart of the braincase. The sagittal crest is prominent and continues forward
as far as the interorbital region. The upper inner incisor has a faint
indication of a cusp near the outer tip, while the lower incisors are marked
trifid. The upper canine is strongly in contact with the large second upper
premolar, with the tiny first premolar hidden between the canine and second
· The species is phylogenetically close to Scotomanes, and is placed in the tribe Nycticeiini, not the Pipistrellini as previously thought (Thabah et al. 2007). .
This widespread species has been recorded from Northern South
Asia, much of Southern and Central China, and Northern Southeast Asia. In South
Asia this species is presently known from India (Assam and Meghalaya) and Nepal
(Western Nepal) (Molur et al. 2002). In China, it has been recorded from
Sichuan, Guizhou, Anhui, Jiangxi, Hunan, Guangxi, Jiangsu, Yunnan, Shaanxi and
Hubei (Smith and Xie 2008). In Southeast Asia, it ranges from Myanmar in the
west, eastwards into Thailand, Lao PDR and Vietnam. It has been recorded
at elevations of 200 m to 1,700 m asl.
China; India; Lao People's Democratic Republic; Myanmar; Nepal; Thailand; Vietnam
Range Map: Click here to open the map viewer and explore range.
The largest known population is of close to a hundred
animals in Nepal (G. Csorba pers. comm.). In Thailand
populations are up to about 20 individuals (S. Bumrungsri pers. comm.).
Population Trend: Unknown
Habitat and Ecology:
This species is associated with tropical moist forest, where
it is exclusively a cave roosting species. It has been found in areas of
pristine mixed and deciduous forest (Thailand), wet
(Vietnam). It has often been reported from limestone karst areas, however, it is
found in non-limestone areas in Vietnam (Thong pers. comm.). Roosts in
caves. Emergence and flight pattern
· Ia io has a high wing loading (15.4 Nm -2 ), average aspect ratio (6.9) and a high tip shape index (1.1), features associated with fast and efficient flight (Thabah et al. 2007).
· This is a carnivorous bat and feds extensively on birds. It evolved this remarkable feeding habit independently of Nyctalus lasiopterus, which seems to specialise in capturing migrating birds in the air (Ibanez et al. 2001). In India (Meghalaya) the diet comprises mainly Coleoptera and birds, although Lepidoptera and traces of Diptera, Orthoptera and Hemiptera were also found (Thabah et al. 2007). In China, (Guizhou Province) bats were captured in early November, and fresh droppings were also collected from underneath the roost. Bird feathers comprised 82% of the bats' droppings by volume (Thabah et al. 2007).
Ia io emits relatively low frequency echolocation calls and sometimes produces two-toned calls, a characteristic of species that echolocate distant targets. A waveform and spectrogram from a bat recorded in India below (Thabah et al. 2007).
The table below shows call characteristics from two-toned
calls recorded from hand-released bats in India (Thabah et al. 2007).
Lower tone Highest energy (kHz)
27.6 ± 1.5
24.8 ± 1.5
Start Frequency (kHz)
34.9 ± 5.9
38.6 ± 2.8
End Frequency (kHz)
21.9 ± 1.8
18.0 ± 1.1
2.4 ± 0.5
3.8 ± 0.6
Pulse Interval (ms)
65 ± 20.5
93 ± 9.3
In Southeast Asia there are no major threats to this species.
It may be locally threatened by general habitat degradation. In South Asia, this
species is threatened by deforestation, generally resulting from logging
operations and the conversion of land to agricultural and other uses. It is also
threatened by disturbance to roosting sites by humans (Molur et al. 2002).
In South Asia there are no direct conservation measures in place for this species, and the species has not been recorded from any protected areas. In Southeast Asia, it has been recorded from some protected areas. In South Asia, further studies are needed into the distribution, abundance, reproduction and ecology of this species. Populations of this species should be monitored to record changes in abundance and distribution (Molur et al. 2002).