Tag Archives: French Polynesia

Coral-destroying starfish research

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This video from Oman says about itself:

The crown of thorns starfish (Acanthaster planci ) [is] one of the oceans’ most efficient coral predators. They can grow to more than 1 m in diameter; have 16 to 18 arms, the entire upper surface of its body covered in long venomous spines. This species was recorded in our … survey at Musandam peninsula.

From Wildlife Extra:

Reef devastation caused [by] Crown-of-thorns outbreaks still a mystery to researchers

Researchers tackle the coral-killing starfish

February 2013. Crown-of-thorns Acanthaster planci is the principle natural enemy of reef-building corals. Outbreaks of this coral-feeding starfish occur periodically, due to reasons that remain unclear. It decimates entire reefs in the space of just a few years, as has been the case in French Polynesia since 2004. A new study conducted by IRD researchers and their partners describes this population explosion around Moorea, the “sister island of Tahiti“. The rate of living coral cover in ocean depths and lagoons alike dropped from 50% (healthy reef) to under 5% in 2009. The ecosystem will need at least a decade to be restored to its original state.

The starfish has spread from island to island

The archipelago has been suffering from a new population explosion of the predatory starfish since 2004. It is one of the most intense and devastating outbreaks ever recorded. The outbreak of Acanthaster began in a very specific location in the Austral and Leeward Islands, then in 2006, the starfish colony spread to Tahiti and Moorea. Thanks to a dozen stations around the island of Moorea, scientists were able to make spatio-temporal observations of the dynamics of the infestation of coral populations. Thus, in a new study published in PLoS One, they described the spread of the coral reef invasion.

Ocean depths and lagoons alike

The starfish first settled in the deeper areas along the outer slopes of the reef, around 20 to 30 metres below the ocean surface. It then rose to a depth of approximately 6 metres, and even colonised certain parts of the lagoon. The damage was gradually observed: from 47% of living coral cover at one of the stations in 2006, for example, this rate dropped to 21% in 2007, 6% in 2008 and 2% in 2009: a disastrous state of affairs that disrupts the structure and functioning of all reef communities (including other coral-feeding species, such as butterflyfish, etc.).

The causes remain unclear – High rainfall is an indicator

What are the reasons behind outbreaks of Acanthaster planci? In Australia, where the pest is also rife, invasions occur after years with high rainfall. Rainfall leads to the excess release of nutrients from human activities and the proliferation of algae on which echinoderm larvae feed. In Polynesia, however, anthropic pressure seems too low and localised to explain such an outbreak of the starfish. The current lack of data on the subject means the phenomenon remains a mystery.

Since the causes of outbreaks remain unclear, there is limited ability to fight against Acanthaster planci in order to protect economic activities around the coral barrier, such as tourism and diving. Researchers are currently studying processes to “recruit” new corals, in other words to repopulate the reef and make it more resilient. Without a new widespread disturbance, a coral ecosystem would need 10 to 30 years to be restored to its original state.

One of the greatest mysteries of modern coral reefs is how they evolved from ancient corals. A critical knowledge gap has long existed in the record of coral evolution. This evolutionary gap occurs during a period of dramatic fluctuations in sea level and changes in the Earth’s climate between 1 and 2 million years ago. During this period many “old” corals went extinct, and the modern reef corals emerged. To fill this key temporal gap and understand the evolutionary and ecological transition to modern Caribbean reefs, the U.S. National Science Foundation (NSF) has funded a University of Miami (UM) project to study corals along the southern coast of the Dominican Republic. It is one of the few areas that contain a record of coral reefs from this period of climatic change: here.

Study finds starfish shed arms to protect against overheating: here.

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Beaked whales of Samoa

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This video says about itself:

Underwater footage of a unique encounter with a Blainville’s beaked whale in French Polynesia. Marine Mammal Study Group (www.gemmpacific.org)

From the New York Times in the USA:

Where the Beaked Whales Are

By SCOTT BAKER

Scott Baker, associate director of the Marine Mammal Institute at Oregon State University, writes from Samoa, where he studies the formation of local communities among dolphins and their genetic isolation from one another.

Wednesday, Aug. 15

I often think that finding a needle in a haystack would be relatively comfortable work compared with finding dolphins in offshore waters. If the dolphins do not approach the boat to ride the bow, the only sighting cue is the dorsal fin or the occasional leap. Add wind, waves and sun glare to create discomfort as well as tedium. Even when you find the dolphins, it is easy to lose them in the waves and whitecaps. It can be frustrating work, but interrupted with moments of excitement and the occasional discovery.

Today, we surveyed the offshore waters along the northwestern tip of Savai’i hoping to find rough-toothed dolphins. Previous studies in Hawaii and the Society Islands (French Polynesia) have found that this species prefers waters of 3,000 to 6,000 feet in depth. To improve our chances, we planned a series of surveys crossing this depth a few miles offshore of Asau, where we had anchored for the night. Although the morning began with calm seas, the wind and swell increased by late morning and the conditions for sighting the dolphins deteriorated. By early afternoon we had abandoned our survey track and were headed back to shore, feeling a little discouraged.

Then our luck changed. Just as I started down the ladder from the flying bridge to the deck, I thought I saw a blow.

As I called out to the others, the animal surfaced again and I could see it was too large for a dolphin. Before we had time to grab our cameras, the whale leapt fully into the air and dived. It was a beaked whale, one of the most elusive and poorly understood mammal groups. More than 20 species are currently described in the Ziphiidae family, some of which have never been seen alive. Beaked whales are primarily deep-diving species, spending much of their lives at great depths in pursuit of squid, their main prey. I have worked for many years on the molecular identification of beaked whales using DNA extracted from bones in museums, but this was my first encounter with a living beaked whale. It was over in an instant.

I knew that it was unlikely we would see the whale again, given the nearly hourlong dives that are common with these species. I quickly sketched what I saw on the back of our sighting form and showed it to Renee, Nevé and Titi. We all agreed that whale was about 20 feet long and robust in girth. The back of the whale was dark, and appeared brown in color. As it leapt, I thought I saw the characteristic “tusks” of a mature male – actually two teeth that erupt from the lower jaw. Beaked whale species are difficult to identify at sea, but it is likely that this was a Cuvier’s beaked whale, one of the most widely distributed members of this family. A biopsy sample would have allowed us to confirm the species identification, but collecting a sample was not possible in these conditions.

Encouraged by this sighting, we continued our offshore track despite the conditions. Remarkably, over the next hour we found a small but uncooperative pod of rough-toothed dolphins and sighted another beaked whale. This time, we had our cameras ready but got only a glimpse of the whale’s back before it dived. Based on the location and time, we think it unlikely that this was the same individual that we had seen an hour earlier.

Back at anchor in Asau, the winds abated and we enjoyed a few of the pleasures of work in Samoa. First, a swim in the warm lagoon with the glow of sunset for a backdrop. Then the melodies of the local musicians playing in the small resort where we anchored. Finally, the intense black night and bright starlight of the South Pacific.

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Pacific islands wildlife research

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This video is called Polynesian Ground Dove, Rangiroa, French Polynesia.

From BirdLife:

Biodiversity survey of paradise in the South Pacific

Mon, Aug 6, 2012

Last June, a team of scientists and technicians joined the Ornithological Society of Polynesia-Manu (SOP-Manu – BirdLife in French Polynesia) to survey the flora and fauna of remote atolls in the south-east Tuamotu Archipelago.

Due to the remote location of the sites, the team travelled by sailboat from Rikitea, braving treacherous landings on the reefs surrounding the closed atolls to access the hidden gems of Morane, Vahanga and Tenarunga.

Fred Jacq is the first botanist to set foot on Morane. For him it was an extraordinary experience: “Morane is an exceptional atoll, because it only has a few groves of coconut palms; being spared the large plantations (as seen on most of the other atolls in the Tuamotu Archipelago) has preserved the native flora.” Mr Jacq also took the opportunity to collect insect specimens which will be identified by a specialized entomologist.

Elodie Lagouy, a marine biologist, explored the lagoon environment: “Of the 53 closed atolls in French Polynesia, 14 remained unexplored by science, including Morane. This initial survey revealed 88 species of fish, 24 hard corals, 8 echinoderms, and a variety of molluscs including Giant Clam and wild pearl oysters.”

One of only 2 atolls free of mammalian predators in the Tuamotu Archipelago (the other being Tenararo), Morane is a haven for birds. Marie-Hélène Burle, a PhD candidate from Canada’s Simon Fraser University, is on her third field season studying the Endangered endemic Tuamotu Sandpiper (“titi”) in key areas of its range. With the help of her assistant François Sanz, she has determined that Morane houses the largest known population of Tuamotu Sandpiper, estimating 500 individuals live on the atoll.

Thomas Ghestemme from the SOP-Manu surveyed landbirds, and carefully combed the atoll for the Critically Endangered Polynesian Ground-dove, or “tutururu”: only 2 individuals were observed. Thomas states: “The tutururu’s situation is very worrying, as Morane was thought to hold 50 individuals, or nearly half of the known population. Due to our current findings we have serious concerns for the future of this species.”

“The diversity and abundance of seabirds observed for Morane underlines the importance of predator-free islands as safe nesting and roosting sites” says Steve Cranwell from BirdLife International. Eleven species of seabird were recorded including the largest breeding population of Near-Threatened Murphy’s Petrel (over 1000 pairs) in French Polynesia. In contrast, less than 10 Murphys petrel and a single breeding pair were found on ‘nearby’ Vahanga Atoll a consequence of the introduced Pacific rat.

After three full days of scouring Morane, the team set sail for the Northern Actéon islands of Vahanga, Tenarunga and Tenararo. The abandoned coconut plantation of Vahanga (more accurately known by its Paumotu name of Vaega) was surveyed in preparation for an operation to eradicate rats from the Atoll in 2013. A predator assessment of Tenarunga confirmed feral cats and Black rat, two voracious predators of native wildlife on islands.

Few birds were observed on either atoll, which is consistent for islands with invasive mammalian predators, and the team was understandably surprised to cross paths with a single Polynesian Ground-dove near the village on Tenarunga. A likely migrant from the nearby predator free atoll of Tenararo.

Unfortunately rough weather caught up with the expedition at this point, and due to safety concerns plans to survey the third atoll of Tenararo had to be abandoned. Predator-free Tenararo is one of the last strongholds of both Polynesian Ground-dove and Tuamotu Sandpiper, and is less than 10km from Vahanga. It is hoped that the eradication operation on Vahanga in 2013 will provide a buffer zone of protection for Tenararo, and a dispersal site for its many at-risk avian species.

New insights into the systematics of the enigmatic Polynesian sandpipers Aechmorhynchus parvirostris and Prosobonia leucoptera: here.

Tuamotu sandpiper research and conservation

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Tuamotu Sandpiper, Tenararo Atoll 23/09/2010, © Dave Williamson

From BirdLife:

Titi Forever: Research supports conservation of Tuamotu Sandpiper

Tue, July 31, 2012

Most of the world’s sandpiper species migrate thousands of kilometers between arctic breeding grounds and subtropical wintering grounds, but in the not-too distant evolutionary past, one group gave up this habit and went native in French Polynesia.

The Endangered Tuamotu Sandpiper, Prosobonia cancellata, known locally as the Titi, is the only surviving representative of a group of at least six species which became full time residents in this region. The other species were extirpated with the arrival of first Polynesians, and later Europeans, and their small mammal associates. Approximately 1,000 Titi remain, limited to four rat-free or partially rat-free atolls.

In 2008, Marie-Helene Burle, from Simon Fraser University, aided by the Ornithological Society of French Polynesia (SOP-MANU – BirdLife in French Polynesia), began an intensive graduate research project on this previously unstudied species, working largely in isolation on uninhabited atolls.

Her first five month field season as followed by a second in 2010, and she currently halfway through a lengthy third, which began as she joined a SOP-Manu organized expedition to visit two of the additional three atolls where Titi remain.

Marie and her collaborators have discovered remarkable adaptations of this bird to its tropical lifestyle.

In sharp contrast to similar-sized migrant shorebirds such as Wandering Tattler, which share the same atolls when not breeding, the TIti is not a bird of the beach or rocky intertidal areas, favoring instead semi-open vegetated areas.

“One reason for this is their reliance on feeding on nectar from flowers, a unique food source for a member of this group”, said Marie-Helene Burle. “Functional morphologists have shown that the bird’s tongue is forked, which may allow it to obtain nectar more efficiently”.

Marie captured and marked nearly all of the birds on two atolls, and documented their social system. Breeding birds live in pairs on quite small territories (e.g. 20x30m).

Marie’s work has sparked others to make observations of the species, and Francis Gazeau discovered that TIti sometimes nest in trees as well as on the ground, in contrast to their arctic-breeding relatives. Females lay 2 eggs per clutch, rather than the 4 laid by arctic-breeding sandpipers. Many eggs disappear, at least some taken by coconut crabs, as caught on video.

Marie took the first photographs ever taken of newly hatched chicks, which had never previously been described. Sadly, the chicks have extremely low survival – most starve to death.

“We speculate that overcrowding in the very few areas where the birds can breed has lead to food shortages and low fledging success”, said Marie.

Towards the end of Marie’s second field season, during a very dry season, a wind-driven swell event caused salt water to overwash parts of her atolls. About a month later, she realized that many of her birds were dying, as were other landbirds such as Spotted Crake. She believes that saltwater intrusion and a lack of rain stressed vegetation, resulting in starvation. About half the birds at her main study site died, and a year later, there has not been a rebound of the population.

The high mortality associated with a local swell event highlights the vulnerability of local populations, which would also be threatened should black rats establish themselves on their four remaining refuges.

Marie Helene also helped to eradicate rodents from a small islet within an atoll which holds rats. “We are waiting to learn whether Titi are now breeding on this rat free site”, said Marie. “For the longer term, however, the species’ future relies on reintroducing it to more distant sites where independent populations can thrive”.

Marie and colleagues are preparing a survey of potential reintroduction sites. Their experience working with the birds, and the knowledge they have obtained about their feeding and breeding ecology and predators provide a sound basis for translocation planning. Building on the success of groups that have removed rats from several islands or atolls, we believe that for this one species at least, meaningful conservation measures can be taken at modest additional cost, to substantially decrease the likelihood of its extinction.

“We are hopeful that we will help ensure the presence of Titi forever”, concluded Marie.