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GCCA & SUPA Newsletter Quarter 4, October-December 2022 : Pacific Impacts Analysis (IA) Methodology

SPREP Publications, Climate Change Resilience, PCCP

Available Online

Lasting impressions this quarter were about reflecting on our expectations a year ago and lessons gained since then. Thirty nationals from ten countries have since met to share practical experiences and insight on topical matters centred on tracking impact of adaptation in the Pacific.

GCCA & SUPA Newsletter Quarter 3, July-September : Pacific Impacts Analysis (IA) Methodology

SPREP Publications, Climate Change Resilience, PCCP

Available Online

This past quarter, with the practiced confidence from the field trial of the tailored impact analysis methodology for adaptation in the Pacific, has been all about connecting with others and sharing ideas through communications.

GCCA & SUPA Newsletter Quarter 2, April-June : Impact Methodology

SPREP Publications, Climate Change Resilience, PCCP

Available Online

Segment one of April focused on freshwater security in atolls with case example of Nukuoro atoll, Pohnpei in the Federated States of Micronesia.

GCCA & SUPA Newsletter Quarter 1, Jan-March : Impact Methodology

SPREP Publications, Climate Change Resilience, PCCP

Available Online

This yer kickstarted with assembling field results from the four countries participating in this trial application of draft impact analysis methodology. To tells stories with data on residual impacts of climate change adaptation interventions unique or similar type to another island setting were shared during the 1-2 March review workshop.

On the verge of a biological crisis: the state of invasive species in the Pacific

Island and Ocean Ecosystems, BRB

Available Online

Cas Vanderwoude

A report prepared by the Invasive Partnership for the Pacific Islands Forum Leaders Meeting, Palau July 2014 as requested by the Micronesian Chief Executives in Resolution 19-01

Multi island, multi invasive species eradication in French Polynesia demonstrates economies of scale

Available Online

Coulston, G.

Cranwell, S.

Derand, D.

Ghestemme, T.

Griffiths, R.

Hall, T.

Pott, M.

Will, D.

Zito, J.

Eradication of invasive vertebrates on islands has proven to be one of the most effective returns on investment for biodiversity conservation. To recover populations of the critically endangered Polynesian ground dove (Gallicolumba erythroptera), the endangered white-throated storm-petrel (Nesofregetta fuliginosa), the endangered Tuamotu sandpiper (Prosobonia cancellata) as well as other native plant and animal species, a project was undertaken to eradicate five species of invasive alien vertebrates: Pacific rat (Rattus exulans), ship rat (R. rattus), feral cat (Felis catus), rabbit (Oryctolagus cuniculus) and goat (Capra hircus), on six islands spanning 320 km of open ocean in the Tuamotu and Gambier Archipelagos of French Polynesia. Using a ship to deliver supplies and equipment, a helicopter for offloading and bait application, and ground teams for follow up trapping and hunting, invasive vertebrates were successfully removed from five of the six islands. Pacific rats survived at one site. The project was planned and executed by a partnership consisting of international and local conservation NGOs, working together with local communities. Combining the different eradication operations into one expedition added complexity to project planning and implementation and increased the risk of the operation failing on any one island but generated greater returns on investment allowing six islands to be targeted at significantly less cost than if each island had been completed individually. An extensive and thorough planning effort, effective relationships with local stakeholders and communities, a good operational strategy and a partnership of stakeholders that each brought complementary capacities to the project contributed to its success.

Rat eradication in the Pitcairn Islands, South Pacific: a 25-year perspective

Island and Ocean Ecosystems, BRB

Available Online

Brooke, M.de L.

This essay offers a 25-year overview of eff orts to remove Pacific rats (Rattus exulans) from the four islands of the Pitcairn group. Following the 19911992 discovery that rats were severely reducing breeding success of gadfly petrels (Pterodroma spp.), Wildlife Management International proposed eradication. Eradication success was achieved using ground-based baiting on the small atolls of Ducie and Oeno in 1997, and there is now evidence of petrel recovery on Oeno, but two eradication attempts on inhabited Pitcairn (1997 and 1998) failed. By the early 2000s, the development of aerial baiting through the 1990s placed an eradication operation on the fourth island, Henderson, within reach. Preparatory fieldwork in 2009 allayed doubts in two key areas: the feasibility of maintaining a captive back-stop Henderson rail (Porzana atra) population, and bait uptake by crabs (Coenobita spp.). Royal Society for the Protection of Birds (RSPB) expertise secured the necessary funding of £1.5 million, and 75 tonnes of brodifacoum-containing bait were dropped in August 2011. Despite extensive mortality of free-living rails, the population, supplemented by released captive birds, returned to pre-operational levels in 23 years. Meanwhile those tending captive rails saw no rat sign before leaving Henderson in November 2011. Unfortunately, a rat was sighted in March 2012, and continuing rat presence confirmed in May 2012. Subsequently rat numbers have returned to pre-operational levels without any sign of population overshoot as observed on Pitcairn. Genetic analysis suggests around 80 rats, roughly 1 in 1,000, survived the bait drop. With no evidence of imperfect bait coverage or deficiencies in bait quality or brodifacoum resistance, it seems some animals chose not to eat bait. Choice tests on Henderson Island rats suggest some rats prefer natural foods over bait. This adverse situation may have been exacerbated because, in August 2011, natural fruits were more abundant than anticipated due to drought earlier in the year. To overcome rat preference for natural food, any second Henderson attempt might benefit from more attractive bait. Without such developments, a second attempt risks another failure. Hendersons biota will survive the delay.

Seasonal variation in movements and survival of invasive Pacific rats on sub-tropical Henderson Island: implications for eradication.

Island and Ocean Ecosystems, BRB

Available Online

Bond, A.L.

Churchyard, T.

Donaldson, A.

Duffield, N.

Havery, S.

Kelly, J.

Lavers, J.L.

McClelland, J.T.W.

Oppel, S.

Proud, T.

Russell, J.C.

Invasive rodents are successful colonists of many ecosystems around the world, and can have very flexible foraging behaviours that lead to differences in spatial ranges and seasonal demography among individuals and islands. Understanding such spatial and temporal information is critical to plan rodent eradication operations, and a detailed examination of an islands rat population can expand our knowledge about possible variation in behaviour and demography of invasive rats in general. Here we investigated the movements and survival of Pacific rats (Rattus exulans) over five months on sub-tropical Henderson Island in the South Pacific Ocean four years after a failed eradication operation. We estimated movement distances, home range sizes and monthly survival using a spatially-explicit Cormack-Jolly-Seber model and examined how movement and survival varied over time. We captured and marked 810 rats and found a median maximum distance between capture locations of 39 ± 25 m (0107 m) in a coastal coconut grove and 61 ± 127 m (01,023 m) on the inland coral plateau. Estimated home range radii of Pacific rats on the coral plateau varied between territorial (median: 134 m; 95% credible interval 106165 m) and roaming rats (median: 778 m; 2901,633 m). The proportion of rats belonging to the roaming movement type varied from 1% in early June to 23% in October. There was no evidence to suggest that rats on Henderson in 2015 had home ranges that would limit their ability to encounter bait, making it unlikely that limited movement contributed to the eradication failure if the pattern we found in 2015 is consistent across years. We found a temporal pattern in monthly survival probability, with monthly survival probabilities of 0.352 (0.0810.737) in late July and 0.950 (0.8460.987) in late August. If seasonal variation in survival probability is indicative of resource limitations and consistent across years, an eradication operation in late July would likely have the greatest probability of success.

Bait colour and moisture do not affect bait acceptance by introduced Pacific rats (Rattus exulans) at Henderson Island, Pitcairn Islands.

Island and Ocean Ecosystems, BRB

Available Online

Bond, A.L.

McClelland, G.T.W.

OKeefe, S.

Warren, P.

Rodent eradications are a useful tool for the restoration of native biodiversity on islands, but occasionally these operations incur non-target mortality. Changes in cereal bait colour could potentially mitigate these impacts but must not compromise the eradication operation. Changing bait colour may reduce mortality of Henderson crakes (Zapornia atra), an endemic globally threatened flightless bird on Henderson Island, Pitcairn Islands, South Pacific Ocean. Crakes had high non-target mortality in a failed 2011 rat eradication operation and consumed fewer blue than green cereal pellets. We examined which cereal bait properties influenced its acceptance by captive Pacific rats (Rattus exulans) on Henderson Island. We held 82 Pacific rats from Henderson Island in captivity and provided them with non-toxic cereal bait pellets of varying properties (blue or green, moist or dry). We estimated the proportion of rats consuming bait using logistic generalised linear mixed models. We found no effect of sex, females reproductive status, bait colour or bait moisture on rats willingness to consume baits. Rats bait consumption was unaffected by cereal bait properties (colour or moisture). The use of blue bait is unlikely to affect future eradication operational success but may reduce non-target mortality of Henderson crakes. Timing cereal bait distribution in relation to precipitation may also reduce crake mortality without compromising palatability to rats.

Recovery of introduced Pacific rats following a failed eradication attempt on subtropical Henderson Island, South Pacific Ocean

Island and Ocean Ecosystems, BRB

Available Online

Bond, A.L.

Churchyard, T.

Cuthbert, R.J.

Duffi eld, N.

Havery, S.

Kelly, J.

Lavers, J.L.

McClelland, G.T.W.

Oppel S.

Proud, T.

Torr, N.

Vickery, J.A.

Rodent eradications in tropical environments are often more challenging and less successful than those in temperate environments. Reduced seasonality and the lack of a defined annual resource pulse influence rodent population dynamics differently than the well-defined annual cycles on temperate islands, so an understanding of rodent ecology and population dynamics is important to maximise the chances of eradication success in the tropics. Here, we report on the recovery of a Pacific rat (Rattus exulans) population on Henderson Island, South Pacific Ocean, following a failed eradication operation in 2011. We assessed changes in the rat population using capture rates from snap-trapping and investigated seasonality by using capture rates from live-trapping. Following the failed eradication operation in 2011, rat populations increased rapidly with annual per capita growth rates, r, of 0.485.95, increasing from 6080 individuals to two-thirds of the pre-eradication abundance within two years, before decreasing (r = -0.25 -0.20), presumably as the population fluctuated around its carrying capacity. The long-term changes in rat abundance may, however, be confounded by short-term fluctuations: four years after the eradication attempt we observed significant variation in rat trapping rates among months on the plateau, ranging from 36.6 rats per 100 corrected trap-nights in mid-June to 12.6 in late August. Based on mark-recapture, we also estimated rat density fluctuations in the embayment forest between 20.4 and 42.9 rats ha-1 within one month in 2015, and a much lower rat density on the coral plateau fluctuating between 0.76 and 6.08 rats ha-1 in the span of two months. The causes for the short-term density fluctuations are poorly understood, but as eradication operations on tropical and subtropical islands become more frequent, it will be increasingly important to understand the behaviour and ecology of the invasive species targeted to identify times that maximise eradication success.

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