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Special Issue Article: Tropical rat eradication. Improving the odds: Assessing bait availability before rodent eradications to aid in selecting bait application rates. Biological Conservation. Volume 185, May 2015

Island and Ocean Ecosystems, BRB

Available Online

Berentsen. A.R

Brooke. M.L

Cuthbert. R.J

Griffiths. R.

Holmes. N.D

Howald. G.R

Pitt. W.C

Pott. M

Ramos-Rend¢n. G

Russell. J.C

Samaniego-Herrera. A

Wegmann. A.S

Rodent eradications undertaken on tropical islands are more likely to fail than eradications undertaken at higher latitudes. We report on 12 independent rodent eradication projects undertaken on tropical islands that utilized the results of an in situ bait availability study prior to eradication to inform, a priori, the bait application rate selected for the eradication. These projects also monitored bait availability during the eradication. The results from our analysis verified the utility of bait availability studies to future rodent eradication campaigns and confirmed the influence of two environmental factors that can affect bait availability over time: precipitation prior to the study and the abundance of land crabs at the study site. Our findings should encourage eradication teams to conduct in-depth assessments of the targeted island prior to project implementation. However, we acknowledge the limitations of such studies (two of the projects we reviewed failed and one removed only one of two rodent species present) and provide guidance on how to interpret the results from a bait availability study in planning an eradication. Study design was inconsistent among the twelve cases we reviewed which limited our analysis. We recommend a more standardized approach for measuring bait availability prior to eradication to provide more robust predictions of the rate at which bait availability will decrease during the eradication and to facilitate future comparisons among projects and islands.

Special Issue Article: Tropical rat eradicationBest practice guidelines for rat eradication on tropical islands. Biological Conservation. Volume 185, May 2015

Island and Ocean Ecosystems, BRB

Available Online

Boudjelas. S

Broome. K

Cranwell. S

Griffiths. R

Keitt. B

Millett. J

Pitt. W

Samaniego-Herrera. A.

Invasive vertebrates are a leading cause of the extinction on islands and rats (Rattus spp.) are one of the most damaging to island ecosystems. Methods to eradicate rates from islands are well established and there have been over 580 successful eradications to date. Increasingly, rat eradications are being implemented on tropical islands, a reflection of the need to protect the threatened biodiversity in the tropics. Yet rat eradications on tropical islands fail more frequently than those in temperate climates. In an effort to identify the main reasons for the lower success rate on tropical islands and possible solutions, a workshop was convened with the 34 experts in rat eradication, tropical rodent and island ecology and toxicology. The workshop focused on projects using aerial broadcast of brodifacoum, a 2nd generation anticoagulant, because this approach had provided the highest success rate for eradicating rodents from islands. The workshop participants reviewed previously identified challenges to successful rat eradications on tropical islands including increased insect and crab densities resulting in competition for bait, year round or unpredictable timing of breeding rats and increased or unpredictable availability of alternative, natural foods. They also identified a number of new, likely reasons for the lower success rate on tropical islands and provided recommendations for how to address these risks in the planning and implementation of rat eradications. While the success rate of aerial broadcast rat eradications in tropical environments is quite high at 89%, it is hoped that by following the recommended best practices provided in this paper, future success rates will be closer to the 96.5% demonstrated for aerial broadcast rat eradication on temperate islands.

Special Issue Article: Tropical rat eradication. The response of black rats (Rattus rattus) to evergreen and seasonally arid habitats: Informing eradication planning on a tropical island. Biological Conservation. Volume 185, May 2015

Island and Ocean Ecosystems, BRB

Available Online

Grant A. Harper

James C. Russell

Martijn van Dinther

Nancy Bunbury

Rat eradications on tropical islands have been less successful than operations in temperate climates. This is likely due to poor understanding of the factors unique to tropical regions that rat populations respond to, such as high numbers of land crabs, aseasonal climates and habitats not found at higher latitudes. On Aldabra Atoll, southern Seychelles, black rats were monitored for one year in three habitats over three climatic seasons to investigate changes in density and breeding to inform planning for a possible rat eradication. Rats bred all year in mangrove forest and in two of three seasons, including the dry season, in Pemphis forest, probably resulting from the saline tolerance of these habitats: lush vegetation and seeds were available there during the dry season. In contrast, rats from the adjacent mixed-scrub habitat only bred in the wet season due to desiccation of vegetation and lack of fresh water during other times of the year. Bait consumption trials showed that all rats ingested dyed bait when applied at 15 kg/ha, despite high rat densities and substantial bait interference by non-target species, but not at an application rate of 10 kg/ha. A novel bola technique was tested for distributing bait into mangrove forest, where aerially applied rat bait would normally be lost due to tidal inundation. The method is likely to improve rat exposure to bait in mangrove forest and other habitats on tropical islands, and warrants further development.

Special Issue Article: Tropical rat eradication. Invasive rat interactions and over-invasion on a coral atoll. Biological Conservation. Volume 185, May 2015

Island and Ocean Ecosystems, BRB

Available Online

Anderson S.H

Caut. S

Lee. M.

Russell. J.C

Invasive rats are found on most island groups of the world, and usually more than one species has invaded. On tropical islands populations of different invasive rat species can co-exist on very small islands, but the population dynamics of such co-existing rat species, their impact on each other, and the mechanisms of coexistence are not well known. This lack of knowledge is a barrier to improving the success rate of tropical island rat eradications. Through an exhaustive trapping eradication campaign on a small tropical island, we study the population structure of historically established Rattus exulans where R. rattus have colonised within the last fifty years and over-invaded. We contrast this R. exulans population with a nearby island population where R. exulans exist alone. Recently invaded R. rattus numerically and morphologically dominate R. exulans; however stable isotope analyses show that the trophic position of R. exulans remains consistent regardless of the presence of R. rattus, once differences in trophic foundations of islands are accounted for. Although the trophic position of both rat species is indistinguishable, R. rattus is able to dominate R. exulans through interference competition. Our eradication attempt was interrupted by a tropical cyclone and ultimately unsuccessful, but there is some evidence that R. rattus reduced control device availability to R. exulans, which has important implications for multi-species control operations.

Special Issue Article: Tropical rat eradication. Trophic roles of black rats and seabird impacts on tropical islands: Mesopredator release or hyperpredation? Biological Conservation. Volume 185, May 2015

Island and Ocean Ecosystems, BRB

Available Online

Le Corre. M.

Ringler. D

Russell. J.C

Rats contribute to the decline of tropical seabird populations by affecting their breeding success through direct predation of eggs and chicks. When they coexist with other predators, invasive rats may also generate indirect interactions via the changes they impose on the structure of communities and trophic interactions following invasion (hyperpredation process), or when apex predators are eradicated from the ecosystem (mesopredator release effect). Understanding these effects is necessary to implement restoration operations that actually benefit threatened seabird populations. We investigated these processes on two French tropical seabird islands of the western Indian Ocean, Europa and Juan de Nova, where black rats coexist with two different apex predator species (introduced cats and potentially native barn owls). The parallel use of several methods (diet analysis, stable isotopes, seabird monitoring) to identify trophic roles of rats revealed that the direct impact of rats on seabirds was particularly high on Europa where only rats and owls occur, with high consumption of chicks resulting in low breeding success for several seabird species. We also suggested that hyperpredation associated with top-down regulation of cats is occurring on Juan de Nova, although territoriality of cats may buffer this process. Conversely we found evidence that mesopredator release effect is unlikely, irrespective of the apex predator identity. Considering the most likely effects on both islands we provided recommendations on eradication priorities to mitigate the risk of local extinction that seabirds are currently facing.

Invasion - Little Fire Ants in Hawaii (video)

Available Online

Maui Invasive Species Committee (MISC)

Stop little fire ants (80 sec video)

Available Online

SPREP

Report on the distribution of the introduced seaweeds (Codium arenicola and Spatoglossum macrodontum) and the distribution and density of the crown of thorns starfish (Acanthaster planci) Reports 1 & 2 in Samoa

Island and Ocean Ecosystems, BRB

Available Online

Division of Environment & Conservation

Marine Conservation Section

Ministry of Natural Resources

An initial survey of the marine environment carried out in 2008 byDr.Posa Skelton and the Marine Conservation Section of the Division of Environment and Conservation, assessed selected sites for the presence of introduced species and the potential impacts on the marine environment. Surveys were conducted around the Apia harbour, Mulinuu and the Palolo Deep Marine Reserve- a total of eleven (11) sites. Findings from this initial assessment confirmed the presence of introduced species that were potentially invasive. This included two introduced seaweeds, Codiumarenicolaand Spatoglossummacroduntum that were observed distributed and well established across these sites.

Island Invasives: Eradication and Management. Proceedings of the Conference on Island Invasives.

Available Online

Cloud, M. N. (ed.)

Towns, D. R. (ed.)

Veitch, C. R. (ed.)

The papers and abstracts published in this book are the outcome of the conference on Island Invasives: Eradication and Management held at Tamaki Campus, University of Auckland, New Zealand from 5 to 12 February 2010, hosted by the Centre for Biodiversity and Biosecurity (University of Auckland and Landcare Research), in collaboration with the IUCN/SSC Invasive Species Specialist Group. This conference had "islands" and "eradication of invasive species" as the focus, with emphasis on the work done and results or learning achieved. The conference endeavoured to cover the full breadth of this work by breaking the subject down to: Gaining political, community, financial, and physical support; Eradication techniques tested and used; The immediate results of eradication operations; The longer-term outcomes as seen in the biota of the island and among communities involved; Biosecurity measure for such islands from planning to implementation.

Alien Invasive Species : Report of Workshop on Alien Invasive Species Global Biodiversity Forum South and Southeast Asia Session

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