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  • Author Asian Development Bank
    X
  • Author Global Environment Facility
    X
Bait colour and moisture do not affect bait acceptance by introduced Pacific rats (Rattus exulans) at Henderson Island, Pitcairn Islands.
Biodiversity Conservation, BRB
Available Online

Bond, A.L.

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McClelland, G.T.W.

,

O’Keefe, S.

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Warren, P.

2019
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
Biodiversity Conservation, BRB
Available Online

Bond, A.L.

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Churchyard, T.

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Cuthbert, R.J.

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Duffi eld, N.

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Havery, S.

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Kelly, J.

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Lavers, J.L.

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McClelland, G.T.W.

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Oppel S.

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Proud, T.

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Torr, N.

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Vickery, J.A.

2019
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 0.48–5.95, increasing from 60–80 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.
A region at risk - The human dimensions of climate change in Asia and the Pacific
Climate Change Resilience, Biodiversity Conservation
Available Online

Asian Development Bank

2017
The Asia and Pacific region is extremely vulnerable to the impacts of climate change. Unabated warming could significantly undo previous achievements of economic development and improvements of living standards. At the same time, the region has both the economic capacity and weight of influence to change the present fossil-fuel based development pathway and curb global emissions. This report sheds light on the regional implications of the latest projections of changes in climate conditions over Asia and the Pacific. The assessment concludes that, even under the Paris consensus scenario in which global warming is limited to 1.5°C to 2°C above preindustrial levels, some of the land area, ecosystems, and socioeconomic sectors will be significantly affected by climate change impacts, to which policy makers and the investment community need to adapt to. However, under a Business-As-Usual (BAU) scenario, which will cause a global mean temperature rise of over 4°C by the end of this century, the possibilities for adaptation are drastically reduced. Among others, climate change impacts such as the deterioration of the Asian “water towers”, prolonged heat waves, coastal sea-level rise and changes in rainfall patterns could disrupt ecosystem services and lead to severe effects on livelihoods which in turn would affect human health, migration dynamics and the potential for conflicts. This assessment also underlines that, for many areas vital to the region’s economy, research on the effects of climate change is still lacking.