Palaeozoology of Palawan Island, Philippines
Introduction
The study of archaeologically-derived animal bone assemblages provides invaluable information on the origin, dispersal and evolutionary history of different vertebrate communities. The data offer long-term perspectives on climatic and environmental change, the timing of the introduction of invasive species, extinction in native taxa and the impacts of people on ecological communities (Lyman, 2006). Current knowledge of the natural history of Island Southeast Asia and Wallacea is still limited, but studies of past animal communities in Borneo (Cranbrook, 2000, Cranbrook, 2009, Cranbrook and Piper, 2007), Java (Morwood et al., 2008), Flores (van den Bergh et al., 2009, Hocknull et al., 2009) and East Timor (O’Connor and Aplin, 2007) suggest that substantial ecological changes occurred in past millennia as a result of environmental change and human activities (Heinsohn, 2003).
This study focuses on the Terminal Pleistocene and Holocene mammal faunas of the Philippine island of Palawan (Fig. 1). Palawan is 425 km in length with a maximum breadth of just 40 km, and covers approximately 11 785 km2. It divides the South China Sea to the north from the Sulu Sea to the south. It is located on the north-eastern margins of the shallow ocean platform surrounding Peninsular Malaysia, Java, Sumatra, Bali and Borneo, known as the Sunda Shelf (Mollengraaff, 1921).
The present-day environment of Palawan is broadly similar to that of north Borneo, comprising lowland tropical rainforest to approximately 1200 m, grading into submontane and eventually montane forest above 1600 m (Heaney, 2001). The contemporary mammal community comprises 58 native and four non-native species (Esselstyn et al., 2004). Thirteen species (22% of the total and 54% of the native non-flying species) are endemic to Palawan. Of these, 12 are non-bat and, along with almost all the native mammals, have their closest relatives on the Sunda Shelf. The only exceptions are the endemic fruit bat Acerodon leucotis whose nearest relatives inhabit the oceanic Philippines, and four other species that are widespread throughout the Sundaic region and the rest of the Philippine archipelago: the long-tailed macaque (Macaca fascicularis subsp.), common palm civet (Paradoxurus hermaphroditus), Malay civet (Viverra tangalunga) and leopard cat (Prionailurus bengalensis). As a result of these affinities, Palawan is considered to represent the north-eastern boundary between the Sundaic biogeographic region and the isolated oceanic islands of Wallacea. This is an impoverished fauna compared with the 285 species of mammals (including 103 bat species) on the neighbouring landmass of Borneo. Borneo does, however, demonstrate fairly high endemicity, with 19% of all mammal species (or 28% excluding bats) only found on that island (Cranbrook, personal communication, 2010).
During Pleistocene glacial maxima when sea levels were lowered by as much as −116 to −139 m (Rohling et al., 1998, Hanebuth et al., 2000), Palawan was much larger than at present and joined to many smaller adjacent islands such as Culion, Coron and Busuanga to the north and Balabac to the south, forming what is known as the Greater Palawan region (Heaney, 1985). The Balabac Strait between Palawan and Borneo was considerably narrower and at times of sea-level low stands the two islands might have joined through a land bridge, facilitating the migration of Sundaic species to and from Palawan (Cranbrook, 2000, Tougard, 2001).
In their study of the sub-fossil faunas from cave sites in central Palawan, Reis and Garong (2001) identified six orders, 11 families and 14 species of mammals dating back almost 12 000 years. The taxonomic composition of the assemblages studied, which consist almost exclusively of small mammals, reptiles and birds, is more likely to represent natural accumulations rather than the results of human intervention. In that study there was no conclusive evidence for a land bridge between Palawan and Borneo during the Last Glacial Maximum (LGM) around 18–20 ka, with Palawan demonstrating many characteristics of an isolated island with low taxonomic diversity and relatively high endemism in comparison to the rest of the Sundaic region. More extensive research was called for by Reis and Garong (2001) to develop a better understanding of the palaeozoological history of the island.
The animal bone assemblage from Ille Cave provides one such opportunity. Excavations have produced more than 50 000 bone fragments from well-stratified archaeological sequences dating from ca. 14 000 cal. BP to less than 4000 cal. BP (Lewis et al., 2008). The assemblage accumulated through two major mechanisms. Numerous small mammal and reptile inhabitants of the cave and its immediate surroundings accumulated as part of natural death assemblages. However, the majority of animal bones derive from intermediate and large-sized taxa, and represent human food debris. Hunter-gatherer populations often target preferred resources (Cranbrook and Piper, 2007, Rabett and Barker, 2007, Piper et al., 2008b, Piper and Rabett, 2009), but humans are generally opportunists and will, over time, collect a relative sample of the wild fauna available, providing a good indication of the range of taxa present in the local and regional environment at different phases in the history of the site.
All radiocarbon (14C) dates are reproduced as calibrated years before present.
Section snippets
Archaeological background
Ille Cave is located in the Dewil River valley in north Palawan, close to the village of New Ibajay at 11°11′46″N; 119°30′19″E. The cave is on the base of the south side of a ca. 75 m high limestone karst tower, with two main openings (east and west) and an adjoining short passageway no more than 5 m in length. Both entrances open onto a relatively flat platform 3–15 m wide, covering a total area of approximately 450 m2 and ending in a sharp, short downward gradient onto lightly wooded ground and a
Methodology
This study concentrates primarily on the mammal remains from the Terminal Pleistocene deposits (ca. 14 000 cal. BP) up to the mid-Holocene shell middens (5000–7000 cal. BP). The layers produced discrete, well-dated animal bone assemblages that presented an opportunity to identify a chronological sequence of change in the composition of the faunal community during these periods. The more recent phases of cave use involved the interment of several hundred people, which has reworked and mixed
Taxonomic accounts
A total of 26 090 bone fragments were studied from Ille Cave; 28 mammal taxa from 19 families were identified from the Late Pleistocene and early–late Holocene deposits (Table 1). This includes the first identification of the tiger (Piper et al., 2008a), at least two species of deer and a canid. Discussion focuses on new identifications and not those already outlined in Reis and Garong (2001). Numbers preceded by the abbreviations “ICWM” and “ICEM” indicate bone identification numbers whereas
Discussion
The zooarchaeological record from Ille Cave has produced evidence for seven orders, 25 genera and 23 species of mammals from the Terminal Pleistocene and Holocene sedimentary sequences. This assemblage provides a deeper temporal dataset for the study of macro-evolutionary and biogeographic processes on the island, particularly those relating to colonization, environmental change and extirpation. Throughout the cave sequence, there are striking patterns in the distribution of certain taxa that
Conclusion
The zooarchaeological analysis of the Terminal Pleistocene and early Holocene animal remains from Ille Cave has produced fossil evidence for many extant mammals and for four taxa that are locally extinct on Palawan. This dataset includes new records of several small and intermediate mammals, such as the Palawan pangolin, stink badger, common palm civet and bear cat, and confirms their presence on the island since the end of the last glacial period.
The presence of the tiger and possibly the
Acknowledgments
The authors would like to thank Angel Bautista and the National Museum of the Philippines for access to zooarchaeological comparative assemblages, and the El Nido municipal government, Mayor Leonor Corral and the Palawan Council for Sustainable Development (PCSD) for their cooperation and assistance. Many thanks to Dr. Lawrence Heaney for his expert advice on Palawan biogeography and to Dr. Ryan Rabett and the Earl of Cranbrook for reading and commenting on an early draft of this paper, and the
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