Hot Topics in Ecology

At high densities kangaroo grazing can reduce biodiversity

Over-abundant kangaroos reduce the diversity of native wildlife and are a danger to threatened species
Brett W A Howland, Australian National University, Pr. Don A. Driscoll, Deakin University
  • Eastern grey kangaroos reach very high densities in south-eastern Australia due to the absence of predators and ready access to permanent water in farm dams.
  • At high densities, kangaroos reduce abundance and diversity of plants and reptiles, degrade bird habitat and threaten an endangered mammal.
  • Detection of the vulnerable striped legless lizard declines dramatically with high kangaroo densities.
  • The literature recommends that grazing pressure be reduced where kangaroos are over-abundant to prevent biodiversity loss.
Overabundant kangaroos graze away the habitat that other native species depend on for survival. Photo by Graeme Coulson

Over-grazing by herbivores can simplify the structure, composition and function of vegetation communities by reducing vegetation cover and diversity, increasing soil degradation and driving biodiversity loss. European colonisation has created ideal conditions for the eastern grey kangaroo in south-eastern Australia, thanks to dingo eradication, new permanent watering points, protection from hunting and increased pasture availability. Consequently, in some areas, kangaroo population densities have risen to levels where impacts on other native species are occurring. At high densities, kangaroo grazing can: (1) reduce the occurrence, height and seeding rates of some native grasses; (2) reduce the diversity and cover of native shrubs following fire; (3) reduce the abundance and diversity of beetles; (4) reduce the overall abundance and diversity of reptiles; (5) reduce the quality of habitat for some species of legless lizards and the three-toe earless skink; (6) reduce the occurrence of the vulnerable striped legless lizard; (7) reduce the quality of habitat for many species of bird; and (8) reduce the quality of habitat for endangered eastern barred bandicoots, threatening a reintroduction program. In particular, the striped legless lizard appears very sensitive to high grazing. One recent study suggested that detection of this species more than halved with each doubling of kangaroo density. The impacts of high density kangaroo grazing on biodiversity in Australia are consistent with studies on native herbivores overseas, where predation and hunting that regulated herbivore density have diminished. Managing grazing pressure is often required to prevent biodiversity loss and ecosystem degradation.

Hot Topic Lead Author: 
Name: Brett Howland
Email: brett.howland@anu.edu.au
Phone: 03 92517609

Name: Professor Don Driscoll
Email: d.driscoll@deakin.edu.au
Phone: 03 92517609

ID Title Location Type
8548 Mysterud, A. (2006). "The concept of overgrazing and its role in management of large herbivores." Wildlife Biology 12(2): 129-141 Europe, North America, Africa Review paper
8539 Brown, K., Paczkowska, G., & Gibson, N. (2016). "Mitigating impacts of weeds and kangaroo grazing following prescribed fire in a Banksia woodland." Ecological Management & Restoration 17(2): 133-139. Swan Coastal Plain, WA manipulative experiment
8540 Winnard, A. L., & Coulson, G. (2008). "Sixteen years of Eastern Barred Bandicoot Perameles gunnii reintroductions in Victoria: a review". Pacific Conservation Biology 14(1): 34-53. Various conservation areas in Vic review paper
8532 Neave, H. M. and M. T. Tanton (1989). "The Effects of Grazing by Kangaroos and Rabbits on the Vegetation and the Habitat of Other Fauna in the Tidbinbilla Nature Reserve, Australian-Capital-Territory." Australian Wildlife Research 16(3): 337-351. Tidbinbilla Nature Reserve, ACT manipulative experiment
8533 Meers, B. T. and R. Adams (2003). "The impact of grazing by Eastern Grey Kangaroos (Macropus giganteus) on vegetation recovery after fire at Reef Hills Regional Park, Victoria." Ecological Management & Restoration 4(2): 126-132. Reef Hills Regional Park, Victoria manipulative experiment
8534 Barton, P. S., A. D. Manning, H. Gibb, J. T. Wood, D. B. Lindenmayer and S. A. Cunningham (2011). "Experimental reduction of native vertebrate grazing and addition of logs benefit beetle diversity at multiple scales." Journal of Applied Ecology 48(4): 943 Goorooyarroo nature reserve, ACT manipulative experiment
8535 Manning, A. D., R. B. Cunningham and D. B. Lindenmayer (2013). "Bringing forward the benefits of coarse woody debris in ecosystem recovery under different levels of grazing and vegetation density." Biological Conservation 157(0): 204-214. Goorooyarroo and Mulligans Flat nature reserves, ACT manipulative experiment
8536 Howland, B., D. Stojanovic, I. J. Gordon, A. D. Manning, D. Fletcher and D. B. Lindenmayer (2014). "Eaten out of house and home: impacts of grazing on ground-dwelling reptiles in Australian grasslands and grassy woodlands." PLoS ONE 9(12): e105966. Various conservation areas in ACT, NSW and Victoria Pre-existing contrasts
8537 Howland, B. W. A., D. Stojanovic, I. J. Gordon, J. Radford, A. D. Manning and D. B. Lindenmayer (2016). "Birds of a feather flock together: Using trait-groups to understand the effect of macropod grazing on birds in grassy habitats." Biological Conservati Various conservation areas in ACT, NSW and Victoria Pre-existing contrasts
8538 Howland, B. W. A., D. Stojanovic, I. J. Gordon, D. Fletcher, M. Snape, I. A. Stirnemann and D. B. Lindenmayer (2016). "Habitat preference of the striped legless lizard: Implications of grazing by native herbivores and livestock for conservation of grassla Various conservation areas in the ACT Pre-existing contrasts

Further information about this topic contact:

Brett Howland
brett.howland@anu.edu.au
03 92517609

Chair, Hot Topics Editorial Board
Dr Rachel Standish
R.Standish@murdoch.edu.au