8 Dec 2017

Clones vs drones: Tahiti battles nine invasive species to save iconic bird

Pounced on by rats, attacked by Myna birds and devoured by killer clone ants: it sounds like a horror film, but this year the Tahiti Monarch of French Polynesia has reached record numbers thanks to the herculean efforts of conservationists and volunteers, supported by new technology.

Drones from local company Matarai were used to combat invasive ants © Alice Bousseyroux
Drones from local company Matarai were used to combat invasive ants © Alice Bousseyroux
By Jessica Law

When its recovery program started in 1998, conservationists were only able to locate 12 Tahiti Monarch Pomarea nigra individuals. We already know that invasive species are a huge problem for island birds, but on its home island of Tahiti, the Monarch was cursed with not one, but nine invasive menaces, all ranked among the 100 most invasive species on the planet.

Against such staggering odds, some conservationists might have declared the beleaguered passerine a lost cause: with the population so low, and the predators so unmanageable, they might have argued that the cost of saving it was too high.

But luckily, Tahiti didn’t desert this beautiful and treasured bird, and their story is one of hope and triumph, with the heroic Tahiti Monarch snatching victory from the (sometimes literal!) jaws of defeat.


This year, Tahiti Monarch populations have reached record numbers © Caroline Blanvillan


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Rogue’s Gallery


First, to understand the scale of the achievement, we need to see what the Monarchs had to contend with:

Black rats Rattus rattus scuttled up from the ground to guzzle the eggs and chicks, sometimes even ambushing the adult females, who stay in the nest overnight.

Common Myna birds Acridotheres tristis, native to India, descended from the skies to fight the adults and eat the chicks, mobbing the nests in groups of up to five.

Cats took advantage of the Tahiti Monarch’s naïve behavior, the result of having lived on an island without predators for more than a million years.

Red-vented Bubuls Pycnonotus cafer aggressively competed with the monarchs for territory and food, ganging up on lone adults and post-fledgling chicks with fatal results.

Swamp harriers Circus approximans were, ironically, thought to have been introduced by the German Consul in 1885 to reduce the rats. But, like the nursery rhyme of the old woman who swallowed a fly, they only succeeded in making matters worse, with no effect whatsoever on rat populations.


Attack of the clones


And as if the horror couldn’t get any worse, Little Fire Ants Wasmannia auropunctata have recently started encroaching upon the borders of Monarch territories. This ant establishes giant colonies of thousands of queens that clone themeselves and advance their battalions by 50-100 metres a year. Three giant colonies covering 50 hectares of land have been detected since 2014, spanninng two of the three Tahiti monarch’s valley entrances. This new exotic species competes for food, predates the bird’s nests and, worryingly, loves to live in trees.

And the threats don’t just come from animals. The Miconia (Miconia calvescens), with its garish violet leaves, now covers 75% of Tahiti Forest, irrevocably changing the landscape. Not to mention goats, pigs and other invasive plants, all of which impoverish the Monarch’s habitat.

The list seems too long for the Tahiti Monarch to overcome. However, thanks to the intervention of SOP Manu (BirdLife in French Polynesia), together with funding from both local and worldwide charities and government*, not to mention the heroic efforts of hundreds of volunteers, the population is now recovering and increasing continuously from year to year.


Clones vs drones


The conservation project is, understandably, time consuming and challenging, but those involved are already beginning to see the rewards of their efforts. One Little Fire Ant colony has already been expunged, and two more have been fiercely forced back with the help of more than 130 land owners and the use of an exciting new technology.


A drone being prepared for its mission © Alice Bousseyroux


Drones provided by local company Matarai were deployed to drop specially-developed ant bait onto Little Fire Ant infestations in inaccessible areas. These included 300-metre high cliffs and forest canopies bordering the Monarch territories. So far, this new technique has made a significant dent in Little Fire Ant numbers. And if its success continues, drones could provide important new ammunition against Little Fire Ant invasions across the whole Pacific.


Don’t look down!


SOP Manu staff scale the cliffs in search of ant colonies © Michoud Shmidt


Before the use of drones, SOP Manu staff were forced to abseil down sheer precipices in their attempts to eradicate the ants. Te Maru Ata valley, with its vertical and inaccessible cliff faces, is a particular stronghold of the Tahiti Monarch due to its inaccessibility to rats. SOP Manu Conservation Projects Manager Caroline Blanvillain gives her account of the hair-raising experience:

“For our field work in Te Maru Ata, we were obliged to climb five waterfalls of 10-20 meters. First you’re afraid: you can feel the adrenaline coursing through your veins. Then you become an addict: you’re looking for the adrenaline!

But the cliffs in Te Maru Ata are nothing compared to the waterfall at the valley bottom, which is 300 meters high! As goats may be dislodging rocks onto you from above, it is too dangerous to go through the entire cliff. We just stayed at the entrance, at our own risk and peril.”


Just another day in the office for Caroline Blanvillan © S Ricatte


But it’s not just fire ants that are feeling the burn. Mynah birds have been eliminated from the Tahiti Monarch’s range thanks to four years of trapping by volunteers, and rats are now under strict control. Hundreds of gardeners are waging war against the invasive vegetation to improve Monarch habitats.


Back from the dead


As a result, the Tahiti Monarch is truly back from the dead, reproducing rapidly and ready to colonise new areas. It’s had its ups and downs, with five young disappearing last year under mysterious circumstances. But during the last breeding season, a record 21 fledglings were produced, and at the beginning of 2017 around 70 adults were spotted in Tahiti valleys. This is a fantastic achievement, given that until recently, the entire population was only producing 2-7 chicks a year.

Since the number of breeding pairs is only 14, for the moment the species remains critically endangered on the IUCN Red List. But the Tahiti Monarch is a fighter, and the end of the tunnel is not far off for this species - even if its survival on Tahiti will require long-term conservation action.


A new hope


To secure the Tahiti Monarch’s safety in the long term, SOP Manu plans to establish the species on an island free from introduced predators. Great care needs to be taken in selecting a suitable location, and ensuring that the Monarch population on Tahiti is large enough to source the birds from. The hope is that eco-tourism will also help to sustain the protection of the Tahiti Monarch’s population, spreading their incredible story even further.

This work has been brought to you by the BirdLife Preventing Extinctions Programme.

*Pest control was funded by:

  • European Union voluntary scheme for Biodiversity and Ecosystem Services in EU Outermost Regions and Overseas Countries and Territories (BEST 2.0)
  • Government (DIREN: Environment Directorate of [the French Overseas Territory of] French Polynesia; and DRRT: Regional Delegation for Research and Technology
  • BirdLife International
  • Local sponsors (Punaauia District, EDT, OPT, YUNE TUNE and Vini).
  • Eight anonymous donors who adopted a bird