Trident leaf-nosed bat | Asellia tridens

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Tracks

Roosts are in caves, mines, rock cavities, underground irrigation channels (foggaras and qanats) and in buildings, cellars and tombs. Beneath roosting spots lie droppings with remains of beetles, moths, flies and grasshoppers. The bats hang freely from the ceiling. Colonies range from a few individuals to very large groups, up to 5,000 in Iranian caves; a roost usually holds only this species, sometimes together with the Egyptian fruit bat, Triaenops persicus or mouse-tailed bats. The bats emerge shortly after sunset. On a bat detector covering frequencies above 120 kHz the species is recognised by the high, constant tone; many simple detectors do not reach that high.

Identification

A medium-sized bat with a short muzzle and a large, complex noseleaf; the rear edge of the noseleaf bears three triangular projections. A sella with a lancet, as in horseshoe bats, is absent. The ears are large, broad and pointed and have no tragus. The fur is beige to pale brownish grey on the back and paler below. Head-body 41 to 60 mm, tail 16 to 29 mm, ear 14 to 22 mm, forearm 45 to 55 mm, weight 6 to 13 g. It is the largest species of the genus Asellia. Echolocation consists of calls with a constant frequency of 115 to 120 kHz followed by a short frequency-modulated sweep; the constant frequency varies between individuals and is lower in larger bats. In Tunisia the frequency of maximum energy averaged 118.9 kHz.

Similar species

In the desert regions of North Africa and the Middle East the horseshoe bats (Rhinolophus) are the only other bats with a large noseleaf. Their noseleaf has a horseshoe-shaped part, a sella and an erect, pointed lancet; in the trident leaf-nosed bat the sella and lancet are absent and the noseleaf ends at the back in three points. In the hand, leaf-nosed bats have two phalanges in each toe, horseshoe bats three in most toes. On a bat detector the constant frequency of the trident leaf-nosed bat lies above that of the horseshoe bats in the same regions, although the lesser horseshoe bat (Rhinolophus hipposideros) comes close in some areas. The mouse-tailed bats (Rhinopoma), which use the same roosts, have a small nose fold and a long, thin tail.

Habitat

Desert and semi-desert of various kinds, with a preference for oases and dry riverbeds (wadis). The species usually lives at low elevations but has been found up to 2000 m. Roosts are underground or in buildings; foraging areas lie 1.5 to 2 km from the roost, in palm gardens, near water and over vegetated wadis.

Distribution

The subspecies A. t. tridens lives in North Africa from Morocco, Mauritania and Senegal east through Egypt and Sudan to Eritrea, Ethiopia, Djibouti and Somalia; A. t. murrianus lives in the Middle East, from Syria, Iraq, Israel, the Palestinian territories and Jordan across the Arabian Peninsula to western Afghanistan and southern Pakistan. Up to four subspecies were formerly recognised; molecular work supports two. In the northern part of the range records come from Israel and the Palestinian territories, Egypt, Tunisia, Morocco, Algeria and, in small numbers, Syria and Jordan, in each case along the desert edge south of the Mediterranean zone. The species does not occur in Europe.

• Native
• dark = core range, pale = thinly spread

Way of life

Nocturnal. The bats emerge shortly after sunset; males have two activity peaks per night, females one, with the highest activity immediately after sunset. They hunt low over the ground for large insects: beetles, moths, flies and grasshoppers. Breeding is seasonal, with one young a year in summer. In Africa females are pregnant in April and May and dependent young are present in July; in the Middle East they are pregnant from April to June, the young are born in June and July and lactation lasts about 40 days. Pregnant females form separate maternity colonies, and numbers in a roost change with the season. Both sexes lay down fat in autumn. Across much of the Middle East the bats disappear from their roosts in winter and return in April or May; whether they migrate or enter winter torpor elsewhere has not been established.

Where and when to look

The species is best observed at emergence from a cave entrance, an old qanat or an abandoned building near an oasis, on a warm evening between April and October. Acoustic recording requires a detector that covers frequencies up to about 125 kHz; a recording with a constant tone around 118 kHz points to this species in the desert regions of North Africa and the Middle East. Maternity roosts are not entered from April to August.

Conservation status

Least Concern (LC, 2017), on the basis of its large range, much of which lies in remote, arid areas. In countries that are parties to the EUROBATS Agreement the species is covered by it. Because a large part of a local population can gather in a single roost, disturbance of a cave, mine or irrigation channel affects many bats at once.

Scientific name

Asellia tridens | (É. Geoffroy Saint-Hilaire, 1813)

É. Geoffroy Saint-Hilaire described the species in 1813 as Rhinolophus tridens; because it was later moved to another genus, the author and year stand in brackets. Asellia probably goes back to Latin asellus, 'little donkey', a diminutive of asinus, 'ass'; Gray nowhere explains the name. tridens is Latin for 'trident', from tres, 'three', and dens, 'tooth', after the nose-leaf that ends in three points. The specimen the first description was based on came from Egypt, Luxor.