How did you get the science so wrong?

Please review some of the science behind this issue and alter your article accordingly:
1) Kangaroo populations fluctuate in response to seasonal conditions, not the commercial harvest. No Australian scientists blame the decline after 2001 on the harvest, rather the worst drought in recorded history. Numbers have started to rise again flowing the breaking of this drought. This data is available at It’s worth noting that even at the peak of the drought, populations were only marginally less than the long term average.
2) The report by Hacker et al does not at any place refer to numbers “per sq kilometer would result in a threatened or endangered status to the local population” . Do a word search. Rather it invented a term ‘quasi-extinction’ to discuss a situation reflecting the probability of densities being below the minimum density (the nominal value) for an unharvested population. I can forward an extensive critic by Hacker et al of the ‘Decimation of an Icon’ report in which they point to wide and gross miss-representations of their work.
Thus I would put it to you that it’s more likely that Australian scientist are not ‘concerned that sustainability of the species is being mishandled’, than the opposite.
3) Kangaroos are not classified as pests. All the State Management Plans list them as sustainable resources, not pest.
4) The 2010 UTS report you are citing compared the amount of meat produced from a kangaroo to a sheep to come to the conclusion that kangaroos could never replace sheep. Unfortunately they had to invent a 49 kg ‘average sheep carcass weight’ to do so. This would mean that these sheep were 110 kg live, and if that’s the average then there would be some at say 130-150 kg, which is the size of the average sumo wrestler. The UTS report is currently being extensively criticised by a group of informed kangaroo managers, this article will be published soon.
5) Joey mortality is allowed for in calculations of the quota, it’s taken into account in the extensive modelling which predicts populations changes in response to seasonal conditions and harvest level.

The kangaroo harvest is widely held by informed Australian scientists to be a model of wise and sustainable resource utilisation. And to potentially point the way to a more sustainable use of our arid grazing rangelands, perhaps you could cite the work of some of these scientist rather than just the few who oppose it on ethical grounds driven by an animal liberation paradigm.



  1. 0 Votes

    We get science so wrong becuase were not actually right in every project we do were not the nature were the humans who study it we are never going to get the right answer were just getting a predicamint Thats it

  2. 0 Votes

     It’s pretty easy to miss important points if you first hear about an issue from certain sources, especially if you’re not a trained scientist. So, try not to be too harsh on the author.  Nevertheless, while we may not be perfect, it’s important we try to make our articles as accurate as possible. So, thank you for bringing the errors in this piece to our attention. 

  3. 0 Votes

    1) I did not claim that anyone blamed the kangaroo decline on harvesting. I claimed that the harvest percentage does not decrease during droughts, a possibly unsustainable practice. In the link you cite (which is included twice in the article), kangaroos are reported to recover fully from severe drought in 7 years. The last major drought caused a 43 million roo population to go down to 23.6 million. In 2010 the population is 25.1 million. I do no consider this number to show that kangaroo populations are recovered or on the rise, even after 9 years. My point is that if drought such as the ones that have occurred once a decade for the last 30 years can wipe out half the population, shouldn’t harvesting allow for a near full recovery and adjust the quota as such?

    2)The Hacker et all report says “Only very small areas are economically harvestable at kangaroo densities less than or equal to 5/sq km…strategies that produce average densities of less than 5/sq km would result in minimum densities less than 2/sq km and could be considered a threat to species conservation” and “populations below 2 kangaroos per sq km would generally be considered at risk of extinction.’ I maintain that my article summarizes this information accurately. You did not provide a link to your article that refutes their claims, so I am not able to comment on that, but the authors of Decimation of an Icon are concerned, regardless of what other literature is out there, and that is all that I claim.

    3)I did not claim State Management Plans classified roos as pests. I said “ranchers have a history of regarding them as pests.” Yes, I agree that many consider them as a resource, especially State Management Plans. This does not reflect the regard of the culture however.

    4)I did not claim that kangaroos wouldn’t replace sheep because of weight differentiation. I spoke of farmers having small pastures not conducive to switching to harvesting kangaroos, and the lack of a livestock farming decrease in the 20 years so far. Who is a “group of informed kangaroo managers” and are they possibly benefiting from kangaroo harvest profit? If there is an article that is not yet out, then how am I to refer to it?

    I have some concern to citing authors who directly benefit from kangaroo profit. They may be informed, but they may also be biased. Much like claiming that a product is safe because the company says so, I wanted to go to other sources. I did not see anything to indicate that their science was, as you put it “so wrong.”

    • 0 Votes

      1) I think almost anyone would interpret the lines:

      The total population of the species of kangaroos harvested dropped from 57 million in 2001 to 23 million in 2006. What is driving this decrease? Economic interests is a major factor…….

      as you suggesting the decline was due to the commercial harvest.

      The quota DOES change with population levels. It is a variable percentage of total population, so if populations fall quota falls also. Indeed even the level of quota changes. If regional populations are falling dramatically in response to seasonal conditions then quota may only be 10%. If they are increasing it may rise to 20% in regions. There are also mechanism to shut down the harvest in regions altogether if need be. Typical quotas are 12%.

      The populations of 2000-01 were unusually high in response to a run of extremely good seasons. Some 70% higher than the previously recorded high in fact, they could in no way be considered ‘normal’ (although as anyone who is informed on the rangeland environment recognises, there is no normal, it is a highly variable ecology). See the graph below:

      The long run average pop is approx 23 million, the current pop (even after the worst drought on record) is 25 million. So the problem is???? Nothing other than population fluctuations in an animal perfectly adapted to an environment with high variations in seasonal conditions.

      2) See below a direct quote from Hacker et al in their critic of Decimation of an Icon regarding the quotes you refer to at point 2.

      The average densities referred to are long-term average densities – not populations that can fall to 5 kangaroos per sqkm (or lower). Harvested populations that have a long term density of > 30 per (some places in Queensland) can fall to lower than 5 per and can still be harvested sustainably. There is both modelling and empirical evidence to support this. But if a population had a long-term average density of 5 (or lower) I would argue strongly that harvesting that population would be very risky and given that the outcome is unknown, should not be harvested at currently accepted rates (i.e. 15-17% per annum) (unless there was evidence that it could be done sustainably).

      What we said on p37- in relation the effect of harvest strategies on long term average kangaroo densities – was:
      ‘The relationship between (long-term) mean kangaroo density and minimum kangaroo density for these [900] options is shown in Fig. 19. Density of unharvested populations in these simulations rarely fell below a minimum of 5 individuals per sq km. Although the critical minimum density is not clearly defined, populations below 2 per sq km would generally be considered at risk of extinction. On this basis, Fig. 19 suggests that any option resulting in an average long term density of less than 10 per sq km should be rejected since in all such cases the minimum density is likely to fall below the ‘critical’ level.

      Clearly their data has been used incorrectly, they are refering to long term average densities, not short term ones. Densities in all regions are now increasing dramatically. They have as I mentioned extensively critiqued the ‘report’ you are citing, I can send their critic if you are interested.

      I am sure that all the independent scientists who have authored the list of articles below examining the kangaroo industry and commenting favourably on its sustainability would be concerned about being labelled as ‘profiting’ from the industry. They are all responsible, highly regarded scientist attempting to do their bit to improve the sustainability of our environment who have no financial interest in the industry what-so-ever. To suggest otherwise is, I would suggest, a little out of line.

      Flannery, T. 1996. The Future Eaters, Reed Publishing.
      Fletcher, M., Southwell, c, Sheppard, N, Caughley, G, Grice, D, Grigg, G, and Beard, L. (1990) Kangaroo population trends in the Australian rangeland, 1980-87. Search vol 21 no1
      Garnuat, R. (2008) The Garnaut Climate Change Review. Cambridge University Press. Melb
      Hale, P. (2001) Kangaroo genetics, Impacts of Harvesting. Conservation Biology Program, The Ecology Center, University of Queensland, Brisbane
      McLeod, S.R, Hacker, R.B. and Druhan, J.P. (2001) Sustainable management of age-structured kangaroo populations
      Olsen, P. and Braysher, M (2001) Situation Analysis Report: Current state of scientific knowledge on kangaroos in the environment, including ecological and environmental impact and effect of culling. A report for NSW NPWS.
      Pople A (1996) Effects of harvesting upon the demography of red kangaroos in Western Queensland. University of Queensland Thesis.
      Pople, A.R and Grigg, G (2001) Commercial Harvesting of Kangaroo in Australia. Environment Australia. Canberra
      Australasian Wildlife Management Society 2004. Position Paper on the Commercial Harvesting of Macropods. Available at [26 February 2008
      jonzen, N., Pople, A.R., Grigg, G.C. and Possingham, H.P. 2005. Of sheep and rain: large-scale population dynamics of the red kangaroo. Journal of Animal Ecology 74: 22-30.
      Olsen, P. and Low, T. 2006. Situation Analysis Report: Update on Current State of Scientific Knowledge on Kangaroos in the Environment, Including Ecological and Economic Impact and Effect of Culling. Prepared for the Kangaroo Management Advisory Panel. Kangaroo Management Advisory Committee, NSW.

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