Assessing the effectiveness of groundbased baiting for the control of wild dogs
A. Robley, L. Woodford, P. Lee, V. Kingston, W. Peters, D.
Klippell, A. Gormley
2009
Arthur Rylah Institute for Environmental Research
Technical Report Series No. 193
Arthur Rylah Institute for Environmental Research Technical Series No. 193
Assessing the effectiveness of ground-based baiting
for the control of wild dogs
Alan Robley, Luke Woodford, Peter Lee, Vaughn Kingston, Wayne Peters, David
Klippell, and Andrew Gormley
Arthur Rylah Institute for Environmental Research
123 Brown Street, Heidelberg, Victoria 3084
October 2009
In partnership with:
Department of Primary Industries, Victoria
Arthur Rylah Institute for Environmental Research
Department of Sustainability and Environment
Heidelberg, Victoria
Report produced by:
Arthur Rylah Institute for Environmental Research
Department of Sustainability and Environment
PO Box 137
Heidelberg, Victoria 3084
Phone (03) 9450 8600
Website: www.dse.vic.gov.au/ari
© State of Victoria, Department of Sustainability and Environment 2008
This publication is copyright. Apart from fair dealing for the purposes of private study, research, criticism or review as
permitted under the Copyright Act 1968, no part may be reproduced, copied, transmitted in any form or by any means
(electronic, mechanical or graphic) without the prior written permission of the State of Victoria, Department of
Sustainability and Environment. All requests and enquiries should be directed to the Customer Service Centre, 136 186
or email customer.service@dse.vic.gov.au
Citation: Robley, A., Woodford, L., Lee, P., Kingston, V., Peters, W., Klippell D., and Gormley, A. (2009) Assessing
the effectiveness of ground-based baiting for the control of wild dogs. Arthur Rylah Institute for Environmental
Research Technical Report Series No. 193. Department of Sustainability and Environment, Heidelberg, Victoria
ISSN 1835-3827 (print)
ISSN 1835-3835 (online)
ISBN 978-1-74242-294-7 (print)
ISBN 978-1-74242-295-4 (online)
Disclaimer: This publication may be of assistance to you but the State of Victoria and its employees do not guarantee
that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore
disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in
this publication.
Front cover photo: Wild Dog (Alan Robley)
Authorised by: Victorian Government, Melbourne
Printed by: PRINTROOM 77 St Georges Rd, Preston 3072
ii
Contents
List of tables and figures ...................................................................................................................2
Acknowledgements ............................................................................................................................3
Summary ............................................................................................................................................4
1
Introduction .............................................................................................................................5
2
2.1
Methods ....................................................................................................................................6
Study site ...................................................................................................................................6
2.2
Wild dog capture .......................................................................................................................7
2.3
Baiting .......................................................................................................................................7
2.4
2.5
Cameras.....................................................................................................................................8
Wild dog area of use..................................................................................................................9
2.6
Movement rates .........................................................................................................................9
3
3.1
3.2
Results ......................................................................................................................................9
Wild dogs at Deptford and Merrijig. .........................................................................................9
Bait take ..................................................................................................................................10
3.3
4
3.2.1
Deptford. ..................................................................................................................10
3.2.2
Probability of encountering and taking a bait ...........................................................11
3.2.3
Merrijig ....................................................................................................................12
Area of use and rates of movement ............................................................................................. 12
3.3.1
Deptford. ..................................................................................................................12
3.3.2
Merrijig ....................................................................................................................12
3.3.3
Comparisons of area used ........................................................................................14
Discussion...............................................................................................................................15
References ........................................................................................................................................17
Appendix 1 Example images of the nine wild dogs identified by cameras at Deptford ................19
Appendix 2 Estimated costs of wild dog control at Deptford (eastern Victoria) and Merrijig
(north-eastern Victoria) ..................................................................................................................21
Assessing the effectiveness of ground-based baiting for the control of wild dogs
List of tables and figures
List of tables
Table 1. Details of wild dogs captured at Deptford and Merrijig ........................................................ 9
Table 2. Number of baits taken and the number of detections of species taking baits or present at
bait stations at Deptford. ......................................................................................................... 10
Table 3. Wild dog home range estimates from studies in Australia .................................................. 14
List of figures
Figure 1. Deptford study location........................................................................................................ 6
Figure 2. Merrijig study location. ........................................................................................................ 6
Figure 3. Wild dog fitted with GPS/satellite collar ............................................................................. 7
Figure 4. Digital heat-in-motion camera set at bait station.................................................................. 8
Figure 5. Wild dogs recovered at Deptford. ...................................................................................... 11
Figure 6. Cumulative bait take by wild dogs at Deptford recorded from digital cameras ................. 11
Figure 7. Area of activity (95% MCP) for the four wild dogs at Deptford, August 2008–January
2009 showing track network and location of cameras and bait stations .................................. 13
Figure 8. Area of activity (95% MCP) for the six wild dogs at Merrijig, February–May 2009
showing track network and location of cameras and bait stations........................................... 13
2
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
Assessing the effectiveness of ground-based baiting for the control of wild dogs
Acknowledgements
We thank the Department of Primary Industries (DPI) for logistical support throughout this project.
This project was funded by the DPI, Victoria. Wildlife Unlimited assisted in the collection of field
data. We thank the Gippsland and North East Wild Dog Management groups for their continued
support. This work was conducted under the Department of Sustainability and Environment (DSE)
Animal Ethics Committees permit number 09/09. Our thanks to Dave Forsyth and Lindy Lumsden
for improving earlier drafts of this report.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
3
Assessing the effectiveness of ground-based baiting for the control of wild dogs
Summary
Baits containing the poison 1080 (sodium fluoroacetate) are a common tool used to reduce wild dog
numbers around Australia. In Victoria, the use of ground-based baiting is part of an integrated wild
dog management strategy.
This project aimed to quantify the effectiveness of buried baiting for the control of wild dogs in
Victoria. We assessed the number of captured and released wild dogs that were subsequently killed
by baiting. We also used cameras placed at bait stations that were activated by heat-in-motion to
assess the visitation rate of wild dogs to bait stations.
We captured and attached Global Positioning System (GPS) data-logging collars to four wild dogs
at a site near Deptford in Gippsland during spring 2008 and six wild dogs at a site near Merrijig
during autumn 2009 in the north-east of Victoria. The nightly capture probability at Deptford (0.73
± 0.36 SE) was similar to Merrijig (0.95 ± 0.38 SE) indicating that underlying dog density was
similar at the two sites.
Digital heat-in-motion activated cameras placed at bait stations recorded the presence of a further
five dogs at Deptford and three dogs at Merrijig. The combined method of recording collared dogs
and individually identified dogs captured by cameras provided an estimate of the known population
of wild dogs at each site.
Poisoned baiting was undertaken by Department of Primary industries, Victoria (DPI) staff using
standard operating procedures at both sites for seven weeks with predator meat baits containing 4.5
mg of 1080. Baiting killed six wild dogs at Deptford (70% of the known population) and one wild
dog at Merrijig (11% of the known population).
The probability that a dog would encounter a bait station with bait in it over the course of the
operation was on average 43%, and having encountered the bait station, the probability of a dog
taking bait was on average 25% at Deptford.
Lace Goannas (Varanus varius) (at Deptford) and foxes (Vulpes vulpes) (at Merrijig) were the main
species that consumed bait. A range of other species were recorded at bait stations, including nontarget wombats, lyrebirds, native and introduced rodents, and wallabies.
Wild dog controllers’ assessment of bait take by various species differed from that recorded by
digital cameras. The difference is likely to be due to the difficulty of reliably identifying tracks
several days after the species has taken the bait. In light of this, we recommend that bait take not be
used as a measure of reduction in wild dog numbers following a baiting operation.
The results from these trials indicate that buried baiting is likely to be a cost-effective tool in the
management of wild dogs. Variation in success between the two sites could in part be accounted for
by differences in landscape features, e.g. road density, which contributed to a difference in the
spatial arrangement of baits in relation to the area used by wild dogs.
4
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
Assessing the effectiveness of ground-based baiting for the control of wild dogs
1 Introduction
Baits containing the poison 1080 (sodium fluoroacetate) are commonly used to reduce wild dog
numbers around Australia. Despite this widespread use in other parts of Australia, baiting in
Victoria is limited by a lack of quantitative data on its effectiveness under Victorian conditions.
In temperate south-eastern Australia, the predation of livestock by wild dogs—wild-living members
of the species Canis familiaris, including feral dogs (C. f. familiaris), dingoes (C. f. dingo) and their
hybrids—affects the profitability of graziers whose holdings are adjacent to or within terrain
inhabited by wild dogs (Fleming and Kom 1989). In accessible terrain in NSW, ground baiting is
preferred by Wild Dog Control Association members to aerial baiting for the control of wild dogs
(Fleming et al. 1996). Ground baiting requires fewer baits and the baiters have more control over
the placement of baits. However, the efficacy of existing ground-baiting programs in Victoria
remains unclear.
The Victorian Wild Dog Management Strategy’s two main aims are to ensure best practices are
used in the control of wild dogs and effective research is undertaken to fill gaps in our knowledge.
The North East and Gippsland Wild Dog Management Plans both indicate that baiting should be
incorporated into regular control programs. A key gap in our knowledge is a robust and generalised
demonstration of the effectiveness of the buried-baiting technique under Victorian conditions. The
targeted use of baits would greatly reduce the amount of toxin in the environment, and enable
public land managers to establish clear guidelines for best management practices.
A number of studies using changes in indices of abundance have investigated the effectiveness of
baiting for the control of wild dogs in Australia. A ground-based baiting campaign with small meat
baits containing 20 mg of 1080 in central Australia achieved a 69% reduction in dingo sign (Best et
al. 1974). In the arid zone of South Australia, a single placement of 430 baits achieved a reduction
of 10–13% of 300–400 dingoes that were watering at a single bore (Bird 1994). Fleming et al.
(1996) assessed the efficacy of a baiting program that replaced taken baits on a daily basis. Wild
dog abundance indices were calculated from visits to stations containing non-toxic baits before and
after a replacement-baiting program. The program achieved a mean reduction of 76.1% in the index
of wild dog abundance. Only one other study has assessed the actual kill rate of a baiting program.
In New South Wales, using two placements of poisoned meat baits, two of nine (22%) radiocollared wild dogs were killed (McIlroy et al. 1986).
We used both direct and indirect measures of changes in wild dog abundance to assess the
effectiveness of buried baiting. We attached GPS collars to wild dogs to provide a direct measure of
individuals killed from baiting. This also allowed for an assessment of wild dog movement in areas
adjacent to private land.
Heat-in-motion activated cameras have been used to survey the presence of a wide range of species
both in Australia and elsewhere (Tobler et al. 2008; Towerton et al. 2008). Remote cameras can
operate in all weather conditions, collect more reliable information on species’ identity, and for the
information returned, they are cost effective. Images collected by heat-in-motion activated cameras
can be used to assess the rate of bait take by target and non-target animals.
This project aimed to quantify the effectiveness of buried baiting for the control of wild dogs in
Victoria by assessing the number of captured and released wild dogs that succumbed to baiting and
by assessing the visitation rate of wild dogs to bait stations via images recorded by heat-in-motion
activated cameras placed at bait stations. This will provide critical information for future
management of the control of wild dogs.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
5
Assessing the effectiveness of ground-based baiting for the control of wild dogs
2 Methods
2.1 Study site
We captured wild dogs in state forest north of Bairnsdale in eastern Victoria at a site near Deptford
(147o 35E, 37o 37S; Fig. 1) in August 2008. A second site was north-east of the township of
Merrijig in north-east Victoria (146o 9E, -37o 2S; Fig. 2), with trapping occurring in January 2009.
Both sites were within 3–5 km of the public/private land interface, and had no wild dog control
within the previous 12 months.
ÊÚ
Ú
Ê
Deptford
LEGEND
Deptford study area
Roads
Sealed road
Unsealed track
Land Tenure
Freehold
State Forest
Bullumwaal
N
0
2
4 Km
Figure 1. Deptford study location.
ÊÚ
LEGEND
Study area
Roads
Sealed road
Unsealed road
Land Tenure
Freehold
State Forest
Parks
N
Merrijig
0
Figure 2. Merrijig study location.
6
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
2
4Km
Assessing the effectiveness of ground-based baiting for the control of wild dogs
2.2 Wild dog capture
At Deptford, 26 padded Lanes dog traps (Coast to Coast Vermin Traps, Baldivis, WA) were set for
21 consecutive days in August 2008 (i.e., a total of 546 trap nights). At Merrijig, 30 Lanes dog
traps were set for 21 consecutive days in January and February 2009 (i.e., a total of 630 trap
nights). All traps were operated by wild dog controllers from the Victorian Department of Primary
Industries (DPI) following standard operating procedures (DCE 1991). Traps were set on dog sign
identified by the wild dog controller (scat or scratching). All traps were set within 1 m of the side of
tracks and roads. Traps were checked daily and captured dogs were initially subdued using a ketchall pole (Ketch-all Co., California, USA), and restrained on a holding board with broad straps fitted
to their waist, shoulders and neck. Each dog had its capture location, sex, and weight recorded.
Each dog was fitted with a collar housing a GPS data logger (Sirtrack, Haveloch North, New
Zealand; Fig. 3) linked to the Argos satellite network (http://www.argos-system.org). The GPS unit
estimated a location every 60 minutes. Data from GPS–Argos linked collars include a horizontal
dilution of position (HDOP) as well as the number of satellites used to calculate the location. A low
HDOP value represents better GPS positional accuracy due to the wider angular separation between
the satellites used to calculate a GPS unit’s position. The maximum allowable error (MAE) in
location accuracy was determined using the formula: A * HDOP, where A is the GPS device
accuracy (MAE; http://www.developerfusion.co.uk/show/4652/3/). The GPS receiver was a
Navman Callisto module and had an estimated accuracy of 2.5 m (Navman Wireless OEM
Solutions 2006). Thus, the MAE for a HDOP of six is 15 m; we excluded all locations with a
HDOP of > 6 in all analyses.
Collars were also fitted with a Very High Frequency (VHF) transmitter and a timed-release
mechanism programed to release 75 days after wild dogs were captured. Collars were retrieved
after the release date by tracking the VHF transmitter on foot.
Figure 3. Wild dog fitted with GPS/satellite collar.
2.3 Baiting
The DPI wild dog controllers conducted the baiting operation. Predator meat baits (150–200 g
boneless red meat) containing 4.5 g of 1080 (sodium fluoroacetate) were prepared by Gippsland
Environmental Services Pty, Bairnsdale, Victoria. Baits were placed in pre-prepared bait stations,
to a depth of 5–10 cm. When changing baits, wild dog controllers from DPI attempted to identify
species that either took bait or visited bait stations from sign.
At Deptford, baits were checked and replaced every two weeks initially and then on a weekly basis
for the final three weeks. The change in replacement rate was initiated to reduce bait decay after
daily temperatures exceeded 30oC. At Merrijig, baits were checked and replaced on a weekly basis.
A sample of liver was retrieved from dead dogs and sent to the Alan Fletcher Research Station,
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
7
Assessing the effectiveness of ground-based baiting for the control of wild dogs
Queensland Primary Industries and Fisheries Department for assays to determine the presence of
residual 1080.
We determined the nature of the distribution of bait stations at each site using the nearest neighbour
method in Arcview 3.3 (ESRI California), which determines if a distribution is clumped, uniform or
random. The distance of each individual bait station to its nearest neighbouring bait station was
recorded. For two individual stations that are each other’s nearest neighbour, the distance is
recorded twice, once for each station. The average distance between nearest neighbours is
compared to the expected distance in the case of random distribution to give the ratio R:
mean distance
R= 1
density
2
If R is equal to 1 then the population is randomly dispersed. If R is significantly greater than 1 the
population is evenly dispersed. Lastly, if R is significantly less than 1 the population is clumped.
2.4 Cameras
Heat-in-motion triggered digital cameras were set at 26 bait stations from 17 September 2008 to 15
November 2008 (1539 camera days) at Deptford. At Merrijig, cameras were set at 23 bait stations
from 2 February 2009 to 8 April 2009 (1495 camera days). Images of animals at bait stations or
passing on the road were recorded using Reconyx RapidFireTM ProPC90 heat-in-motion activated
digital cameras (Reconyx, LLP Wisconsin, USA; Fig. 4). These cameras record 3.1 mega-pixel
colour images during daylight and 3.1 mega-pixel infra-red images at night. These cameras were
set to record three images as fast as possible once motion was detected (on average two images
every three seconds) and to keep recording images as long as motion was detected.
Individual dogs were identified by first grouping images by broad coat colour, (e.g. yellow, sable,
black, and brindle). Within these groups, individual dogs were identified by assessing multiple
images and comparing markings (e.g. presence, location and size of socks, colouration around
muzzles, and chest markings), signs of age (e.g. grey muzzle and greying of coats), sex (males v
females where visible) and physical condition. Dogs that could not be assigned to an individual
were not counted.
Digital camera
Bait station
Figure 4. Digital heat-in-motion camera set at bait station.
8
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
Assessing the effectiveness of ground-based baiting for the control of wild dogs
2.5 Wild dog area of use
Area of use of each individual fitted with a GPS collar was calculated by the 95% minimum convex
polygon (MCP) (Jenrich and Turner 1969) using the Home Range Analysis extension (Jenness
Enterprises, Arizona, USA) in ArcView 3.2. We also compared the areas of use with estimates
from previous Australian studies.
2.6 Movement rates
Movement rate was calculated by first determining the distance (m) moved between each
successive location and the time interval (h) between the two locations and then dividing distance
moved by the time to derive mean hourly velocity (m h-1).
3 Results
3.1 Wild dogs at Deptford and Merrijig
Four wild dogs were captured (0.73 captures per 100 trap nights ± 0.36 SE) and collared at
Deptford (two males and two females; Table 1). One female had swollen nipples indicating recent
weaning.
Six wild dogs were captured and collared (0.95 captures per 100 trap nights ± 0.38 SE) at Merrijig
(three females and three males; Table 1).
Table 1. Details of wild dogs captured at Deptford and Merrijig.
Location Capture date ID
Sex Weight Dog colour
(kg)
Date found
dead
Deptford
26/08/2008
D904
F
17
Brindle
13/11/2008
Deptford
3/09/2008
D905
F
19
Yellow / Brindle
–
Deptford
29/08/2008
D907
M
25
Yellow
–
Deptford
3/09/2008
D909
M
20
Yellow
15/11/2008
Merrijig
16/01/2009
D906
F
14
Black, white chest, white
feet
–
Merrijig
15/01/2009
D911
F
13
Black, white legs, grey
muzzle
–
Merrijig
18/01/2009
D914
F
14
Yellow/ginger, faint white
feet
–
Merrijig
28/01/2009
D910
M
19
Black, white chest and
socks, white tip tail
–
Merrijig
18/01/2009
D912
M
16
Ginger
–
Merrijig
17/01/2009
D915
M
17
Sable, yellow, white legs
–
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
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Assessing the effectiveness of ground-based baiting for the control of wild dogs
3.2 Bait take
3.2.1
Deptford
Thirty bait stations were established at Deptford (26 with cameras). This represented one bait
station for every eight kilometres of road in the area used by collared dogs or 0.10 baits/ km2. The
average distance between bait stations was 1493 m. The nearest neighbour analysis indicated that
bait stations were randomly distributed (z = 1.171 and R = 0.880).
A total of 192 poison baits were laid over the 51 days of baiting. DPI wild dog controllers recorded
bait take by wild dogs (7), wild dog/fox (13), and fox (9; Table 2). No other species were identified
by sign at bait stations by wild dog controllers.
Nine individual wild dogs were identified from images captured by the digital cameras, including
three collared dogs (Appendix 1). Wild dogs were detected by cameras at 54% of bait stations. This
included wild dogs walking past, investigating, and taking bait.
Table 2. Number of baits taken and the number of detections of species taking baits or present at
bait stations at Deptford
DPI records
*
Camera Records
Species
Bait taken
(including bait
stations with
no cameras)
Bait taken
(only at bait
stations with
cameras)
Wild dog
11
7
6
7
Wild dog/fox
18
13
–
–
Fox
18
9
1
5
Unknown
8
3
–
–
Rodent spp
0
0
1
0
Goanna
0
0
10
19
Wombat
0
0
0
21
Total
55
32
18
52
Bait taken
Present at
bait
station*
Present—walking on, sniffing and /or scratching around bait station.
Digital cameras detected six wild dogs taking baits (70% of the identifiable dogs in the area; Table
2). Two of the four collared wild dogs were recorded taking baits and both dogs were subsequently
recovered dead (Fig. 5). One of these was recovered two days after being photographed taking a
bait. Analysis of a small portion of liver was unable to detect residual traces of 1080. The second
dog was recovered in a decayed and mummified state and no tissue sample was available for
analysis. Cameras also detected wild dogs at bait stations on seven other occasions during the
baiting program.
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Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
Assessing the effectiveness of ground-based baiting for the control of wild dogs
Figure 5. Wild dogs recovered at Deptford.
Bait take by wild dogs tended to occur more towards the later stages of the 51 days of the program
(Fig. 6).
7
Cumulative bait take
6
5
4
3
2
1
0
1
5
9 13 17 21 25 29 33 37 41 45 49
Day
Figure 6. Cumulative bait take by wild dogs at Deptford recorded from digital cameras.
Digital cameras recorded foxes at eight of the 26 bait stations on 17 separate occasions. Over the
course of the entire baiting program (51 days) foxes walked past bait stations on 11 occasions
(22%), investigated bait stations five times (10%) and were detected taking bait on one occasion
(2%).
Feral cats were detected at 19 of the 26 bait stations, but were never recorded investigating or
taking bait. Over the course of the baiting program, goannas were recorded at 17 bait stations on 23
occasions (45%). Goannas were detected taking bait on 10 occasions and scratching at bait stations
on 10 occasions. Wombats were detected scratching and walking over 13 bait stations but never
taking bait.
3.2.2
Probability of encountering and taking a bait
The probability that a dog encountered a bait station on a single day at Deptford was 0.015 ±
0.0033 SE. However, there were times when bait stations did not contain bait due to another wild
dog, a fox or goanna having already taken the bait. The corrected probability that a wild dog
encountered a bait station with bait present on a single day was 0.0115 ± 0.0031 SE.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
11
Assessing the effectiveness of ground-based baiting for the control of wild dogs
At Deptford, wild dogs were recorded at bait stations with baits present on 13 occasions, with six of
these resulting in bait take; hence the corresponding probability of bait take given an encounter
with a baited bait station was 0.429 ± 0.132 SE.
The probability that a wild dog encountered a bait station with bait present and took the bait on any
given day is 0.0115*0.429 = 0.00494 ± 0.0020. During the course of the Deptford trial (51 days),
the overall probability that a bait was taken was 0.25 ± 0.10 or 25%.
3.2.3
Merrijig
Twenty-three bait stations were established at Merrijig. This represented one bait station for every
four kilometres of road within the area used by all the collared dogs (0.19 baits / km2). The average
distance between bait stations was 2960 m. The nearest neighbour analysis indicated that bait
stations had a tendency towards clumping (z = 3.304 and R = 0.640).
A total of 184 poison baits were laid over the 62 days of baiting. DPI wild dog controllers recorded
bait take by wild dog (1), fox (3) and unknown (34). No other species were identified from sign at a
bait station by wild dog controllers.
Cameras operated for an average of 63 days (range 45–65 days). Six individual wild dogs were
identified from images captured by the digital cameras, including three collared dogs. Wild dogs
were detected by cameras at 35% of bait stations. This included wild dogs walking past,
investigating, and taking bait. Digital cameras detected wild dogs at eight of the 23 bait stations on
nine separate occasions, and one wild dog taking bait (11% of the identifiable dogs in the area) on
the 9 February, 6 days into the baiting program. No collared wild dogs were recorded taking baits.
Digital cameras recorded foxes at 16 of the 23 bait stations on 42 separate occasions and were
detected taking bait on 15 occasions (65%). Feral cats were detected at 22 of the 23 bait stations on
23 separate occasions, but were never recorded investigating or taking bait. No goannas were
recorded at bait stations. Wombats were detected at 17 bait stations on 46 separate occasions.
Wombats were detected 21 times scratching and walking over bait stations but never taking bait.
The low level of bait take at this site prevented us from determining the probability of bait being
taken.
3.3 Area of use and rates of movement
3.3.1
Deptford
GPS data at Deptford were collected between August 2008 and January 2009. Wild dogs had areas
of use ranging between 48 km2 and 94 km2 for the six month period of the study. All wild dogs had
access to bait throughout the study (Fig. 7).
Mean hourly distance moved by males was 241 m h-1 (range 1–19,559 m h-1; median 49 m h-1) and
for females 230 m h-1 (range 1–9844 m h-1; median 37 m h-1).
3.3.2
Merrijig
GPS data at Merrijig were collected between February 2009 and May 2009. Wild dogs had areas of
activity ranging between 17 km2 and 30 km2 for the 2.5 month period of the study. All wild dogs
had access to some baits throughout the study (Fig. 8).
Mean hourly distance moved by males was 243 m h-1 (range 1–3499 m h-1; median 92 m h-1) and
for females 261 m h-1 (range 1–3219 m h-1; median 91 m h-1).
12
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
Assessing the effectiveness of ground-based baiting for the control of wild dogs
ÊÚ
#
#
#
#
#
#
#
#
Ú
Ê
Deptford
#
#
#
#
#
#
Deptford
#
#
LEGEND
Camera locations
●
Bait stations
Home Range
F-905 (94 km2)
F-904 (54 km2)
M-909 (48 km2)
●
#
#
#
#
#
#
Bullumwaal
Bullumwaal
#
#
#
#
#
#
#
#
##
#
#
##
#
#
#
#
#
#
#
#
##
#
#
# ##
#
#
#
#
M-907 (73 km2)
Roads
#
Sealed road
Unsealed track
#
#
#
#
Land Tenure
Freehold
State Forest
#
#
#
N
2
0
4 Km
Figure 7. Area of activity (95% MCP) for the four wild dogs at Deptford, August 2008–January
2009 showing track network and location of cameras and bait stations.
#
#
#
# #
#
#
#
Ú
Ê
●
#
#
●
●
#
#
●
#
#
#
#
#
#
#
LEGEND
Bait & camera locations
Home Range
F-906 (17 km2)
M-910 (23 km2)
#
F-911 (22 km2)
M-912 (30 km2)
F-914 (25 km2)
M-915 (23 km2)
Roads
Sealed road
Unsealed road
Land Tenure
Freehold
State Forest
Parks and Reserves
Merrijig
0
2
N
4Km
Figure 8. Area of activity (95% MCP) for the six wild dogs at Merrijig, February–May 2009
showing track network and location of cameras and bait stations.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
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Assessing the effectiveness of ground-based baiting for the control of wild dogs
3.3.3
Comparisons of area used
Differences in data collection and analysis methodologies, time of year, length of study and sample
size and composition (age and sex) make direct comparisons of areas of use between studies
difficult. Bearing these differences in mind, the area of use at Merrijig was smaller than reported in
other studies, while Deptford was comparable to studies from Western and Central Australia.
Female home ranges have generally been reported as smaller than males, but at Deptford this was
not the case. This may in part be explained by the fact that at Deptford only two females were
tracked.
Table 3. Wild dog home range estimates from studies in Australia
Author(s)
Method of estimation
Location
Mean home range size
(km2)
All
Males
Females
Harden (1985)
100% MCP
South-east Australia
–
27
–
McIlroy et al. (1986)
100% MCP
South-east Australia
22
25
20
Catling (pers. comm. in
McIlroy et al. 1986)
Not reported
East Australia
10
10
11
Catling (pers. comm. in
McIlroy et al. 1986)
Not reported
East Australia
18
20
12
Corbett (1995)
Not reported
Central Australia
67
98
47
Thomson (1992)
95% MCP
Western Australia
–
85
56
Eldridge et al. (2002)
95% MCP
Northern Territory
–
157
272
Claridge et al. (2009)
MCP
South-east Australia
90
100
79
Robley et al. (in press)
100% MCP
South-east Australia
100
156
55
78
124
45
95% MCP
Deptford (this study)
95% MCP
South-east Australia
67
60
74
Merrijig (this study)
95% MCP
South-east Australia
23
25
21
14
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Assessing the effectiveness of ground-based baiting for the control of wild dogs
4 Discussion
The aims of this study were to assess the effectiveness of ground-based baiting as a technique for
reducing wild dog numbers, and to determine the probability of a wild dog encountering a bait
station, and once encountered, the probability of bait being taken.
We assessed the fate of 10 wild dogs fitted with GPS–Argos satellite linked collars at two locations
during a poison baiting operation. We also used digital cameras placed at bait stations to determine
the number of dogs without collars visiting bait stations. Using information from the cameras, we
were able to determine the probability that a wild dog would encounter a bait station, and
subsequently take bait.
The baiting operation at Deptford removed 70% of the identifiable wild dog population, including
two of the four collared wild dogs, with bait take at this site tending to increase later in the baiting
period. Non-target species (foxes and goannas) were also recorded taking baits, reducing the
availability of baits to wild dogs. Non-target bait take contributed to a moderate probability of a
bait being taken once found by a dog (25%). At Merrijig, 11% of the wild dog population, or one
wild dog, was recorded taking bait. Foxes were a key non-target species recorded taking baits; no
goannas were recorded at this site. The low level of bait take at this site prevented us from
determining the probability of bait being taken.
Results indicate that buried baiting is likely to be a useful and effective tool for killing wild dogs.
However, the varied results indicate that its effectiveness may not be uniformly successful at all
locations and at all times, and the moderate probability of bait take when a bait was encountered
needs to be interpreted with care as it is based on data from only one site.
There are a range of possible factors that may influence the success of a baiting program (e.g.
degradation of 1080 in the baits over time, the removal of baits by non-target species, and/or the
availability of natural prey; McIlroy et al. 1986). Other factors may include the underlying density
of wild dogs in relation to the density of baits, and the density of baits in the landscape in relation to
the movement patterns and area of use of wild dogs.
A greater percentage of the population was killed by the baiting program at Deptford than at
Merrijig. In part, this can be explained by the distribution of baits in the landscape. Baits at
Deptford were randomly distributed across the area used by wild dogs compared to the clumped
distribution at Merrijig. This difference was a result of the spatial arrangement of the roads at each
site. Road density (length of road / total km2) was higher at Deptford compared to Merrijig
(0.85/km2 v 0.75/km2). The higher road density provided the opportunity to spread baits more
widely across the landscape than at Merrijig, allowing a greater opportunity for wild dogs to
encounter a bait station.
The timing of the baiting program differed at each site. Baiting at Deptford was undertaken in late
spring to early summer, and at Merrijig it was undertaken in late summer to early autumn. Baiting
campaigns are traditionally undertaken from spring to autumn, although generally later in autumn
and earlier in spring than was the case in our study (Fleming et al. 2001). Baiting at this time of
year is related to either wild dog ecology (e.g. breeding season—autumn—or possible dispersal and
movement of pups—spring) or livestock protection (e.g. lambing in spring). Differences in season
per se are unlikely to explain the differences in the results in this study.
At Deptford, cameras identified nine individual wild dogs, with 70% of these killed by the 51 day
buried baiting program compared to the 21 days of trapping that potentially removed 40%, thus
trapping removed more dogs per week (0.19) than baiting (0.12) in that area at that time. However,
the requirement under the Prevention of Cruelty to Animals Act 1986 is to check traps on a 24 hour
basis, whereas current Government policy is that baits can remain unchecked for 14 days. In the
program at Deptford, this means that trapping would be approximately five times more expensive
than baiting (Appendix 2). At Merrijig, traps caught six wild dogs and baiting removed one, hence
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
15
Assessing the effectiveness of ground-based baiting for the control of wild dogs
trapping potentially removed more dogs per day than baiting (0.29 and 0.02 respectively) and cost
40% less (Appendix 2).
At both sites, bait take by non-target species was an issue. At Deptford, goannas removed 5% of
baits, potentially reducing the effectiveness of that program, while at Merrijig, foxes removed 8%.
McIlroy et al. (1985) assessed the sensitivity of V. varinus to 1080 poisoning, and from limited data
suggested a LD50 of 119 g / kg-1. They concluded that it is unlikely that reptiles face any direct
poisoning risk from pest-poisoning campaigns involving 1080, given their high tolerance and the
enormous amounts of poisoned bait that would have to be eaten. Thus it is extremely unlikely that
goannas at Deptford would have suffered any mortality from consuming the predator meat baits
which contain 4.5 mg/bait. Foxes are a known predator of stock and native wildlife and are targeted
in control operations around Australia. Integrated pest management is a strategic aim of many
control programs, thus the reduction of foxes, while impacting on programs specifically aimed at
protection of stock from wild dog attacks, provides a benefit to both livestock and wildlife.
The reason for the discrepancy between the number of bait takes and the species taking baits
recorded by DPI and the digital cameras is not clear. It is likely to be a combination of the digital
cameras failing to record bait takes on some occasions and wild dog controllers incorrectly
assessing bait as being taken, when in fact it was still present in a bait station. Predator meat baits
are 250 g of moist horse or kangaroo meat. Dirt from bait station adheres to the bait making it
difficult to distinguish from sods of dirt. Placing the bait into a small hole and sieving dirt back on
top of the bait may reduce the incidence of this happening. Differences in the identity of the species
taking bait could be attributed to the difficulty in assessing species from sign several days after bait
has been taken. In light of this we would recommend that bait take be discontinued as a measure of
control program success.
This work provides initial information on the efficacy of baiting as a control tool for wild dogs and
non-target species encounters with bait stations. To assess the optimal strategies for the control of
wild dogs adequately, we need meaningful a priori expectations of the level of population coverage
achievable by differing densities of control devices (baits and/or traps). Spatially explicit models
can simulate encounter rates between wild dogs and control devices at different road and control
device densities. By applying a modelling approach, we can objectively control for confounding
effects of differing bait and trap density, length of toxic bait availability, spatial constraints in
placement of baits and traps, and different population densities. Population density is an issue
because home-range size, and hence the probability that a wild dog will interact with devices
located at different points within its home range, is likely to vary with density. The result will be
that for a given underlying dog and road density we will be able to estimate the required control
device density for a given reduction in wild dogs. This approach has been applied to optimising bait
station density for the control of possums in New Zealand (Tompkins and Ramsey 2007). We
recommend that the next phase of work be undertaken using the approach outlined above.
16
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Assessing the effectiveness of ground-based baiting for the control of wild dogs
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Assessing the effectiveness of ground-based baiting for the control of wild dogs
Appendix 1 Example images of the nine wild dogs identified
by cameras at Deptford.
Identification of individuals was based on multiple images of animals from a variety of angles and
times of day. These images are presented as examples only.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
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Assessing the effectiveness of ground-based baiting for the control of wild dogs
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Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
Assessing the effectiveness of ground-based baiting for the control of wild dogs
Appendix 2 Estimated costs of wild dog control at Deptford
(eastern Victoria) and Merrijig (north-eastern Victoria)
Activity
Task
Person
days
Number of
operational
days
No.
dogs
killed
Dogs
killed
per day
Cost per dog
killed* ($)
Deptford
Baiting
Prepare bait stations and
check and replace baits
7
52
6
0.12
583
Trapping
Set and check traps
25
21
4
0.19
3125
Baiting
Prepare bait stations and
check and replace baits
7
52
1
0.02
3500
Trapping
Set and check traps
25
21
6
0.29
2083
Merrijig
* Assumes $500/day labour and material costs
Arthur Rylah Institute for Environmental Research Technical Report Series No. 193
21
Assessing the effectiveness of ground-based baiting for the control of wild dogs
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