Kerivoula pellucida Waterhouse 1854

Sedlock, Jodi L., Heaney, Lawrence R., Balete, Danilo S. & Ruedi, Manuel, 2020, Philippine bats of the genus Kerivoula (Chiroptera: Vespertilionidae): Overview and assessment of variation in K. pellucida and K. whiteheadi, Zootaxa 4755 (3), pp. 454-490 : 467-469

Kerivoula pellucida Waterhouse 1854

Type locality: Philippines.

Specimens examined. Given in Appendix A .

Distribution. Borneo, Java, the Malay Peninsula, the Philippines (Cebu, Jolo, Mindanao, Mindoro, and Palawan), and Siberut ( Fig. 2 ; see also Corbet & Hill 1992: 154).

Description. Total length 83–97 mm, tail 43–50 mm, ear 16–18.5 mm, forearm 31.1–35.2 mm, tibia 16.6–19.4, mass 4.0– 5.7 mm ( Table 4 ). Dorsal pelage is long and soft with a slightly woolly appearance, and pale reddish-

brown buff; hairs slightly paler at base than at tips, lacking distinct color bands; ventral pelage paler ( Fig. 5D, E ). The ears are pale brown, and unusually large ( Fig. 5A, B ). A thin scattering of inconspicuous hairs is present over the dorsal surface of the interfemoral membrane, some of which project over its posterior edge ( Fig. 5A ). The wing and tail membranes are very pale brown, nearly translucent ( Fig. 5A, C ). Tragus long and slender ( Fig. 5B ). Skin is nearly transparent giving the face, wing- and leg bones a reddish-pink hue in live animals. The wing membrane inserts onto the side of the outer toe well above the base, not at its base ( Fig. 5C ). There do not appear to be striking regional differences within the Philippines in appearance; however, specimens from Bohol are slightly darker brown than those from Mindanao and Cebu; those from Palawan are palest. Palawan specimens have more reddish-brown tips on the dorsum than those from Bohol and Cebu.

Skull as shown in Figure 6 . GTL14.06–15.03, CCL 12.75–13.44 mm, GBB 7.04–7.55 mm, BH 5.69–6.33 mm, PC 2.98–3.15, C–M 3 5.63–6.05 mm, M 2 –M 2ext 4.88–5.16 mm, C 1 –C 1 1.62–1.86 mm, C–M 3 6.05–6.50 mm, MDL 10.19–11.16 mm ( Table 1 ). The skull is narrow with a highly inflated braincase that forms a steep forehead. The post-palatal region extends far posterior to the molar tooth row, and the bullar cochleae are moderately large. The upper tooth rows are slightly convergent anteriorly. Infraorbital canal is short, above P 3 to middle of M 1. The upper incisors are conical; the first upper incisor is more than twice the height of the second upper incisor, which is often separated from the canine by a narrow space. The first lower incisor ( Fig. 7B ) usually has four cusps (occasionally three), the second has three cusps, and the third has two prominent cusps and usually a third (at the posterior edge). The upper and lower canines are high and conical with a cingulum that extends from the anterior edge lingually to the posterior margin, about twice the height of the first premolars. The first upper premolar is nearly circular in outline, and the second is slightly compressed laterally ( Fig. 7A ). The third upper premolar is partially molariform, with a broad lingual shelf. The first lower premolar is roughly circular in outline only slightly compressed laterally; the second and third are more compressed laterally, but not strongly so. The upper and lower molars are typical for the genus ( Hill 1965). Philippine specimens are slightly larger than a small series from Malaysia ( Fig. 3 ; Tables 1 , 4 ).

Comparisons. Kerivoula pellucida differs from K. whiteheadi in having dorsal and ventral pelage that is paler at the base than at the tips ( Fig. 5D, E ) (rather than dark at the base), reddish-brown at the tips, and slightly paler at mid-shaft, giving a tri-banded appearance. The wing and interfemoral membranes of K. pellucida are pale and nearly transparent, rather than moderately dark brown as those of K. whiteheadi . The tail membrane of K. pellucida has shorter, less conspicuous hairs (though still few and scattered) than that of K. whiteheadi . The wing membrane inserts up onto the side of the toe ( Fig. 5C ), rather than at the base of the outer toe. Most individuals of K. pellucida have greater total length than in K. whiteheadi , but much of this is due to having a longer tail (at least 43 mm, rather than 41 mm or less). The forearm is typically longer (usually 32 or more, rather than 31 mm or less), and the ear averages longer, though there is overlap ( Table 4 ). The rostrum, palate, and braincase of K. pellucida are proportionately broader than those of K. whiteheadi ( Fig. 6 ), the upper and lower premolars are less laterally compressed, there is more space between the molars lingually in K. pellucida , and the toothrows are typically longer ( Fig. 7 ). The posterior palatal extension in K. pellucida is longer and narrower.

Kerivoula pellucida differs from the Philippine K. hardwickii (i.e., K. “ hardwickii A” and K. “ hardwickii B”) in having larger and more pointed ears (rather than smaller and rounded; Heaney et al. 2010, 2016). The pelage of K. pellucida is paler at the base of each hair ( Fig. 5D, E ), rather than much darker at the base. Wing membranes of K. pellucida are pale and nearly transparent ( Fig. 5A ), rather than moderately dark brown and not transparent. Skin over the wing bones on individuals in the K. hardwickii group are darkly pigmented, not nearly transparent giving the bones the appearance of white stripes in preserved specimens and a pinkish hue in live animals, as in K. pellucida . Hairs on the tail membrane of Philippine K. hardwickii are very sparse and short, but a fringe of short hairs is often visible along the posterior edge. The wing membranes attach at the base of the outer toe, not part way up as in K. pellucida ( Fig. 5C ). The average total length of K. pellucida (91.4 mm) is longer than K. “ hardwickii A” (82.8 mm) and K. “ hardwickii B” (85.0 mm); but the average forearm length of K. pellucida (32.9 mm) is similar to K. “ hardwickii A” (33.0 mm) and smaller than K. “ hardwickii B” (35.0 mm) ( Table 4 ; Heaney et al. 2010; unpublished data). The skull in K. pellucida is generally proportionately longer and narrower than Philippine K. hardwickii ( Fig. 8 ). The post-palatal extension of Philippine K. hardwickii is broader and shorter than that of K. pellucida . Finally, the palate is proportionately narrower in K. pellucida than in Philippine K. hardwickii .

Kerivoula pellucida differs from Philippine K. papillosa in being much smaller in all respects ( Fig. 3 ; Heaney et al. 2010, 2016); the average forearm length of K. pellucida is 32.9 mm compared to 42.6 mm in K. papillosa ( Heaney et al. 2010; unpublished data). The pelage of K. pellucida is much paler overall than K. papillosa , which is a dark brown. The skull is smaller and more delicate, with conspicuously narrower rostrum, palate, and braincase ( Figs. 6 , 9 ). The second upper incisor reaches only one-third toward the tip of the first incisor, rather than more than halfway ( Figs. 7A, B , 10A, B ). All of the premolars and molars are proportionately more massive.

Echolocation. Philippine K. pellucida (4 individuals from Bohol, 1 from Cebu) have extremely broadband (132 kHz), short duration (2 ms), high frequency (peak = 138 kHz) calls similar to those recorded in Peninsular Malaysia ( Fig. 11 ; Table 5 ; Kingston et al. 1999, Schmieder et al. 2010). They are also similar to those of Philippine K. whiteheadi with respect to peak frequency, although K. pellucida calls had a broader bandwidth ( Table 5 ). Both species’ calls start at a similarly high frequency (194 kHz), but K. pellucida calls terminate at a lower frequency.

Ecology. In the Philippines, K. pellucida occupies a broad range of elevations (sea level to about 1200 m), though most records are from below 700 m. They also occupy a wide range of habitats; examples include an isolated patch of second growth forest surrounded by vegetable farms on Cebu Island, disturbed second growth forest on limestone on Bohol Island, and pristine montane forest on Mindanao Island. Its roosting habits are poorly known in the Philippines, but one adult female with a suckling young was captured by hand from dried banana leaves on Palawan Island (J. Esselstyn, pers. com.). Payne et al. (1985) also reported it roosting in dried banana leaves, and Kingston (2006) reported a group roosting in a clutter of dead understory leaves. In Peninsular Malaysia, they roost in small groups of up to 15 individuals and appear to have small home ranges, evidenced by short recapture distances (<100 m) and distinct “hot spots” of high genetic autocorrelation among individuals ( Rossiter et al. 2012). On Bohol Island, on three occasions, multiple individuals were captured either in the same or adjacent harp traps simultaneously, usually a male and a female (Sedlock et al. 2014). In Peninsular Malaysia, K. pellucida exhibits asynchronous reproduction giving birth throughout the year, although the highest proportion of pregnant individuals was captured during the rainy season when insect abundance was highest ( Nurul-Ain et al. 2017). In the Philippines, five lactating females were captured in July, during the rainy season (Sedlock et al. 2014), and one female was captured with a suckling young in late March (J. Esselstyn, pers. com.). Its echolocation behavior is highly adapted for distinguishing prey from background clutter at close range allowing it to forage within the forest understory ( Schmieder et al. 2012).

Figures

FIGURE 2. Map of the Philippines indicating the collecting localities of Kerivoula pellucida and K. whiteheadi. The land exposed during the Pleistocene Last Glacial Maximum is shown in light green.

FIGURE 3. Bivariate plot of condylo-canine length vs. height of braincase for specimens of Kerivoula summarized in Tables 1 and 3. Color indicates geographic region and symbol indicates taxon. Philippine specimens of each taxon are enclosed within polygons.

FIGURE 5. Photograph composite of K. pellucida showing the nearly translucent wing membranes (A), pelage color, and ears with tapered tragus (B), membrane attachment on foot and membrane with male gland (C), dorsal (D) and ventral (E) pelage lacking distinct color bands. A: Bohol I. (no voucher); B–C: FMNH 205817, Cebu I.; D–E: FMNH 202785, Bohol I.

FIGURE 6. Scanning electron microscope images of K. pellucida cranium and mandible, FMNH 202782 from Bohol Island, Philippines.

FIGURE 7. Scanning electron microscope images of upper toothrow and lower incisors of K. pellucida (FMNH 202782, A and B) and K. whiteheadi (FMNH 214092, C and D).

FIGURE 8. Photographs of K. hardwickii cranium and mandible, FMNH 202779 from Bohol Island, Philippines.

FIGURE 9. Photographs of K. papillosa cranium and mandible, FMNH 205342 from Luzon Island, Philippines.

FIGURE 10. Photographs of upper toothrow and lower incisors of K. hardwickii (FMNH 202779, A and B) and K. papillosa (FMNH 205342, C and D).

FIGURE 11. Power spectra, waveform and spectrograms of representative K. pellucida and K. whiteheadi calls (frequency in kilohertz on y-axis, time in milliseconds on x-axis; FFT 512).

APPENDIX A. List of all Kerivoula specimens examined. Specimens included in morphological analysis and comparisons are in bold. § Holotypes * Paratype.