Bulosao Watershed Forest Reserve is regarded as one of the most important areas in terms of biodiversity in the island of Samar and within the greater Mindanao faunal region. Four study sites representing different habitat types, elevation range and degree of human disturbance were surveyed for their faunal composition. Standard faunal survey methods such as transect survey, mist netting, and trapping were used during the entire duration of the study. The methods were augmented with observations and ethnobiological interviews.
Of the 98 species of wild fauna recorded from the site, 41 species are birds, 11 are mammals, 6 amphibians and 12 reptiles. The 41 species of birds belong to 12 orders, 25 families and 35 genera. Of these, twenty-nine percent are endemic to the Philippines and one to the greater Mindanao faunal region. Among avian species, sixteen (40%) are considered threatened or at risk.
Of the 11 mammals, which belong to 6 orders and 9 families, 64% are endemic to the country. Three (42%) of these are endemic to the greater Mindanao faunal region. Five (46%) of these species are considered threatened or at risk.
Of the 6 species of amphibians recorded, 2 are introduced and the rest are native to the Philippines. Of the 12 reptiles species, five (42%) are endemic to the country and 2 are endemic to the greater Mindanao faunal region. Among herpetofauna, only one species is considered threatened or at risk.
Major threats to the wildlife population in the reserve include hunting and habitat alteration. Hunting among the local community is not only for subsistence but also for commercial purposes. Major activities leading to habitat destruction include conversion of logged-over areas into cultivation, illegal logging and indiscriminate collection of other forest products.
Being home to many species of fauna of national and international significance, Bulosao Watershed Forest Reserve needs to be managed and protected from the various forms of unsustainable resources exploitation.
The Bulosao Watershed Forest Reserve is located in the southern part of the island of Samar and lies within the coordinates 11°22'N and 125°20'E. Having an area of about 4,055 hectares, it was declared as a watershed forest reserve through Proclamation Number 106 on 10 December 1992, for inclusion in the National Integrated Protected Areas System (NIPAS) by virtue of R.A. 7586 (DENR, 2003). It is under the administrative jurisdiction of the municipality of Lawaan, Eastern Samar.
Samar is within the greater Mindanao faunal region. This faunal region is comprised of Mindanao Island and all islands that were connected to it at low sea level periods of the Pleistocene such as Samar, Leyte, Bohol, Basilan, Dinagat and Siargao. Considered biologically the richest and one of the most distinctive in the Philippines, this faunal region contains at least 29 species of endemic birds and 26 species of endemic mammals (DENR, 1997).
Recently, the Birdlife International and the Haribon Foundation (Mallari et al 2001) recognized Samar as an endemic bird area with three important bird areas (IBA), one of which is the Bulosao Watershed Forest Reserve. Avifaunal diversity survey in this IBA however is still in the pipeline due to some constraints.
The wild fauna of the Bulosao Watershed Forest Reserve is still virtually unknown. The extensive forests in this reserve must support important populations of several of the threatened and endemic species of the greater Mindanao faunal region. With the current resource utilization patterns, which are responsible for the degradation of highly sensitive and fragile ecosystems in this landscape, the biodiversity is likely to be heavily affected. The study is a modest attempt to determine the existing faunal biodiversity, which must have resulted from the constant interaction between the local community and the resources base. The study is timely and significant, as it would serve as valuable input in formulating integrated conservation strategies that would promote biodiversity conservation at the same time address the economic needs of the local communities.
Bulosao Watershed Forest Reserve is adjacent to the MacArthur Mountains, and straddles the boundary of Samar and Eastern Samar Provinces. The highest peak is Mt Honop at 731 m. The northern and western boundaries of the IBA approximately follow the Sulat River. Closed canopy lowland dipterocarp forest covers c.2,624 ha (65%) of the watershed, open canopy lowland dipterocarp forest covers c.952 ha (24%), cultivated areas with brush cover c.208 ha (5%), coconut plantations cover c.171 ha (4%) and contract reforestation plots (planted with exotic tree species) cover c.100 ha (2%). There are a few small settlements present in the area, and the small patches of agricultural land and kaingin are planted with coconut, banana and fruit trees (Mallari et al 2001).
Duration of the Study
The wildlife inventory (rapid assessment) of Bulosao Watershed Forest Reserve was conducted on January 3 to 6 and February 18 to 22, 2003.
Sampling in the area was done in four sites, which cover different habitat types, disturbance levels and altitudinal gradients. Sampling site 1 was located in a heavily disturbed lower mountane forest dominated by agricultural cultivation particular devoted to coconut below 100 meters above sea level (masl). Sampling site 2 was situated in a disturbed lower montane forest dominated by cultivated areas with patches of secondary forest and regeneration areas between 100 and 200 masl. Sampling site 3 was located in the upper montane forest with patches of primary and secondary forests, reforestation, and cultivation between 200 and 300 masl. Sampling site 4 was situated in the less disturbed upper montane forest dominated by a mix of primary and secondary forests with patches of regeneration and active cultivation from 300 to 400 masl.
Rapid assessment of faunal diversity was employed in the conduct of inventory of all four major vertebrate groups (reptiles, amphibians, birds, and mammals) within the Bulusao Watershed Forest Reserve. Different techniques or methods of faunal inventory include trapping of non-volant mammals, mist netting of non-volant mammals, and transect survey of birds, reptiles and amphibians. Indirect methods of faunal survey such as footprints, fecal droppings, roosting and nesting sites, other physical evidences and ethnobiological interviews that may indicate the probable presence of wildlife in the area were also employed.
Composition and distribution of avian species were assessed using the transect survey method based on Mallari (1992). Transect lines measuring 2 kilometers each were set in every sampling site. The number of transect lines in each sampling site vary depending upon the variability of the sites. All species of birds encountered along the transects were recorded. For each species seen or heard, the following information were noted: species name, number of individuals, and habitat types. The avifaunal inventory was conducted early in the morning (from 6:00 to 9:00) and late in the afternoon (from 3:00 to 6:00). Identification was up to the species level whenever possible. Nomenclature and classification were based on Kennedy et al (2000).
Sampling sites cover different habitat types, disturbance levels and altitudinal gradients. The Sorensen's Index of Similarity (Magurran, 1988) was used to compare species composition between sampling sites. Similarity values (expressed in percentage) were calculated using the following equation:
2K SI = __________ x 100 A + B Where, K = number of species common to sites A and B; A = number of species for site A, and B = number of species for site B.
Species richness for each sampling site was measured using Menhinick's Richness Index (Magurran, 1988) with the following equation:
R = S /ÖN, Where: S = total number of species per sampling site/elevation, N = total number of individuals per sampling site/elevation.
The overall pattern of species richness in each site was determined by plotting the values of species richness indices against the sampling sites in a line graph.
Diversity was computed for each sampling site using Shannon's Diversity Index (Magurran, 1988):
H¢ = -S [ n1 / n ] In [ n1 / n ] Where: n1 = number of individuals per species and n = total number of individuals.
The overall pattern of species diversity was determined by plotting computed Shannon diversity indices of sampling sites in a line graph.
Mist nets for volant mammals and live traps for non-volant mammals were used in mammalian survey. Nomenclature and classification were based on Rabor (1986).
Mist-netting stations were set up in strategic locations either singly or a series and operated for days in specific study sites. Each net has an average mesh size of 36 mm and an average height of 2 meters. Nets were set 2 meter high with a ground clearance of about 0.5 meter. Species captured were identified up to the species level whenever possible.
Trapping of non-volant mammals involved setting of cage traps baited with cooked coconut meat, sliced ripe mango or dried fish, on the ground near fallen logs or holes, along possible runways or root system of trees or stumps. Similarly, trapped or captured animals were identified up to the species level whenever possible.
Tracks and fecal matters were also used to estimate the presence of wildlife in each transect route used in avifaunal survey.
Random sampling along the transect route used for avifaunal survey for reptiles and amphibians was done whenever possible. Sampling was done along streams, rivers or near bodies of water or any site believed to be harborages of herpetofauna. Animals were either collected by hand or captured by nets for further verification. Nomenclature and classification was based on Alcala (1986) and Alcala and Brown (1998).
Other methods of Faunal Survey
Ethnobiological interviews were conducted to determine the presence of other vertebrates that were not recorded during the field observations. Information on vernacular or local names, habitat type, socioeconomic importance and other patterns of behavior were noted. Other activities related to the overall decline or loss of wildlife species in the area were also recorded.
A total of 41 bird species were recorded in the four study sites primarily based on transect survey results (Table 1). These species belong to 12 orders, 25 families and 35 genera. The most represented order is Passeriformes with 18 species belonging to 13 families. The second most represented order is Columbiformes with 8 species belonging to two families. This is followed by four orders represented by two species each: Coraciliformes, Cuculiformes, Psittaciformes and Stringiformes.
Columbidae is the most represented family with 5 species of dove and 1 species of pigeon. It is followed by family Pycnonotidae with three species of bulbul. Most Columbidae species are frugivoruos and are often encountered in brushlands bordering secondary forest areas. Their ability as good agents for seed dispersal enables them to play vital role in the forest ecosystem.
Of the 41 avian species recorded in Bulosao Watershed Forest Reserve, twelve (29%) are endemic to the Philippines. Only one is endemic to Samar and the rest of Greater Mindanao faunal region.
The distribution of bird species in the four sites is shown in Table 2. Site 3 had the highest number of species with a total of 31; site 2 had the lowest with 16. Site 1 and 4 had 23 and 20 species, respectively.
Six species were found to be present in the four sites and are considered common. Nine species were recorded in a single site only. The rest (26) were observed either in 2 or in 3 sites.
Most frequently occurring and most abundant species were the bulbuls and the sunbirds. Most of these species are either insectivorous, or nectivorous or both. The presence of dense undergrowth in regeneration areas which harbor high insect population and the availability of fruit-bearing (mostly pioneer) tree species across the four sites warrant the steady supply of food for these group of birds species.
Of the nine species, which appeared to be in their restricted range as they were recorded in a single site only, the Philippine Grass-owl (Tyto capensis) was the only avian species observed in Site 1 where there are vast grasslands near active cultivation.
Green Imperial Pigeon (Ducula aenea), Dark Throated Oriole (Oriolus xanthonotus), Yellowish Bulbul (Hypsipetes everetti), White Collard Kingfisher (Halcyon chloris), Common Moorhen (Gallinula Chloropus) and Asian Glossy Starling (Aplonis panayensis) were observed only in Site 3. Green Imperial Pigeon, Dark Throated Oriole and Yellowish Bulbul were observed deep in the interior of intergrading secondary and primary forests. White Collard Kingfisher and Common Moorhen were found in relatively open area near a creek. Surprisingly, several Asian Glossy Starlings were observed in a reforestation site feeding on the fruits of buntan (Engelhardia rigida), a naturally occurring pioneer species in reforestation sites.
Steere's Pitta (Pitta steerii), Philippine Tailorbird (Orthothomus castaneiceps) and Philippine Eagle-owl (Bubo philippensis) were all observed in Site 4 only. Steere's Pitta and Philippine Tailorbird were observed in the interior of primary forest while Philippine Eagle-owl was observed in the edge of a primary forest near a headwater of a creek.
Table 1. List of avian taxa recorded in Bulosao Watershed Forest Reserve, Lawaan, Eastern Samar, c. 2003 (See table)
Table 2. Distribution of bird species recorded in the four sampling sites in Bulosao Watershed Forest Reserve, Lawaan, Eastern Samar, c. 2003 See table
The similarity indices of the 4 sites are shown in Table 3. Site 1 and 3 had the highest index of similarity (74%). Site 2 and 3 ranked second (63%) while site 1 and 4 had the lowest percentage (46%).
The similarity in terms of degree of habitat heterogeneity and the habitat types present could explain the high similarity between Site 1 and 3. These sites were composed mainly of a combination of secondary forests, agricultural cultivation, and regeneration areas under coconut plantations. This combination of habitats provided adequate and quality food sources to a many species of birds particularly those with broad food preference and wide altitudinal range. Dense under growth of secondary forests and regeneration areas supports high diversity of insects and fruits, which are the primary sources of food of these bird species.
The low similarity of Site 4 when compared to the rest of the sites could be attributed to the difference in habitat types and structural complexity. Site 4 being at the highest altitudinal range among the four sites, was composed mainly of a mix of primary and secondary forests and small openings in cultivation areas. The less structural complexity associated to this site condition made it fit to harbor mostly interior bird species, which are usually adapted to the secondary and primary forests.
Table 3. Avifaunal similarity indices of the study sites in Bulosao Watershed Forest Reservation, Lawaan, Easteren Samar, c. 2003 (See table)
Species Richness and Diversity
As shown in Table 4, site 4 had the highest species richness of 1.61 with 156 individual belonging to 20 species. Site 2 had the lowest species richness of 1.43 with 125 individuals belonging to only 16 species. Figure 1 shows that generally species richness increases with elevation.
The increasing trend in species richness along altitudinal gradient could be due to the decreasing abundance of individuals in a species and the increasing number of species. The decrease in the number of individuals per species could be a result of limited amount of food for a specific species. The limited amount of food inhibits increase of species population especially that of specialist species. The increasing number of species could be attributed to the decreasing degree of disturbance along altitudinal gradient. Site 2 was highly disturbed and highly homogenous because it was close to settlements and areas under cultivation. Site 4, on the other hand, was situated far from settlement thus less disturbed and probably must support a variety of small niches for specialization.
Site 1, on the other hand, had the highest diversity while site 4 had the lowest. Species diversity generally decreases with elevation (Figure 2). The decreasing diversity along altitudinal gradient could be due to the decreasing evenness of distribution of individuals among species and the increasing dominance of few aggressive species. In site 1, aside from the high abundance due to the seemingly unlimited and highly diverse food materials because of overlapping habitats, individuals were evenly distributed among the different species. In site 4 where food materials were of limited supply due to less diverse habitats and less structural complexity, some species tend to dominate thereby decreasing the evenness. As a result of stiff competition, the disadvantaged species would be restricted to expand its food preferences thus would tend to specialize.
Table 4. Species richness and diversity of the four study sites in Bulosao watershed Forest Reservation, Lawaan, Eastern Samar, c. 2003 (See table)
Conservation status of avian species recorded in Bulosao Watershed Forest Reserve is presented in Table 5. The conservation status of at least twenty-four species appeared in various literature such as the IUCN Red List Category of Species, CITES, and Birdlife International and Haribon Foundation. Of the twenty species recognized by IUCN, 16 were considered near threatened (nt), 2 vulnerable (VU), 1 lower risk (LR) and 1 endangered (E). Under CITES, 4 were listed in Appendix II and 1 in Appendix I. The Birdlife and Haribon Foundation recognized 1 as threatened, 1 restricted and 1 threatened and restricted to Samar only.
The Birdlife International and Haribon Foundation has recognized the whole island of Samar as endemic bird area (EBA) in Mallari et al (2001). The Bulosao Watershed Forest Reserve was recognized as one its important bird areas (IBA) in the Southern Samar mountains along with Mt Yacgun-Mt Sohoton complex, and Mt Cabalantian-Mt Capoto-an complex. The different bird species found in Samar Island as reported by Mallari et al (2001) is presented in Table 6. Unfortunately, only three species encountered in the field survey were included in the list. This calls for a thorough and intensive survey to determine what is actually left of the bird biodiversity of Bulosao Watershed Forest Reserve.
One important species that has been observed in the area was the Rufous Hornbill (Buceros hydrocorax), which normally inhabits secondary and primary forests. This species, however, was observed in flocks of six to ten individuals perching on a toog (Petersianthus quadrialatus) tree in an active cultivation near a falls. Toog, the tallest tree in most cultivated fields in the area, is usually left uncut during logging operation because of its poor lumber quality. This avian species is recognized as Lower Risk species by IUCN and listed in CITES Appendix II.
Another important species that has been observed in the area was the Tariktik Hornbill (Penelopides panini), which is considered Endangered by the IUCN and CITES Appendix II. A local resident had caught one individual of this bird species during the field survey. Sadly, the bird has suffered gunshot from an air rifle. This species is primarily hunted for its meat.
Table 5. Conservation status of avian species recorded in, Lawaan, Eastern Samar, c. 2003. (See table)
Table 6. Threatened and restricted-ranged bird species found in Samar Island as reported by Mallari et al (2001). Highlighted cells indicate avifauna species observed during the avian survey.(See table)
A total of 11 mammals were recorded in four study sites (Table 7). These belong to 6 orders and nine families. Five species were observed during the field survey and six were discerned from ethnobiological interviews. Of these 11 mammals, seven (64%) are endemic to the Philippines of which 3 (42%) are endemic to the greater Mindanao faunal region.
Three of the species were considered Vulnerable by IUCN (Table 8). These include the Philippine Warty Pig, Common Palm Civet and Philippine Flying Lemur. The Philippine Tarsier is considered as Conservation Dependent. Only the Philippine Macaque is listed under CITES Appendix II.
Several tracts and fecal matters of Philippine warty pigs were observed in most transect routes used in the avifaunal survey. Snares and traps intended for this animal were likewise encountered validating its presence in three of the four study sites. In one makeshift hut encountered along a transect route, several jaws of wild pig was noted along with a couple of bills of hornbills.
A Common Palm Civet was captured by one of the field guides whose residence was located at the edge of a regeneration area near his farm. Local residents usually capture this animal because it destroys livestock particularly chicken.
Philippine Flying Lemur was observed in one study site. The animal was observed at dusk in a small open area close to a secondary forest. Dried skin of monkey was also noted in one makeshift hut in the same spot, which was according to local key informants would be used as bait for wild pig hunting.
Philippine Field Rat was observed in 3 study sites. Trapping success however was considered low even in areas adjacent to active cultivation. Key informants attributed this low abundance of rats to the presence of a good number of predators in the area particularly the Philippine cobra and raptors.
Table 7. Partial list of mammalian species recorded in Bulosao Watershed Forest Reserve, Lawaan, Eastern Samar, c. 2003.(See table)
Table 8. Consrvation status of mammalian species recorede in Bulosao Watershed Forest Reserve, Lawaan, Eastern Samar, c. 2003.(See table)
Other mammals recorded were based on ethnobiological account. The presence of other mammalian species cannot be strongly ascertained because of insufficient evidence.
A total of six species of amphibians belonging to three families were observed in the four study sites in Bulosao Watershed Forest Reserve (Table 8). Of these, five were encountered during field observation and only one was discerned from ethnobiological interviews. Of the six species, two are introduced (Bufo marinus and Rana erythraea) and the rest are native. All the three species of Ranids are associated to bodies of water. The Common Tree Frog (Polypedatus leucomystax) occupies a wide variety of habitats from open areas near cultivation to forest interior. The Giant American Toad (Bufo marinus) is a cosmopolitan species and oftentimes seen in agricultural and other disturbed areas.
Of the 11 reptiles belonging to seven families recorded from the different study sites, nine were encountered during field observations while the rest were discerned from ethnobiological interviews (Table 9). Of these, five (45%) are endemic to the Philippines with only one endemic to the greater Mindanao faunal region.
The Malayan Freshwater Turtle is associated to bodies of water from highly disturbed areas near cultivation to the forest interior. All the species of geckos and lizards were seen in or close to human dwellings. One species of skinks is common in coconut plantations and other one is common secondary and primary forest.
Reticulated Python is found in a variety of habitats. During the conduct of faunal survey, a juvenile individual was observed in the possession of a local resident. The local residents confirmed the presence of two species of cobra in the area. This was primarily the reason why the observers were not able to find the roosting place of giant fruit bats in the area, which according key informants, are abundant in one specific location in the area. Local guides and key informants refused to accompany the observers to these roasting sites for fear of encountering cobras. The Samar Cobra is a subspecies of the Philippine Cobra endemic to the place and the greater Mindanao faunal region (Alcala, 1986).
The presence of Monitor Lizard in the area was manifested by the skin of the animal chanced upon by the observers in a makeshift hut in one of the study sites. Key informants revealed that the skin would be used as bait in hunting wild pig. The Sailfin Water Lizard was captured alive in one of the study sites near a creek.
Table 9. Partial list of herpetofaunal species recorded in Bulosao Watershed Forest reserve, Lawaan, Eastern Samar, c. 2003. (See table)
In Bulosao Watershed Forest Reserve, the most serious threat to wildlife is hunting. Wildlife is not just hunted for subsistence but also for commercial use. The primary target species are the big games particularly wild pig and deer because of their large amount of meat per catch and the associated high price if traded commercially. The population of deer however has declined tremendously in recent years according to local informants, so that most commercial hunters in the area focus only in the pursuit of wild pig. With the changing trend from subsistence to commercial hunting in wild pig, sophistication in hunting techniques has also improved to increase catch per hunting effort.
During most desperate hunting trips, monkeys are hunted just to compensate time and effort used in hunting. Other mammals like Palm Civet and Malay Civet are hunted occasionally to prevent crop and livestock depredation.
Birds are not just hunted for food but also sold live as pet in the market. Most preferred bird for hunting is the Jungle Fowl (Gallus gallus) followed by the doves and pigeons owing to their large meat. Key informants revealed that a good number of local hunters possessed air rifle for hunting birds. Most preferred birds collected for pet trade are Colasisi (Loriculus philippensis) and Blue-naped Parrot (Tanygnathus lucionensis). Several individuals of White-eared Brown Fruit Dove (Phapitreron leucotis) were observed in the possession of local residents. These will be used as live lure in hunting the same species.
Among herpetofaunal species, only the Monitor Lizard is considered by the local people as an important hunting target for its meat and skin. Another economically important reptile is the Sailfin Water Lizard, which is hunted for its meat. Occasionally, local residents are able to catch Reticulated Python for its meat. Local people are not mindful about the amphibians probably because edible frogs are still abundant in the locality.
Habitat alteration is another threat to wildlife in Bulosao Watershed Forest Reserve. The conversion of forest to agricultural cultivation through slash-and -burn and illegal logging operations are serious threats to wildlife. Aside from lumber, local residents are also extracting timber to be made into boat keels, which is indirectly associated to the fishing industry in Lawaan and adjoining municipalities. Clearing of forests to some extent may be beneficial to wildlife because of increased habitat diversity and complexity. However if the trend continues, forests may be decimated to the disadvantage of those highly sensitive interior species of wildlife, which are mostly affected by the habitat transformation.
Of 668 bird species in the Philippines, 41 are recorder in Bulosao Watershed Forest Reserve. These species belong to 12 orders, 25 families and 35 genera. The most represented order is Passeriformes with 18 species belonging to 13 families. The second most represented order is Columbiformes with 8 species belonging to two families. Columbidae and Pycnonotidae is the most represented family.
Of the 41 avian species recorded in the Reserve, twenty-nine percent are endemic to the Philippines. Only one is endemic to Samar and the rest of Greater Mindanao faunal region.
Twenty species of birds are included in the IUCN Red List Category. Of these, 16 are considered near Threatened, 2 Vulnerable, 1 Lower risk and 1 Endangered. Under CITES, 4 were listed in Appendix II and 1 in Appendix I. The Birdlife and Haribon Foundation recognized 1 as threatened, 1 restricted and 1 threatened and restricted to Samar only.
A total of 11 mammals are recorded in the reserve. These belong to 6 orders and nine families. Of these 11 mammals, sixty-four percent are endemic to the Philippines of which 3 are endemic to the greater Mindanao faunal region.
Three species of mammals are considered Vulnerable and one Conservation Dependent under the IUCN. Only one is listed under CITES Appendix II.
A total of six species of amphibians belonging to three families were observed in the Reserve. Of these, two are introduced and the rest are native. Of the 11 reptiles belonging to seven families recorded from the reserve, forty-five percent are endemic to the Philippines with only 1is endemic to the greater Mindanao faunal region. Monitor Lizard is the only species of herpetofauna that is listed in CITES II.
The most serious threat to wildlife in the reserve is hunting for both subsistence and commercial purposes. With increasing trend of hunting towards commercial purposes, increased sophistication of hunting techniques for the most sought game, the wild pig, is becoming more evident in the area. The possession of air rifle of many villagers in the area also poses great threat to bird population particularly the doves and pigeons, the favorite hunting target bird species. Aside fro hunting for meat, collection of birds for the pet trade is also becoming evident.
Habitat alteration brought about by conversion of forests to agricultural cultivation through slashes and burn cultivation, continued illegal logging activities and indiscriminate collection of non-timber products in the reserve are also great threat to wildlife.
Considering the magnitude of the present and foreseeable disturbances in the reserve, there is therefore an urgent need to implement some conservation measures. Such conservation measures must integrate economical viable and socially acceptable livelihood alternatives for the local communities in order to lessen their dependence on the resources of the reserve.
Ecological studies on threatened fauna must be carried out before any conservation measures are effectively implemented. More intensive faunal survey must be done to fully account for other important species that might not have been covered by the present faunal inventory.
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