Seychelles sheath-tailed bat

Last updated

Seychelles sheath-tailed bat
Seychelles sheath-tailed bat - dead.jpg
A dead Seychelles sheath-tailed bat collected for research
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Chiroptera
Family: Emballonuridae
Genus: Coleura
Species:
C. seychellensis
Binomial name
Coleura seychellensis
(Peters, 1868)
Seychelles Sheath-tailed Bat area.png
Seychelles sheath-tailed bat range

The Seychelles sheath-tailed bat (Coleura seychellensis) is a sac-winged bat found in the central granitic islands of the Seychelles. They are nocturnal insectivores that roost communally in caves. The species was previously abundant across much of the archipelago, but has since seen a substantial loss of habitat. The International Union for Conservation of Nature has listed the species as being critically endangered, due to population decline. This is mainly due to an increase in land development and the introduction of invasive species.

Contents

Ecology

Seychelles sheath-tailed bat in a cave Seychelles sheath-tailed bat in cave.jpg
Seychelles sheath-tailed bat in a cave

The weight of Seychelles sheath-tailed bats averages about 10–11 grams (0.35–0.39 oz). Bats in this genus generally roost in caves and houses, in crevices and cracks. In the 1860s, the Seychelles sheath-tailed bat was reported to fly around clumps of bamboo towards twilight, and in the daytime to be found roosting in the clefts of the mountainside facing the sea and with a more or less northern aspect. These hiding places were generally covered over with the large fronds of endemic palms. The Seychelles sheath-tailed bat is insectivorous. It feeds predominantly on marsh-associated Ceratopogonidae, in contrast to Curlionidae in palm woodland. Its colonies are apparently divided into harem groups.

It has been the focus of recent intensive research, which has determined that it is a species associated with small clearings in forests where it feeds on a wide variety of insect species. Observations of coastal or marsh feeding are thought to be bats that have been forced into feeding in unusual situations due to habitat deterioration. Although the species is not a specialist and has a high reproductive potential, it is very vulnerable to disturbance and requires several roost sites within healthy habitat.

Status

It was probably abundant throughout the Seychelles in the past, but it has declined drastically and is now extinct on most islands. The International Union for Conservation of Nature lists this bat as being critically endangered. [1] In 2013, Bat Conservation International listed this species as one of the 35 species of its worldwide priority list of conservation. [2]

It is one of the most endangered animals, fewer than 100 are believed to exist in the world. The Seychelles sheath-tailed bat has suffered from habitat deterioration due to the effects of cultivation of coconut plantations and the introduction of the kudzu vine, both of which have reduced the incidence of scrub and the availability of insect prey. [1] The largest surviving roost is on Silhouette Island, although small roosts do exist in Mahé and also Praslin and La Digue islands. [1] Its lifespan is 20 years; its length is 55–65 mm (2.2–2.6 in).[ citation needed ] It finds its mates by fighting with another male bat in front of the females.

Echolocation

Echolocation in bats is the combination of producing sound waves via a bat's vocalization, using echoes from an environment, and highly evolved ears in bats. These sound waves are projected from an origin (the individual bat) until they come upon an object and are promptly bounced back to the origin at a lesser frequency and received by the source individual. [3] The variation in the return frequency can then be used by the individual to make a "visual" map of the environment in order for the bat to find their food or perform other tasks such as navigation as well as just communicating with other individuals in the colony. [3] There are a few different and important variables that can affect acoustic signals and soundwaves, first of which includes time/length (temporal character) of the calls by an individual. [3] Temporal control can be important in perceptual organization of echoes as they are returning back to a source individual from various directions and distances. [3] A second variable is speed/rate (spectral character) at which an individual calls and is important in helping an individual to perceptually visualize their surroundings when they are flying through terrain. [3] The speed (frequency) that an individual calls also can become faster as they close the distance between themselves and a food source, which is how they hunt flying insects such as Lepidoptera. [4] The speed at which calls can be adjusted from an individual also is important to keep track of each echo in more complex audio terrain. [3]

In order to use echolocation effectively bats have gone through much evolution to specialize in this method of movement and hunting. The two evolutionary pathways of echolocation in the two current suborders of bats, Yinpterochiroptera and Yangochiroptera are first, that echolocation has evolved separately between the two suborders, and second, that echolocation evolved from a single point in bat ancestral history and later was lost in some, but not all, Yinpterochiroptera suborder species. [5] There are two different structures that can be utilized for the inner ear of bats, the wall-less canal or the fenestral canal. [5] The wall-less canal allows for ganglion axons to cluster together without restrictions and allows for more space for more neurons. [5] The fenestral canal is more restrictive and does not allow for the increase of space for more neurons and also does not allow the clustering of ganglion axons which makes this structure more restrictive when concerning the variation of ganglion. [5] The highly derived spiral ganglion structure of the inner ear in Yangochiroptera, the suborder of Coleura seychellensis, is referred to as a trans-otic ganglion with a wall-less Rosenthal canal and is what makes echolocation work so well in bats of a similar evolutionary pathway. [5]

Vocalization

Within echolocation, there is vocalization which can be best described as how a frequency is altered for different purposes and needs. At a family level (Emballonuridae) four call structures have been described, broadband FM (Frequency modulation), narrowband FM, long multi-harmonic calls and short multi-harmonic calls. [6] Broadband FM is simply an FM sweep, narrowband FM is a downwards FM sweep that is then followed by a more narrow band tail. Long multi-harmonic calls are calls that have a minimum of 4 narrowband FM harmonics in a 2 ms period. Similarly, short multi-harmonic calls are ones that also have 4 narrowband FM harmonics but in under 2 ms. [6] The structure of calls can be altered for a specific need, they can be faster, slower, louder, or quieter from a source individual depending if they are hunting, navigating, communicating, protecting territory, or courting a mate. To date, there are 21 simple syllables and 62 composite syllables in Saccopteryx bilineata males which are in the same family, Emballonuridae, as Coleura seychellensis. [7]

Using these syllables there are seven vocalization types in the species S. bilineata , identified as pulses, barks, chatter, whistles, screeches, territorial songs, and courtship songs. [8] Pulses have a CF (constant frequency), start with an upward FM hook, end with a downward FM hook, and last about 7.4 ms. [8] Barks are similar to pulses but are longer at about 10.5 ms and mainly come from males. [8] Chatter calls are in sequences of up to 50 calls in about 5.5 ms, a single chatter call can resemble pulses but usually has a higher degree of FM. [8] Whistles are very loud and tonal vocalizations by males hovering in front of females and last about 66.7 ms, start with a FM upstroke, increasing in fundamental frequency, and end with a FM downstroke. [8] At the same time females vocalize a screech that can last up to 300 ms and are related to territorial conflicts and response to males hovering, these calls, also vocalized by males, typically have a duration of about 97 ms. [8]

Territorial songs are the most noticeable vocalizations in a colony with 10-50 tonal calls that first have an upward FM, then a V-shaped call in the middle, ending with a lower fundamental frequency that is headed by a noisy buzz. [8] The territorial calls can last anywhere from 10 ms to 100 ms and their structure can vary throughout the day. [8] Complex songs in mammals are rare and uncommon in S. bilineata but are used as courtship songs by males. The complex courtship songs also allow for individual identification of males by females in the species S. bilineata . [8] These courtship calls will only happen after territorial calls are finished in the morning and before territorial calls start in the evening and require ultrasound recording systems because they are above 20 kHz, that is, out of human hearing range (About 20 Hz - 20 kHz). [8] These courtship songs also can last for up to 1 hour while being directed at a single female. [8] As mentioned, S. bilineata are in the same family as C. seychellensis and while there is not as much known for C. seychellensis, 4 types of calls have been categorized specifically for C. seychellensis: complex calls, orientation calls, orientation calls in open areas, and foraging calls. [9]

Complex social calls have a wide frequency range and are mainly directed at other bats with no repetition in call structure. [9] Orientation calls are used for orientation in various terrains, usually in confined spaces. [9] Orientation calls in open areas involve no changes in frequency or amplitude. [9] Last, foraging calls are similar to orientation calls in open areas but include two alternating CF pulses. [9] Lower frequencies are usually used for navigation in C. seychellensis while higher frequencies are used for prey detection when an individual is in a more clustered environment. [9]

Related Research Articles

<span class="mw-page-title-main">Animal echolocation</span> Method used by several animal species to determine location using sound

Echolocation, also called bio sonar, is a biological sonar used by several animal species. Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects. Echolocation is used for navigation, foraging, and hunting in various environments.

<span class="mw-page-title-main">Microbat</span> Suborder of mammals

Microbats constitute the suborder Microchiroptera within the order Chiroptera (bats). Bats have long been differentiated into Megachiroptera (megabats) and Microchiroptera, based on their size, the use of echolocation by the Microchiroptera and other features; molecular evidence suggests a somewhat different subdivision, as the microbats have been shown to be a paraphyletic group.

<span class="mw-page-title-main">Greater bulldog bat</span> Species of mammal

The greater bulldog bat or fisherman bat is a species of fishing bat native to Latin America. The bat uses echolocation to detect water ripples made by the fish upon which it preys, then uses the pouch between its legs to scoop the fish up and its sharp claws to catch and cling to it. It is not to be confused with the lesser bulldog bat, which, though belonging to the same genus, merely catches water insects, such as water striders and water beetles.

<span class="mw-page-title-main">Mexican free-tailed bat</span> Species of mammal (Tadarida brasiliensis)

The Mexican free-tailed bat or Brazilian free-tailed bat is a medium-sized bat native to the Americas, so named because its tail can be almost half its total length and is not attached to its uropatagium. It has been claimed to have the fastest horizontal speed of any animal, reaching top ground speeds over 99 mph (160 km/h). It also flies the highest among bats, at altitudes around 3,300 m (10,800 ft).

<span class="mw-page-title-main">Emballonuridae</span> Family of bats

Emballonuridae is a family of microbats, many of which are referred to as sac-winged or sheath-tailed bats. They are widely distributed in tropical and subtropical regions around the world. The earliest fossil records are from the Eocene.

<span class="mw-page-title-main">Common pipistrelle</span> Species of mammal

The common pipistrelle is a small pipistrelle microbat whose very large range extends across most of Europe, North Africa, South Asia, and may extend into Korea. It is one of the most common bat species in the British Isles. In Europe, the northernmost confirmed records are from southern Finland near 60°N.

<span class="mw-page-title-main">Greater sac-winged bat</span> Species of bat

The greater sac-winged bat is a bat of the family Emballonuridae native to Central and South America.

<span class="mw-page-title-main">Short-eared bat</span> Species of bat

The short-eared bat is a bat species found in Brazil, Costa Rica, Guyana and Nicaragua. It is the only species within its genus.

<span class="mw-page-title-main">Lesser sac-winged bat</span> Species of bat in the family Emballonuridae

The lesser sac-winged bat or lesser white-lined bat is a bat species of the family Emballonuridae from South and Middle America.

<span class="mw-page-title-main">Seba's short-tailed bat</span> Species of bat

Seba's short-tailed bat is a common and widespread bat species in the family Phyllostomidae. They are found in Central America, the northern parts of South America, and in the Antilles islands.

<span class="mw-page-title-main">Nathusius's pipistrelle</span> Species of bat

Nathusius' pipistrelle is a small bat in the genus Pipistrellus. It is very similar to the common pipistrelle and has been overlooked in many areas until recently but it is widely distributed across Europe. It was described by two German naturalists, Alexander Keyserling and Johann Heinrich Blasius, and named by them after Hermann von Nathusius, in gratitude for his support of their research.

<span class="mw-page-title-main">Greater mouse-eared bat</span> Species of bat

The greater mouse-eared bat is a European species of bat in the family Vespertilionidae.

<span class="mw-page-title-main">Gray sac-winged bat</span> Species of bat

The gray sac-winged bat is a species in the family Emballonuridae which comprises the 51 species of sac-winged bats. It is found in Mexico from Baja California Sur and Sonora to Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica and northern Colombia, at elevations up to 1,500 metres (4,900 ft).

<span class="mw-page-title-main">African sheath-tailed bat</span> Species of bat

The African sheath-tailed bat is a species of sac-winged bat in the family Emballonuridae.

<i>Coleura</i> Genus of bats

Coleura is a genus of sac-winged bats in the family Emballonuridae. It contains three species:

<span class="mw-page-title-main">Yellow-bellied sheath-tailed bat</span> Species of bat

The yellow-bellied sheath-tailed bat, also known as the yellow-bellied sheathtail or yellow-bellied pouched bat, is a microbat species of the family Emballonuridae found extensively in Australia and less commonly in parts of Papua New Guinea.

<span class="mw-page-title-main">Hildegarde's tomb bat</span> Species of bat

Hildegarde's tomb bat is a species of sac-winged bat in the family Emballonuridae. It is found near the coast in Kenya and Tanzania where it feeds in tropical dry forests and roosts in caves. It is a diurnal species and the International Union for Conservation of Nature has assessed its conservation status as "endangered". The specific name hildegardeae was given in honour of anthropologist Hildegarde Beatrice Hinde.

<span class="mw-page-title-main">Mauritian tomb bat</span> Species of bat

The Mauritian tomb bat is a species of sac-winged bat in the family Emballonuridae that is found in central and southern Africa and Madagascar. It was discovered in 1818 by Étienne Geoffroy Saint-Hilaire, and is characterized by an all-white ventral surface, grizzled dorsal coloration, and conical face. It has exceptionally good eyesight, a trait which is common in old world bats and enables it to find roosting locations. It has adapted itself to a wide range of habitats including subarid scrub to semi-tropical savanna and can be found throughout much of Africa south of the Sahara, including many of the surrounding islands. They often seek out refuge in cool dry areas. Mauritian tomb bats help control pest populations, including insects that carry human diseases. These bats tend to be nocturnal hunters and their normal prey consists of moths, butterflies, and termites. Not prone to large-scale roosting, T. mauritianus is most often spotted on the sides of buildings or on the trunks of trees in groups of around five individuals. They breed on average once or twice a year and rear usually one pup, though twins are occasionally reported. They usually deposit their hungry offspring in areas where they can feed ferociously, most often in berry bushes. This species is listed as least concern on the IUCN Red List due their wide distribution and stable population.

<span class="mw-page-title-main">Lesser mouse-tailed bat</span> Species of bat

The lesser mouse-tailed bat is a species of microbat in the family Rhinopomatidae. Also referred to as Hardwicke's lesser mouse-tailed bat and long-tailed bat, it is named after Major General Thomas Hardwicke (1755–1835), an English soldier and naturalist who served many years in India. It is found in North Africa, some parts of central and eastern Africa, West Asia and east to the Indian subcontinent.

References

  1. 1 2 3 4 Mondajem, A.; Gerlach, J.; Mickleburgh, S.; Hutson, A.M.; Bergmans, W. (2017). "Coleura seychellensis". IUCN Red List of Threatened Species . 2017: e.T5112A22089794. doi: 10.2305/IUCN.UK.2017-2.RLTS.T5112A22089794.en . Retrieved 13 November 2021.
  2. "Annual Report 2013-2014" (PDF). batcon.org. Bat Conservation International. August 2014. Archived from the original (PDF) on July 7, 2017. Retrieved May 1, 2017.
  3. 1 2 3 4 5 6 F., Moss, Cynthia. Auditory scene analysis by echolocation in bats. OCLC   935319435.
  4. Fenton, M B; Portfors, C V; Rautenbach, I L; Waterman, J M (1998-06-01). "Compromises: sound frequencies used in echolocation by aerial-feeding bats". Canadian Journal of Zoology. 76 (6): 1174–1182. doi:10.1139/z98-043. ISSN   0008-4301.
  5. 1 2 3 4 5 Sulser, R. Benjamin; Patterson, Bruce; Urban, Daniel; Neander, April; Luo, Zhe-Xi (2022). "Evolution of inner ear neuroanatomy of bats and implications for echolocation". Nature. 602 (7897): 449–454. Bibcode:2022Natur.602..449S. doi:10.1038/s41586-021-04335-z. PMID   35082447. S2CID   246297015.
  6. 1 2 Hughes, Alice C.; Satasook, Chutamas; Bates, Paul J. J.; Soisook, Pipat; Sritongchuay, Tuanjit; Jones, Gareth; Bumrungsri, Sara (December 2011). "Using Echolocation Calls to Identify Thai Bat Species: Vespertilionidae, Emballonuridae, Nycteridae and Megadermatidae". Acta Chiropterologica. 13 (2): 447–455. doi:10.3161/150811011x624938. ISSN   1508-1109. S2CID   86104703.
  7. Davidson, Susan M.; Wilkinson, Gerald S. (2002). "Geographic and individual variation in vocalizations by male Saccopteryx bilineata (Chiroptera: Emballonuridae)". Journal of Mammalogy. 83 (2): 526–535. doi: 10.1644/1545-1542(2002)083<0526:GAIVIV>2.0.CO;2 . S2CID   15908577.
  8. 1 2 3 4 5 6 7 8 9 10 11 Behr, Oliver; Helversen, Otto von (4 March 2004). "Bat serenades—complex courtship songs of the sac-winged bat (Saccopteryx bilineata)". Behavioral Ecology and Sociobiology. 56 (2): 106–115. doi:10.1007/s00265-004-0768-7. S2CID   472801 via SpringerLink.
  9. 1 2 3 4 5 6 Gerlach, Justin (2009). "Vocalisations of the Seychelles sheath-tailed bat Coleura seychellensis" (PDF). Le Rhinolophe. 18: 17–24.

Further reading