Tetiaroa Habitat Restoration Program

The Tetiaroa Society Conservation and Sustainable Use Plan (CASUP) envisages an atoll where the motu habitat has been restored to as close to its original native form as possible. To that end, the removal of invasive species and restoration of native species is a priority for Tetiaroa Society. The Tetiaroa Habitat Restoration Project (HRP) focuses on the most significant invasive species on the atoll: the ship rat and the Polynesian rat. These rats severely reduced the native bird population of Tetiaroa and threaten the nesting bird populations we now have on “Bird Island” and our other motu where rats have not yet successfully invaded. With both species of rat successfully removed, Tetiaroa would become a major sanctuary for not just birds but also other native fauna and flora. This would open the potential for transplanting very rare and threatened species from the small remaining populations elsewhere in FP to Teitaroa.

Endangered local birds

Tuamotu sandpiper

Blue lorikeet

Tuamotu warbler

Atoll fruit dove

Rat Eradication and its Consequences

As has been seen on many other islands, rat removal has a huge positive effect on native flora and fauna (see PNAS paper), and indeed the entire ecosystem including the marine environment and coral reefs (see Chagos paper). The most immediate effect of eliminating rats on Tetiaroa would be to stop predation on the nesting bird populations. Cautious planning is necessary however, to assess any unintended consequences. Predicting the precise ecological impact of species removal is a complex scientific challenge (see Tetiaroa IDEA and Research Programs). The removal of rats on Palmyra, for example, had the unexpected, but also positive, effect of causing the extinction of a species of mosquito (see Palmyra Paper). The increase in bird populations has knock on effects also, for example, through the increased nutrients brought to the island by seabirds. The effects from this will cascade down through plant, invertebrate, soil, and marine community ecology. Studies in Chagos have shown these effects can benefit coral reefs. Tetiaroa Society scientists are actively collaborating with the teams who worked in both the Palmyra and Chagos cases, and there is excitement to test hypotheses generated in those archipelagos on Tetiaroa. To summarize, the removal of rats very likely has some effect on virtually every species on the island in both terrestrial and marine environments, and the HRP would be designed in collaboration with the research community (led by Tetiaroa Societies Scientific Advisory Board) to leverage this conservation action to learn as much as possible about tropical ecosystem functioning.

Invasive Invertebrates

In parallel to the main focus on rats, other invasive species would also be targeted for eradication. These would include: (i) two species of mosquitoes (a significant nuisance for humans and potential disease vector for all terrestrial vertebrates on Tetiaroa), (ii) one species of biting flies (nonos), (iii) two species of invasive ants (which are major ecosystem engineers like rats). Removal of these species would both make the motu much more comfortable for visitors and move the motu ecosystem a long way towards a “natural” state.

Invasive Plants

The third major component of the HBR would be to follow recommendation from the Flora and Vegetation chapter of the CASUP and work on removing some percentage of the coconut palms that are in unnaturally dense stands due to the farming of coconuts from the 1930s to 1966. This would allow for other native trees and plants to repopulate the motu. Experiments on the removal of coconut palms need to be carried out and monitored to see how best to restore native motu forest.

Program Plan

The Habitat Restoration Plan has three phases which are informed from previous work on the atoll over the past decade, including the preliminary baseline studies across the atoll (e.g., vegetation plots, fish counts, reef monitoring stations). Phase 1 is already underway and covers Motu Reiono, Phase 2 would cover work on Motu Rimatuu and result in rat eradication on the Southern Motu, and Phase 3 would cover all of the Northern Motu.

Phase 1: Reiono – Cost $140K

This Phase is already underway and resulted from a study that was commissioned by Island Conservation (USA), University of Auckland, and Royal Society for Protection of Birds (RSPB). It is being conducted in collaboration with, and is partly subsidized by Tetiaroa Society. The project, which was headed up by Dr. Araceli Samaniego from the University of Auckland was described as follows:

Managing invasive rats at Tetiaroa
Eradications of invasive rodents from tropical islands have a lower success rate compared to temperate islands. Understanding why is essential to improve our methods and hence increase the chance of eradication success. Tetiaroa is a great site to conduct research as there are two rodent invasive species present, several islands with different habitats, all three main groups of land crabs, low human disturbance, and the Ecostation. The main questions are 1) Do all rodents eat bait at the same rate regardless their age, reproductive condition and habitat? 2) Do reproductive females behave or eat differently than non-reproductive individuals? 3) Where do rats nest when the ground is dominated by land crabs? 4) Can we deter crabs from eating bait? Results will inform the eradication plan for the whole Tetiaroa Atoll, as well as rodent eradication and biosecurity strategies for larger tropical islands.

The original study informs questions that have come up from other failed rat eradications around the Pacific (Palmyra, Henderson, Wake and Kamaka). A set of experiments was begun on Reiono and Rimatuu in November of 2017 with the intention of finishing with final experiments by December 2018.

The research group originally concluded that, pending funding, there would be an attempt to eradicate rats on both motu using the information garnered during the study. The group could already fund eradication on Reiono, as part of their experiments, with in-kind and field support from TS. Attempts at that time to secure additional external funding to eradicate rats on Rimatuu was unsuccessful and so the program carried on with an eradication attempted only on Reiono in August 2018. As of mid-September all signs point to a successful eradication on Reiono with no rats seen moving by researchers or remote cameras since August 25th.

Phase 2: Rimatuu – Cost $350K

Following the eradication program on Reiono the next step will be to carry out a full ground-based restoration plan on Motu Rimatuu. This would consist of the following:

• Conduct detailed baseline studies of bird populations, plant distribution and phenology, insect populations, terrestrial crabs, marine nutrients, fish populations, marine invertebrates, and soil nutrients.
• Map out the motu vegetation types, bird communities, turtle nesting sites.
• Set up coconut palm removal experiment to see effects of rat removal on native tree populations.
• Hire Island Conservation to eradicate rats on the motu at a cost of approximately $250K. Planning and experimentation before eradication would take one to two years.
• Monitor bird populations, plant distribution and phenology, insect populations, terrestrial crabs, marine nutrients, fish populations, marine invertebrates, and soil nutrients.
• Continue with best practices (according to conclusions of experiments) to reduce coconut palm density and restore native forest.
• Once it is established that all rats have been eradicated, consider re-introduction of endangered native plants and bird species.

Successful implementation of this Phase would secure the southern motu as a rat-free zone and protect the birds already nesting on Motu Tahuna Iti (Bird Island) and Rahi. Because Motu Rimatuu has a representative version of every motu habitat, the planning and experimentation done there will be sufficient for future work on the Northern motu.

This Phase would also be the time to test new technologies that would increase efficiency and decrease costs of future eradications here and elsewhere. This includes the use of drones in delivering poison bait.

Phase 3 – Cost $1.1m

The Northern motu (from Honuea in the West to Horoatera in the East) need to be worked on simultaneously because of the short distances between them allowing rats to migrate regularly among them (Tetiaroa rat genetics study). Therefore, all of them need to be done at once. The program would be similar to that carried out on Rimatuu with the exception that less preparation and planning would be needed, as requisite baseline studies will have already taken place in Phase 1 and 2.

• Coordinate studies of bird populations, plant distribution and phenology, insect populations, terrestrial crabs, marine nutrients, fish populations, marine invertebrates, and soil nutrients.
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• Compare and contrast motu according to size, vegetation type, bird communities, turtle nesting sites.
• Set up coconut palm removal experiment on one or more motu to see effects of rat removal on native tree populations.
• Hire Island Conservation to eradicate rats across the atoll at a cost of approximately $600K.
• Monitor bird populations, plant distribution and phenology, insect populations, terrestrial crabs, marine nutrients, fish populations, marine invertebrates, and soil nutrients.
• Continue with best practices (according to conclusions of experiments) to reduce coconut palm density and restore native forest.
• Once it is established that rats have been eradicated, re-introduce endangered native plants and bird species.

Work underway

Phase 1: Reiono

The Phase 1 experiments and attempt at eradication on Motu Reiono will be finished by December 2018. A final report on that project will be prepared shortly after.

The Experiment Workshop

Tetiaroa Society (through its SAB) will organize a workshop in late Oct/Nov 2018 to develop a detailed experimental design (THE Experiment), validate monitoring protocols, and review other scientific aspects of the Habitat Restoration Program. In addition, the workshop will identify funding sources (agencies in USA, France, UK, and New Zealand) and prepare
proposals for scientific research that would expand the core activities described for each Phase.

Nono Project

Herve Bossin has secured funding for an international team to work on Culicoides belkini (nonos). There will be a survey in 2019 with testing of suppression techniques at the end of the year.

New Technologies

Discussions in New Zealand are underway with Yamaha and other companies to consider new drone technologies to deliver rat poison. Yamaha is testing its Fazer remote helicopter to determine payload levels and bait delivery. If successfully implemented in phase 2, these technologies could reduce costs in phase 3.

Funding

The Habitat Restoration Program has been designated as the highest priority CASUP program. In August 2018 Tetiaroa Society has already raised $61,000 from donors. Much of this is unrestricted and can be used to begin Phase 2. It might also be used to generate matching funds from foundations and other funding agencies.