Ecological Surveys



The principal aims of the project were to establish and map remaining forest in the Polillo Islands, report the presence of key indicator species and subsequently to survey selected forest patches more intensively. Floral and faunal surveys throughout the Polillos were conducted to determine the status of remaining forests and wildlife. Map 2 depicts the location of study sites. Each of the studies are summarized below. Click on the abstract to download each of the full survey reports as a pdf file.




by Katie Hampson

From June to December 2001 transect surveys were used to assess amphibian populations across the Polillo Islands, and to determine the effects of forest fragmentation on species abundance and distribution. Aural transects were used as an effective tool to estimate density and abundance of rare, sensitive and cryptic species for which visual transects were inadequate. Two new records brought the total number of species on Polillo to 19, including two undescribed species and the endemic Polillo forest frog Platymantis polillensis. Bufo marinus, Rana vittigerra, Polypedates leucomystax, Kaloula picta and K. conjuncta were demonstrated to be agriculture specialists; Rana woodworthi, R.. similis, Platymantis dorsalis, Occidozyga laevis, and P. luzonensis were found at their highest densities in forest; and P. polillensis, P. sp., and Rhacophorus appendiculatus were rare species recorded exclusively in forest. Several habitat characteristics correlated strongly with distance from forest edge forming a gradient of increasing habitat quality. The density of five forest dependant species increased significantly with respect to these factors. Consequently forest was concluded to be the most important habitat for amphibian conservation, supporting several rare and restricted range species and key sites across Polillo were identified that harbour the rarest species. Habitat fragmentation and forest edge effects are significant factors determining amphibian distribution and abundance. CLICK HERE FOR FULL REPORT (PDF)


by Susan Walker

Formal survey work between the months of July and December, 2001 was conducted in remnant forest patches on the Polillo Islands. Further observations were made between March and May 2002. Avian inventories were produced and the analysis focused particularly on the island-endemic, globally threatened and forest-indicator species. All seven island subspecies (six observed directly) and seven internationally recognised threatened birds were reported. The critically endangered Philippine Cockatoo, Cacatua haematuropygia was sighted on Patnanungan Island and the near-threatened endemic Blue-naped Parrot, Tanygnathus lucionensis hybridus was observed in Patnanungan and Panukulan, with the latter site supporting a breeding pair (May 2002). Species with distributions more widespread than previously thought include the Philippine Forest Kingfisher, Ceyx melanurus and the Polillo-endemic Philippine Trogon, Harpactes ardens minor. In addition to the primary old growth forest of Sibulan watershed reserve, these species were also found in more disturbed patches of logged primary forest. The pressures imposed by deforestation are exacerbated by direct persecution. The Luzon Bleeding Heart, Gallicolumba luzonica and the Colassisi, Loriculus philippensis are among the more commonly caught birds. A small hunting network is still prevalent. CLICK HERE FOR FULL REPORT (PDF)


by Tom Clements

The present project aimed to:

Produce a list of tree species known from Polillo islands, with the aid of botanical experts, Identify local names for these species that are used with accuracy and to conduct surveys of forest fragments throughout the islands, and compare the structure and species composition of these fragments. CLICK HERE FOR FULL REPORT (PDF)

By Mark Reyes


The Philippine crocodile is a critically endangered species whose range has dwindled to the extent that it is known from just a handful of areas. In April 2002 we investigated reports that the species occurs on the island of Jomalig in the Polillo group. Although we found no absolute proof of the animals' occurrence it seems highly likely that it still occurs there based on reports from local hunters, some of whom are actively hunting them. CLICK HERE FOR FULL REPORT (PDF)

by Daniel Bennett, Katie Hampson, Susan Walker, Tom Clements and Phillip Alviola.


Tunnel trapping and mist netting at nine sites brings the total number of microchiropteran bats known from the Polillo islands to 20 species. Hipposideros coronatus was found for the first time since its description in 1871. Evidence from ultrasound recordings suggests the total speciosity of communities on Polillo is still underestimated and that more intensive surveying techniques are required for a proper understanding of the composition and structure of bat communities. The foundation of a library of echolocation calls of Polillo bats is intended to facilitate the acceptance of standardised and adequate sampling programmes throughout the Philippines. CLICK HERE FOR FULL REPORT (PDF)

by Daniel Bennett and Katie Hampson


Non-destructive methods were developed to study Gray's monitor lizard (Varanus olivaceus), the largest frugivore in the Philippines and one of the world's largest lizards. The species occurs at a number of forested sites on Polillo Island but is absent from other islands in the group. Around Sibulan watershed reserve the lizards moved further in trees than on the ground and fed mainly on the fruits of Pinanga, Pandanus and Canarium. Evidence that the lizards forage for fruit in trees r ather than on the ground was obtained and the presence of Pinanga as a major food item is hypothesized to be the result of a shortage of preferred fruits during the study period. The methods developed allow areas to be surveyed for evidence of the species without disturbance to the animals, allows individuals to be captured with the minimum of risk and enables the collection of high quality data on movement and feeding habits. CLICK HERE FOR FULL REPORT (PDF)
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