population and management assessment of the black-footed
TRANSCRIPT
Low Ecological Services P/L
PO Box 3130, Alice Springs, NT 0871
Ph: (08) 89 555 222 Fax: (08) 89 555 722
Email: [email protected] Web: www.lowecol.com.au
Population and management assessment of the black-footed tree-rat for the Jabiru
power station development March 2021
Prepared for CDM Smith Australia Pty Ltd Environment, Planning and Economics
Level 1, 48-50 Smith Street, Darwin NT 0800
Prepared by Low Ecological Services P/L
March 2021
Low Ecological Services P/L
Jabiru BFTR survey and management report March 2021 i
DOCUMENT CONTROL
Disclaimer
This document has been prepared by Low Ecological Services P/L for CDM Smith Australia Pty Ltd, on
behalf of the Northern Territory Government (NTG) Department of the Chief Minister and Cabinet.
Low Ecological Services has prepared this document using the skill and care expected from
professional scientists to provide factual and technical information and reasonable solutions to
identified risks. It does not constitute legal advice.
Acknowledgements
Low Ecological Services acknowledges the assistance of Tony Griffiths and the Flora and Fauna
Division, NTG Department of Environment, Parks and Water Security, for providing the survey design
and protocol, expertise and advice, equipment, and field supervision. We also acknowledge the
Djurrubu Rangers for providing logistical and technical information, and assistance on site. Justin Bott
from Connect Environmental assisted in the field and provided useful background information about
previous surveys of the site in 2020. Celeste Lymn from the Department of Agriculture, Water and
Environment helped with permits and assisted on site. Low Ecological Services staff involved in the
field work: Kate Stevens, Joe Rosewarne, Mac Moyses, Claire Treilibs, Xavier Tingle and Nicola
Hanrahan. This report was prepared by Claire Treilibs and reviewed by Bill Low.
Document Details
Name of Document: Population and management assessment of the black footed tree-rat for the Jabiru power station development
Authors: Claire Treilibs
Client: CDM Smith Australia Pty Ltd
Name of Project: Jabiru Lot 2303 black-footed tree-rat survey
Document Control
Approvals Name Signature Date
Originator: Low Ecological Services P/L 24/3/21
Reviewer: Bill Low 24/3/21
Administrator: CDM Smith Australia Pty Ltd
Approver: CDM Smith Australia Pty Ltd
Custodian: CDM Smith Australia Pty Ltd
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Jabiru BFTR survey and management report March 2021 ii
Table of Contents
Document control .................................................................................................................................... i
Executive summary ................................................................................................................................ iii
1 Introduction .................................................................................................................................... 1
1.1 Context .................................................................................................................................... 1
1.2 Scope of survey ....................................................................................................................... 1
2 Method ........................................................................................................................................... 1
2.1 Survey design .......................................................................................................................... 1
2.2 Data analysis ........................................................................................................................... 2
3 Results and discussion .................................................................................................................... 3
4 Conclusion and recommendations ................................................................................................. 4
5 References ...................................................................................................................................... 4
Low Ecological Services P/L
Jabiru BFTR survey and management report March 2021 iii
EXECUTIVE SUMMARY
Low Ecological Services was commissioned by CDM Smith Australia Pty Ltd to undertake a population
survey of the threatened black-footed tree-rat, Mesembriomys gouldii, at the site of the proposed Jabiru
hybrid power station (Lot 2303, Jabiru). In September 2020, the black-footed tree-rat was detected at
14 of 20 camera traps within Lot 2303, but these data could not be used to determine the number of
individuals. Feasibly, the number could range from a single active and broad-ranging individual to many
animals. This current survey aimed to accurately determine the number of individual tree-rats within Lot
2303 as well as adjacent similar habitat, and test the extent of movement of individuals into and out of
the lot.
To ensure appropriate survey design and techniques, the Flora and Fauna Division of the NT
Department of Environment, Parks and Water Security were consulted throughout the survey. The
Division provided the survey design and supervised the field program. One hundred and ninety-one
traps were set for five nights (191 x 5 = 955 trap nights) within the vegetated area of Lot 2303 and the
surrounding woodland. No black-footed tree-rats were trapped. Northern brown bandicoots, Isoodon
macrourus, were captured eight times; seven within Lot 2303 and one outside, with at least one
identifiable re-capture.
Given the substantial trapping effort, and the highly trap-able nature of tree-rats, expert opinion is that
the zero tree-rat result is a true absence of the species from Lot 2303 and surrounds. The tree-rats that
were detected in Lot 2303 in September 2020 (late dry season) now appear to be absent from the site.
One explanation is that the tree-rats have dispersed to surrounding areas that have now become more
suitable during the above average wet season conditions, for example with fruiting trees, ground cover
and hollow-bearing logs.
While the trapping data show no current resident population of black-footed tree-rats, the habitat within
Lot 2303 is in good condition and supports a population of northern brown bandicoot among other
fauna. We recommend spotters be used to check for animals ahead of the machinery when the
vegetation is cleared. The Djurrubu rangers would be well placed to take on this spotter role. Certain
staff members of the Djurrubu Rangers also have the skills to care for injured animals and are keen to
assist. We also recommend that the bottom of the boundary fence of Lot 2303 be lifted or folded along
the entire perimeter to allow fleeing animals to escape. We recommend vegetation be cleared
incrementally over a few days so that animals have an opportunity to relocate between clearing efforts,
and that the project area is cleared from west to east, in the direction away from the rubbish tip, so that
animals might move toward more intact habitat.
Low Ecological Services P/L
Jabiru BFTR survey and management report March 2021 1
1 INTRODUCTION
Low Ecological Services was commissioned by CDM Smith Australia Pty Ltd to undertake a population
density survey of the threatened black-footed tree-rat, Mesembriomys gouldii, at the site of the proposed
Jabiru hybrid power station (Lot 2303, Jabiru). The black-footed tree-rat had recently been detected
within Lot 2303, and there is a risk that clearing of the vegetation for the power station development
could significantly impact a population of this threatened species. The findings from this population
survey will help to assess management options for the black-footed tree-rat.
The black-footed tree-rat is currently listed in Northern Territory and National legislation as Vulnerable
(NT Territory Parks and Wildlife Conservation Act) and Endangered (Environmental Protection and
Biodiversity Conservation Act 1999). Across northern Australia and Kakadu National Park, the species
has undergone a rapid and severe decline in recent decades along with a suite of other medium-sized
mammal species (Woinarski et al 2011).
1.1 Context
A survey using camera traps within Lot 2303 in September 2020 detected black-footed tree-rat at 14 of
20 camera locations (Connect Environmental 2021). This finding, combined with an absence of tree
rats from all but one of 35 camera traps locations in the broader Jabiru area sampled in
November/December 2020 (Connect Environmental 2021), suggested that Lot 2303 may provide
important habitat for a local subpopulation of this species.
However, the data from the September 2020 sample cannot be used to determine the number of
individuals using the habitat within Lot 2303. Feasibly, the number could range from a single active and
broad-ranging individual to many animals. This current study aimed to accurately determine the number
of individual tree-rats within Lot 2303 as well as adjacent similar habitat, and test the extent of movement
of individuals into and out of the lot.
Mammologists from the NTG Darwin Flora and Fauna division, Department of Environment, Parks and
Water Security, advised that live trapping was the most suitable technique for estimating the population
size and spatial use of tree-rats, and provided a survey design and trapping protocol to assess the
population. Data from captured and re-captured animals (marked using PIT tags) over sequential nights
could then be used to provide a robust estimate of population size. The movement of individual animals
would also help determine tree-rat habitat use within and adjacent to the project area, and appropriate
management options.
1.2 Scope of survey
The scope of this survey was to:
1. Determine the population size and spatial use of black-footed tree-rats within and adjacent to
Lot 2303, the development area for the Jabiru hybrid power station.
2. Assess management options for the black-footed tree-rat population occupying the
development area.
2 METHOD
2.1 Survey design
A trapping grid was designed to overlay the vegetated portion within Lot 2303 (n = 66) and a 200 m
buffer in the adjacent woodland (n = 150), with traps positioned 50 m apart (Figure 1). However,
difficulties laying traps in inundated areas on the western side, and hazardous areas around the landfill
Low Ecological Services P/L
Jabiru BFTR survey and management report March 2021 2
sites, resulted in a decision to remove the ‘rubbish tip block’ of 25 traps from the survey after the first
night (see Figure 1). The remaining 191 traps were set for five nights to ensure the recapture rates
would be sufficient for population estimates (191 x 5 = 955 trap nights).
Figure 1 Trapping grid over Lot 2303 and adjacent woodland
Small cage traps were baited with a mixture of peanut butter, oats and honey. Traps were baited and
set in the late afternoon and cleared at first light each morning. All traps were cleared by 8:30 am each
day to reduce heat stress on animals and were closed during the day to avoid animals entering the
traps. Traps were uniquely coded so that movement of uniquely identified individual animals could be
tracked.
Upon capture of a trapped tree-rat, LES staff were instructed in the Flora and Fauna Division protocol;
tree-rats would be processed immediately at each trap location, and each animal weighed (g), sexed
and a unique Passive Implant Transponder (PIT tag) inserted with a sterile applicator beneath the skin
on the back of the neck, and the details recorded with date, time and trap location. Once processed,
each animal would be released at the point of capture. Where trapped animals are recaptures, the PIT
tag ID and trap location would be recorded with a hand held reader and the animal released at the site
of capture. Data would be recorded to a suitable proforma and subsequently transferred to Excel in a
format that could be easily manipulated for analysis. If species other than black-footed tree-rat were
captured, the date, identity and location would be recorded. If other threatened mammal species were
captured, it was recommended that these were also PIT-tagged, providing this could be done within the
time available and permit conditions allowing. If unexpected adverse events occur, the protocol
described in the AEC permit approval were to be enacted.
2.2 Data analysis
Experienced members of the Flora and Fauna Division planned to use a closed capture-mark-recapture
population model to estimate population size. Capture data would have been summarised to create a
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2T2S2R2Q2P2O2N2M2L2K2J2I2H2G2F2E2D2C2B2A
3T3S3R3Q3P3O3N3M3L3K3J3I3H3G3F3E3D3C3B3A
4T4S4R4Q4P4O4N4M4L4K4J4I4H4G4F4E4D4C4B4A
5T5S5R5Q5P5O5N5M5L5K5J5I5H5G5F5E5D5C5B5A
6T6S6R6Q6P6O6N6M6L6K6J6I6H6G6F6E6D6C6B6A
7T7S7R7Q7P7O7N7M7L7K7J7I7H7G7F7E7D7C7B7A
8T8S8R8Q8P8O8N8M8L8K8J8I8H8G8F8E8D8C8B8A
9T9S9R9Q9P9O9N9M9L9K9J9I9H9G9F9E9D9C9B9A
10T10S10R10Q10P10O10N10M10L10K10J10I10H10G10F10E10D10C10B10A
11T11S11R11Q
12T12S12R12Q
13T13S13R13Q
14T14S14R14Q
Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN,
and the GIS User Community
266800
266800
267200
267200
267600
267600
86
00
000
86
00
000
86
00
400
86
00
400
Low Ecological Services P/LPhone: (08) 89555 222
Web: [email protected]
Universal Transverse Mercator (UTM)
Map Grid of Australia (MGA) Zone 53
Horizontal Datum: GDA 1994
Vertical Datum: AHD (m)
Black-footed tree-ratpopulation survey
Trap grid designLow Ecological Services P/L 2021
0 50 100 150 200 250 Metres
¯
traps not set in inundated areas
traps set for one night then removed
traps set for five nights
Fence
Lot 2303Rubbish tip block
Low Ecological Services P/L
Jabiru BFTR survey and management report March 2021 3
capture history of each individual over the five trap nights. Data would have been analysed in Program
MARK v9.0 to estimate capture probability (p) and the recapture probability (c) to estimate population
size (N).
3 RESULTS AND DISCUSSION
No black-footed tree-rats were trapped over the 955 trap nights. Northern brown bandicoot, Isoodon
macrourus, were trapped in eight instances (examples Figure 2); seven within Lot 2303 and one outside
(trap 5A, see Figure 2). At least one bandicoot was re-captured, identified as the same individual from
an old eye injury and a missing tail, at traps 7N and 8N.
Figure 2 Examples of northern brown bandicoots captured at 7I (left) and 8N (right)
Figure 3 Trap locations of captured northern brown bandicoots in Lot 2303 and adjacent woodland
1T1S1R1Q1P1O1N1M1L1K1J1I1H1G1F1E1D1C1B1A
2T2S2R2Q2P2O2N2M2L2K2J2I2H2G2F2E2D2C2B2A
3T3S3R3Q3P3O3N3M3L3K3J3I3H3G3F3E3D3C3B3A
4T4S4R4Q4P4O4N4M4L4K4J4I4H4G4F4E4D4C4B4A
5T5S5R5Q5P5O5N5M5L5K5J5I5H5G5F5E5D5C5B5A
6T6S6R6Q6P6O6N6M6L6K6J6I6H6G6F6E6D6C6B6A
7T7S7R7Q7P7O7N7M7L7K7J7I7H7G7F7E7D7C7B7A
8T8S8R8Q8P8O8N8M8L8K8J8I8H8G8F8E8D8C8B8A
9T9S9R9Q9P9O9N9M9L9K9J9I9H9G9F9E9D9C9B9A
10T10S10R10Q10P10O10N10M10L10K10J10I10H10G10F10E10D10C10B10A
11T11S11R11Q
12T12S12R12Q
13T13S13R13Q
14T14S14R14Q
Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN,
and the GIS User Community
266800
266800
267200
267200
267600
267600
86
00
000
86
00
000
86
00
400
86
00
400
Low Ecological Services P/LPhone: (08) 89555 222
Web: [email protected]
Universal Transverse Mercator (UTM)
Map Grid of Australia (MGA) Zone 53
Horizontal Datum: GDA 1994
Vertical Datum: AHD (m)
Black-footed tree-ratpopulation survey
Non-target speciesLow Ecological Services P/L 2021
0 50 100 150 200 250 Metres
¯
traps not set in inundated areas
traps set for one night then removed
traps set for five nights
Fence
trapped_bandicoots_20mbuffer
Lot 2303Rubbish tip block
Low Ecological Services P/L
Jabiru BFTR survey and management report March 2021 4
Given the substantial trapping effort, and the highly trap-able nature of tree-rats, there is a high degree
of confidence that the zero tree-rat result is a true absence of the species from Lot 2303 and surrounds
(T. Griffiths pers. comm. March 2021). The tree-rats detected in Lot 2303 in September 2020 (late dry
season) now appear to be absent from the site. One explanation is that the tree-rats have dispersed to
surrounding areas that have now become more suitable during the above average wet season
conditions, for example with fruiting trees, ground vegetation and hollow-bearing logs.
4 CONCLUSION AND RECOMMENDATIONS
While the trapping data show no current resident population of black-footed tree-rats, the habitat within
Lot 2303 is in good condition and supports a population of northern brown bandicoot among other
fauna. We strongly recommend spotters be used to check for animals ahead of the machinery when
the vegetation is cleared. The Djurrubu rangers would be well placed to take on this spotter role. Certain
staff members of the Djurrubu Rangers also have the skills to care for injured animals and are keen to
assist (Shay Wrigglesworth has a Wildlife caring permit). We also recommend that the bottom of the
boundary fence of Lot 2303 be lifted or folded along the entire perimeter to allow fleeing animals to
escape. We recommend vegetation be cleared incrementally over a few days so that animals have an
opportunity to relocate between clearing efforts, and that the project area is cleared from west to east,
in the direction away from the rubbish tip, so that animals might move toward more intact habitat.
5 REFERENCES
Connect Environmental. (2021). Biodiversity assessment report, Lot 2302, Jabiru, NT. Darwin.
Woinarski, J.C.Z., Legge, S., Fitzsimons, J.A., Traill, B.J., Burbidge, A.A., Fisher, A., Firth, R.S.C., Gordon, I.J., Griffiths, A.D., Johnson, C.N., McKenzie, N.L., Palmer, C., Radford, I., Rankmore, B., Ritchie, E.G., Ward, S. and Ziembicki, M. (2011), The disappearing mammal fauna of northern Australia: context, cause, and response.
Conservation Letters, 4: 192-201. https://doi.org/10.1111/j.1755-263X.2011.00164.x