| Triaenops menamena | |
|---|---|
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| Skull ofTriaenops menamena | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Chiroptera |
| Family: | Rhinonycteridae |
| Genus: | Triaenops |
| Species: | T. menamena |
| Binomial name | |
| Triaenops menamena Goodman and Ranivo, 2009 | |
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| Distribution ofTriaenops menamena (in green) and other species ofTriaenops | |
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| Triaenops menamena range | |
Triaenops menamena is abat in the genusTriaenops found onMadagascar, mainly in the drier regions. It was known asTriaenops rufus until 2009, when it was discovered that that name had been incorrectly applied to the species.Triaenops rufus is asynonym ofTriaenops persicus, a Middle Eastern species closely related toT. menamena— the Malagasy species had previously been placed as asubspecies ofT. persicus by some authors.Triaenops menamena is mostly found in forests, but also occurs in other habitats. It often roosts in large colonies and eats insects such asbutterflies and moths. Because of its wide range, common occurrence, and tolerance ofhabitat degradation, it is not considered to be threatened.
With a forearm length of 50 to 56 mm (2.0 to 2.2 in) in males and 46 to 53 mm (1.8 to 2.1 in) in females, this is a medium-sized bat. Its fur color is variable, ranging from reddish brown to gray, but it is generally darker than the species in the closely related genusParatriaenops which also occur on Madagascar. The skull contains a pronounced swelling around the nose and the second upperpremolar is displaced outside the toothrow. The maximum frequency of theecholocation call averages 94.2 kHz and the species can easily be recognized on the basis of its call.
In 1881,Alphonse Milne-Edwards described two new species in the genusTriaenops on the basis of specimens supposedly collected byLéon Humblot on Madagascar: the reddishTriaenops rufus and the larger, grayT. humbloti.[2]Jean Dorst, who reviewed MadagascanTriaenops in 1947, retained both as separate species; in another review, published in 1982,John Edwards Hill considered the two to represent the same species. In 1994,Karl Koopman consideredrufus itself to be part of the Middle Eastern and mainland African speciesTriaenops persicus, a possibility Hill had discussed,[3] but most authors regarded the two as distinct species.[4] In 2006, Julie Ranivo andSteven Goodman revised MadagascanTriaenops and found little variation among specimens ofT. rufus from throughout the dry parts of the island.[5] Three years later, they published another paper which showed that the original material ofT. rufus andT. humbloti was distinct from Madagascan specimens identified as "Triaenops rufus" and more similar toT. persicus.[6] On his journey to Madagascar, Humblot had stayed in Somalia and Yemen, and Goodman and Ranivo concluded that he had probably collected theTriaenops there, after which their provenance was incorrectly recorded.[7] Thus,rufus andhumbloti cannot be used for the Madagascan species, and Goodman and Ranivo proposed the new nameTriaenops menamena for the species formerly known asT. rufus. Thespecific namemenamena isMalagasy for "reddish", referring to the animal's coloration.[8] "Rufous trident bat" has been used as acommon name forTriaenops rufus.[1]
Triaenops menamena is currently one of four living species in the genusTriaenops; a 2009 revision by Petr Benda and Peter Vallo split off the AfricanT. afer and the YemeniT. parvus fromT. persicus and removed three other species, including two from Madagascar, to the separate genusParatriaenops.[9] An extinct species,Triaenops goodmani, is known from northwestern Madagascar.[10] In 2007 and 2008, Amy Russell and colleagues usedphylogenetic andcoalescent methodologies to investigate the history of theTriaenops group. They found thatT. menamena (asT. rufus) was closest to mainland AfricanTriaenops (but did not study Middle Eastern bats) and concluded thatT. menamena and the species ofParatriaenops (then still placed inTriaenops) independently reached Madagascar from Africa; the colonization of the island byT. menamena was dated to about 660,000 years ago.[11] Benda and Vallo also studied phylogenetic relationships inTriaenops and included Middle EasternT. persicus andT. parvus in their analysis. They found little resolution of relationships withinTriaenops, but some evidence suggested thatT. menamena is more closely related to the Middle Eastern species than toT. afer in mainland Africa; therefore,T. menamena may have reached Madagascar from the Middle East or northeastern Africa. They also placed the split betweenT. menamena and the other species much further back, at around 4 million years ago.[12]
| Sex | n[Note 1] | Total length | Tail | Hindfoot | Ear | Forearm | Mass |
|---|---|---|---|---|---|---|---|
| Male | 28[Note 2] | 90–104 | 27–38 | 6–9 | 14–17 | 50–56 | 8.2–15.5 |
| Female | 67 | 86–98 | 28–39 | 6–9 | 12–17 | 46–53 | 6.6–11.5 |
| Measurements are in millimeters (except weight in grams) and in the form "minimum–maximum". | |||||||
Triaenops menamena is a medium-sized species with variable fur coloration, ranging from reddish brown to gray. It is larger and darker thanParatriaenops auritus andP. furcula.[14] Among livingTriaenops species, it is smaller thanT. persicus andT. afer, but somewhat larger thanT. parvus.[15] The extinctTriaenops goodmani, which is known only from threemandibles (lower jaws), is also larger.[10] In the complexly shapednoseleaf (a group of fleshy structures around the nose and mouth),[16]T. menamena has the trident structure characteristic ofTriaenops andParatriaenops: three adjacent lancets (projecting structures) on the posterior leaf. InT. menamena, the two outer lancets are shorter than the middle one and curved, whereas the three lancets are more equal inParatriaenops.[17] The anterior leaf contains a broad, flat, horizontalprocess and the intermediate leaf contains a pointed process.[18] The ears are small and broad[16] and contain notches on the inner side.[14] The fur is silky and the hairs on the body are about 5 to 6 mm long. The wing membrane is dark and translucent and the end of the tail usually projects from theuropatagium (tail membrane).[18] Males average slightly larger than females.[13] Wingspan is 270 to 305 mm (10.6 to 12.0 in).[19]
The skull is similar to that of MadagascanParatriaenops, but thepremaxilla is longer. The rostrum (front part of the skull) is well-developed and contains a pronounced nasal swelling, which is less pronounced than inParatriaenops; the depression behind the swelling is relatively shallow.[20] Compared to other species ofTriaenops, the rostrum is relatively narrow and short, similar toT. parvus;T. afer andT. persicus have a broader rostrum.[15] The front margin of the rostrum is cast back between the left and right corners. A transverse line passes over the roof of the rostrum.[20] Theinfraorbital foramen, an opening in the skull, is oblong in shape. Thezygomatic arches (cheekbones) are not broadened towards the sides, are connected to themaxillaries by broad bones, and contain clear crests on their upper sides. InT. menamena, these crests are rectangular in form and larger than inParatriaenops.[21] Thebraincase is lower than in other species ofTriaenops.[22] Thesagittal crest, which is on the roof of the braincase, is poorly developed.[21] In the mandible, thecoronoid process is blunt and rounded, but theangular process (bothprocesses at the back of the bone) is small.[23]
The upperincisors have two cusps and the uppercanine has three—a large central one, a small but well-developed one at the back, and a small cuspule at the front.[23] The front upperpremolar is projected outside the toothrow, so that the canine before it and back premolar behind it touch.[14] The first lower incisor has two cusps and the second has three.[23] On the second lower molar, theprotoconid cusp is notably taller than thehypoconid; these cusps are about as high inT. goodmani.[10]
The species can easily be identified from recordings of itsecholocation call.[24] The call consists of a component with constant frequency followed by a short one with changing frequency. The call takes 6.5 to 13.5 ms, averaging 10.1 ms, and the period between two calls is 22.7 to 86.3 ms, averaging 42.7 ms. The maximum frequency averages 94.2 kHz, the minimum frequency averages 82.0 kHz, and the call emits the most energy at a frequency of 93.2 kHz.[25]
Triaenops menamena mainly occurs in the dry regions of western Madagascar, but has also been recorded in humid areas in the far southeast and northeast,[8] and is found up to 1300 m (4300 ft) above sea level.[1] It mainly occurs in forests,[26] but has also been recorded outside forest and is not dependent on it.[1] An obligate cave dweller,[27] it is known to roost in large colonies, with one cave colony estimated to contain over 40,000 bats; this cave also contained an estimated 10,000Paratriaenops furcula.[28] Theeffective population size of the species is estimated to be about 121,000.[29]Lepidoptera (butterflies and moths) form the main component of its diet, but it also eatsColeoptera (beetles) andHemiptera (bugs) and fewer members of some other insect orders.[30] It is unclear how theecological niches ofTriaenops and the less frequently capturedParatriaenops furcula are separated, as both eat lepidopterans and occur in the same regions.[31]
UnderTriaenops rufus, theIUCN Red List lists this species as being of "Least Concern", citing its common occurrence over a wide distribution and tolerance of human modifications of its habitat, even though its forest habitat is being destroyed in places. It has been recorded in numerousprotected areas.[1] Bats, mainly the largeHipposideros commersoni, are sometimes hunted for food in southwestern Madagascar, andT. menamena is also taken incidentally.[32]
