Rhinopoma hardwickii, Gray, 1831

Don E. Wilson & Russell A. Mittermeier, 2019, Rhinopomatidae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 164-176 : 175-176

4.

Lesser Mouse-tailed Bat

Rhinopoma hardwickii

French: Rhinopome de Hardwicke / German: Kleine Mausschwanzfledermaus / Spanish: Rhinopoma pequeno

Other common names: Hardwicke's Lesser Mouse-tailed Bat, Lesser Rat-tailed Bat

Taxonomy. Rhinopoma hardwickii|. E. Gray, 1231 ,

“Bengal,” India.

The specific epithet was emended to hardwicker (because the collector was Major-General T, Hardwicke) and has been widely used, but from a nomenclatural standpoint, the original nameis valid and is retained. The name was long applied to denote all small-sized forms of Rhinopoma , with all later taxa considered its subspecies. After subsequent separation of R. muscatellum , R. macinnesi , and the African, Arabian, and Levant populations as R. ¢ystops, R. hardwickii is restricted to the form traditionally considered as the nominate subspecies, distributed from south-eastern Iraq to India. Molecular genetic data, on which the latter rearrangement was based, further revealed relatively deep divergence (4:6% in cytochrome-b) between the Iranian population and the Indian sample (a single individual from Rajasthan) that strongly indicated a separate subspecific status for the form from the western part of the distribution. A separate subspecific status also can be expected for populations from southern India because of the considerable distributional gap separating them from other Indian populations and remarkable differencesin life histories. Formerly reported occurrence in Bangladesh is now considered doubtful; no recent record is available. The same is true in Myanmar, suggested only by very old references without exact localities. A single historical record from Thailand was later referred to R. microphyllum . No recent record confirms occurrence in Sunda Archipelago indicated by historical museum specimens (i.e. form sondaicum). Western part of the distribution might have an unnamed subspecies. Subspecific taxonomy requires reassessment.

Distribution. Polycentric, W part of distribution restricted to narrow belt from SE Iraq to W margin of Strait of Hormuz in SW Iran, E part from E Afghanistan and N & E Pakistan to most of India. The E margin of distribution is not clear; extreme Indian record is from Calcutta, West Bengal, 88° E.

Descriptive notes. Head-body 53-65 mm, tail 54-78 mm, ear 16-20 mm, hindfoot 10-13-5 mm, forearm 46-65 mm; weight 6-5—-12 g. The Lesser Mouse-tailed Bat is distinctly smaller (greatest lengths of skull 15-18 mm) than the Greater Mouse-tailed Bat ( R. microphyllum ) and has a longertail, clearly longer than forearm. Pelage of the Lesser Mouse-tailed Bat is unicolored, light pale gray-brown to darker brown, somewhat lighter on chest and belly. Autumn deposition of white fat makes abdominal and uropatagial regions markedly light colored. Noseleaf is pointed, with distinct transverse dermal ridge. Skull is slender, nasal swelling is rounded, and dorsal surface of nasal swelling is flat without distinct lateral crests and central groove. Sagittal crestis relatively low, usually restricted to frontal region only. Palatal notch is rounded, extending to level of M* protocone. C' is elongated, with distinct distal cusp usually in contact with mesial cusp of P*. Talon of P* is broad, with high cingular wall terminating in distinct mesiopalatal cusp. Talons of M' and M? are quite robust, with uplifted palatal emargination extended distally up to mesial margins of neighboring tooth. M’ retains distinct metacrista mostly parallel to distal crown margin. Cingular shelf on mesiopalatal wall of C, is indistinct or absent, P, is distinctly smaller than P,, and its longitudinal axis stays in tooth row. Chromosomal complement has 2n = 36 and FN = 68 in India.

Habitat. Mostly dry semi-desert habitats, oases, and rocky wadi at elevations up to 1100 m in Pakistan. The Lesser Mouse-tailed Bat roosts in shallow caves, fissures in rocky niches, dry wells, underground irrigation tunnels, and rooms in abandoned human structures, often in mixed colonies with the Greater Mouse-tailed Bat. Colony of 76 Lesser Mouse-tailed Bats was found roosting in a tree cavity in subtropical evergreen forest in northern Pakistan —obviously exceptional.

Food and Feeding. The Lesser Mouse-tailed Bat forages for medium-sized insects in open spaces above vegetation at heights of ¢. 10 m. Data from Rajasthan suggest considerable seasonal variation in diets. In winter when most individuals are inactive, feeding is restricted to prey available at surroundings of the roost ( Gryllidae , Scarabaeidae, Dyctioptera , etc.). These items also occur in diets in dry summer (March—June) when percentage of Lepidoptera (mostly Noctuidae and Arctidae) increases (17% of diets) and winged termites begin to appear (10%); increased proportion of Dytiscidae (4%) suggests frequent foraging over water. A distinct dietary shift occurs in monsoon period (July-September) when insect abundance dramatically increases: winged soft-bodied termites become dominant prey (28%), Dictyoptera nearly disappears, and almost all other groups remain in diets but in smaller percentages. In post-monsoon period (October-November) when availability of winged termites decreases, they comprise only 7% of diets, and beetles (38%: Scarabaeidae , Curculionidae , and Carabidae ) and ants (7-5%) increase. In an October sample from Iran, beetles (50%: 40% Scarabaeidae and 10% Carabidae ), Auchenorhyncha (25%), nematoceran Diptera (20%), and spiders (5%) occurred in diets.

Breeding. Female Lesser Mouse-tailed Bats give birth to single young each year. In Uttar Pradesh, India, females were found inseminated from late February to mid-April, but ovulation was first recorded on 11 March. Progressively more females ovulated and conceived during subsequent weeks until the end of April. One ovum from either ovary was released with nearly equal frequency. A single conception was carried in the ipsilateral uterine horn during each cycle. Gestation lasted 95-100 days, and births occurred between the second week of June and end of July. Young were weaned at 5-6 weeks old. Females attained sexual maturity at ¢.9 months old, and males show completed spermatogenesis at 16-17 months old. Females were segregated during lactation; during the rest of the year, males and females lived together. Scarce data from Iran and Afghanistan suggest the same pattern, with samples from spring and autumn colonies containing males and females. In tropical conditions of southern India where seasonality is less distinct, births occur from May to late September and peak in May-July; weaning extends to November.

Activity patterns. Lesser Mouse-tailed Bats usually leave roosts 10-15 minutes after sunset, hunting in open spaces at heights of 10-15 m. They emerge from colony roosts in large groups. Prior to emergence, activity of colony increases with intensive audible vocalization and regrouping to spaces close to roost exit. Except for the southern Indian population, individuals are inactive in winter and often in large mixed colonies with the Greater Mouse-tailed Bat (up to 7000 individuals reported from Rajasthan). Multiharmonic QCF calls with maximum energies at second harmonic of 30-40 kHz. During search flight in open spaces, repetition rates are c.10 Hz, and durations are 20-40 millisecond. When landing, repetition rate increases up to 40 Hz, and calls change to short (3-5 milliseconds) frequency-modulated (FM) notes with 5-10 kHz sweeps of particular harmonics. Audiogram shows peak sensitivity at 35 kHz. J. Habersetzer in 1981, studying echolocation behavior of Lesser Mouse-tailed Bats under natural conditions in Madurai, southern India, found significant increase of between-individual differences in frequencies of CF-calls when they flew in a group (frequencies were in three different bands: 30 kHz, 32-5 kHz, and 35 kHz), compared to common mean frequency 32-5 kHz when they flew alone. He proposed frequencyshift as a behavioral mechanism ofjamming avoidance.

Movements, Home range and Social organization. Seasonal disappearance of Lesser Mouse-tailed Bats from summer roosts in winter indicating regular seasonal migrations are reported from Iran, Afghanistan, Pakistan, and northern regions of India. Homing experiments with 25 bats in Rajasthan showed that 50% returned from 12 km but only 13% from 20 km, indicating that homing capacity was weaker than for the Greater Mouse-tailed Bat. Scarce data indicate sexual segregation in summer throughout the distribution range, but it is probablyless strict than in the Greater Mouse-tailed Bat. Roost occupancy of Lesser Mouse-tailed Bats is characterized by a pronounced fission—fusion dynamics: in most instances, a colony is dispersed into a number (up to 80) of neighboring diurnal roosts, each occupied by few individuals or smaller groups of 10-40 individuals. Individuals generally roost away from each of other and do not form compact clusters. Total size of a colony varies from ten to 1000 individuals, with the vast majority of records reporting colonies of 20-100 individuals. There is wellpronounced philopatry in use of traditional colony roosts. In Rajasthan during the cold winter, the Lesser Mouse-tailed Bat aggregates in mass winter colonies up to 7500 individuals composed of compact clusters colonizing deep underground spaces. Size of summer colonies is usually 20-100 individuals, but large breeding colonies of 1000 individuals are reported from Rajasthan, and 50-500 individuals from Bihar. Lesser Mouse-tailed Bats are regularly admixed in large colonies of Greater Mouse-tailed Bats. The population of Lesser Mouse-tailed Bats in southern India (i.e. tropical zone with warm winter, 28°C) does not have to respond to seasonal effects experienced elsewhere: e.g. winter torpor, changes in roost occupancy and colony structure, migrations, and autumn accumulation of fat reserves. Annuallife cycle and life history patterns of the Lesser Mouse-tailed Bat in that region was studied in detail by K. Usman during three years of monitoring of a colony of 1500 individuals roosting in a cave in Madurai (3502 bats handled, 1000 banded, and 1299 recoveries). The cave was inhabited throughoutthe year, bats stay active throughout the year, and no migrations or seasonal changes in spatial organization of the colony were observed. Males and females were segregated in the roost even during non-breeding season. Males dominated in all samples; male:female sex ratios were 1:0-43-1:0-5. Synchronization of individual stages of reproduction was clearly less distinct than in the northern populations. Annual mortality rates established by marking-recapture data were 0-09-0-13, annual birth rates of the colony were 0-14-0-15, and probability of survival over the years of study was 0-8, with small differences between sexes.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Lesser Mouse-tailed Bat is widespread and common, with no major conservation threats.

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Figures

1. Greater Mouse-tailed Bat (Rhinopoma microphyllum), 2. Muscat Mouse-tailed Bat (Rhinopoma muscatellum), 3. Hadramaut Mouse-tailed Bat (Rhinopoma hadramauticum), 4. Lesser Mouse-tailed Bat (Rhinopoma hardwicku), 5. Arabian Mouse-tailed Bat (Rhinopoma cystops)

Distribution. Polycentric, W part of distribution restricted to narrow belt from SE Iraq to W margin of Strait of Hormuz in SW Iran , E part from E Afghanistan and N & E Pakistan to most of India . The E margin of distribution is not clear; extreme Indian record is from Calcutta, West Bengal, 88° E.