The Mammals of Mt. Amuyao: a Richly Endemic Fauna in the Central Cordillera of Northern Luzon Island, Philippines
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Mammalia 2016; 80(6): 579–592 Eric A. Rickart*, Danilo S. Balete, Phillip A. Alviola, Maria J. Veluz and Lawrence R. Heaney The mammals of Mt. Amuyao: a richly endemic fauna in the Central Cordillera of northern Luzon Island, Philippines DOI 10.1515/mammalia-2015-0132 Received August 3, 2015; accepted November 10, 2015; previously Introduction published online January 20, 2016 Oceanic islands are well known for their richly endemic Abstract: Faunas of old oceanic islands often have biotas, but mammals on such islands have been surpris- extremely high levels of endemism and are considered ingly poorly documented. At 103,000 km2 (United Nations highly susceptible to anthropogenic disruption. We sur- Environmental Programme 2010), Luzon, in the northern veyed the richly endemic small mammal fauna on Mt. Philippine archipelago, is the largest island that is entirely Amuyao in the Central Cordillera of northern Luzon oceanic. Recent studies on Luzon have documented at Island, Philippines. We tested hypotheses regarding least 47 native non-flying mammals, of which 42 (89%) are elevational patterns of species richness and community endemic (Heaney et al. 2013a, 2014a,b, 2016, Balete et al. composition, community response to habitat disturbance, 2015), and it seems certain that other endemic species are and interactions of native and non-native mammals. Our yet to be discovered in poorly explored areas. study revealed greater species richness and faunal hetero- Luzon has a long and complex geological history (Hall geneity within the Central Cordillera than previously sus- 2012) which is closely associated with faunal diversifica- pected. We documented 15 native species (14 rodents and tion, much of which resulted from autochthonous spe- 1 insectivore), and two species of non-native rodents. All ciation (Jansa et al. 2006, Heaney et al. 2011, 2013b, 2016, of the native species are endemic to the Philippines, eight Justiniano et al. 2014). Although progress has been made being restricted to the Cordillera. Twelve of the 14 native in documenting the mammal faunas in many portions of rodents belong to two ancient endemic clades, indicating Luzon, little has been published on mammals of the largest that most of the regional diversity is the product of in situ and most species-rich area, the Central Cordillera, and this speciation. Native mammal assemblages are ecologically has limited our perspective on the evolution, ecology, and diverse, and include species with varied trophic habits, conservation of this richly endemic fauna. activity patterns, and climbing ability. Some native species The Cordilleran mammal fauna was introduced are restricted to relatively pristine habitat, whereas others to science in the late 19th century through specimens are highly tolerant of disturbance. Non-native species are obtained from Mt. Data (2310 m) and elsewhere by British restricted to highly disturbed habitats and apparently are naturalist John Whitehead (Figure 1, Thomas 1898). displaced by natives where habitat has regenerated from During the 20th century, Mt. Data remained the principal past disturbance. focus of collecting efforts on Luzon (Sanborn 1952, Rabor 1955). Our 2000–2003 study in Balbalasang-Balbalan Keywords: biogeography; conservation; elevational National Park (Rickart et al. 2011b) was the first com- gradients; endemism; species richness. prehensive survey of mammals in the Cordillera region, involving standardized sampling along a local elevational habitat gradient to facilitate quantitative comparisons *Corresponding author: Eric A. Rickart, Natural History Museum of with gradient surveys conducted in other regions of the Utah, 301 Wakara Way, University of Utah, Salt Lake City, UT 84108, Philippines (Heaney et al. 1989, 2006, Rickart et al. 1991). USA, e-mail: [email protected] However, that study was conducted on Mt. Bali-it, a peak Danilo S. Balete and Lawrence R. Heaney: Field Museum of Natural that reached only 2238 m, well short of the maximum ele- History, 1400 S Lake Shore Drive, Chicago, IL 60605, USA vation in the Cordillera (2930 m). Phillip A. Alviola: Museum of Natural History, University of the Philippines at Los Baños, College, Laguna 4031, Philippines Here, we report results of surveys undertaken in 2007 Maria J. Veluz: National Museum of the Philippines, Rizal Park, and 2011 on Mt. Amuyao (2702 m), the fourth highest Manila, Philippines mountain on Luzon. To determine the nature and extent of 580 E.A. Rickart et al.: Mammals of Mt. Amuyao, Luzon, Philippines both of which are located within the same contiguous area of highland habitat above 1500 m (Figure 1). The Central Cordillera, extending nearly 300 km from the northern tip of Luzon south to the Central Valley, is an uplifted mag- matic arc associated with subduction in both the East Luzon Trench and the Manila Trench. The core of the Cordillera consists of Eocene–Oligocene plutonic rocks with associated marine sedimentary rocks. Uplift and vol- canic activity occurred during the Late Oligocene–Middle Miocene (33–12 Ma) in conjunction with westward subduc- tion of the Philippine Sea Plate along the Manila Trench, followed by Pliocene–Quaternary (5–0 Ma) uplift and extensive magmatism (Ringenbach et al. 1990, Hall 2002, 2012, Hollings et al. 2011). Much of the Cordillera west of Mt. Amuyao has exposed extrusive and intrusive igneous Figure 1: Map of northern Luzon Island showing areas of highland rocks (andesite and granite), whereas to the east under- habitat and location of Mt. Amuyao in relation to other peaks in the lying sedimentary rocks include sandy shale and sand- Central Cordillera. stone, of which the latter predominates on the surface of Mt. Amuyao (Smith 1915: 192). possible faunal variation within the Central Cordillera, we We surveyed mammals from 17 February to 26 March sought to survey a new site geographically distinct from 2007 and from 5 to 27 April 2011 at 15 localities along an Balbalasang. We were particularly interested in access- elevational gradient on the northern aspect of Mt. Amuyao ing areas at elevations higher than those available at Bal- from the nearby town of Barlig (ca. 1500 m) to the moun- balasang. In order to gain greater insight into the effects tain summit (2702 m). These localities encompassed the of anthropogenic disturbance on native and non-native range of natural forest habitats and included areas with mammals, we surveyed habitats ranging from agricultural varied levels of natural and anthropogenic disturbance lands and early second growth to relatively undisturbed from agricultural land to nearly pristine forest (Figure 2). mature forest. Detailed information on the plants of Mt. Amuyao, includ- Some of the data from the Mt. Amuyao survey have ing an assessment of plant diversity across elevation, can appeared in previous publications describing newly dis- be found elsewhere (Salcedo 2001). The following descrip- covered taxa (Balete et al. 2012, Heaney et al. 2014a), new tions of our survey localities are based on our field notes. distributional records of bats (Heaney et al. 2012), and the Where our localities and those of Salcedo (2001) coin- impact of habitat disturbance on small mammals (Rickart cided, we list the dominant plants from her study. et al. 2011a). Here, we present the comprehensive results – Locality 1. 1.0 km S, 0.6 km E Barlig Municipal Hall, from our elevational transect survey of the non-flying 1510 m elev., 17.04030°N, 121.10583°E. 21–22 February small mammals, placing them within the broader context 2007. At this locality southeast of Barlig we trapped of our earlier gradient studies. Much of the data presented in early second-growth habitat on abandoned rice ter- here constitutes the first information on several species races overgrown with saplings, tree ferns (Cyathea), endemic to the Central Cordillera. shrubs, and cane grass (Saccharum). – Locality 2. 1.1 km S, 0.6 km E Barlig Municipal Hall, 1530 m elev., 17.03797°N, 121.10424°E. 18–20 February 2007. At this locality we trapped in areas of active agri- Materials and methods culture that included terraced vegetable gardens and along grassy margins of rice fields (Figure 2A). Study area – Locality 3. 0.5 km S, 0.2 km E Barlig Municipal Hall, 1535 m elev., 17.04109°N, 121.10291°E. 18–20 February Mt. Amuyao is located in the east-central portion of the 2007. This locality was on a steep slope with grasses, Central Cordillera, approximately 60 km south of Mt. shrubs, scattered pines (Pinus kesiya), cultivated Bali-it from which is it separated by intervening land banana (Musa), and sweet potato (Ipomoea). below 1500 m elevation, and approximately 30 km north- – Locality 4. 2.15 km N, 1.25 km W Mt. Amuyao summit, east of Mt Data and 50 km north of Mt. Pulag (2922 m), 1650 m elev., 17.03270°N, 121.11604°E. 19–27 April 2011. E.A. Rickart et al.: Mammals of Mt. Amuyao, Luzon, Philippines 581 A B 2007. Habitat at this locality was secondary pine forest with undergrowth of cane grass, forbs, and bracken fern (Pteridium). Undergrowth was periodically burned to promote herbaceous vegetation for live- stock forage. – Locality 6. 0.3 km N Barlig Municipal Hall, 1760 m elev., 17.04694°N, 121.09801°E. 18–23 February 2007. This locality (Figure 2B) was along a ridge in open pine forest with trees between 12 and 20 meters in height, the largest of which had dbh of ca. 60 cm. The under- story, which was regularly burned, included cane grass and bracken fern with scattered shrubs (Rubus, C D Melastoma, and Vaccinium). Ground cover included pine needles and dead grass over moderately rocky volcanic soil. – Locality 7. 0.6 km N Barlig Municipal Hall, 1800 m elev., 17.04820°N, 121.09977°E. 21–25 February 2007. This locality was in remnant montane forest near sec- ondary pine forest (locality 6). Height of the forest can- opy was 10–15 m, and emergent trees reaching 20 m.