Rivers as obstacles to home range expansion by the brushtail possum

Cook, Briar; Wellington, Zero Invasive Predators, Waiapu Road,; Mulgan, Nick; Nathan, Helen

doi:10.20417/nzjecol.45.5

Cited by 5 publications

(4 citation statements)

References 17 publications

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“…It is likely that most, if not all, of the animals detected after TA#2 were resident survivors. Small-scale field trials suggest that rivers may be an obstacle at least to immediate reinvasion by most possums and rats, particularly in non-dispersal periods (Cook et al 2021;ZIP 2019b). In contrast, rats detected on cameras after the dual 1080 field trial in Nugent et al (2019) were found at the edges of the treatment blocks (no natural barriers), on a similar timeline (4-6 weeks), and assumed to be re-invaders.…”

Section: Discussionmentioning

confidence: 99%

Dual aerial 1080 baiting operation removes predators at a large spatial scale

Nichols¹,

Ltd²,

Wellington³

et al. 2021

NZJE

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As New Zealand attempts to become predator free by 2050, transitioning aerial 1080 (sodium fluoroacetate) operations from predator control to complete predator removal has become an important research objective. Aerial 1080 operations may not remove every last target animal, but they may be able to remove a very high proportion (> 0.99). We trialled a modified [dual] aerial 1080 operation for the removal of brushtail possums (Trichosurus vulpecula), ship rats (Rattus rattus), and stoats (Mustela erminea) at large spatial scale. Our trial involved two toxin applications (TA#1 & TA#2), each preceded by two applications of non-toxic pre-feed bait. Different types of cereal baits and lures were used for each toxin application. Camera traps (n = 142; 200-1431 m asl) were used to detect the target species and to incidentally observe house mouse (Mus musculus), birds, and ungulates across the study area. The operation had no significant impact on the number of cameras detecting most birds and ungulate species; however, house mouse, blackbird (Turdus merula), and red deer (Cervus elaphus) were detected on significantly fewer cameras after TA#1 than before. Numbers of cameras that detected target species were significantly reduced for all three target species after TA#1, and significantly reduced again for possums after TA#2, when no stoats were detected on cameras and a small number of cameras detected rats. Mean relative abundance estimates based on camera trap indices (proportion of camera trap days that target species were detected) showed the operation appears to have removed over 99% of ship rats, stoats, and possums.

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Section: Discussionmentioning

confidence: 99%

Dual aerial 1080 baiting operation removes predators at a large spatial scale

Nichols¹,

Ltd²,

Wellington³

et al. 2021

NZJE

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“…Possum reinvasion can be reduced by selecting sites that utilise natural barriers to movement, such as alpine ranges and cold, fast rivers [ 30 , 34 , 35 ]. Here, we present a case study illustrating this approach to possum elimination at the >11,000 ha scale in the Perth River Valley, South Westland, New Zealand, focusing on detection and removal.…”

Section: Introductionmentioning

confidence: 99%

Targeted Mop up and Robust Response Tools Can Achieve and Maintain Possum Freedom on the Mainland

Cook

Mulgan

2022

Animals

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Unfenced sites on mainland New Zealand have long been considered impossible to defend from reinvasion by possums, and are thus unsuitable for eradication. In July 2019, we began eliminating possums from 11,642 ha (including approximately 8700 ha of suitable possum habitat) in South Westland, using alpine rivers and high alpine ranges to minimise reinvasion. Two aerial 1080 (sodium fluoroacetate) applications, each with two pre-feeds, were used. Here, we detail the effort to mop up existing possums and subsequent invaders in the 13 months following the aerial operation. Possums were detected and caught using a motion-activated camera network, traps equipped with automated reporting and a possum search dog. The last probable survivor was eliminated on 29 June 2020, 11 months after the initial removal operation. Subsequently, possums entered the site at a rate of 4 per year. These were detected and removed using the same methods. The initial elimination cost NZD 163.75/ha and ongoing detection and response NZD 15.70/ha annually. We compare costs with possum eradications on islands and ongoing suppression on the mainland.

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“…The remove and protect strategy is best served by treating large areas, ideally in the tens of thousands of hectares. This reduces reinvasion pressure by shrinking the boundary-to-treatment-area ratio and improving the flexibility to use natural barriers to movement [14,15].…”

Section: Introductionmentioning

confidence: 99%

Assessing Two Different Aerial Toxin Treatments for the Management of Invasive Rats

O’Malley

Stanley

Russell

2022

Animals

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Aotearoa–New Zealand has embarked on an ambitious goal: to completely eradicate key invasive mammals by 2050. This will require novel tools capable of eliminating pests on a large scale. In New Zealand, large-scale pest suppression is typically carried out using aerial application of the toxin sodium fluoroacetate (1080). However, as currently applied, this tool does not remove all individuals. A novel application method, dubbed ‘1080-to-zero’, aims to change this and reduce the abundances of target pests to zero or near-zero. One such target is black rats (Rattus rattus), an invasive species challenging to control using ground-based methods. This study monitored and compared the response of black rats to a 1080-to-zero operation and a standard suppression 1080 operation. No difference in the efficacy of rat removal was found between the two treatments. The 1080-to-zero operation did not achieve its goal of rat elimination or reduction to near-zero levels, with an estimated 1540 rats surviving across the 2200 ha treatment area. However, 1080 operations can produce variable responses, and the results observed here differ from the only other reported 1080-to-zero operation. We encourage further research into this tool, including how factors such as ecosystem type, mast fruiting and operational timing influence success.

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Rivers as obstacles to home range expansion by the brushtail possum

Cited by 5 publications

References 17 publications

Dual aerial 1080 baiting operation removes predators at a large spatial scale

Dual aerial 1080 baiting operation removes predators at a large spatial scale

Targeted Mop up and Robust Response Tools Can Achieve and Maintain Possum Freedom on the Mainland

Assessing Two Different Aerial Toxin Treatments for the Management of Invasive Rats

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