Saturday, 1 January 2011

Kitti's Hog-nosed Bat: World's smallest bat and mammal

Man streching a Kitti's Hog-nosed Bat (Craseonycteris thonglongyai)
 Photo by Jeffrey A. McNeeley
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Chiroptera
Family: Craseonycteridae
Genus: Craseonycteris
Species: Craseonycteris thonglongyai
Conservation Status: Vulnerable (Threatened)
Common Name(s): Kitti's Hog-nosed Bat, Bumblebee bat

The small creature depicted on the image above is a Kitti's Hog-nosed Bat, the sole representative of the family Craseonycteridae. The species is best known for being the world's smallest bat and mammal, with an average weight of only 2 g!

Distribution and Habitat
This little critter occurs exclusively in western Thailand and southeast Burma, occupying limestone caves along rivers, within dry evergreen or deciduous forests.

In Thailand, the species can only be found in a small region of the Tenasserim Hills in Sai Yok District, Kanchanaburi Province, within the drainage basin of the Khwae Noi River.

In Burna, the first Bumblebee bat specimen was collected in 2001. Since then, at least nine separate roost sites have been identified in the limestone outcrops of the Dawna and Karen Hills outside the Thanlwin, Ataran, and Gyaing Rivers of Kayin and Mon States.

Map showing the distribution of the Kitti's Hog-nosed Bat
Bumblebee Bat Distribution

Adults have an average weight of 2 g (0.071 oz) and are 2.9 to 3.3 cm (1.1 to 1.3 in) long, roughly the size of a large bumblebee, hence their second common name. This tiny bat is the world’s smallest bat and depending on how size is defined, the world's smallest mammal. If we define size by length, than the Bumblebee bat is the winner. However, if we define size by mass, then the winner is the Etruscan shrew (Suncus etruscus) which is lighter, with a weight ranging from 1.2 to 2.7 g (0.042 to 0.095 oz), although longer, measuring 3.6 to 5.3 cm (1.4 to 2.1 in) from head to tail.

Their body is covered by a reddish-brown or grayish coat that is paler on the underside. They have a distinctive, swollen and pig-like snout with thin and vertical nostrils. The ears are relatively large while the eyes are small and predominantly covered by fur.

The wings are large and darker in color, with long tips. These tips allow them to hover, much like a hummingbird does. The small feet are interconnected with a large piece of skin (called uropatagium) that is believed to assist them in flying and catching insects. The species has no tail bones or calcars for flight control.

The small mouth contains teeth that are typical for insectivorous bats. They have 28 teeth, with relatively large incisors. The lower incisors are long and narrow.

Males have a large swelling in the gland that is at the base of the throat.

Their lifespan is unknown, but believed to be around 5 to 10 years, guessing from the lifespan of other closely related bats.

Close up of a Kitti's Hog-nosed Bat
Credit: Daniel Hargreaves

Bumblebee bats usually rest on the roof domes of caves in limestone hills, far away from the entrance and far apart from each other. The average population size per cave is about 100 individuals, however there have been recorded roosts containing only 10 to 15 bats and roosts containing up to 500 individuals.

The species is active for only a very brief period of the day, leaving their roost for 20 to 30 minutes in the evening and 10 to 20 minutes at dawn. However, these brief periods of activity are halted in days with heavy rain and/or cold temperatures outside. They go out to forage within fields of cassava and kapok or around the tops of bamboo clumps and teak trees, covering distances of up to one kilometer from their cave.

They are insectivorous animals that use echolocation when hunting. Their diet primarily consists of small flying insects, like flies, but they also eat some spiders. They are aerial feeders, meaning that they catch prey while flying.

The majority of prey is consumed in air, however some insects and spiders are trapped in their foliage as they fly, only to be consumed later after they return to their caves. They usually forage around the tops of teak trees and bamboo clumps
A man holds a Bumblebee bat in his fingers
Credit: Medhi Yokubol Faculty of Science,
Prince of Songkla University

Little is known about the reproductive patterns of the species. We know that they mate at the end of winter and give birth late in the dry season (April) of each year, to a single offspring. During feeding, the youngs either stay in the roost or remain attached to the mother, at one of her two vestigial pubic nipples It takes several months for the youngs to be able to fly and hunt for themselves.

Conservation Status Threats and Measures
As of 2008, the species is listed by the IUCN as vulnerable, with their population having a declining trend. Since the species was first described in 1974, some roosting sites have been disturbed, thanks to tourism, scientific collection and research and the collection and sale of individuals as souvenirs. However, the aforementioned factors are believed to have only a minor impact to the overall population. This, because most colonies exist in hard-to-access locations, with only a few major caves having been disturbed by direct human activity.

The greatest threat for the Thai population is habitat degradation, mainly due to the annual burning of forest areas, which is most prevalent during the bat's breeding season. Furthermore, the upcoming construction of a pipeline running from Burma to Thailand may pose a serious threat in the future. The threats affecting the Burmese populations are not studied and thus are largely unknown.

It is estimated that about 2,000 individuals remain in Thailand. The status of the population in Burma is unknown, but recent surveys give a number that is greater than 2,000.

Today, the Kitti's Hog-nosed Bat is protected under the Wild Animals Reservation and Protection Act (WARPA) in Thailand. The 500 km² Sai Yok National Park was created in 1980 specifically to protect and conserve the species. The park covers most of the caves these strange animals reside in.

Interesting Facts about the Kitti's Hog-nosed Bat
- Although the Thai and Burmese populations are morphologically identical, their echolocation calls are distinct. Whether the two populations are reproductively isolated is yet to verified.
- The species' common and scientific names are in honor to its discoverer, Thai zoologist Kitti Thonglongya (1928-1974) . Thonglongya worked with a British partner, John E. Hill, in classifying bats of Thailand. After Thonglongya died suddenly in February 1974, Hill formally described the species they had discovered together in 1973, giving it the binomial name Craseonycteris thonglongyai in honor of his colleague.

Stuffed Kitti's Hog-nosed Bat specimen in the National Museum of Nature and Science, Tokyo, Japan.
Stuffed specimen in the National Museum of Nature and Science, Tokyo, Japan.

References & Further Reading
- Puechmaille, S., Soisook, P., Yokubol, M., Piyapan, P., Ar Gouilh, M., Mie Mie, K., Khin Kyaw, K., Mackie, I., Bumrungsri, S., Dejtaradol, A., Nwe, T., Hla Bu, S., Satasook, C., Bates, P., & Teeling, E. (2009). Population size, distribution, threats and conservation status of two endangered bat species Craseonycteris thonglongyai and Hipposideros turpis Endangered Species Research, 8, 15-23 DOI: 10.3354/esr00157
- Surlykke, A., Miller, L., Mhl, B., Andersen, B., Christensen-Dalsgaard, J., & Buhl Jrgensen, M. (1993). Echolocation in two very small bats from Thailand Craseonycteris thonglongyai and Myotis siligorensis Behavioral Ecology and Sociobiology, 33 (1), 1-12 DOI: 10.1007/BF00164341
- Hulva, P., & Horáček, I. (2002). (Chiroptera: Craseonycteridae) is a Rhinolophoid: Molecular Evidence from Cytochrome Acta Chiropterologica, 4 (2), 107-120 DOI: 10.3161/001.004.0201
- 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.
- Chiroptera Specialist Group. 1996. Craseonycteris thonglongyai. In: IUCN 2006. 2006 IUCN Red List of Threatened Species.
- Nowak, R.M. 1999. Walker's Mammals of the World. Sixth edition. The Johns Hopkins University Press, Baltimore and London.
- 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.

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