Philippine Turtle Islands


Using satellite telemetry, this site tracks the green turtles of the Turtle Islands at the border of Sabah, Malaysia and Tawi-Tawi, Philippines. The tracking results tell some very interesting stories about these endangered species'  time around the islands and their migration.

The Turtle Islands are the first trans-frontier protected area for sea turtles in the world and Southeast Asia's single most important green turtle conservation area

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Turtle Islands, Tawi-Tawi, is located at the southwestern tip of the Philippines, about 1,000 km southwest of Manila, the country's capital. This municipality is right on the edge of the international treaty limits separating the Philippines and Malaysia. The group of islands, namely, Boan, Lihiman, Langaan, Great Bakkungan, Taganak, and Baguan, is situated south of Palawan, northwest of the Tawi-Tawi mainland and northeast of Sabah, Malaysia. The location of the six islands is approximately defined by the intersection of 6o 10' N latitude and 118o 10' E longitude.

Philippine Turtle Islands (WWF-Philippines, 1990) (click map to enlarge)

Geo-physical Features

The islands have an aggregate land area of 308 hectares. The smallest island, Langaan, measures about 7 hectares, while the largest, Taganak, is about 116 hectares.

The islands are mostly tadpole-shaped and elongated along the northeast-southwest direction, with the highest portion in the northeast. This orientation follows the submerged Cagayan "Mapun" ridge, which is also elongated along the northeast-southwest direction and runs parallel to Palawan Island and the Sulu archipelago. The ridge was submerged to its present level as water levels rose during the last 15,000 years.

Taganak, the largest island, has the highest point of land, which is approximately 148 meters above sea level. Langaan, the smallest island, is relatively flat and nested on an extensive coral reef platform. Except for Langaan, the terrain of the islands is generally undulating to rolling, particularly at the northern end. A unique feature is the presence of "mud volcanoes," the most prominent of which is on Lihiman, where violent mud extrusions have formed a 20-meter crater on the hill at the northeast portion. Mud extrusions or volcanoes are also present on Bakkungan and Boan.

Five of the six islands have permanent residents, and on them the land cover in large areas is dominated by houses. Typical of other rural areas in the Philippines, human settlements are mixed with agriculture. The relative dominance of the settlements is mainly due to the limited land area and the resulting high population density level, which is more than four times the national average (see Socio-Economic Profile). Natural land cover types are classified as wooded, mangrove, brush/shrub, grass and bare. Most of the areas used for agriculture are planted with coconut.

The islands are experiencing the effects of active geomorphological processes, both short-term, seasonal and long-term movements. These processes have resulted in changes in shoreline configuration and a certain degree of erosion. The effects of sea level rise on the islands have not been adequately evaluated, though studies indicate they could range widely from minimal to catastrophic.

Table 1. Summary of the Physical Characteristic of the Islands of the Turtle Islands Group (Bate, 1998)

Length of
Type of Beach and Length (meters)
Basalt and coralline sand
Sandstone, mud and coralline sand
Mud and coralline sand
Mud and coralline sand
Coralline sand
Basalt and coralline sand

Table 2. Summary of Physical Characteristics (Bate, 1998)

geomorph- ological
Groundwater Availability
Taganak Moderately steep to rolling, with very limited coastal flat lands Volcanic, fringed by beach alluvial deposit of sand and coralline rubble. Red clay soil covers the volcanic rock Soil erosion and shoreline retreat at the western side Shallow groundwater in sand and weathered portion of volcanic rocks
Boan Flatland with low undulating hills at the northern part Sandstone, mud and coralline sand Accretion of coralline rubble at the northeastern part, where the mangroves are. Beach erosion at the southern part . Diapiric extrusion dormant Shallow groundwater available in the sandy flatlands
Bakkungan Flatland and undulating to rolling hills at the northern end Mud coralline sand Active diapiric intrusion. Beach erosion at the southeastern beach Shallow groundwater in the flatlands
Lihiman Flatland and rolling hills at the northern end Mud coralline sand Active (violent) diapiric intrusion. Baech erosion at the eastern side Shallow groundwater in the flatland
Langaan Flat coralline island Coralline sand Coralline sand Beach erosion at the western side and accretion on the eastern side Shallow groundwater in the coralline sand
Baguan Flatland with moderately steep volcanic hills Volcanic rocks and coralline sand Beach erosion at the southern end and deposition at the eastern side and western corners Shallow groundwater in the coralline sand

Climate and Temperature

The northeast and southwest monsoons prevail from November to March and from June to September, respectively, governing the climate of the Turtle Islands. The North Pacific Trades dominate during the transition between the two monsoons.

Meteorological data from Cagayan de Tawi-Tawi show that the wettest period in the southwestern Sulu Sea is during the transition season (October and November), while data from Sandakan indicate that high rainfall occurs during the early part of the northeast monsoon (December and January). Although meager, rainfall data gathered from Baguan show that the island has more or less the same rainfall pattern as Sandakan, with the highest rainfall recorded during the months of December and January.

The Turtle Islands are typified by warm and humid conditions. Data from the Sandakan weather station (1956-1957) indicate a mean minimum temperature range from 22.06oC to 23.69oC and a mean maximum temperature range from 28.95oC to 32.87oC. The diurnal temperature is about 7o C. Relative humidity averages 70 % because of the high temperature, high rate of evaporation, and heavy rainfall.

Monthly rainfall data collected by the Sandakan station for a period of 52 years (1905-1957) show an annual average of 3138.93 mm of rain. The annual average rainfall from the Cagayan de Tawi-Tawi station is 2,286.2 mm.

Plant Life

Marine Flora . Typical of low-island flora, the Turtle Islands marine macrobenthic flora (large, bottom-dwelling plants) is characterized by low species diversity. The populations are sparsely distributed on the fringing reef and do not form apparent or distinct communities. According to a 1998 report by Filipino seaweed expert Dr. Gavino Trono, algae (seaweeds) grow among the piles of dead coral branches, on dead portions of coral heads and mixed with seagrasses, which form very thin stands on sandy bottoms near the shore. Of the 62 species found in the area, 27 are members of the Chlorophyta (green algae), 22 are Rhodophyta (red algae) and six Phaeophyta (brown algae). The Turtle Islands' flora represents only a little more than one-third of that found at Santiago Island in Bolinao, Pangasinan, which supports 170 species.

The seagrass community at the Turtle Islands is represented mainly by pioneer species such as Halophila ovalis, Cymodocea rotundata, Halodule pinifolia, H. uninervis and Syringodium isoetifolium. These species colonize small sandy patches near the shore. Intermixed with the seagrasses are some seaweed populations such as Halimeda macroloba, Udotea geppii and Caulerpa serrulata.

The seaweed and seagrass populations of the islands appear to be at their seral stages of development. This is shown by the presence of pioneer and ephemeral or opportunistic species. Almost all species have some known economic value. Only those food species, when developed, are likely to be of immediate economic benefit to the local populations, however. These include Caulerpa racemosa, C. lentillifera, Gracilaria eucheumoides, Halymenia durvillaei, Gelidiella acerosa and Kappaphycus alvarezii. G. acerosa is a known agar source, while K. alvarezii is a carrageenan source. These last two species are important raw materials for making gel-like desserts. G. acerosa, in particular, appears to have some commercial applications, but it does not seem to occur in the area abundantly enough for commercial harvest and utilization.

Terrestrial flora. Typical of most disturbed low-lying small island ecosystems, the terrestrial flora of the Turtle Islands group is a mosaic of remnants of sea coast or strand vegetation and ornamental and weed species attendant to agricultural and human settlement areas.

The vegetation of the islands is typically of limited growth, development and complexity, which is mainly a function of relatively recent geologic age and, more importantly, anthropogenic influence. Typical beach vegetation forms a narrow strip of woodland along the sandy and gravelly shores of the seacoast, gradually giving way to other types of forest formation depending on topography, size of the island and other factors. The principal woody species that occur in the Philippines in general and the Turtle Islands group in particular are Terminalia catappa, Desmodium umbellatum, Pandanus tectorius, Premna serratifolia, P. obtusifolia, Erythrina variegata, Barringtonia asiatica, Thespesia populnea, Hibiscus tiliaceus, Sterculia ceramica, Callphyllum inophyllum, Guettarda speciosa, Xylocarpus moluccensis, Pongamia pinnata and Scaevola frutescens.

Succession may be in more advanced stages in areas that are less influenced by human activity, such as slopes, enclosed area and the sanctuary, as well as in islands with larger areas. This is shown by the presence of pioneering tree species like Macaranga tanarius.

Agricultural crops, ornamental plants and associated weeds in human settlements comprise 60% of the plant species identified in all the islands. It is common practice for residents to propagate plants introduced from outside the Turtle Islands.

Most species are widely distributed and no local endemic species have been observed.

Animal Life

Marine fauna. The benthic communities of the Turtle Islands, especially on the north and northeast coasts of the islands, are of the fringing reef type, well-developed and in relatively good condition. Although the area experiences appreciable terrigenous run-off from Sabah, the islands have a fair hard coral cover (28-46%) and high coral diversity (24-27 genera).

Growth forms are mostly non-Acropora branched corals, which indicates that the reef slope has relatively calm conditions and has adapted to silt run-off. Great Bakkungan and some parts of Baguan have abundant branching Acropora, mostly A. bruegemanni in the former, and more silt-resistant species (e.g., A. echinata) in the latter. The other parts of Baguan, as well as Langaan, have more massive or dome-shaped corals. This indicates that the coral communities correspond with a gradient from offshore (clear, wave-exposed) to inshore (silted, wave-sheltered), complicated by depth and aspect. Comparison of the results of a survey conducted in 1998 indicates that the presence of Acropora corals is much higher at Baguan in the northeastern and northern side, where the fringing reef is widest, while the other sites have higher cover of corals other than the Acroporaspp. There is no obvious difference in total hard coral cover among the sites, however.

Also noticeable is the higher algal cover in sites outside Baguan. Control of fishing activities and destructive fishing methods (such as dynamite and cyanide) around the Baguan Island Marine Turtle Sanctuary may have allowed for higher biomass of grazing or herbivorous fishes, which has controlled algal abundance.

The 1998 survey also recorded a total of 7,342 individual reef fishes representing 155 species and 25 families at Baguan; the other islands were found to have lower diversity and biomass. All told, 232 reef fish species in 33 families were observed in the entire Turtle Islands area.

The diversity in coral genera and high percentage of cover of branched live corals contribute to the high fish species diversity in the Turtle Islands. The reef fish assemblages are dominated by Pomacentridae (damselfishes) and Labridae (wrasses), with 44 and 45 species, respectively. The fishes of these families are generally characterized as small in size but often colorful and usually found hovering in large aggregations over reef slopes or at the bottom of the reef. The most common fish species in the area are Pomacentrus alexanderae, Chromis ternatensis and Pomacentrus smithi (damselfishes). The most common of the economically important species are Caesio pisang and Pterocaesio chrysozona (both species are commonly known as fusilier, or "dalagang bukid" in the local dialect). These fishes are mostly planktivores.

Terrestrial fauna. The terrestrial vertebrate fauna of the Philippine Turtle Islands is predominantly composed of avian species. Thirty-four avian species have been observed to occur in the entire Turtle Islands. Of this number, 30 species have been observed on Taganak, Langaan, Lihiman, Great Bakkungan and Boan. Baguan has four species not found on the other islands; these are the Lesser Frigatebird (Fregata ariel), Common Sandpiper (Actitis hypoleucos), Grey Imperial Pigeon (Ducula pickeringii), and the Chestnut-cheeked Starling (Sturnus philippensis). Nine species found on the other islands, on the other hand, have not been recorded on Baguan; these include the Spotted Dove (Streptopelia chinenis), Island Collared Dove or Philippine Turtle Dove (Streptopelia bitorquata), Greater Coucal (Centropus sinensis), Pied Triller (Lalage nigra), Yellow-vented Bulbul (Pycnonotus goiavier), Yellow-breasted Wren-warbler (Gerygone sulphurea), Pied Fantail (Rhipidura javanica), Chestnut Munia (Lonchura malacca), and White-breasted Wood-swallow (Artamus leuccorhyncus).

The species composition of the Philippine Turtle Islands is very similar to that of the Turtle Islands Park of Sabah, but species diversity in the Philippine Turtle Islands is relatively lower. None of the birds identified is endemic to the Philippines.

The only native terrestrial mammalian species observed on the islands is the large fruit bat, Pteropus hypomelanus, and the only other non-domesticated species found is the field rat, Rattus argentiventer. Residents of Taganak Island report a high incidence of rats in their homes, although the species has yet to be confirmed. Common domesticated mammals found on the islands include dogs (Canis familiaris), cats (Felis catus domesticus), cattle (Bos indicus), and goats (Capra aegagrus).

The islands are known primarily as a nesting area for sea turtles (Chelonia mydas and Eretmochelys imbricata). The other most common reptilian species seen in the area is the monitor lizard, Varanus salvator. The blue-tailed skink, Emoia caeruleocauda, is also often observed, especially on Great Bakkungan and Boan. The Mabuya sp. is also quite common on all the islands.

The Malay box turtle, Cyclemys dentata, has apparently been introduced on Great Bakkungan (the species is not seen on the other islands or even the Turtle Islands Park of Sabah). Sea snakes (Lauticauda colubrina) and terrestrail snakes (Dendrolaphis caudolineatus) are also encountered.

Socio-economic Profile

As of 1995, the population of the five permanently inhabited islands on the Philippine side of the Turtle Islands was 2,644 representing 424 households. With a total land area of only 308 hectares, the islands have a population density of 858 persons per sq km, way above the average national density of 202 persons per sq km. Although the population growth rate of 0.44% is much lower than the national average of 2.4% and the regional average of 2.2%, in-migration is alarmingly high. Almost 36.8% of the population migrated into these islands during just the last 10 years (PCP, 1995 [census and registration of the residents of the proposed protected area]). The high rate of in-migration coupled with the very limited land area suggests that the carrying capacity of the islands may be exceeded. Most of the newly settled migrants come from within the region (Mindanao). Economic opportunities in Sabah, Malaysia have made the Turtle Islands an attractive transient point for these migrants.

Over time, the migration pattern in the Turtle Islands has changed in its ethnic composition. During the 1970s and 1980s, the islands were dominated by the Jama Mapun, a subgroup of Samals who are associated with Cagayan de Tawi-Tawi. By the 1990's, the Tausug constituted a greater proportion of the population (50%). The Jama Mapun today is reduced to a minority (45% of the population). The remaining 5% is made up of other tribes and in-migrants from Luzon, Visayas and Mindanao.

Like the Sama Badjao and the Yakan, the Jama Mapun are peace-loving, docile, conventional and orthodox compared to their Tausug counterparts, who are reputed to be more aggressive, enterprising, adventurous and inclined to take risks. Consequently, the Jama Mapun are more involved in farming and traditional fishing and the collection of turtle eggs while the Tausug are more adept in trade and other non-traditional economic activities like buying of permits from authorized egg collectors.

The islands' population is dominated by males who comprise 54% of the population. The male to female ratio is 119:100, which is much higher than the national ratio of 102 males to 100 females. Fifty-one percent of the population is under 15 years old.

Almost 65% of the residents live below the national poverty level, which is set at P92,500 (USD2,310) per year. The majority of the local work force is under-employed or unemployed. The local economy is highly dependent on the marine resources for subsistence, with most produce marketed in nearby Sabah, Malaysia. Almost 61% of the total number of families own motorized or non-motorized boats used for fishing. Although 54% of the families engage in some form of farming, agriculture is relatively underdeveloped because of poor soil quality and the limited arable land available. Coconut is the traditional agricultural product, but it is no longer economically viable because coconut trees on the islands which have become unproductive are not being replaced. All basic commodities -- including rice, the staple food -- are purchased from Sandakan, Malaysia.

The regulated collection of turtle eggs is an important and traditional source of livelihood for the residents. A few traders who can enter Sabah sell turtle eggs in Sandakan. These traders market basic commodities from Sandakan to the islands and make a lucrative income from the trade. Most of these traders own small stores from which residents can buy their basic needs. For this reason, the Malaysian Ringgit is the favored tender over the Philippine Peso. Also, Sabah, Malaysia is looked upon as the main source of employment. The municipality is thus unable to generate sufficient revenues to support even basic services; it is classified as a sixth class municipality, the lowest classification in terms of municipal income level.

Access Routes

Access to the Turtle Islands is difficult. There is no regular means of transportation to the area, though six access routes are available:

a. Manila - Zamboanga City - Mapun Municipality - Taganak Route. A one and one-half hour flight or two days sea travel from Manila to Zamboanga City and a 25-30 hour sea journey to the Municipality of Mapun. From Mapun, a motor launch can be chartered for Php 6,000.00. This leg normally takes about 8-11 hours.

b. Manila - Zamboanga City - Bongao, Tawi-Tawi - Taganak Route. A one and one-half hour flight or two days sea journey from Manila to Zamboanga City. From Zamboanga, one can take a one hour flight or 18 hours sea journey to Bongao, Tawi-Tawi. A motor launch can be hired from Bongao to Taganak Island and this normally takes 10 hours.

c. Manila - Turtle Islands Route. One can hitch a ride on a fishing boat from Navotas, Metro Manila to the company's fishing ground at the Turtle Islands. From the fishing grounds, a motor launch can be chartered to reach Taganak Island. The availability of transportation depends on the fishing operations of the company in the area.

d. Manila - Zamboanga City - Sandakan, Sabah - Taganak Route. Plane or sea journey from Manila to Zamboanga City. From Zamboanga, one takes a scheduled ferry to Sandakan, Sabah. For ASEAN nationals, a two-week visa is issued at the port of entry; regular visas are required for other nationalities. From Sandakan, one can hire a speedboat to reach Taganak.

e. Manila - Kota Kinabalu - Sandakan - Taganak Route. By air from Manila to Sabah and by land or air to Sandakan. From Sandakan, hire a speedboat to Taganak Island.

f. Manila - Brooke's Point (Palawan) - Mapun Municipality - Taganak Route. By air or sea to Puerto Princesa City, Palawan and overland to Brooke's Point. A passenger vessel is taken to reach Mapun Municipality. A motor launch is chartered to reach Taganak Island.


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