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Objective 1 Reducing the cost of ground control 1.Automatic traps for rats and stoats: Compare the cost-effectiveness of the newly developed automatic kill trap (Henry) with arrays of single- capture traps (e.g. Victor professional). 2.Wireless networks for remote detection and monitoring of traps. 3.Applications of long-life baits (e.g. Kiwicare gel bait) – includes possum behaviour around permanent and new bait stations
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Are multiple-capture traps always better than
single-capture ones?
Bruce Warburton and Andrew Gormley Landcare Research
MSI Strategic Technologies for MSPCProgramme Objectives
• Obj 1: Reducing the costs of aerial and ground-based control
• Obj 2: Reducing the adverse impacts of aerial and ground-based control (welfare,
residues, non-targets)
• Obj 3: Reducing community opposition to pest programmes (increasing community
participation in pest programmes)
Objective 1Reducing the cost of ground control
1.Automatic traps for rats and stoats: Compare the cost-effectiveness of the newly developed automatic kill trap (Henry) with arrays of single-capture traps (e.g. Victor professional).
2.Wireless networks for remote detection and monitoring of traps.
3.Applications of long-life baits (e.g. Kiwicare gel bait) – includes possum behaviour around permanent and new bait stations
Multiple vs Single Capture Traps
Two stage approach:
1. Model control efficiency to determine optimal trap combinations and costs
2. Field test model predictions and obtain empirical data for critical parameters
Spatial Model
G(0) = Probability of a capture at the centre of the home range over one night
σ = measure of home range size (2.45 σ includes 95% of range)
Species G(0) SigmaPossum 0.05 63Stoat 0.05 400Rat 0.05 30
Inputs...1
Species Densities Trap spacingPossums 0.5-3.0/ha 50 x 100
Stoats 0.02-0.12/ha 200 x 800
Rats 1-11/ha 25 x 100
Inputs...2Trap type Cost Set up times
(min)Reset times
(min)Henry $150 5 3Sentinel $28 5 2Leghold $12 3 2Victor rat trap $7.50 4 2DOC 150 $90 3 3
• Time per 100m between traps = 6min• Cost/day $350
Assumptions
• G(0) was the same for all trap types
• Long-life bait available for all traps
• Populations were closed (no immigration or breeding)
Results – Possums...1
0
500
1000
1500
2000
2500
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
Num
ber o
f tra
ps
Density
Catch=1
Catch=0
0.5
0.6
0.7
0.8
0.9
1
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3Pr
opoti
on o
f ani
mal
s ca
ught
Density
Potential captures per site = 1
Results – Possums...2
Potential captures per site = 2
0
500
1000
1500
2000
2500
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
Num
ber o
f tra
ps
Density
Catch=2
Catch=1
Catch=0
0.5
0.6
0.7
0.8
0.9
1
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3Pr
opoti
on o
f ani
mal
s ca
ught
Density
Results – Possums...3
0
0.25
0.5
0.75
1
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
Prop
ortio
n of
ani
mal
s ca
ught
Density
T.max=1
T.max=2
T.max=3
T.max=6
T.max=12
Results – Stoat...1
Potential captures per site = 1
0
10
20
30
40
50
60
70
80
90
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12
Num
ber o
f tra
ps
Density
Catch=1
Catch=0
0
0.25
0.5
0.75
1
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12Pr
opoti
on o
f ani
mal
s ca
ught
Density
Results – Stoat...2
Potential captures per site = 3
0
10
20
30
40
50
60
70
80
90
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12
Num
ber o
f tra
ps
Density
Catch=3
Catch=2
Catch=1
Catch=0
0
0.25
0.5
0.75
1
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12Pr
opoti
on o
f ani
mal
s ca
ught
Density
Results – Stoat...3
0
0.25
0.5
0.75
1
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12
Prop
ortio
n of
ani
mal
s ca
ught
Density
T.max=1
T.max=2
T.max=3
T.max=6
T.max=12
Results – Rat...1
0
0.25
0.5
0.75
1
1 2 3 4 5 6 7 8 9 10 11
Prop
ortio
n of
ani
mal
s ca
ught
Density
T.max=1
T.max=2
T.max=3
T.max=6
T.max=12
$-
$100,000
$200,000
$300,000
$400,000
$500,000
$600,000
$700,000
$800,000
$900,000
1 2 3 4 5 6 7 8 9 10 11 12
Henry
Sentinel
Costs – Possums
0
0.25
0.5
0.75
1
0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
Prop
ortio
n of
ani
mal
s ca
ught
Density
T.max=1
T.max=2
T.max=3
T.max=6
T.max=12
Costs – Stoats
$-
$20,000
$40,000
$60,000
$80,000
$100,000
$120,000
1 2 3 4 5 6 7 8 9 10 11 12
Henry
Victor
DOC150
0
0.25
0.5
0.75
1
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12
Prop
ortio
n of
ani
mal
s ca
ught
Density
T.max=1
T.max=2
T.max=3
T.max=6
T.max=12
Costs – Rats
$-
$500,000
$1,000,000
$1,500,000
$2,000,000
$2,500,000
$3,000,000
1 2 3 4 5 6 7 8 9 10 11 12
Henry
Victor
DOC150
0
0.25
0.5
0.75
1
1 2 3 4 5 6 7 8 9 10 11
Prop
ortio
n of
ani
mal
s ca
ught
Density
T.max=1
T.max=2
T.max=3
T.max=6
T.max=12
Conclusions
• For possums and stoats, three traps/site is maximum needed
• For rats, six traps/site is maximum needed• Additional capture capacity is redundant• For possums, three Sentinel traps set at a
site is more cost-effective than the Henry• For stoats and rats Henry more cost-
effective than DOC 200, but not Victor snap-back
