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In January 2009, the Western Pacific Regional Fisheries Management Council contracted the Secretariat of the Pacific Regional Environment Programme to conduct an on-the-ground survey of leatherback turtle nesting beaches on Bougainville Island. The main leatherback turtle nesting beaches are located in the west and south-west areas of Bougainville Island where much of the topography is dominated by rugged mountains, with human populations concentrated on the coastal plains. In the south of Bougainville Island, most villages are located inland. Population densities for these areas range from 10-18 people/km2 (Bourke & Betitis 2003).

The survey covered six days from the 19-26 January 2009. The total trip length was 565 km, with 389 km surveyed by running parallel to the beach in a 23 ft fiberglass dinghy at a distance of 20-50 m at a speed of 8-15 km/h, depending on sea conditions. Of this 389 km, 38 km was surveyed physically by walking the beaches, of this 38 km, 28 km was walked during the daytime, and 10 km was walked during night surveys (the distance is actually 20 km in total, because the return leg was over the same distance). Areas that were walked were those previously highlighted by the 2007 aerial survey, as were areas where nesting was observed from the dinghy.

When nests were observed from the dinghy, the survey team disembarked into the open sea and waded to shore to begin recording and walking the beaches to determine if there were other nests in the vicinity. Local inhabitants were also asked about recent nesting locations, and on occasion acted as guides. All nests were recorded using a Garmin GPSmap 60CSx. Coordinates were also recorded on paper as backup. The daily routes the dingy followed were recorded, as well as the routes of the day and night beach walk surveys. All data were later downloaded and converted to ArcGIS shape file format with DNR Garmin (Minnesota Department of Natural Resources, USA). The data were then cleaned, coordinates converted from decimal degrees, the GPS native format, to degrees, minutes, and seconds. Photographs were also taken at each nest site and recorded as an attribute of each site.

During the survey, consultation was also conducted with local inhabitants, when they were encountered out fishing, or in beach camps or in more formal community meetings. These consultations were used to collect information on the level of consumptive use, any general information about the status of leatherback turtles in their area, as well as any traditional knowledge and management regimes. All surveys, interviews and community consultations were conducted in ‘pidgin,’ as this is the lingua franca used by Bougainvilleans (the lead author is proficient in ‘pidgin’).

A total of 46 leatherback nests and one false crawl were recorded during the survey, with the highest concentration of leatherback nesting located along a 5.4 km stretch between the hamlets of Papona and Naboi on the central west coast. Nineteen nests and one false crawl were recorded in this area. It was later reported that five additional leatherbacks nested in this section of beach in the week following (K. Anana, pers. comm.). This small stretch of beach accounted for approximately 43 % of all leatherback turtle nesting activity observed on Bougainville Island during the survey. The second area of concentrated leatherback turtle nesting (n = 13) were the beaches south of Mamerego Point, covering an area of 34.7 km. Leatherback turtles nesting in other areas were sparse and sporadic, due in part to unsuitable beach or offshore morphology.

Figure 1. Aerial survey sites, 2005-2007.

During the 2005 and 2006 aerial surveys, most leatherback nests were observed on the southeastern and northwestern coasts of Bougainville Island. The January 2005 aerial survey data (Benson 2006) indicate that Bougainville beaches accounted for about 14% (41/284) of leatherback turtle nesting activity in PNG for this year. However, in contrast, during the 2007 aerial survey, Bougainville accounted for 41% (57/140) of all nests recorded for PNG. Thus, leatherback turtle nesting on Bougainville Island represents a significant but variable proportion of total nesting activity during the austral summer. When the results of the aerial survey and the recent survey are compared, there is consistency in locations of primary nesting activity (Figures 1 and 2).

Figure 2. January 2009 survey sites.

Predators upon leatherback eggs include monitor lizards (Varanus indicus), local dogs (Canis familiaris) and ghost crabs (Ocypode cordimanus). Dogs were regularly observed on beaches, particularly in fishing camps during the survey. One fatal attack by a saltwater crocodile (Crocodylus porosus) on a leatherback was reported on Duse Beach, southwest Bougainville, in 1999. Of the 46 leatherback nests recorded during the survey, 26 definitely had eggs removed, while another 12 were presumed to have had their eggs taken, making a total of 83% of all nests harvested for eggs. On one occasion, a group of fishermen were encountered who had just harvested a leatherback nest that morning. These fishermen had removed 107 eggs, and rejected 21 eggs because they were malformed and yolkless.

Surveys and interviews with local inhabitants suggest that leatherback turtles are taken relatively frequently by communities on Bougainville Island in the past. During our consultations, we heard that a total of 21 leatherbacks were taken for food in the last decade, in those areas where consultations occurred. On two occasions, sites where leatherbacks had been killed the previous year were shown. Perceptions of abundance amongst villagers varied, but the consensus was that leatherback turtle numbers had declined within the last 30-50 years. Reasons for the decrease were unanimously given as wide-scale egg take and the killing of adult nesting leatherback females.

During consultations, the leatherback turtle was claimed as a totem animal only by one clan in the northwest of Bougainville, and this prohibited clan members from consuming leatherback turtle meat and eggs. Interestingly, one group of inland (‘bush’) people at Duse claimed that their clan’s historic arrival from the Solomon Islands was done by using the upturned carapaces of leatherbacks as canoes. Despite this ancestral support, there are no prohibitions on consuming leatherback turtle meat or eggs.

Local knowledge with regards to leatherback nesting was reported to peak during the Christmas period, with hatchlings observed around Easter. Leatherbacks were also reported to nest during stormy periods (“when there is lightning, there will be leatherback turtles coming up”), and also when a local pigeon (Ducula spp.) is heard; this pigeon nests in shoreline vegetation during the Christmas period.

The beaches on Bougainville Island are subject to seasonal or storm-related erosion and accretion. Severe beach erosion was observed during our survey around Bougainville Island. Problems of beach erosion were reported to have begun in the 1960s, with increasing acceleration since the 1980s (Bourke & Betitis 2003). Several leatherback turtle nests were reported lost at Papona in 2008 during especially high tides and wave action.

While it has not been empirically linked to increased mortality of PNG leatherback turtles, longline fishing in the Pacific Ocean has been documented as a large threat to multiple stocks of leatherback turtles in the northern and southern Pacific oceans (Spotila et al. 2000). Previous consultation with both the Secretariat of the Pacific Community and PNG’s National Fisheries Authority has shown no records of leatherback turtle interaction with tuna fishing vessels in PNG’s Exclusive Economic Zone (Kinch 2006). While fishing is carried out by local fishermen around Bougainville Island, this is mainly done by handline from small dugout canoes, or by beach gillnets. We heard no reports of leatherback turtles being caught in local fishing gear.

Traditionally, ‘chiefs’ in the ARB would implement bans or ‘tambu’ on the harvesting of certain resources for a certain period of time. This was observed as a recent activity at Koiari Village (near Papona and Naboi hamlets), whereby villagers had been prohibited from harvesting shellfish from the river and the beaches. In general though, there does not appear to be any great concern over the fate of the leatherback turtle in Bougainville, despite that people were well aware that they were, in part, the ‘agents’ of their decline. There are, however, some local initiatives that do show some conservation concern.

For example, the Catholic Priest at Koiari Village has told local villagers and their neighbors, that when they take leatherback eggs from a nest, they should leave some in the nest, so as to replenish the population. While this may be considered a conservation measure, it is ineffective in the overall recovery of leatherback populations for this area, as most villagers only returned a few eggs to the nest, from which hatching and successful emergence is unlikely. One ‘rule of thumb’ is that at least 75% of all eggs must remain in situ on a nesting beach to produce enough hatchlings to keep a sustainable adult population returning (C. Limpus, pers. comm.).

At Mamorego Village, the Chief has placed a ban on killing leatherback turtles for the last five years. This ban was violated in 2007, when a man killed a leatherback, and was subsequently fined PGK 100 (approximately USD $30). The harvesting of leatherback turtle eggs has also been banned, though the harvesting of eggs from other sea turtle species is permitted.

Whilst at Orava Village, the local Chief has also declared a ‘tambu’ on the taking of leatherback turtles. This village is uniformly Seventh Day Adventist in religious affiliation, and is thus restricted from consuming any creature that lives in the water and does not have fins and scales (see Leviticus 11: 9-12).

Apart from Mamerego Village, there was no awareness of any government legislation protecting leatherback turtles. In PNG, the leatherback turtle is the only sea turtle that is considered a protected animal under the 1976 Fauna (Protection and Control) Act. The 1976 Fauna (Protection and Control) Act also provides for the establishment of protected areas. A Wildlife Management Area (WMA) provides a mechanism for local control of fauna on land and in waters held under customary tenure, and has been the most common form of area-based conservation in PNG to date. Currently, the only protected area in the ARB is the Pirung WMA (declared in 1989), located along the east-central coast and encompassing an area of some 43,200 ha. This WMA was established essentially to limit access by outsiders who do not have customary use-or-access rights to the area.

It is apparent that leatherbacks populations in the ARB are under severe pressure, which has implications for leatherback nesting numbers in Morobe Province, and possibly also the Solomon islands, given the presumed shared leatherback stocks throughout this area, and the excessive egg take and the killing of nesting leatherbacks that is occurring. The combined data from 2005-2009 confirm that leatherback nesting occurs regularly at ARB, and the total number of nests may represent a substantial portion of the austral summer nesting activity in the Western Pacific.

Acknowledgements: The authors acknowledge the support of the Western Pacific Regional Fisheries Management Council for funding the on- the-ground survey (Contract No: 08-WPC-017), and the NOAA Pacific Islands Regional Office for funding the aerial surveys. We also thank Asuka Ishizaki, Karin Forney and Jeffrey Seminoff for comments on an earlier draft. In PNG, the authors would also like to express gratitude to Jinro Boisen, Robin, Francis, Pias, Jonathan, Aloysius, Geraldine Paul and their families; and finally, David Melick and Vagi Rei. We also thank the pilots of North Coast Airlines and aerial observer teams for their skill and contributions to the aerial surveys.

BENSON, S. R. 2006. Preliminary report on aerial surveys of leatherback turtle nesting beaches in Papua New Guinea during January 2005. Unpublished Report submitted to the Pacific Islands Regional Office, Honolulu, Hawaii.

BENSON, S.R., K.M. KISOKAU, L. AMBIO, V. REI, P.H. DUTTON & D. PARKER. 2007. Beach use, inter-nesting movement, and migration of leatherback turtles, Dermochelys coriacea, nesting on the north coast of Papua New Guinea. Chelonian Conservation & Biology 6: 7-14.

BOURKE, R. & T. BETITIS. 2003. Sustainability of agriculture in Bougainville Province, Papua New Guinea. Australian National University, Canberra. <http://rspas.anu.edu.au/papers/lmg/SustainAg_Bvill_text.pdf>

DUTTON, P.H., C. HITIPEUW, M. ZEIN, S.R. BENSON, G. PETRO, J. PITA, V. REI, L. AMBIO & J. BAKARBESSY. 2007. Status and genetic structure of nesting populations of leatherback turtles (Dermochelys coriacea) in the Western Pacific. Chelonian Conservation & Biology 6: 47-53.

KINCH, J.P. 2006. A socio-economic assessment of the Huon Coast leatherback turtle nesting beach projects (Labu Tale, Busama, Lababia and Paiawa), Morobe Province, Papua New Guinea. Western Pacific Regional Fisheries Management Council, Honolulu. <http://www.wpcouncil.org/protected/Documents/Kinch%20report_final.pdf>

SPOTILA, J.R., R.D. REINA, A.C. STEYERMARK, P.T. PLOTKIN & F.V. PALADINO. 2000. Pacific leatherback turtles face extinction. Nature 405: 529-530.