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ACRIS Kangaroo Density Update 2004-2008 Updated information to that provided in

Rangelands 2008 – Taking the pulse

Gary Bastin, ACRIS Management Unit CSIRO, PO Box 2111, Alice Springs NT 0871

(email: Gary.Bastin@csiro.au)

This project is supported by Ninti One Limited, through funding from the Australian Government's Caring for our Country.

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The views and opinions expressed in this publication are those of the authors and do not necessarily reflect those of the Australian Government or the Minister for Sustainability, Environment, Water, Population and Communities. While reasonable efforts have been made to ensure that the contents of this publication are factually correct, the Commonwealth does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication.

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Change in kangaroo densities between 1993 and 2003 was reported for the New South Wales rangelands and parts of Queensland and South Australia in the ‘Total grazing pressure’ section of Rangelands 2008 – Taking the pulse (Bastin et al. 2008) (see pages 64-67).

This brief report updates changes in kangaroo density between 2004 and 2008, and also includes information for the southern and western parts of the WA rangelands (2009 data also available for WA).

Key points

Systematic surveys of kangaroo numbers continue across the NSW rangelands, the sheep-grazed pastoral tenure of SA and much of western Queensland. Similar surveys also occur in the southern and western parts of the WA rangelands and these data are now available to ACRIS.

Additional data since 2003 show that:

• The combined density of kangaroo species in WA (reds and western greys) was much lower than the combined density of species in eastern states (including SA).

• There has been a general decline in kangaroo populations in all bioregions (with available data for reporting) since 2003. Regional densities in 2008 were generally considerably below the average for the 1984-93 period (used as a base for reporting change).

• Density declines were related to drier years (poorer seasonal quality) in the middle years of the last decade. For the example bioregions examined (see Figure 5) there has been a variable response with better seasons towards the end of the reporting period. Kangaroo densities have remained largely unchanged in some regions and slowly increased in others.

Kangaroo management

Kangaroos are harvested in Queensland, NSW, SA and WA based on survey numbers and quotas set by the Australian Government under the EPBC Act 1999. Harvested species include: red kangaroos (Macropus rufus), all states; eastern grey kangaroos (M. giganteus), Queensland and NSW; and western grey kangaroos (M. fuliginosus), NSW, SA and WA.

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Harvest quotas are based on periodic aerial surveys, annual for most jurisdictions and triennial for much of WA (see Figure 1). Box 1 provides more information on data sources.

Figure 1. Location of aerial survey transects for monitoring the density of red and western grey kangaroos in WA. Flight lines are separated by 0.5o of latitude. Note that euro monitor blocks were not surveyed in 2010. Map: WA Department of Environment and Conservation.

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Box 1. Data on kangaroo numbers

Each state monitors its kangaroo populations on a one to three year basis and harvest quotas are generally set at between 15-20% of the estimated population of each species. Since about 1980 most states have used fixed-wing aircraft flown along set transects to monitor kangaroo numbers. Queensland now uses helicopters for their aerial surveys.

Kangaroo density data for Queensland, NSW and SA are reported by kangaroo management zones (alternatively, harvest zones), see Map 1. The Queensland zones approximate bioregions and in SA, the zones are the former Soil Conservation Board districts (with survey effort concentrated south of the Dog Fence).

Kangaroo density data for NSW data are available on-line (http://www.environment.nsw.gov.au/wildlifemanagement/KMPPopulationEstimatesWest.htm, accessed 20 July 2009). Updated data for SA were obtained from the Department of Environment and Natural Resources and Queensland updates were provided by Geoff Lundie-Jenkins, Department of Environment and Resource Management. ACRIS provided financial assistance to the WA Department of Environment and Conservation to digitise their historic paper records. Winston Kay subsequently supplied all available WA data (1981 to 2009) aggregated to 1o blocks along the flight lines shown in Figure 1.

The ACRIS-MU converted kangaroo density data from management zones to those bioregions predominantly covered by the various zones (Map 1). Kangaroo densities were then converted to dry sheep equivalents (DSE) for comparison with domestic stocking densities, as per Rangelands 2008 – Taking the pulse (Bastin et al. 2008). For current reporting, a factor of 0.35 is used to convert the density of red kangaroos to dry sheep equivalents (see Box 2).

Map 1. Regions surveyed for kangaroo numbers.

Map compiled by ACRIS-MU from shape files provided by Queensland, NSW and SA agencies contributing to ACRIS.

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As for Rangelands 2008 – Taking the pulse, two sets of maps are used to report change: (i) change in kangaroo densities by bioregion for each year between 2004 and 2008, and (ii) the percentage change in densities between 1994 and 2008 relative to the average of the

preceding 1984-1993 period. The average for 1984 to 1993 is used as a base to accommodate data now available from WA.

Change in kangaroo density

The combined density of red, eastern grey and western grey kangaroos was higher in the eastern states (particularly NSW) compared with WA (Figure 2). Densities in WA bioregions were <1 DSE km-2 in most years and maximal (at 2.1 DSE km-2) in the Central Band, Nullarbor Plain sub-IBRA between 2004 and 2006.

For Queensland, NSW and SA, the combined density of kangaroo species declined between 2003 and 2005 and then either remained relatively stable or increased (particularly in the south-eastern bioregions of southern Queensland, NSW and eastern SA). Bioregional densities in recent years were also considerably lower than those reported between 1993 and 2003 in Rangelands 2008 – Taking the pulse (partly due to the lower [0.35] DSE factor). Note that scaling for the equivalent density map in that report (Figure 3.33, page 66) was between <2 and >20 DSE km-2 (compare 0 to >5 DSE km-2 in Figure 2).

Figure 3 further illustrates that recent kangaroo densities in Queensland, NSW and SA were considerably lower than in the 1990s and start of the last decade. Here, the yearly density for each bioregion has been ranked against the average density for 1984-1993 (all densities reported as DSE using the 0.35 conversion factor). Values above 100 indicate yearly densities above the base (i.e. increased density) and values less than 100 mean a decline. The recent decline for NSW is particularly marked with individual bioregions between 2004 and 2008 having densities of 14% to 67% of the 1984-1993 base. Most SA bioregions had approximately 50-75% of their base density over the same period. In Queensland, densities for the two main bioregions (Mulga Lands and Mitchell Grass Downs) declined by about a third during the 2004-2008 period compared with the average for the 1984-1993 base period.

Note that the scaling in Figure 3 is the same as for Figure 3.34 (page 66) in Rangelands 2008 – Taking the pulse but the base period has been adjusted slightly to better accommodate available WA data. (The base period for the 2008 report was 1984-91 compared with 1984-93 used here.)

There have also been recent declines in kangaroo density for most WA bioregions compared with their 1984-1993 base value. Densities reduced to as much as 30% of the base value in most bioregions in the 2004-2006 and 2007-2009 periods (and fell to as low as 15% of the base in the Pilbara). The one exception was the Carnarvon bioregion where there has been a recent increase in density compared to the 1984-1993 base period (Figure 3).

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Figure 2. Combined densities of three kangaroo species (red, eastern grey, western grey) in eastern, southern and western rangeland bioregions between 2003 and 2008. Note that WA densities are for three-year blocks,

Map compiled by the ACRIS-MU using data supplied by Queensland, NSW, SA and WA.

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Figure 3. The percentage change in density of kangaroos between 2003 and 2008 relative to the mean density for the 1984-1993 period.

Map compiled by the ACRIS-MU using data supplied by Queensland, NSW, SA and WA.

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Recent declines in kangaroo density are graphed for selected bioregions in Figure 4.

Figure 4. Percentage changes in the combined density of three kangaroo species between 1994 and 2008 (2009 for WA) for an example bioregion in each rangeland state. Note that the WA data are aggregated into three-year blocks. Change is expressed relative to the average density for each region for 1984 to 1993. Graph compiled by the ACRIS-MU using data supplied by Queensland, NSW, SA and WA. Relative changes based on the 1984-1993 average for all bioregions with suitable data are tabulated in Appendix 1. Box 2. Kangaroos converted to dry sheep equivalents (DSE)

Kangaroo densities are converted to dry sheep equivalents (DSE) for comparison with domestic stocking densities where one red or grey kangaroo equals 0.35 DSE. This factor is based on studies of the field metabolic rate (i.e. energy requirements) of both red kangaroos and merino sheep (Munn et al. 2008). Adam Munn (University of Sydney) advises that the same factor is appropriate for eastern and western grey kangaroos (Adam Munn, pers comm. 2/12/2009). Adam suggests that taking account of digestibility and feed conversion rates, kangaroos may have a slightly greater equivalence (perhaps 0.42 to 0.45 DSE rather than the 0.35 DSE used here). Further research is required to confirm the most appropriate DSE conversion based on feed-intake

Note that the current DSE conversion is different to that used for Rangelands 2008 – Taking the pulse reporting (i.e. red kangaroos = 0.6 DSE, eastern and western greys = 0.5 DSE in that report).

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40

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1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

% C

hang

e in

Kan

garo

o D

ensi

ty (D

SE) -

198

4-19

93 b

ase

NSW Broken Hill ComplexQLD Mitchell Grass DownsSA GawlerWA Murchison

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Kangaroo density and rainfall

It is well known that the density of kangaroo species increases in wetter years and decreases in droughts. Examples of changes in kangaroo density and seasonal quality were provided in Rangelands 2008 – Taking the pulse (Figure 3.36, page 67). Further examples are provided here (Figure 5).

In the NSW Broken Hill Complex bioregion, the combined density of kangaroos decreased sharply between 2001 and 2003 (compared to the average for 1984 to 1993) following much below median rainfall. Kangaroo density then increased slowly to 2008 with three of the years preceding 2008 having slightly above median rainfall.

There was a similar rapid decrease in kangaroo density with drier years between 2001 and 2003 in both the Queensland Mitchell Grass Downs and SA Gawler bioregions. This reduced density then more-or-less held until 2008 in both bioregions despite some better seasons in the Gawler IBRA and progressively increasing rainfall in the Mitchell Grass Downs.

The seasonal trends were less apparent for the Murchison bioregion in WA. Kangaroo density declined between 1998-2000 and 2004-2006 with some drier years. There was a subsequent small increase in density in 2007-2009 with above-median rainfall.

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NSW – Broken Hill Complex bioregion Queensland – Mitchell Grass Downs bioregion

SA – Gawler bioregion WA – Murchison bioregion Figure 5. Changes in kangaroo densities in relation to seasonal quality indicated by decile rainfall for four example bioregions between 1992 and 2008. Note that the WA kangaroo data are aggregated into three-year blocks. Change is expressed relative to the average density for each region for 1984 to 1993. Map: the ACRIS-MU. Data sources: rainfall, Bureau of Meteorology; kangaroo density, data supplied by Queensland, NSW, SA and WA kangaroo management agencies contributing to ACRIS.

References

Bastin, G. & the ACRIS Management Committee (2008). Rangelands 2008 – Taking the Pulse. Published on behalf of the ACRIS Management Committee by the National Land and Water Resources Audit, Canberra. Available at: http://www.environment.gov.au/land/rangelands/acris/index.html

Munn, A. J., Dawson, T. J., McLeod, S. R., Croft, D. B., Thompson, M. B. and Dickman, C. R. (2008). Field metabolic rate and water turnover of red kangaroos and sheep in an arid rangeland: an empirically derived dry-sheep-equivalent for kangaroos. Australian Journal of Zoology, 57, 23-28.

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3

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7

8

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10

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Seas

onal

qua

lity

(dec

ile ra

infa

ll)

20

40

60

80

100

120

140

160

180

% o

f 198

4-93

bas

e ka

ngar

oo d

ensi

ty

decile rainfall

kangaroo density

0

1

2

3

4

5

6

7

8

9

10

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Seas

onal

qua

lity

(dec

ile ra

infa

ll)

20

40

60

80

100

120

140

160

180

% o

f 198

4-93

bas

e ka

ngar

oo d

ensi

ty

decile rainfall

kangaroo density

0

1

2

3

4

5

6

7

8

9

10

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Seas

onal

qua

lity

(dec

ile ra

infa

ll)

20

40

60

80

100

120

140

160

180

% o

f 198

4-93

bas

e ka

ngar

oo d

ensi

ty

decile rainfall

kangaroo density

0

1

2

3

4

5

6

7

8

9

10

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Seas

onal

qua

lity

(dec

ile ra

infa

ll)

20

40

60

80

100

120

140

160

180

% o

f 198

4-93

bas

e ka

ngar

oo d

ensi

ty

decile rainfall

kangaroo density

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Appendix 1. Percentage changes in the combined density of three kangaroo species between 1994 and 2008 (2009 for WA) for bioregions in each rangeland state. Note that the WA data are aggregated into three-year blocks. Change is expressed relative to the average density for each region between 1984 and 1993.

Bioregion 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 NSW Murray Darling Depression

105 114 86 105 90 95 71 90 97 48 48 38 37 48 62

NSW Riverina 122 108 119 104 100 115 89 93 115 69 58 55 52 55 61 NSW Darling Riverine Plains

78 82 56 80 110 91 106 115 148 70 49 28 42 41 40

NSW Mulga Lands

81 79 72 102 98 87 88 120 107 38 43 38 34 39 45

NSW Simpson Strzelecki Desert

84 87 78 129 126 77 76 108 65 34 39 45 30 36 50

NSW Channel Country

86 84 78 131 129 76 76 110 63 33 38 46 29 34 48

NSW Cobar Peneplain

92 102 95 97 113 119 107 130 149 80 60 60 47 44 51

NSW Broken Hill Complex

74 111 76 114 95 84 71 96 84 36 49 33 39 56 67

NSW Brigalow Belt South

83 69 30 59 143 86 151 126 160 66 33 14 39 49 39

QLD Darling Riverine Plains

51 44 60 54 84 93 94 121 161 89 83 95 91 90 85

QLD Mulga Lands

63 58 79 80 107 133 141 178 195 107 68 88 71 77 84

QLD Mitchell Grass Downs

115 67 94 59 113 123 152 128 124 107 66 65 77 65 83

SA Murray Darling

121 150 171 114 101 79 79 66 120 90 84 51 56 102 89

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Bioregion 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Depression SA Broken Hill Complex

103 127 128 117 138 91 88 113 69 50 48 39 37 43 42

SA Gawler 115 171 150 99 126 141 144 107 107 75 75 66 76 55 79 SA Flinders Lofty Block

90 116 122 97 115 86 84 103 77 54 66 58 58 56 61

SA Stony Plains (south of Dog Fence)

85 137 129 70 89 87 122 98 102 63 65 58 58 35 39

WA Carnarvon 27 125 83 83 118 WA Coolgardie (Eastern Goldfields sub-IBRA)

56 206 118 94 74

WA Gascoyne 53 135 92 30 39 WA Murchison 51 115 100 50 59 WA Nullarbor (Central Band sub-IBRA)

61 64 74 95 70

WA Pilbara 36 279 46 22 15 WA Yalgoo 51 118 55 40 98