Reducing the rat threat to island birds

Abstract

SummaryInvasions of alien mammals, particularly predators such as rats Rattus spp., have been a major cause of the disproportionately high number of extinctions of island birds. This paper outlines how introduced rodents affect these birds, describes administrative, management and scientific measures which should be taken to prevent the spread of these mammals to additional islands and to limit their impact, and provides practical information about how to control or eradicate the rodents. We use examples from New Zealand's experiences with islands and rats to illustrate the problems and solutions. The information and recommendations in the paper are directed particularly towards legislators, administrators and managers all over the world who are responsible for the conservation of island faunas. The paper gives examples of rat-free islands deserving the highest level of protection, and a step-by-step checklist for action to minimize the risks of rodent invasion.

Biology and Impacts of Pacific Island Invasive Species. 11.Rattus rattus,the Black Rat (Rodentia: Muridae)

“…One notable exception is islands and areas that have never had rats or have eradicated rats and maintained biosecurity measures to prevent reestablishment. Formal regulations against R. rattus transport and establishment are lacking for most Pacific islands (Moors et al 1992). However, the International Health Regulations of 1969 states that all ships containing overseas goods must have a certificate stating that their vessel is maintained as rodent-free or is "periodically deratted"; certificates are issued by the health authority at approved ports and they are valid for 6 months ( World Health Organization 1995).…”

Population monitoring for the flightless rail Dryolimnas cuvieri aldabranus

“…Rats are present on both main subislands (Malabar and Polymnie) and, whilst they are responsible for considerable mortality of the endemic giant tortoise Geochelone gigantea and of passerine species (Prys-Jones 1979, Piys-Jones and Diamond 1984), they have apparently not yet prevented the rail from breeding successfully. However, there are no records to indicate the population density or nesting success the rail reached before rats were introduced, and it should be noted that predation impact may vary greatly between rat populations on nearby islands (MacFarland et al 1974, Moors et al 1992.…”

Rodent control and island conservation.

“…Such devices need to detect rodents at low densities and research has demonstrated that systems involving a combination of measures give the best results (Russell and MacKay, 2005). Many of New Zealand's off-shore islands now have permanent rodent invasion surveillance systems installed on them but these are regularly checked because dispersal of invasive rats happens rapidly (Moors et al, 1992). Current best practice suggests that checking should be undertaken at least every six months, as invading rats can establish a large population in less than a year after arrival (Russell et al, 2008a).…”