Philippine Journal of Science 150 (S1): 121-133, Special Issue on Biodiversity ISSN 0031 - 7683 Date Received: 24 Sep 2020

Mammals of Mt. Pinatubo, Island, : Extreme Resilience Following Catastrophic Disturbance

Eric A. Rickart1*, Lawrence R. Heaney2, and Danilo S. Balete2†

1Natural History Museum of Utah, 301 Wakara Way, Salt Lake City, UT 84108 USA 2Field Museum of Natural History, 1400 S Lake Shore Drive, Chicago, IL 60605 USA

The catastrophic eruption of Mt. Pinatubo in 1991 destroyed the forests that covered the peak and impacted the surrounding habitat over a broad area of . Information on the fauna of Mt. Pinatubo prior to the eruption is limited but documents a variety of native . In 2011 and 2012, we surveyed mammals at localities along an elevational gradient on the eastern slope of the mountain where vegetation had been devastated by pyroclastic flows and subsequent , and habitat reflected early stages of plant succession. We documented eight species of bats (five fruit bats and three insectivorous bats), seven species of small non- volant mammals (two non-native and five native ), and two native large mammals. Additional species of bats and non-volant mammals present in the vicinity of Mt. Pinatubo prior to the eruption or recently documented at other localities in the Mountains may be present in remnant forest habitat elsewhere on Pinatubo. Across five survey localities where habitat was in the early stages of regeneration, native species of small non-volant mammals were more widespread and much more abundant than were non-natives. The most abundant native species, Apomys sacobianus, may be endemic to Mt. Pinatubo. It is an extreme example of a “disturbance specialist” that thrives in a severely disturbed habitat. Results underscore the disturbance tolerance of many native small mammals of Luzon and reveal a resilience that is remarkable for a highly endemic insular fauna. Mt. Pinatubo presents opportunities for further studies on how natural disturbance has shaped the evolution of the Philippine biota and may influence its future conservation.

Keywords: bats, biogeography, disturbance tolerance, elevational gradients, endemism, faunal recovery, habitat recovery, rodents, volcanic eruption

INTRODUCTION large in its place, thereby reducing the height of the peak by 250 m. Subsequent heavy precipitation from Mt. Pinatubo, a volcanic peak in central Luzon Island, seasonal typhoons and monsoons created a caldera lake Philippines, was long considered dormant until it erupted and triggered destructive lahars that continued for many explosively on 15 Jun 1991 in the second most powerful years following the eruption (Newhall et al. 1996). terrestrial volcanic eruption of the 20th century. The eruption covered the upper slopes of the mountain with Dormant for about 500 years preceding the 1991 eruption, massive amounts of ejecta in the form of falling ash and Mt. Pinatubo and surrounding lowlands had supported pyroclastic flows, destroying the summit and creating a old-growth forest. Although the lowlands of central Luzon were largely deforested during the 20th century (Heaney *Corresponding Author: [email protected] et al. 2016b), remnant mature dipterocarp forest remained †Deceased 01 Jul 2017

121 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity in portions of , and the upper portions of 1956. As discussed below, the presence of a potentially Pinatubo were heavily forested prior to the 1991 eruption rare endemic species prior to the eruption raised the (Punongbayan et al. 1996). question of its possible extinction, given the frequent assumption that rare mammals on oceanic islands are In 2006, 15 years after the eruption, an assessment of intrinsically susceptible to extinction following significant plant succession on Mt. Pinatubo revealed a predominance ecological disturbance (Berglund et al. 2009; Walsh et of non-native plants and the influence of elevation on al. 2012). species richness, diversity, and plant cover (Marler and del Moral 2011). Although there were no comprehensive surveys of the mammals of Mt. Pinatubo prior to the eruption, there are specimens housed at the United States STUDY AREA AND METHODS National Museum of Natural History (USNM) from Clark Air Base and nearby localities at low elevations in and provinces. These include rodents reported Location and Geology from rice croplands (Barbehenn et al. 1973), and bats and Mt. Pinatubo (15.13°N, 120.35°E; current elevation 1,486 rodents obtained by D.H. Johnson and others (records m), is a dacitic-andesitic stratovolcano and caldera located summarized in Heaney et al. 2010). However, there is no in the Zambales Mountains of central Luzon on the tripoint direct information on the mammals that may have been boundary of Pampanga, Tarlac, and Zambales provinces present at higher elevations on Pinatubo prior to its eruption. (MGB 2010). It is one of several volcanoes along the Lineament formed by the eastward subduction Several previous studies have dealt with the disturbance of the Eurasian Plate beneath the Philippine Mobile ecology of the mammals of Luzon. These have utilized Belt along the Trench (Wolfe and Self 1983). field surveys of small mammals across gradients of The eruptive history of Pinatubo consists of two phases. habitat disturbance ranging from relatively pristine old- “Ancestral” Pinatubo was a massive stratovolcano that growth forests to heavily disturbed human-modified may have had an elevation approaching 2,300 m. It has landscapes. The principal results of these studies can be been dated at around 1.1 Ma and left no evidence that it summarized as follows: although some native species are erupted explosively. In contrast, “modern” Pinatubo had at highly tolerant of disturbance, in general, diversity and least six periods of explosive eruption, each separated by abundance of native species decline with increasing levels longer periods of inactivity. Its earliest eruption occurred of disturbance whereas the opposite is true for non-native more than 30,000 BP and the most recent (prior to 1991) species (Rickart et al. 2011, 2013; Heaney et al. 2016b; ca. 500 BP. The 1991 eruption was estimated to be one Reginaldo and Ong 2020). of the least powerful in the discernable geological record of Pinatubo (Newhall et al. 1996). Here, we present the results of a survey of the mammals of Mt. Pinatubo conducted in 2011 and 2012. This work was undertaken to determine the nature of the pioneering Survey Localities mammal community in early successional habitat two Our survey was conducted in 2011 and 2012 on the eastern decades after the 1991 eruption. Based on disturbance slope of Mt. Pinatubo in Pampanga Province, between gradient surveys elsewhere on Luzon (Rickart et al. 2011, 300 and 1,100 m elevation (Figure 1). Survey localities 2013) we developed the following hypotheses to inform and were selected in consultation with the indigenous Aeta direct the work on Mt. Pinatubo, which we test in this paper: who manage the area as their ancestral domain. In 2011, we surveyed three localities in portions of the rolling hills • Non-native small mammals are numerically (300–700 m) in , Pampanga Province near the dominant in the most severely disturbed habitat. boundary of , Tarlac Province, on the northeastern • A subset of native species that tolerate severe flank of Mt. Pinatubo north of the Sacobia (Figure habitat disturbance coexists with non-native 2A). In 2012, we surveyed the upper eastern slope of Mt. species. Pinatubo (680–1,100 m), near the northern tributaries of Pasig-Potrero River in the western-most portion of • Native small mammals are resilient, moving Mabalacat, Pampanga Province. Localities were in areas into areas of regenerating habitat and ultimately of early-stage plant succession with sparse tree cover, as displacing non-native species as native vegetation described below. Because of the steep slopes and loose matures. substrate, erosion was especially severe along riverbanks and gullies (Figure 2B). Of special interest to us was the status of Apomys sacobianus, a native mouse that was known only from the Locality 1: 8.4 km N, 12.3 km E Mt. Pinatubo peak, holotype captured on the lower slopes of Mt. Pinatubo in 365 m elev., 15.20556o N, 120.46278o E; 27 Feb–04

122 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity

Figure 1. Map of Mt. Pinatubo showing the location of numbered survey localities along the eastern slope of the mountain. Contour intervals 400 m. Inset map shows the location of Mt. Pinatubo on Luzon.

Figure 2. Habitat features in areas surveyed on Mt. Pinatubo in 2011 and 2012. A) View downslope from a point on the northeastern flank of Mt. Pinatubo north of the Sacobia River illustrating the general nature of the regenerating habitat surrounding localities 1–3 in March 2011. B) View upstream along an upper tributary of the Pasig-Potrero River showing the eroding lahar and nature of the surrounding regenerating vegetation in March 2012; the camp at locality 4 was in the left-center of the image (a small tarp is barely visible) and locality 5 was on the steep slope above and beyond the camp.

Mar 2011. This locality, selected as a base camp, was Climbing and erect bamboos (Dinochloa and Bambusa) a nursery established by the Aeta of Sitio Burog in an were common along the steep stream banks. A narrow attempt to reforest the surrounding area. Trees planted strip of riparian habitat along a stream included a variety here included Eucalyptus (ca. 12 m tall), Leucaena, of native palms (Areca, Arenga, Caryota, and Calamus) Swietenia, and particularly Gmelina, along with native and other scattered trees up to 20 m tall (Afzelia, Alstonia, Pterocarpus. Ground cover was dominated by the exotic Artocarpus, Ficus, Garcinia, Hibiscus, Parkia, Premna, shrub Lantana camara, grasses including cogon (Imperata Macaranga, Mangifera, Myristica, Pterocarpus, and cylindrica) and “talahib” (Saccharum spontaneum), Terminalia). Within the remnant riparian vegetation, and thick but isolated clumps of wild banana (Musa). velvet bean (Mucuna), jade vine (Strongylodon), and

123 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity chestnut vine (Tetrastigma) were present but uncommon. included saplings of taller trees and a few tree ferns Epiphytes, mainly ferns, were uncommon, and orchids (Cyathea). Grasses, ferns, and scrambling Lantana and mosses were rare. Leaf litter was sparse, and there comprised the ground vegetation. Canopy vines were was no humus layer. Adjacent to this locality the Aeta sparse and consisted mainly of Mikania and Mucuna. had active taro farms, and sections of the steeper slopes There was a thin (ca. 1–3 cm) layer of leaf litter in flat were regularly burned to clear trails and facilitate hunting areas but with no humus layer. Abundant rocks were of wild pigs. exposed on the ground. Fallen logs were rare but on slopes, erosion had exposed buried tree trunks charred in Locality 2: 7.0 km N, 11.7 km E Mt. Pinatubo peak, 490 the 1991 eruption. m elev., 15.19222o N, 120.45722o E; 05–10 Mar 2011. Vegetation here was similar to that at Locality 1 but with a Locality 6: 2.8 km N, 5.3 km E Mt. Pinatubo peak, 1,080 m more extensive cover of wild banana and bamboo. It also elev., 15.15611o N, 120.39570o E; 12–17 March 2012. The had more interspersed trees of similar height (15–20 m) vegetation at this uppermost site resembled that at Locality and composition as those at Locality 1, with the addition 5, but Parasponia was less abundant and Muntingia of Radermachera and Spathodea. Epiphytic ferns and appeared to be absent, and taller trees with greater dbh orchids were present but uncommon. Leaf litter was were more numerous. Ficus and Musa were abundant, largely absent and there was no humus layer. This locality as were Mikania and Mucuna vines. The area toward the bordered “kaingins” (slash-and-burn farming areas), some highest point (ca. 1,100 m) was covered predominantly fallow and some newly cultivated by the Aeta, planted with Saccharum with scattered Ficus and Musa. with root crops (cassava, sweet potato, taro, and yams), as well as other vegetables and fruit. Field Methods Locality 3: 6.2 km N, 10.7 km E Mt. Pinatubo peak, To facilitate comparability of results, survey methods 670 m elev., 15.18611°N, 120.44972o E; 13–18 Mar followed standardized techniques developed during 2011. Vegetation was similar to that found at Locality 2, previous surveys of Philippine small mammals (Heaney characterized by extensive wild banana and bamboo cover et al. 2013; Rickart et al. 1991, 2013; Balete et al. 2009; but with more extensive riparian vegetation. Scattered Alviola et al. 2011). Latitude and longitude (decimal trees, including some dipterocarps (Shorea) and nutmegs degrees, based on the Luzon, Philippines datum), and (Myristica), were 30–40 m tall with diameters at breast elevation (m) of each locality were determined using height (dbh) of 50–70 cm. Cultivated kaingins, like those a hand-held GPS (global positioning system) device. Locality 2, also were present. Under the taller trees leaf Locality coordinates were plotted on 1:50,000 topographic litter had accumulated up to 3 cm. maps and straight-line N-S and E-W distances (in km) measured to the peak of Mt. Pinatubo (Figure 1). At each Locality 4: 2.0 km N, 5.1 km E Mt. Pinatubo peak, 680 m locality, we sampled within ± 50 m of the central elevation. elev., 15.14944o N, 120.39694o E; 13–16 Mar 2012. This locality, which served as our base camp in 2012, was along We used mist nets set in likely flyways to survey small fruit an upper tributary of the Pasig-Potrero River east of the bats and insectivorous bats. Nets were tended continually Pinatubo caldera. The habitat here was in the early stage during the early evening period of peak bat activity of forest development involving mainly two tree species: (dusk to 20:00 h), then every 30 min until 22:00h, and Parasponia rugosa, a widespread native species, and a thereafter left open until dawn. We did removal trapping common introduced species, Muntingia calabura. Figs, to survey small (< 500 g weight) non-volant mammals, particularly Ficus minahassae, were common. Grasses using snap traps baited with either roasted coconut coated (including Imperata, Saccharum, and Andropogon) – with peanut butter (“coconut bait”), or live earthworms along with ferns, shrubs (Lantana), and vines (Mucuna collected locally. Most traps were set on the ground and Dolichos) – covered exposed ridges and gaps between surface at burrow openings, along runways, beneath the the narrow stands of trees. Musa was uncommon. Only ground cover, and in root tangles. Some coconut-baited limited mist netting for bats was conducted at this locality. traps were placed above the ground surface as “arboreal” traps. At each locality, traplines were set in all accessible Locality 5: 2.5 km N, 5.4 km E Mt. Pinatubo peak, 960 microhabitats and operated for three consecutive days m elev., 15.15333o N, 120.39972o E; 06–12 March 2012. before moving them to a new site for another three-day Vegetation at this site consisted of abundant wild bananas, period. This procedure was continued until all local along with a sparse cover of figs (Ficus minahassae, microhabitats were sampled, after which we proceeded to F. nota, and F. hispida) and clumps of Saccharum. On a new locality. Traps were serviced twice daily to remove exposed ridges and steeper slopes, Mallotus, Muntingia, captured and replenish bait: the early morning and Parasponia were common, ca. 5–6 m tall (rarely after sunrise and the late afternoon before sundown (ca. reaching 10 m), and 15–50 cm dbh. Understory species 07:00h and 17:00h, respectively). Specimens recovered

124 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity in the morning were considered nocturnal-crepuscular captures. Overall ground trapping success, as a proxy for captures and those in the late afternoon as diurnal captures. relative abundance, was expressed as weighted (by bait type) and unweighted (equalized) percentages of captures. Approximately 40% of the bats, including individuals Weighted trap success was determined by dividing the total of all species documented, were prepared as voucher number of individuals captured by the total trap-nights at specimens and the remainder was released following the locality, and the quotient multiplied by 100 to calculate identification. Some non-volant mammals damaged by the percent trap success. Unweighted trap success was scavengers were discarded after identification; all others computed by averaging the trap successes for the two bait (> 90%) were prepared as voucher specimens. Prior types at each locality. In assessing the significance of the to their preservation, standard external measurements diel activity, expected capture frequencies were computed were recorded for each specimen, and a sample of based on the duration of the diurnal (10 h) and nocturnal/ muscle tissue was preserved for future genetic analyses. crepuscular (14 h) activity periods. Specimens were preserved whole in fluid or prepared as complete skeletons. All specimens were deposited at the We used the χ2 test to determine the significance of Field Museum of Natural History, Chicago (FMNH) for differences in abundance across survey localities and to verification of field identification and further taxonomic evaluate patterns of diel activity and bait attractiveness. studies. After completion of these studies, half of the We conducted χ2 tests only on total samples of 20 or more specimens will be returned to the National Museum of individuals, with five or more individuals per “treatment” the Philippines, Manila. in at least 80% of the treatments (e.g. per elevation or bait type). For sample size less than 20, we determined Mammal nomenclature follows Heaney et al. (2010, significance with binomial tests where appropriate. We 2016b). Capture, handling, and collection of animals in used Spearman’s coefficient of rank correlation (rs) the field were done under permits from the Philippine to assess relationships of species richness and relative Department of Environment and Natural Resources abundance with elevation. (DENR) and were conducted in accordance with all relevant Philippine laws and regulations.

Data Analysis RESULTS In assessing the elevational range of occurrence across the survey gradient, we inferred the presence of species Bats at a given elevation if it was documented at higher and Surveys across six localities yielded 308 captures of lower localities (Rickart et al. 1991). Our unit of sampling fruit bats representing five species (Table 1). Cynopterus effort for non-volant small mammals was a trap-night (one brachyotis, the most abundant species, accounted trap set for 24 h) and for bats, a net-night (one mist net for nearly half (49%) of the captures, followed by set for 24 h). To measure the adequacy or completeness Macroglossus minimus and Ptenochirus jagori. These of our survey for nonvolant small mammals, we used three species were documented (or inferred to occur) at species-accumulations curves showing the cumulative all sampling localities. Eonycteris spelaea and Rousettus number of species captured as a function of sampling amplexicaudatus were less abundant; the former was effort (number of trap-nights). We plotted accumulation recorded at the three lowest localities, and the latter was curves for each survey locality, and a total curve for all captured at 365 m only. We captured 15 insectivorous localities combined, starting at the lowest elevation and bats representing three species – Hipposideros bicolor, proceeding to the highest. We do not present any species H. diadema, and Myotis horsfieldii (Table 1). Data were accumulations curves for bats because of low sampling not sufficient for more detailed assessments of distribution effort and disrupted netting schedules due to poor weather. and abundance. Relative abundance was measured as trapping (or netting) success. For bats, it was expressed as the number Non-volant Small Mammals captured per net night. For non-volant small mammals, Our total trapping effort consisted of 4,507 trap nights, we calculated the number of captures per 100 trap-nights 3,838 with coconut bait on the ground, 33 coconut (percent trap success): the number of individuals captured “arboreal” trap-nights, and 636 earthworm trap-nights multiplied by 100 and divided by the number of trap- on the ground. In total, trapping yielded 329 captures nights. We used these measures to assess patterns of representing seven species (Table 2) – including distribution and relative abundance of individual species, five native (Apomys sacobianus, A. zambalensis, and native vs. non-native species groups. Bait preference Bullimus luzonicus, mindorensis, and of non-volant mammals was expressed as bait-specific everetti) and two non-native species (Rattus exulans

125 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity

Table 1. Captures of bats at six localities on Mt. Pinatubo, Luzon Island, using mist nets. For fruit bats, captures per net night are shown in parentheses at localities with more than 10 net nights. Capture frequencies greater than expected from χ2 tests based on numbers of net nights at each locality are indicated by bold font. Number of species equals documented (plus inferred). Locality/elevation (m) Species 1 2 3 4 5 6 Total χ2 P 365 490 670 680 960 1,080 Fruit bats Cynopterus brachyotis 18 (1.12) 14 (1.00) 48 (3.20) 4 38 (3.45) 29 151 69.22 < 0.001 Eonycteris spelaea 5 (0.31) 1 (0.07) 6 (0.40) 0 0 0 12 Macroglossus minimus 10 (0.62) 22 (1.57) 42 (2.80) 0a 3 (0.27) 12 89 Ptenochirus jagori 6 (0.38) 1 (0.07) 28 (1.87) 4 8 (0.73) 5 52 Rousettus amplexicaudatus 4 (0.25) 0 0 0 0 0 4 Insectivorous bats Hipposideros bicolor 0 2 0 0 0 0 2 Hipposideros diadema 0 0 1 0 0 0 1 Myotis horsfieldii 12 0 0 0 0 0 12 Net-nights 16 14 15 3 11 4 63 Total fruit bats 43 38 124 8 49 46 308 102.1 < 0.001 Total insectivorous bats 12 2 1 0 0 0 15 No. of species 6 5 5 2 + 1 3 3 8 aPresence inferred from occurrence at higher and lower elevations

Table 2. Occurrence of non-volant small mammals at five localities on Mt. Pinatubo, Luzon Island; values indicate the number caught at each locality (percent trap success in parentheses). Captures greater than expected from χ2 tests based on numbers of trap-nights at each locality are in bold. Number of species equals documented (plus inferred). Locality/elevation (m) Species 1 2 3 5 6 Total χ2 P 365 490 670 960 1,080 Apomys sacobianus 46 (4.96) 40 (4.37) 4 (0.45) 54 (6.32) 82 (9.30) 226 (5.05) 71.40 < 0.001 Apomys zambalensis 3 (0.35) 0b 3 (0.34) 0b 2 (0.30) 8 (0.18) Bullimus luzonicus 1 (0.35) 6 (0.73) 10 (1.12) 0 0 17 (0.38) Chrotomys mindorensis 4 (0.43) 2 (0.24) 2 (0.26) 3 (0.35) 7 (0.79) 18 (0.40) Rattus everetti 12 (1.29) 15 (1.64) 18 (2.01) 9 (1.05) 6 (0.68) 60 (1.34) 7.50 0.112 Rattus exulansa 0 2 (0.22) 2 (0.26) 0 0 4 (0.09) Rattus tanezumia 12 (1.29) 2 (0.22) 0b 0b 1 (0.11) 15 (0.33) Total captures (native species) 66 63 37 66 97 329 28.93 < 0.001 Total captures (non-native) 12 4 2 0 1 19 Total trap nights (ground) 927 915 895 855 882 4474 Total trap nights (arboreal) 9 6 0 3 15 33 No. of native species 5 4 + 1 5 3 + 1 4 5 No. of non-native species 1 2 1 + 1 0 + 1 1 2 aNon-native species bPresence inferred from occurrence at higher and lower elevations

and R. tanezumi). The number of native species reached A. zambalensis and B. luzonicus at localities where they asymptotes at each of the five survey localities (Figure were not recorded, it is unlikely that the total number of 3A) but at two localities (490 and 960 m), we infer species would have increased with additional effort, as the presence of an additional species (A. zambalensis) illustrated by the early asymptote for the entire survey captured at adjacent upper and lower elevations (Table transect (Figure 3B). 2). Although further trapping would likely have added

126 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity

Figure 3. Species accumulation curves for native non-volant small mammals on Mt. Pinatubo A) at individual localities and B) for the entire transect, with the beginning of sampling at each locality starting with the lowest in elevation. Each symbol represents one day of sampling.

The species richness of native non-volant mammals was DISCUSSION nearly uniform across the survey gradient (Table 2). Four of the five native species either were documented Historical Records and Adequacy of Sampling or inferred to occur at all five of the localities. Species Specimen records from low elevations around Mt. Pinatubo richness was not significantly correlated with elevation (summarized in Heaney et al. 2010) provide invaluable (r = –0.62; P = 0.50). Trap success on the ground (Table s background information on the mammal fauna of the study 3) was not significantly correlated with elevation, either area prior to the 1991 eruption. Several species of bats with coconut bait (r = 0.200; P = 0.75) or earthworms s were obtained by D.H. Johnson in 1956, including four (r = 0.60; P = 0.28), nor were weighted or unweighted s fruit bats – Acerodon jubatus and Pteropus vampyrus from overall trap success (r = 0.60; P = 0.28 and r = 0.50; s s Crow Valley in Tarlac Province, and Eonycteris spelaea P = 0.39, respectively). Among native species, Apomys and Ptenochirus jagori from Clark Air Base. The first two sacobianus was the most abundant at four out of five probably were collected at tree roosts, and the second two localities (Table 2) and was by far the most abundant possibly from caves. Thirteen species of insectivorous bats overall with 226 captures (nearly 69% of the total native obtained by Johnson include Hipposideros ater, H. diadema, captures). Rattus everetti was the second most abundant, H. obscurus, Rhinolophus arcuatus, R. inops, R. macrotus, R. followed by Chrotomys mindorensis, Bullimus luzonicus, philippinensis, R. subrufus, R. virgo, Miniopteris schreibersi, and Apomys zambalensis. Of the two non-native species, Myotis horsfieldii, Scotophilus kuhli, and Chaerophon Rattus tanezumi was moderately common at the lowest plicata. Some of these (Hipposideros spp. and Rhinolophus elevation but uncommon or not documented elsewhere, spp.) were collected from day roosts in caves and tunnels and R. exulans was documented at two localities where along the Sacobia River, and others were collected on Clark it was uncommon (Table 2). Air Base, presumably from buildings and other structures Overall trap success was significantly greater with (unpublished data from USNM specimen labels). earthworm compared to coconut bait (Table 3). Earthworm Two additional fruit bats, Haplonycteris fisheri and bait was significantly more effective than coconut in Otopteropus cartilagonodus, occur elsewhere within capturing Apomys sacobianus and Chrotomys mindorensis the Zambales region. They are seldom found outside (Table 4). The remaining species did not exhibit significant forested habitats where they forage in the understory. bait preferences, although only Rattus everetti was caught Both are widespread on Luzon but they seldom occur in sufficient numbers for this to be biologically meaningful together, which suggests segregation due to interspecific (i.e. revealing no significant difference in bait attractiveness competition (Heaney et al. 2016b). Haplonycteris occurs rather than an artifact due to sample size). Capture data on Mt. Natib where it was present below 1,000 m but revealed that all species were overwhelmingly most active uncommon (Rickart et al. 2013). Both species occur on during the nocturnal/crepuscular period (Table 4). Arboreal Mt. Tapulao where Otopteropus was found across a broad trapping was very limited due to the general scarcity of elevational range and Haplonycteris was less common suitable arboreal habitat, resulting in the capture of only a and found only at low to mid-elevations (Balete et al. single Rattus tanezumi (Tables 3 and 4). 2009; unpublished FMNH specimen records). Given its

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Table 3. Summary of overall capture frequencies by bait type and diel period of all native non-volant small mammals along an elevational gradient on Mt. Pinatubo. Captures greater than expected from χ2 tests of ground-traps with the two types of bait are in bold. Locality/elevation (m) 1 2 3 5 6 Total 365 490 670 960 1,080 Coconut bait (ground) Trap nights 846 823 769 734 666 3838 Captures 53 59 28 39 56 236 Percent trap success 6.26 7.17 3.64 5.31 8.41 6.15 Earthworm bait (ground) Trap nights 81 92 126 121 216 636 Captures 13 4 9 27 40 93 Percent trap success 16.05 4.35 7.14 22.31 18.52 14.62 Χ2 9.94 0.96 3.21 38.90 14.61 53.27 P 0.001 0.328 0.073 0.001 0.001 0.001 Overall trap success (%) Weighted 7.12 6.88 4.13 7.72 11.00 7.35 Unweighted 11.16 5.76 5.39 13.81 13.54 10.38 Diel period Diurnal 0 2 0 2 3 7 Nocturnal/crepuscular 66 61 37 64 94 322 Percent diurnal 0 3.17 0 3.03 3.09 2.13 Coconut bait (arboreal) Trap nights 9 6 0 3 15 33 Captures 0 0 0 0 1 0 Percent trap success 6.67

Table 4. Summary of captures of native non-volant small mammals on Mt. Pinatubo by bait type, diel period, and trap position. Captures greater than expected are shown in bold. Bait type Diel period Trap position Total Species Nocturnal/ Ground Above trapped Coconut Worm Diurnal crepuscular surface ground Apomys sacobianus 226 154 72*** 219*** 7 226 0 Apomys zambalensis 8 7 1 8b 0 8 0 Bullimus luzonicus 17 15 2 17b 0 17 0 Chrotomys mindorensis 18 11 7b 17b 1 18 0 Rattus everetti 60 49 11 60*** 0 60 0 Rattus exulansa 4 4 0 4 0 4 0 Rattus tanezumia 15 14 1 15b 0 14 1 aNon-native species bP < 0.05, from binomial distribution ***P < 0.001

occurrence on Mt. Natib and Mt. Tapulao, Haplonycteris All eight species of bats documented in our survey was probably present on Mt. Pinatubo prior to the eruption. (Table 1) are widespread and common in the Philippines. It might persist in areas of remnant forest nearby and if However, four of these (C. brachyotis, M. minimus, R. so may recolonize once adequate forest has developed on amplexicaudatus, and H. obscurus) represent the first the mountain. Because of its limited distribution in the records from Pampanga Province (species distribution Zambales region, Otopteropus is perhaps less likely to maps in Heaney et al. 2016b). Differences between the have occurred on Mt. Pinatubo in the past. historical records and our survey results can be attributed

128 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity to methodology, notably our use of mist nets, which are (Heaney et al. 2016b). In surveys of Mt. Tapulao (Balete very effective but were not widely used in the late 1950s et al. 2009) and Mt. Natib (Rickart et al. 2013) it was when the principal methods were collecting by hand at the most abundant species with the broadest elevational roost sites or through the use of shotguns (Genoways et al. distribution. 2020). We also acknowledge that bat netting was limited at some of our survey localities due to logistical problems. Apomys sacobianus was described on the basis of a single Future surveys in areas of remnant forest and exploration specimen captured along the Sacobia River in 1956 of caves and other roosting sites may add many of the bats (Johnson 1962). After 55 years, its rediscovery during our documented historically along with additional species. Pinatubo survey provided new material that confirmed its taxonomic status (Heaney et al. 2014) and placed it within Although we are confident that non-volant mammal the phylogenetic and biogeographic context (Justiniano trapping was sufficient to document the species present et al. 2015). Our surveys of Mt. Natib and Mt. Tapulao across our survey gradient (Figure 3B), additional species (Balete et al. 2009; Rickart et al. 2013) failed to document may occur elsewhere on Mt. Pinatubo, particularly in A. sacobianus even in areas of second-growth similar areas where the effects of the 1991 eruption may have to habitat in which it was abundant on Mt. Pinatubo, been less severe. Specimen records predating the eruption revealing a much narrower geographic distribution for include those for Tryphomys adustus from Clark Air Base this species. Apomys sacobianus may prove to be endemic and localities to the north in Tarlac Province (Heaney et to Mt. Pinatubo and its immediate surroundings, but al. 2016b). This poorly-known murid rodent is endemic additional field surveys in central Luzon are required to to Luzon Island, with records from central and northern demonstrate this. Luzon and from near sea level to 2,000 m in non-forested habitat ranging from grassy riparian vegetation to areas Data from surveys of non-volant small mammals on of second-growth adjacent to rice fields (Barbehenn et al. mountains throughout Luzon reveal that the number of 1973; Heaney et al. 2016b). From these facts, it is possible native species present on a given mountain is strongly that T. adustus persists in the vicinity of Mt. Pinatubo. correlated with its maximum elevation (Heaney et al. Directed surveys for this species are clearly warranted. 2016a). During our survey of Mt. Pinatubo, lack of potable water made it difficult to work at higher elevations Although our survey did not target large mammals (> 500 beyond a reasonable distance from base camps, and we kg weight), we did gather pertinent information on their were unable to establish survey localities above 1,100 m. status. In 2011, wild pigs (Sus philippensis) were heard Although we think it unlikely that we would have recorded moving through thick stands of Saccharum adjacent to additional species in the regenerating habitat at higher Locality 1. Subsequently, a group of Aeta hunters burned elevations, we acknowledge that the following discussion a section of this grassland and obtained a young adult is based, in part, on conjecture. We documented five female and a piglet. The Aeta reliably reported that deer native species on Mt. Pinatubo (six including historical (Rusa marianna) also were present on the mountain. Other records of Tryphomys adustus as discussed above). At species of large mammals with records from the Zambales its current elevation (1,486 m) the elevation-species Mountains are the arboreal native rodent Phloeomys richness relationship would predict at least five species pallidus, and the non-native carnivores Paradoxurus on Pinatubo, which is the number documented for Mt. Irid philippinensis and Viverra tangalunga (Balete et al. with a slightly lower elevation at 1,469 m (Balete et al. 2009; Heaney et al. 2010; Rickart et al 2013). All three 2013). However, before the 1991 eruption, Mt. Pinatubo species have broad elevational ranges extending into the stood at 1,745 m (Newhall et al. 1996) and its upper slopes lowlands and all often occur in disturbed areas with a were covered with old-growth forest (Punongbayan et al. mix of agriculture and second-growth habitat (Heaney 1996). From the elevation-species richness relationship, et al. 2016b). Although we did not document them, all the predicted total number of species for pre-eruption three probably persist in remnant habitat elsewhere on the Pinatubo would fall between six (as documented for Mt. mountain and would likely increase with the regeneration Palali at 1,707 m; Alviola et al. 2011) and eight (for Mt. of forest cover. Anacuao at 1,850 m; Heaney et al. 2013). This suggests that several species may have been lost as a result of the eruption. Biogeography, Elevation, and Community Structure Of the five species of native rodents documented from In identifying other native non-volant mammals that Mt. Pinatubo, Rattus everetti is a widespread Philippine may have been present on Mt. Pinatubo before the endemic, Chrotomys mindorensis is endemic to Luzon 1991 eruption, we must consider those known to occur and Mindoro, and Bullimus luzonicus is restricted to elsewhere within the Zambales Mountains complex. Mt. Luzon (Heaney et al. 2010). Apomys zambalensis is a Tapulao, the highest peak in the region (2,037 m), has regional endemic widespread in the Zambales Mountains nine species (Balete et al. 2009) of which five have not

129 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity been documented on Mt. Pinatubo. Two of these, Apomys surveyed all had early second-growth habitat in which brownorum and Rhynchomys tapulao, are known only non-native species were much less abundant than native from the summit of Mt. Tapulao and may be endemic species, accounting for only 19 (5.5%) of 348 total to that mountain, and it is unlikely that either occurred animals captured. Non-native rodents were unevenly on Pinatubo. The three remaining species are Crocidura distributed across the survey gradient (Table 2); most grayi (the only native shrew on Luzon), Apomys microdon, were captured at the three lowest localities adjacent to and A. musculus (both are small arboreal mice). All are areas with cultivated kaingin, whereas only one individual widespread on Luzon and have elevational ranges that was captured at a higher elevation where there was no either extend down to near sea level or (in the case of A. kaingin. Most previous disturbance gradient studies on musculus) from the highest peaks down to mid-elevation Luzon involved highly disturbed second-growth habitat montane forest (Heaney et al. 2016b). We conclude that near active agriculture (Rickart et al. 2011; Reginaldo and these species probably occurred on Mt. Pinatubo before Ong 2020). The non-native rodents involved here and in the eruption. All require forest cover to maintain mesic our other studies (Rattus exulans and R. tanezumi) are conditions that particularly favor C. grayi, and to provide human commensals that achieve the greatest abundance the above-ground foraging space and nest sites utilized in croplands or in other human-dominated habitats where by both A. microdon and A. musculus (Heaney et al. they have ready access to food crops or stored produce; 2016b). Although the early-successional habitats of our both are at a severe disadvantage in areas where they survey localities lacked these essential features, areas of compete with native species for naturally occurring foods. remnant forest habitat elsewhere on the mountain may In retrospect, this hypothesis should be amended to read: support these three species. Based on previous studies “non-native small mammals are most abundant in severely cited above, we predict their expansion into regenerating disturbed habitats where they have access to food crops habitat on Mt. Pinatubo once the secondary forest has had or other artificial food sources.” time to develop. • A subset of native species that tolerate severe Another pattern that has emerged from mammal surveys habitat disturbance coexists with non-native elsewhere on Luzon is the significant correlation between species. the local maximum elevation of a mountain range or isolated peak, and the number of non-volant small Results of the Pinatubo survey strongly support this mammals that are locally endemic (Heaney et al. 2016a). hypothesis. Bullimus luzonicus, Chrotomys mindorensi, From this elevation-local endemism relationship, we and Rattus everetti are among the subset of native small would expect pre-eruption Pinatubo to have at least one mammals found to be highly tolerant of disturbance in local endemic. As discussed above, Apomys sacobianus surveys elsewhere on Luzon (Rickart et al. 2011). Apomys may be a Pinatubo endemic. Unlike many of the endemic sacobianus and A. zambalensis are local or regional non-volant mammals of Luzon that are restricted to endemics that share this ability to tolerate disturbance. In mountaintops, A. sacobianus occurs from the lowlands the case of A. sacobianus, “tolerate” is an understatement in to mid-elevations (at least 1080 m; Table 2). It is one that it was by far the most abundant small mammal on the of several species of Apomys (subgenus Megapomys) mountain. This species is discussed in further detail below. that diversified within the lowlands as opposed to the • Native small mammals are resilient, moving highlands (Justiniano et al. 2015). The remaining question into areas of regenerating habitat and ultimately is whether there might have been locally endemic species displacing non-native species as native vegetation restricted to high elevations on Mt. Pinatubo prior to the matures. 1991 eruption. This is highly unlikely given the geological history of frequent explosive eruptions of even greater This hypothesis also is supported by our results but to a magnitude than the 1991 event (Newhall et al. 1996). much greater extent than we anticipated. The native rodents on Mt. Pinatubo are effectively pioneer species, capable of occupying early second-growth habitat. We predict the Disturbance Ecology and Conservation future occurrence of other, less tolerant, native species In light of our results, we review the three hypotheses (e.g. Crocidura grayi and Apomys microdon) with the regarding the expected distribution and abundance of development of suitable forested habitat on the mountain. non-volant small mammals presented in the introduction: The 1991 eruption of Mt. Pinatubo was one of the • Non-native small mammals are numerically most powerful in recent history; however, several more dominant in the most severely disturbed habitat. powerful eruptions occurred earlier in its existence This hypothesis clearly was not supported by our results. (Newhall et al. 1996). Cataclysmic geological events that The five localities where non-volant mammals were are seemingly rare from the perspective of human history are commonplace when viewed over geological time. As

130 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity these events created the physical fabric of the Philippines, al. 2013) demonstrated that it had a restricted distribution they also shaped the evolution of its remarkably rich and raised the specter that, if locally endemic to Mt. biota. Throughout their existence, Philippine mammals Pinatubo, it might have become extinct as a result of the have regularly experienced catastrophic disturbances, eruption. Although A. sacobianus may indeed be restricted some more devastating and widespread than the recent to Mt. Pinatubo and surrounding lowland areas, our eruption of Mt. Pinatubo, not only those associated with results revealed it to be widespread and the most abundant geological processes but also much more frequently by species on the mountain. Among all of the species that we powerful typhoons (Heaney et al. 2016b). documented, it was the most successful in coping with extreme disturbance and thriving under the harsh conditions Although many species of native Philippine mammals characteristic of early-successional habitats. Compared can tolerate substantial disturbance (Rickart et al. 2011, to species that are broadly distributed, range-restricted 2013; Heaney et al. 2016b), we nonetheless find it species such as A. sacobianus are widely considered to remarkable that so many native species were present be less tolerant of habitat disturbance and competitively in areas of early successional habitat on Mt. Pinatubo. inferior, particularly those that are endemic to tropical island Unfortunately, we have no data on the residual mammal systems (Berglund et al. 2009; Walsh et al. 2012). This fauna immediately following the eruption. However, a certainly is not the case for small mammal communities parallel event – the 1980 eruption of Mount St. Helens in on Luzon that are dominated by endemic species, many of SW Washington, USA – provides insight into the probable which are ecological specialists with restricted geographic situation following the eruption of Mt. Pinatubo. In the distributions yet are tolerant of habitat disturbance and months following the Mount St. Helens eruption, small resist invasion by non-native species (Rickart et al. 2011; mammal surveys conducted across a gradient of habitat Heaney et al. 2016b). Among Philippine mammals, Apomys damage revealed stark differences in species occurrence sacobianus is perhaps the most extreme example of a patterns and an inverse relationship between the severity “disturbance specialist,” a range-restricted species that is of habitat damage and the number of residual species highly adapted to life in a landscape that is periodically present (Andersen and MacMahon 1985a). ravaged by catastrophic events. We postulate that mammals on Mt. Pinatubo exhibited a As is the case with sites of other devastating volcanic similar pattern of differential survival across a gradient of eruptions (del Moral and Grishin 1999), Mt. Pinatubo habitat damage, with the greatest numbers and diversity provides an opportunity to study aspects of biotic recovery in areas where damage was least severe, and only the following extreme disturbance – including rates of habitat hardiest surviving in scattered sheltered refugia in areas of regeneration across different levels of local disturbance, greater damage. Burrowing mammals such as Chrotomys changes in species diversity and community composition may have had high survival rates even where habitat over time, and complexities of biotic interactions. Habitat was severely damaged, as was the case with fossorial recovery on Mt. Pinatubo will be a long and complex rodents (Thomomys) on Mount St. Helens that survived process, and coordination of research efforts – as envisioned underground in areas with extreme eruption damage where under the rubric of long-term ecological research (Kim they were instrumental in regenerating soil and promoting et al. 2018) – could greatly enhance efforts to document early revegetation (Andersen and MacMahon 1985b). this process. Furthermore, understanding the process of Bats and large mammals probably dispersed from ecological recovery from cataclysmic natural disturbances surrounding intact areas shortly after the eruption of can augment reforestation and other efforts for ecological Mt. Pinatubo (del Moral and Grishin 1999; Crisafulli et reclamation of human-disturbed landscapes. As such, al. 2015) and, as seed dispersers, undoubtedly played lessons learned from the tragedy of Mt. Pinatubo could an important early role in plant succession (Marler and ultimately support efforts to protect and restore biological del Moral 2011). Fruit bats and frugivorous birds were communities throughout the Philippines and beyond. probably responsible for the diversity and abundance of figs noted at our survey localities and will continue to influence future forest development on the mountain (Utzurrum 1995; Ingle 2003). ACKNOWLEDGMENTS Perhaps the most remarkable aspect of our work on Mt. We gratefully acknowledge our colleagues J. Sarmiento, Pinatubo was the rediscovery of Apomys sacobianus. R. Buenviaje, and R. Plutado, without whose help this Prior to our surveys in central Luzon, we assumed that project would not have been possible. We thank the this species might be more broadly distributed within the mayors and staff of Mabalacat City and Municipality, Zambales Mountains. The fact that we did not find it either and the barangay officials of San Vicente for their on Mt. Tapulao (Balete et al. 2009) or Mt. Natib (Rickart et cooperation. We thank the Aeta of Sitio Burog for their

131 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity assistance and for sharing their knowledge, especially O. DEL MORAL R, GRISHIN SY. 1999. Volcanic dis- Sanchez, C. Tolentino, and R. Tolentino. We appreciate turbances and ecosystem recovery. In: Ecosystems the support of the DENR–Protected Areas and Wildlife of Disturbed Ground. Ecosystems of the World, Vol. Bureau (redesignated the Biodiversity Management 16. Walker LR ed. Amsterdam: Elsevier. p. 137–160. Bureau), especially T.M. Lim, R.L. Calderon, J. de Leon, GENOWAYS HH, MCLAREN SB, TIMM RM. 2020. C. Custodio, M. Mendoza, A.M. Tagtag, and T. Tenazas. Innovations that changed mammalogy: The Japanese DENR Wildlife Gratuitous Permit No. 262 was issued mist net. Journal of Mammalogy 101: 627–629. to Dr. Lawrence Heaney of the Field Museum. The figures were prepared by A. Niedzielski and L. Nassef. HEANEY LR, BALETE DS, ALVIOLA PA, DUYA We thank A. Goldman and A. Niedzielski for preparing MRN, RICKART EA. 2013. The mammals of Mt. specimens for study, and J. Phelps and the late W. Stanley Anacuao, NE Luzon Island, Philippines: a test of for technical support. This project was supported by the predictions of Luzon small mammal biodiversity pat- Negaunee Foundation, the Grainger Foundation, the terns. National Museum of the Philippines: Journal of Brown Fund for Mammal Research, and the Ellen Thorne Natural History 1: 1–13. Smith Fund of the Field Museum. HEANEY LR, BALETE DS, DUYA MRM, DUYA MV, JANSA SA, STEPPAN SJ, RICKART EA. 2016a. Doubling diversity: a cautionary tale of previously unsuspected mammalian diversity on a tropical oceanic REFERENCES island. Frontiers of Biogeography. p. 1–19. ALVIOLA PA, DUYA MRM, DUYA MV, HEANEY HEANEY LR, BALETE DS, RICKART EA. 2016b. LR, RICKART EA. 2011. Mammalian diversity pat- The Mammals of Luzon: Biogeography and Natural terns on Mount Palali, Caraballo Mountains, Luzon. History of a Philippine Fauna. Baltimore: The Johns Fieldiana: Life and Earth Sciences 2: 61–74. Hopkins University Press. 287p. ANDERSEN DC, MACMAHON JA. 1985a. The effects HEANEY LR, BALETE DS, VELUZ MJ, STEPPAN of catastrophic ecosystem disturbance: the residual SJ, ESSELSTYN JA, PFEIFFER AW, RICKART mammals of Mount St. Helens. Journal of Mammal- EA. 2014. Two new species of Philippine forest mice ogy 66: 581–589. (Apomys, , Rodentia) from Lubang and Luzon ANDERSEN DC, MACMAHON JA. 1985b. Plant suc- islands, with a redescription of Apomys sacobianus cession following the Mount St. Helens volcanic erup- Johnson, 1962. Proceedings of the Biological Society tion: Facilitation by a burrowing rodent, Thomomys of Washington 126: 395–413. talpoides. American Midland Naturalist 114: 62–69. HEANEY LR, DOLAR ML, BALETE DS, ESSEL- BALETE DS, HEANEY LR, RICKART EA. 2013. The STYN JA, RICKART EA, SEDLOCK JL. 2010. mammals of Mt. Irid, southern Sierra Madre, Luzon Synopsis of Philippine Mammals. Retrieved on 19 Island. National Museum of the Philippines: Journal Sep 2020 from http://www.fieldmuseum.org/philip- of Natural History 1: 15–29. pine_mammals/ BALETE DS, HEANEY LR, VELUZ MJ, RICKART INGLE NR. 2003. Seed dispersal by wind, birds, and bats EA. 2009. Diversity patterns of small mammals in between Philippine montane rainforest and succes- the Zambales Mts., Luzon, Philippines. Mammalian sional vegetation. Oecologia 134: 251–261. Biology 74: 456–466. JOHNSON DH. 1962. Two new murine rodents. Pro- BARBEHENN K, SUMANGIL JP, LIBAY JL. 1973. ceedings of the Biological Society of Washington 75: Rodents of the Philippine croplands. Philippine Agri- 317–319. culturalist 56: 217–242. JUSTINIANO R, SCHENK JJ, BALETE DS, RICKART BERGLUND H, JÄREMO J, BENGTSSON G. 2009. En- EA, ESSELSTYN JA, HEANEY LR, STEPPAN demism predicts intrinsic vulnerability to nonindigenous SJ. 2015. Testing diversification models of endemic species on islands. The American Naturalist 174: 94–101. Philippine forest mice (Apomys) with nuclear phy- logenies across elevational gradients reveal repeated CRISAFULLI CM, SWANSON FJ, HALVORSON JJ, colonization of isolated mountain ranges. Journal of CLARKSON B. 2015. Volcano ecology: Disturbance Biogeography 42: 51–64. characteristics and assembly of biological communi- ties. In: Sigurdsson H, Houghton B, McNutt S. eds. KIM ES, TRISURAT Y, MURAOKA H, SHIBATA Encyclopedia of Volcanoes, 2nd ed. London: Elsevier H, AMOROSO V, BOLDGIV B, HOSHIZAKI K, Publishers. p. 1265–1284. KASSIM AR, KIM YS, NGUYEN HQ, OHTE N,

132 Philippine Journal of Science Rickart et al.: Mammals of Mt. Pinatubo Vol. 150 No. S1, Special Issue on Biodiversity

ONG PS, WANG CP. 2018. The International Long- WALSH JC, VENTER O, WATSON JEM, FULLER Term Ecological Research–East Asia–Pacific Regional RA, BLACKBURN TM, POSSINGHAM HP. 2012. Network (ILTER-EAP): history, development, and Exotic species richness and native species endemism perspectives. Ecological Research 33: 19–34. increase the impact of exotic species on islands. Global Ecology and Biogeography 21: 841–850. MARLER TE, DEL MORAL R. 2011. Primary suc- cession along an elevation gradient 15 years after the WOLFE EW, SELF S. 1983. Structural lineaments and eruption of , Philippines. Pacific Sci- Neogene volcanism in southwestern Luzon. In: The ence 65: 157–173. Tectonic and Geological Evolution of Southeast Asian Seas and Islands, Part 2. Hayes DE ed. American [MGB] Mines and Geosciences Bureau. 2010. Geology Geophysical Union, Geophysical Monograph 27. p. of the Philippines, 2nd ed. Quezon City, Philippines. 157–172. NEWHALL CG, DAAG AS, DELFIN FG, HOBLITT RP, MCGEEHIN J, PALLISTER JS, REGALADO MT, RUBIN M, TUBIANOSA BS, TAMAYO RA, UMBAL JV. 1996. Eruptive history of Mount Pina- tubo. In: Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines. Newhall CG, Punongbayan RS eds. Quezon City: Philippine Institute of Volcanology and Seismology; Seattle: University of Washington Press. p. 165–195. PUNONGBAYAN RS, NEWHALL CG, HOBLITT RP. 1996. Photographic record of rapid geomorphic change at Mount Pinatubo, 1991–94. In: Fire and Mud: Eruptions and Lahars of Mount Pinatubo, Philippines. Newhall CG, Punongbayan RS eds. Quezon City: Philippine Institute of Volcanology and Seismology; Seattle: University of Washington Press. p. 21–66. REGINALDO AA, ONG PS. 2020. Structure of small non-flying mammal communities in disturbed habitats in the Central Cordillera, Luzon Island, Philippines. Philippine Science Letters 13: 81–94. RICKART EA, BALETE DS, ROWE RJ, HEANEY LR. 2011. Mammals of the northern Philippines: toler- ance for habitat disturbance and resistance to invasive species in an endemic fauna. Diversity and Distribu- tions 17: 530–541. RICKART EA, HEANEY LR, BALETE DS, AL- VIOLA PA, DUYA MRM, DUYA MV, ROSELL- AMBAL G, SEDLOCK JL. 2013. The mammals of Mt. Natib, Bataan Province, Luzon, Philippines. National Museum of the Philippines: Journal of Natural History 1: 31–44. RICKART EA, HEANEY LR, UTZURRUM RCB. 1991. Distribution and ecology of small mammals along an elevational transect in southeastern Luzon, Philippines. Journal of Mammalogy 72: 458–469. UTZURRUM RCB. 1995. Feeding ecology of Philippine fruit bats: Patterns of resource use and seed dispersal. Symposia of the Zoological Society of London 67: 63–77.

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