Four species of Hipposideridae were recorded (H. armiger, H. griffini, H. poutensis, A. stoliczkanus). H. griffini is the first record from Xuan Nha NR. H. larvatus in the previous report from this area (Nguyen et al. 2012) have since been reclassified as H. poutensis following Yuzefovich et al. (2022). H. pomona, previously reported in the region, are reclassified as H. gentillis (Srinivasulu and Srinivasulu 2018), but was not confirmed in this study.

Hipposideros armiger (Hodgson, 1835)

H. armiger is amongst the largest members of Hipposideridae and widely distributed across Southeast Asia (Kruskop 2013). Three individuals were collected, none of the specimens showing signs of reproductive activity. External measurements included HB 87.7–95.7 mm, FA 92.6–98.9 mm and Wt 47–66 g. Dorsal pelage ranged from dark grey-brown (in one female individual) to black fur (two males), with grey ventral fur. A pair of swollen structures was observed above each eye, posterior to the nose-leaf, but these were less developed than in H. griffini individuals. Cranially (Fig. 5), H. armiger shows a large, robust skull, with GTL averaging 32.1 mm and CCL 30.7 mm. The sagittal crest is prominent. The rostrum and supraorbital regions are inflated, giving a distinct cranial profile compared to H. griffini. Dentition is characterised by large upper canines (C¹) closely aligned with P⁴, a reduced and laterally displaced P² and shallow frontal depressions in lateral view.

The echolocation call of a male H. armiger was recorded at the capture site (mist net, 650 m a.s.l.). This individual emitted a narrowband CF-FM structure (Fig. 5, right). The CF component had a peak frequency of 63.6 ± 0.7 kHz (mean ± SD), with a maximum start frequency of 65.8 kHz and a minimum end frequency of 55.7 kHz. The mean call duration was 9.1 ± 0.3 ms, with the longest call lasting 10.2 ms.

Hipposideros griffini Vu, Puechmaille, Denzinger, Dietz, Csorba, Bates, Teeling & Schnitzler, 2012

H. griffini was first described from Cat Ba Island and subsequently recorded in Chu Mom Ray NP (Central Highlands) and Cat Tien NP (southern part of Vietnam) (Vu 2012, Vu et al. 2012, Vu 2015, Vu 2019). In this study, an adult male was captured at approx. 650 m a.s.l. in disturbed secondary forest, together with H. armiger. The external measurements of male were as follows: HB 88.8 mm, T 60.3 mm, HF 16.3 mm, E 28.3 mm, FA 87.6 mm and Wt 54 g (Table 2). This individual has dark grey-black dorsal fur, with paler plumage ventrally. The male also possesses well-developed fleshy outgrowths and prominent glandular sacs behind the posterior nose-leaf.

The skull is robust, with a smooth dorsal cranial profile. The braincase is flattened and less globular, with a short, flattened rostrum lacking the steep slope seen in H. armiger. The rostrum–frontal transition forms a gentle incline, the sagittal crest is well developed and the lambda point is prominent. Zygomatic arches are strong and evenly curved, without the inward bend typical of H. armiger (Fig. 5, left). The upper dentition is massive with molars bearing distinct cusps. The mandible is significantly smaller than in H. armiger. The coronoid process is straight and triangular rather than posteriorly curved. Lower teeth are massive and closely set, but smaller than in H. armiger (Table 3). The specimen clustered with previously published sequences of H. griffini (JN247040–JN247042), forming a well-supported monophyletic group (Fig. 6, right), with pairwise genetic divergence of approximately 0.9% from other H. griffini populations.

The echolocation call of an adult male consisted of narrowband CF-FM signals (Fig. 5, right). The CF had a peak frequency of 74.7 ± 0.5 kHz, with start and end frequencies of 73.8 kHz and 63.4 kHz, respectively. The mean call duration was 7.2 ± 0.3 ms, with the longest call lasting 7.3 ms.

Hipposideros poutensis Allen, 1906

In the study, 39 individuals of H. poutensis (21♂, 18♀) were recorded (Table 1, Suppl. material 1). Amongst females, only three showed active reproductive status as lactating, while the remaining 15 were non-reproductive. H. poutensis is a medium-sized leaf-nosed bat (Fig. 7a), characterised by a slender skull compared to H. armiger or H. griffini, with a developed sagittal crest, a narrow braincase and a slightly swollen rostrum.

The specimen clustered within the H. poutensis lineage on the phylogenetic tree, with strong support and showed the closest genetic relationship with specimens collected from Bai Tu Long Island (OP142137), followed by population from Cat Ba Island (OP142143–OP142145) (Fig. 6, right). Pairwise genetic divergence ranged between 2% and 3.6%. These findings support the recent taxonomic distinction of H. poutensis from H. larvatus as reported by Yuzefovich et al. (2022), with both morphological and molecular analyses confirming its status as the distinct species. Based on recordings of a single male individual, this species emitted narrowband CF-FM calls (Fig. 5, right) with a peak frequency of 85.6 ± 0.7 kHz, starting at 88.7 kHz and ending at 70.7 kHz. Mean call duration was 6.2 ± 0.2 ms, with the longest call lasting 6.5 ms.

Aselliscus stoliczkanus (Dobson, 1871)

A. stoliczkanus is widely distributed across north-western and central Vietnam (Vuong et al. 2015). In this study, three specimens were identified as A. stoliczkanus, based on diagnostic external and cranial traits. These bats are small-sized, with a tricuspid posterior nose-leaf, short bodies and bicoloured dorsal fur (white bases and brown tips), while the ventral fur is paler (Fig. 7b). Cranial features include a slightly swollen rostrum and a relatively elongated snout compared to members of Hipposideridae (Fig. 6, left). The newly-obtained specimens clustered with reference A. stolickzanus sequences (BS = 89–98%) (Fig. 6, right). Genetic divergence between the study specimens and known references ranged from 0.5% to 1.5%.

Two species of fruit bats were recorded during this survey (Table 1). C. sphinx, previously reported from the Reserve, was re-confirmed, while M. niphanae represents a new record for this locality. Both species exhibited signs of reproductive activity during August.

Cynopterus sphinx (Vahl, 1797)

C. sphinx is common, occurring across lowland and edge habitats. Adults show short orange-brown dorsal pelage, a greyish ventral side and a darker mantle region, more pronounced in males. Juveniles are paler with an overall greyish tone. The ears are brown with a distinctive whitish margin and the interfemoral membrane is narrow, but evident, with a short tail extending slightly beyond it. Compared with Megaerops, C. sphinx is larger-bodied, more robust, with a more developed interfemoral membrane and a diagnostic white ear margin (absent in Megaerops). Cranially, the skull is elongate, narrowing anteriorly (Fig. 8), with expanded zygomatic arches and a broad, elongated palate. The dentition consists of robust molars with slightly rounded cusps and elongated upper canines.

Megaerops niphanae Yenbutra & Felten, 1983

This is a small pteropodid bat. The species is easily recognised by its soft, light brownish-grey pelage and absence of a tail. The flight membranes are pale grey with weak pigmentation, while the ears, muzzle and limbs are pale brownish, giving a subtly translucent appearance. Cranially, the skull is short (Fig. 8), with narrow zygomatic arches and a constricted postorbital region. The palate is smooth and lacks strong ridging and the molars are less robust than those of C. sphinx. Of four adult females captured in mid-elevation forests, two were lactating.

Eight species of Rhinolophidae were documented. Four species (R. episcopus, R. siamensis, R. cf. episcopus and R. perniger) are newly recorded, while R. affinis, R. thomasi, R. pearsonii and R. pusillus had previously been reported by Nguyen et al. (2012). R. rouxii, listed in earlier surveys, was not detected. This species is now considered restricted to eastern Asia; therefore, its previous record from Xuan Nha NR is likely a misidentification. Reproductive evidence was observed in R. thomasi and R. pearsonii.

Rhinolophus affinis Horsfield, 1823

Only a female R. affinis was recorded showing no signs of reproductive activity. This species is a medium-sized horseshoe bat. Externally, it has a broad horseshoe with a deep median emargination, rounded connecting process and a moderately convex sella lacking basal lappets; the lancet is subtriangular with an unreduced tip. The pelage is soft, dark greyish-brown. The skull is small, with well-developed lateral nasal compartments and narrow interorbital constriction. The dentition shows a slightly reduced P² within the tooth row. In comparison with R. thomasi (Fig. 9, left), although both species share skull shape typical of the “R. megaphyllus” group (Ith et al. 2015), R. affinis has a slightly larger cranium, a proportionally longer mandible, broader rostrum and more laterally expanded arches. Their dental dimensions (C¹C¹W, M³M³W) are otherwise similar. Molecular data place the specimen within the R. affinis clade, with pairwise genetic distances of 2.5–2.75% (Fig. 9, right).

Rhinolophus thomasi K. Andersen, 1905

One lactating female of R. thomasi was observed. Compared to R. affinis, R. thomasi has slightly smaller zygomatic, braincase breadths and its mandible is thinner and shorter. Externally, it shows a narrow, rectangular horseshoe and a broad, bluntly pointed lancet. The pelage is uniformly light grey with a metallic sheen, dense and velvety, with pale bases and darker tips (Fig. 10a). Echolocation calls of a female exhibited broadband FM–CF–FM structure dominated by CF components, with a peak frequency of 77.4 ± 0.2 kHz, starting at 78.6 kHz and ending at 66.7 kHz. Calls averaged 19.6 ± 0.3 ms in duration, with the longest call lasting 20.3 ms (Fig. 10d).

Rhinolophus pearsonii Horsfield, 1851

A total of 32 individuals of R. pearsonii were captured and were the most common species of Rhinolophus in the survey. Six females were reproductively active (five lactating, one pregnant). This species has a broad rostrum and a well-developed braincase. Cranial dimensions include GTL 22.78–23.85 mm, CM³L 8.97–9.78 mm and ML 16.27 ± 0.28 mm. The molars are marked by high, sharp cusps (Fig. 10c’). Echolocation calls of a male recorded in a tent exhibited broadband FM-CF-FM structure (Fig. 10d), with peak frequency 56.9 ± 0.7 kHz, ranging from 39.6 to 58.9 kHz. Calls averaged 21.6 ± 0.3 ms in duration, with the longest call lasting 22.3 ms.

Rhinolophus perniger Hodgson, 1843

Previously, R. perniger was considered a subspecies within the R. luctus complex; however, studies of Volleth et al. (2017) demonstrated differences between R. perniger and R. luctus sensu stricto. In this study, a single female was captured and clustered with reference R. perniger sequences, showing 1.2% genetic divergence (Fig. 9, right). The individual was non-reproductive. R. perniger is a large horseshoe bat (FA 73.4 mm, Wt 48 g) with a massive skull (GTL 33.54 mm). The horseshoe-shaped nose-leaf is broad, covering the upper lip with a deep median notch. The fur is thick, dark grey dorsally and ventrally. Dentition is robust, with well-developed toothrows. Echolocation calls recorded from the captured female were broadband FM–CF–FM (Fig. 10d), with peak frequency 31.9 ± 0.7 kHz, starting at 32.4 kHz and ending at 22.7 kHz. Calls averaged 33.4 ± 0.7 ms in duration, with the longest call lasting 35.3 ms.

Rhinolophus pusillus Temminck, 1834

This species is amongst the smallest horseshoe bats (Wt 4.2 g, FA 35.4 mm, CCL 11.54 mm), with proportionally small ears and nose-leaf and weakly developed supplementary leaflets (Fig. 10b). The lancet is elongated with a slight forward bend at the tip. The pelage is fine and silky, ranging from light brown to greyish-brown dorsally with a paler underside. The skull is small and delicate (Fig. 9, left), with a short, narrow rostrum, inflated braincase and slender zygomatic arches. The dentition is compact, with small, closely-spaced canines and premolars; the mandible is gently curved with diminutive lower teeth. In the phylogenetic analysis (Fig. 9, right), the specimen grouped within the R. pusillus clade; however, pairwise divergence from Vietnamese R. pusillus populations is high, ranging from 2.0% to 2.5%. This divergence shows a certain genetic differentiation of the studied individual relative to Vietnamese R. pusillus’s populations.

Rhinolophus episcopus Allen, 1923

The male R. episcopus has morphometric measurements: HB 41.8 mm, TL 21.9 mm, HF 8.5 mm, EL 23.4 mm, FA 42.1 mm and Wt 6 g. The bat has light brown pelage, large ears and a well-developed nose-leaf. The horseshoe is broad, covering the muzzle, with small lateral leaflets and a visible median notch. The lancet is elongated with convex margins and a rounded tip (Fig. 11). The anterior median swellings are prominent and elongated, while the posterior swellings are short. The sagittal crest is weakly developed and the frontal depression is shallow. Supraorbital crests are well-defined with sharp ridges.

In the R. macrotis complex, craniodental differences can be detected even amongst sympatric taxa. Comparative measurements between R. episcopus and R. cf. episcopus specimens collected from the same locality revealed that R. episcopus exhibits smaller CCL (13.79 mm vs. 14.16 mm) and BCH (6.73 mm vs. 6.95 mm) relative to R. cf. episcopus. Dental measurements such as CM³L (6.38 mm vs. 6.71 mm) and CP⁴L (2.85 mm vs. 3.05 mm) are smaller in R. episcopus. Conversely, R. episcopus displays a broader interorbital width (IOW). In this study, Cyt b sequencing was attempted for the specimen, but the obtained fragment (~ 500 bp) was insufficient in length and quality to be included in phylogenetic analyses. However, based on external morphology and craniodental traits, the identification of the specimen as R. episcopus is considered reliable. The echolocation call of this male was a broadband FM-CF-FM structure (Fig. 10d). The maximum start frequency was 65.6 kHz and the minimum value was 58.2 kHz, with peak energy at 63.4 ± 0.5 kHz. The mean call duration was 25.2 ± 0.6 ms, with the longest call lasting 26.8 ms.

Rhinolophus siamensis Gyldenstolpe, 1917

R. siamensis initially described as a subspecies of R. macrotis, has since been elevated to species level, with a wide distribution in Southeast Asia (Vuong et al. 2017b, Hutson et al. 2019). This individual represents a small-sized member of the macrotis complex. The FA is 37.3 mm, HB is 40.7 mm and the Wt is only 3.07 g, all lower than corresponding values for R. cf. episcopus. The skull of R. siamensis is not only shorter, but also more gracile, shows a narrower braincase, reduced rostrum width and a shorter mandible (Table 3). Morphologically, R. siamensis has relatively large ears, about half the forearm length and a broad horseshoe covering the muzzle with a distinct median notch. The sella projects forwards and the connecting process is broad and rounded, giving the nose-leaf a structure distinct from other small horseshoe bats. Its pelage is soft and woolly, brown dorsally and paler ventrally.

Rhinolophus cf. episcopus Allen, 1923

In this study, R. cf. episcopus was represented by a single adult male. External measurements included FA of 43.2 mm, E of 23.1 mm and Wt of 4.51 g. The ears were large, approximately half the length of the forearm and the pelage was soft, woolly and brown dorsally with a slightly paler ventral surface. The cranial profile is broad, with MAW of 8.91 mm and ZYW of 8.17 mm. The mandible is well-developed, with a ML of 10.12 mm. The skull morphology shows a more heavily built cranial structure compared to other members of the macrotis group (Fig. 11). Molecular analysis placed the specimen within the R. macrotis complex clade. It clustered most closely with individuals provisionally identified as R. cf. episcopus from Vietnam in the study of Vuong et al. 2017b, with a genetic divergence of approximately 2.5–3%. This level of divergence offers a close relationship, while also showing the possibility of regional differentiation within R. cf. episcopus (Liu et al. 2019).

Several species reported by Nguyen et al. (2012), including P. abramus, P. coromandra, P. javanicus, Ia io, T. fulvida (referred to as T. pachypus) and Murina cyclotis, were not detected in the present survey. Nevertheless, our study expands the species inventory of Xuan Nha NR by providing new records for T. tonkinensis and M. muricola.

Kerivoula cf. dongduongana Vuong, Hassanin, Furey, Nguyen & Csorba, 2018

According to Vuong et al. (2018) and other studies, K. hardwickii sensu lato in Vietnam has been divided into four smaller, closely-related species that are morphologically difficult to distinguish. Based on external and craniodental measurements, our specimen is tentatively assigned to K. dongduongana; however, molecular analysis is necessary to confirm its precise species identity. Morphologically, it shows soft, long fur, with smoky-brown dorsally and lighter greyish-brown ventrally. HB ranges 34.3–40.4 mm, FA 33.5–35.4 mm, with brownish-black translucent wing membranes. K. cf. dongduongana presents a domed braincase with a concave frontal profile. Cranial measurements (GTL 14.03–14.14 mm, ML 6.65–6.75 mm) point out a small and compact cranial structure compared to larger Kerivoula species (Vuong et al. 2018, Liang et al. 2023).

Myotis alticraniatus Osgood, 1932

M. alticraniatus was once considered a subspecies of M. siligorensis in Vietnam, but more recent taxonomic studies by Ruedi et al. (2021) have clarified its status as a distinct species. According to these studies, M. siligorensis is restricted to the Central and Eastern Himalayas, whereas bats occurring further east, including populations in China and Indochina, are now assigned to M. alticraniatus. A female specimen represents a well-preserved example of this small vespertilionid. It has a delicate skull with a low rostrum, domed braincase, steep frontal profile and slightly swollen occipital region. The zygomatic arches are thin and inwardly concave. Dorsal fur is buff to dark brown, with lighter greyish-brown ventrally. Ears are long and narrow, reaching or surpassing the muzzle tip. The upper premolars have a prominent size difference, particularly between P² and P⁴ (Fig. 12). The bat has a delicate mandible with small lower premolars (p₄) and its lower molars are semi-nyctalodont types.

Myotis muricola (Gray, 1864)

A female was collected at 950 m a.s.l. The pelage is soft and dense, pale brownish-grey dorsally and dirty white ventrally with dark hair roots (Fig. 13, left). Ears are long and narrow, the tragus slender and forward-bent and the feet small with short claws. The skull is small with an elongated rostrum, flattened braincase and developed sagittal crest (Fig. 13, right). The zygomatic arch is evenly curved and massive. C¹ are wide and robust, exceeding the height of P⁴. P² are well-developed and aligned in the tooth row. P³ are small, displaced lingually and stand inwards on the inside of the upper tooth row. c₁ are large, pointed and slightly higher than p₄. Lower molars are of the myotodont type. Genetic analysis of Cyt b confirmed the specimen within the M. muricola clade, with 1–1.5% divergence from other conspecific sequences (Fig. 14, left).

Pipistrellus tenuis (Temminck, 1840)

Externally, P. tenuis has dark brown dorsal pelage with a slightly paler ventral side and a short broad tragus (Fig. 15a). The skull is small and delicate, with a narrow rostrum, inflated braincase, weak crests and simple bicuspid upper canines (Fig. 15b). Sequencing of the Cyt b gene positioned the specimen firmly within the tenuis clade. Pairwise genetic distances ranged from 1.0% to 1.7% compared to P. tenuis individuals previously collected from the Tay Con Linh Mountain by Kruskop et al. (2024) (Fig. 14, left).

Tylonycteris tonkinensis Tu, Csorba, Ruedi & Hassanin, 2017

Previously, Vietnamese populations were identified as T. robustula. However, integrative analyses combining genetic and morphological data by Vuong et al. (2017a) confirmed that these bats represent a distinct species, separated from the robustula lineage. Consequently, the taxon was formally described as T. tonkinensis. This very small bat (HB 45.2 mm, Wt 5.1 g) is distinguished by fleshy adhesive pads on the thumbs and soles, a short narrow tragus and uniform mid-brown pelage (Fig. 16a). The skull is flattened, with a depressed braincase and prominent supraorbital tubercles (Fig. 16b). The dentition displays distinctive features: I² are twice smaller in height and crown area than I¹, both bearing small supplementary cusps. The upper canine shows an additional cusp on its posterior blade. Lower molars have the talonid slightly exceeding the trigonid in M¹ and M².

Acoustic recordings revealed FM calls with peak energy at 58.2 ± 1.3 kHz, starting at 88.5 kHz and ending at 38.6 kHz (Fig. 14, right). The mean call duration was 2.1 ± 0.3 ms, with the longest call lasting 10.2 ms. Genetic analysis placed the specimen firmly within the T. tonkinensis clade, with only 0.35% divergence from published Vietnamese sequences (Fig. 14, left).