Using less 1080 in aerial baiting

Graham Nugent, Grant Morriss

Landcare Research, P.O. Box 40, Lincoln 7640

Operational research funded by

Animal Health Board and Department of Conservation

Overview

Completed trials:• Landsborough

• Isolated Hill

• Whanganui

Further bucket

development

Current trials• Cascade

• Maruia

Landsborough Results

(b) Reduction in CTC activity

0% 50% 100%

Not Aligned

Cluster

Aligned

Cluster

Not Aligned

Broadcast

Reduction in CTCI

Std 3kg/ha broadcast with

no prefeed alignment

Clustered 0.25 kg/ha with

prefeed alignment

Clustered 0.25 kg/ha with

no prefeed alignment

• Similar possum kills with broadcast and cluster + aligned prefeed.

• Similar possum kills achieved with 92% less toxic bait.

• Indicates the amount of 1080 needed can be greatly reduced, but further replication is required.

Isolated Hill Results

Reduction in possum activity in relation to rat activity levels

• Suggests high rat numbers reduces possum kill with low sowing rates

Conclusions

• 250 g/ha 1080 bait achieved poorer kills compared to 3 kg/ha.– Possum and rat numbers were moderate

• At 30-40 baits per ha there was evidence of a negative rat effect– Implies competition for bait even though < 10 rats /ha – Implies caching (?)

• At 400-500 baits/ha there was no rat effect– Overbaiting eliminates competition for bait (?)

Whanganui National Park

Wanganui Trial Design

Area divided into 10 blocks (600-1000 ha each):

4 treated with broadcast sowing• Broadcast prefeed with 1.00kg/ha of 6g non toxic baits• Broadcast toxic with 2.00kg/ha of 12g 1080 baits

2 treated same as Isolated Hill• Strip-sown prefeed with 0.50kg/ha of 2g non toxic baits• Cluster-sown toxic with 0.25kg/ha of 6g 1080 baits.

2 strip-sown with swaths 130 m apart• Strip-sown prefeed with 0.60kg/ha of 2g non toxic baits• Strip-sown toxic with 0.60kg/ha of 6g non toxic baits

2 strip sown with swaths 180 m apart• Strip-sown prefeed with 0.45kg/ha of 2g non toxic baits• Strip-sown toxic with 0.45kg/ha of 6g non toxic baits

Results: Cluster sowing

Results: Strip sowing

Discussion

• Outcomes not linked to pre-poison possum abundance (highest numbers at Wanganui where there was best result)

– Indication that rat abundance negatively affected cluster kill at Isolated Hill, but not at Wanganui even though there were as many rats at Wanganui.

– Isolated Hill and Wanganui differed in time between pre-feed and toxin – 12 days vs 7 days.

• New hypothesis: Assuming bait type not crucial, long interval between pre-feed and toxin means changes in where possums are foraging will have dissipated, so possums take a long time to find clusters, giving rats time to find and cache all or most of the bait.

New bucket development

•Lightweight-able to be used by smaller choppers

•GPS control of bait release-caters for varying speed of chopper-potentially greater accuracy in bait placement

Ground- truthing

40 – 60 knots50 or 100 m above groundCluster size -12 x 8mThrow forward - 33-76m

Cascade trial blocks

Testing:-timing between prefeed & toxic-flightline spacing

Maruia trial blocks

Testing:-rat interference-timing between prefeed & toxic-flightline spacing

Discussion

• Cluster sowing at 250g/ha and 100m flight path spacing has matched or bettered possum kills achieved with 2000-3000g/ha broadcast at 100-240m flight path spacing in two of three trials.

> 90% reduction in toxin use & > 70% reduction in direct costs (flying & bait).

• Current trials may increase reliability (i.e. prefeed timing). • New concept (simultaneous prefeed/toxin) may halve flying costs.

Potential for more refinement & savings.

Acknowledgements

Thanks to:

AHB

DOC

Amuri Helicopters, HeliOtago, Beck Helicopters

Tracmap

Bushworks Contractors

Vector Control Services