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Impacts of commercial harvest


Under South Australian and Commonwealth environment legislation, commercial harvest of kangaroos can take place only where it is ecologically sustainable for kangaroos. At a broad level, this translates to ensuring that commercial harvest will not be detrimental to kangaroos. At a finer scale, this means knowing the potential impacts of harvest on kangaroos, and developing and implementing management controls that prevent, mitigate and/or minimise these impacts. In accordance with the requirements of the NPW Act and the EPBC Act, this section details the potential impacts of harvest on kangaroos, and on habitats and ecosystems of which kangaroos form part, and details the management controls that are in place to prevent and minimise these impacts and ensure the sustainability of commercial harvest.

Impacts of harvesting on kangaroos


Commercial harvest has the potential to impact on kangaroo populations, either directly through overharvesting, or indirectly via demographic or genetic impacts on harvested populations. However, it is clear from the 30-plus years of harvesting kangaroos in Australia, and the extensive monitoring and research that has been conducted over that time, that harvest is demonstrably sustainable in terms of population numbers, species distributions and genetic diversity. Scientists and ecologists repeatedly publish evidence of sustainability (e.g. see Pople & Grigg 1999). The endorsement of management plans under legislation, and the upholding of management plans following review by the Administrative Appeals Tribunal (e.g. for South Australia in 2004), demonstrate the sustainability of harvest. A recent formal review of literature and data related to harvesting concluded that there was ‘little doubt that current rates of harvest are sustainable’ (Olsen & Low 2006).

The potential impacts of commercial harvest on kangaroos and management responses are detailed below.


Sustainability of harvest


Harvest at unsustainable levels could impact on the conservation of kangaroo populations.

The sustainability of harvest in South Australia is promoted by:



  • Setting commercial harvest quotas that are based on the direct monitoring of kangaroo populations.

  • Use of conservative species correction factors (Grigg & Pople 1999) that lead to population estimates that underestimate the true size of kangaroo populations. Further, recent revision of correction factors in New South Wales (Cairns & Gilroy 2001) suggests that the factors used in South Australia may considerably underestimate population size in some areas (Pople et al. 2010).

  • Use of a proportional harvest strategy that is appropriate for fluctuating populations (Caughley 1977) and is robust to bias or uncertainty in population estimates (Milner-Gulland et al. 2001).

  • Commercial harvest quotas are set at levels that are ecologically sustainable for kangaroo populations (Caughley 1987). Quotas are sustainable when combined with other mortality factors (including dingo predation north of the dingo-proof fence). The fact that populations are monitored regularly (in most instances, annually) and that quotas are set based on these population estimates, allows for quota setting to incorporate animals that are lost through other mortality factors.

  • Commercial harvest is patchy within management regions and properties, leaving areas of unharvested refuge habitat.

  • State harvest quotas are not completely utilised in South Australia, with harvest tending to equal around 30-70% of the available quota. Actual harvest rates (i.e. the percentage of the kangaroo population that is actually harvested) have been between 5-12%, compared to the sustainable quotas of 15-20% that have been set (Pople et al. 2010).

  • The industry is unlikely to overharvest, as it is not currently viable at kangaroo densities that would be low enough to threaten the conservation of the species.

Sustainability of harvest during drought conditions


Rainfall – through its impact on pasture biomass – is the key regulator of kangaroo populations (see Pople & Grigg 1999). Kangaroo populations decline with the onset of drought conditions and stay low until conditions improve and the availability of food increases. To meet the goal of this plan, it is important that commercial harvest is still sustainable for kangaroo populations during times of drought.

The sustainability of harvest during drought conditions is supported by:



  • A harvesting strategy that is sustainable during, and after, drought conditions (Pople 2003).

  • Quotas set on regular direct monitoring of kangaroo populations. This monitoring allows for quotas to be set with account of the substantial adult mortality that occurs with the onset of drought conditions.

  • The fact that annual harvest quotas have not been completely utilised in recent years, and that there is an economic threshold density below which it is not financially viable to harvest (see Hacker et al. 2004). This means that during times of drought and low kangaroo populations, field processors may cease operating in some areas as it is not financially viable for them to harvest. This provides an added degree of refuge for kangaroo populations during times of drought. This extent of refuge and the density below which it is uneconomic to harvest is dependent upon current market prices. If market forces and prices were to significantly increase, formal regulation of this threshold density at which harvest ceases may be required through a threshold harvesting strategy (Engen et al. 1997, Milner-Gulland et al. 2001).

  • Knowledge that harvesting mortality during drought is compensatory not additive – harvesting removes animals that would die of natural causes during steep population declines (Pople & McLeod 2000). Harvesting tends to remove larger, older, male kangaroos, which are the animals that are generally lost from kangaroo populations with the onset of drought conditions (Pople 1996).

  • A process for developing management responses to evaluate and minimise risk to kangaroo populations in an adaptive approach to management, should the current ongoing drought conditions continue for an extended period of time.


Potential demographic impacts of harvesting


Demography includes the characteristics of populations such as size, growth, distribution and vital statistics including birth and death rates. Commercial harvest of kangaroos has the potential to impact on the demography of harvested kangaroo populations. As Field Processors are paid for carcasses on a per kilogram basis, they preferentially target the larger kangaroos, which tend to be the older males in populations of these sexually dimorphic species.

Commercially harvested populations may have a lower average age compared to that of unharvested populations. The average size of kangaroos in harvested populations is lower, and populations contain a higher proportion of young animals than unharvested populations, but these differences are lessened during drought when older animals are lost from unharvested populations.

The sex bias (i.e. the percentage of harvested kangaroos that are male) of commercial harvest of kangaroos in South Australia varies between each of the harvested species, and also varies between different harvest regions. The sex bias typically varies between 50-60% for red kangaroo, and 60-70% for western grey kangaroo. The sex bias of euro harvest is higher due to the small size of female euros, and the harvest is typically 75-95% male. However, this species is less intensely harvested than the other two species, making up less than 10% of the total harvest in South Australia. The sex bias of harvest varies with the density of kangaroo populations, with Field Processors generally targeting proportionately more females as kangaroo populations decline. In some parts of South Australia, there is a strong relationship between the sex bias of harvest and population size (Pople et al. 2006). In other parts of South Australia the relationship is weak, which limits the applicability of this information for indirect monitoring of kangaroo population trends. Use of this information for indirect monitoring of kangaroo populations will be investigated through Aim 4: Monitor kangaroo populations and Aim 7: Facilitate adaptive management and research.

The demographic impacts of harvest appear to be of little conservation concern (Pople & Grigg 1999). Many of the same demographic effects have been identified in unharvested populations (Pople 1996).

The potential demographic impacts of harvesting are minimised because:


  • Both harvested and unharvested populations show unstable age distributions and a female sex bias (Newsome 1977; Pople 1996). Environmental conditions tend to determine the structure of populations, suggesting that natural influences on population structure are stronger than the influences of harvesting. Demographic impacts of commercial harvest are mirrored in unharvested kangaroo populations following drought (i.e. populations displaying a female sex bias and few large adults).

  • Kangaroos have a high fecundity and the ability to reproduce quickly following losses due to drought or harvesting (see Biology and Ecology section). Populations of kangaroos are not isolated in the landscape, and dispersing individuals are able to contribute to restocking a harvested population.

  • Extent of harvesting is patchy and refugia (e.g. areas that are not harvested) or areas that are lightly harvested occur across the harvested area.

    Both harvest sex bias and the size of harvested kangaroos are monitored through the regular collection of harvest returns. Ways to use this information to guide management will be investigated under this plan (see Aim 4: Monitor kangaroo populations).


Potential genetic impacts of harvesting


The genetic diversity and fitness of animal populations may be influenced by the removal of individuals that display a particular physical characteristic before they can contribute to the next generation. Consequently, there is the potential that the selective harvest of kangaroos (i.e. harvest efforts biased towards older, larger individuals) may lead to genetic impacts.

Harvesting at current rates has been assessed, with the conclusion that it has negligible impacts on kangaroo genetics under present conditions (Hale 2001, 2004; Tenhumberg et al. 2004). This is based on genetic theory, empirical data and modelling.

Potential genetic impacts of harvesting on kangaroos are minimised through:


  • The size of kangaroo populations in relation to the numbers removed through harvesting. The proportional harvest quotas of 20% for red kangaroos, and 15% for western grey kangaroos and euros that will be applied under this plan are well within the 30% harvest levels that Hale (2001, 2004) found to give rise to stable genetic diversity.

  • Dispersal of individuals between populations, and the patchiness of harvest and presence of refugia and lightly harvested areas in the landscape (e.g. due to their remoteness or the fact that they are financially unviable), allow for gene flow between populations, which helps to prevent genetic changes in a population.

  • The large geographic ranges of genetic kangaroo populations relative to the size of the harvested area. This is in part due to the migration of individuals across large distances.

Ensuring animals are killed humanely


Commercial harvest involves the shooting of individual kangaroos and the destruction of pouch young. As such, harvest carries a risk of animals not being killed humanely. This management plan is committed to the humane treatment of kangaroos. Aim 1: Ensure humane treatment of kangaroos clearly sets out the ways in which humane treatment of kangaroos is prescribed by this management plan.

The humane destruction of kangaroos is ensured through:



  • Presence of Commonwealth and State policy and legislation for animal welfare, including the Commercial Code.

  • All kangaroos killed under permit in South Australia must be killed humanely in accordance with the Commercial Code.

  • DEWNR has a zero-tolerance approach to breaches of the Commercial Code .

  • Kangaroo Field Processors must successfully pass mandatory firearms accuracy accreditation specific to kangaroo shooting prior to receiving a permit. This accreditation tests their theoretical understanding and their ability to shoot in accordance with the requirements of the Commercial Code .

  • All kangaroo Field Processors are provided with a copy of the Commercial Code to ensure their awareness of the Commercial Code.

  • Compliance with the Commercial Code is monitored routinely through a compliance program that aims to detect non-compliance and enforce compliance. There are penalties for not shooting in accordance with the Commercial Code, providing an incentive for the industry and landholders to comply.

This management plan will also promote the humane treatment of kangaroos through management actions other than commercial harvest, including: Non-Commercial Code (or a synopsis of the Non-Commercial Code) to ensure their awareness of the Non-Commercial Code.

  • Landholders applying for non-commercial destruction permits are required to show awareness of the firearm specifications listed in the Non-Commercial Code . Landholders are able to list another shooter on the permit if there is a risk that they do not have the competency to shoot in accordance with the Non-Commercial Code.

  • Introducing self-assessment tools for non-commercial destruction permit applicants, so that they can test their competency to shoot in accordance with the requirements of the Non-Commercial Code.

  • All persons engaged to cull kangaroos on reserves must have successfully passed a firearms accuracy accreditation course specific to kangaroo shooting.
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