Kangaroos – struggling for space in a highly urbanised and fragmented landscape
The arrival of Europeans on the Australian continent in 1788 changed the future for indigenous wildlife. Fast forward a little over two centuries and Australia has an inexcusable record of species extinction due to human caused habitat destruction, hunting, and the impacts of introduced species such as foxes, cats, rabbits and cane toads. Thirty mammals are known to have become extinct, the most famous being the Thylacine or Tasmanian Tiger. However, it is an ill wind that blows nobody any good, and some indigenous species have benefited from habitat modification, and those that have adapted to an urban environment, such as the Brushtail Possum, are common in suburban backyards, parks and gardens.
When people think of Australian wildlife, they often think of kangaroos as the most iconic emblem of the unique fauna of this continent. Kangaroos are part of a family of marsupials known as Macropods, an appropriate name meaning “big foot”. This family of marsupials includes kangaroos, wallaroos, wallabies, pademelons, bettongs, potoroos and quokkas. There are about 70 macropod species.
Many smaller macropod species have been severely impacted not only by human-caused habitat destruction but also by predation by introduced cats, foxes and dogs. Eleven of the 28 mammals already listed as extinct (Australian Government, EPBC Act List) are smaller macropods. The lovely Toolache Wallaby (Notamacropus greyi) survived just 85 years after the arrival of Europeans.
Some surviving macropod species that were once widespread, such as the Bridled Nailtail Wallaby (Onychogalea fraenata), and the Brush-tailed rockwallaby (Petrogale penicillata) now have an uncertain future. Gilbert’s potoroo (Potorous gilbertii) is Australia’s most endangered mammal: it was ‘rediscovered’ in 1994 after being thought extinct for almost a century and clings on in a small area of southern Western Australia.
Some larger macropod species, such as the Eastern Grey Kangaroo (Macropus giganteus), Red Kangaroo (Macropus rufus) and Western Grey (Macropus fulinginosus) remain reasonably widespread in their range. In the state of Victoria, an aerial survey in 2017 estimated the population of Eastern Grey Kangaroos to be somewhere between 1 and 2 million (Moloney, Ramsey & Scroggie, 2017). Kangaroos live in an extended family group called a ‘mob’.
Australians have a rather conflicted relationship with kangaroos, valued as quintessentially Australian, they are also “harvested” for meat and pelts and “culled” for competing with livestock. Sometimes they are “culled” to reduce impacts of overgrazing on local biodiversity (Howland & Driscoll 2016). The honest word to use in place of “harvested” and “culled” is simply: killed.
As the relentless march of urban development devours previously open grassland and woodlands on the fringes of cities and towns, mobs of kangaroos on the urban fringes are displaced. They are sometimes encircled or landlocked by new developments. Developers are rarely required to consider the wildlife that will be displaced by their activities. The outcome for these animals is never a happy one, with most eventually being killed by cars or dogs. Relocation of affected mobs is challenging, because kangaroos can suffer from capture myopathy (a life threatening stress reaction), the cost of sedating and transporting large animals is high, and there may be a lack of suitable destination habitat
One study (Brunton, Srivastava & Burnett, 2018) reported that even in urbanised areas where sufficient habitat remained, sharp declines in local populations of kangaroos occurred over a two year period, and vehicle collision accounted for 73% of mortality.
The urban fringe and country roads are dangerous places for kangaroos that are most active once the sun goes down. Risk can be mitigated to some extent by reducing speed, and by installing appropriately designed and placed fencing and crossing structures (Rytwinski et al. 2016).
Kangaroos can be large, with an adult male Eastern Grey Kangaroo weighing as much as a person. A car collision with such an animal typically causes substantial injuries or death to the animal, damage to the vehicle and frequently injury to the car’s occupants as well. Animals can remain mobile with severe injuries, making it difficult to euthanise a suffering animal.
As marsupials, kangaroo young are born in a foetal stage that then crawls into the mother’s pouch where it attaches to teat and continues its development. The unfurred joey is known as a ‘pinky’.
A joey can survive in its dead mother’s pouch on the roadside for several days. This makes it imperative that all marsupials hit by a car, or found dead, have their pouch checked for live young. Wildlife rescuers may need to cut the dead mother’s nipple off to remove a surviving kangaroo joey from the pouch, as the young are so strongly attached that attempts to get it to let go may injure the joey’s jaw. Older joeys may be thrown from the pouch when the mother is hit by a car. A clue for rescuers is that there is an elongated teat in the pouch, but no joey. The lost joey will die unless it can be found, captured and taken into care until it is old enough to survive independently. Some rescuers wait for hours for the joey to return to its dead mother. Fences pose another risk to kangaroos. Although they are excellent jumpers and most can easily clear a standard agricultural fence, sometimes they get a hind leg under rather than over the top wire and then momentum causes them to ‘hang’ on the fence by the leg. When the wire is barbed, horrific injuries can occur. Unless a wildlife rescuer is called, the animal will die a slow and painful death.
Wildlife Victoria provides a statewide wildlife rescue service through a dedicated call centre and network of volunteer rescuers and an associated network of veterinarians and wildlife shelters. Between 2014 and 2018 Wildlife Victoria assisted over a quarter of a million animals, and 18% (over 36,000 animals) of these were kangaroos. In the past year almost half of all animals called in as being hit by a car and requiring assistance were kangaroos. Predictably, the majority of calls about kangaroos in need come from surburbs on the urban fringes, where mobs have been pushed out by development and busy roads intersect the landscape.
Like most wildlife rescue organisations, Wildlife Victoria relies on donations from caring people to continue their service. If you have used a wildlife rescue service, or just because you value wildlife, please make a donation to support your nearest wildlife rescue or care organisation.
References:
Burton, E.A., Srivastava, S.K. & Burnett, S. (2018). Spatial ecology of an urban eastern grey kangaroo (Macropus giganteus) population: local decline driven by kangaroo-vehicle collisions. Wildlife Research, 45: 685-695
Howland, B.W.A. & Driscoll, D.A. (2018). At high densities kangaroo grazing can reduce biodiversity. Hot Topics in Ecology, Ecological society of Australia. Doi: 10.1111/ aec.12600
Moloney, P.D., Ramsey, D.S.L. & Scroggie, M.P. (2017). A state-wide aerial survey of kangaroos in Victoria. The State of Victoria Department of Environment, land, Water and Planning
Rytwinski, T., Soanes, K., Jaeger, J.A.G., Fahrig, L., Findlay, C.S., et al. (2016). How effective is road mitigation at reducing road-kill? A meta-analysis. PLOS ONE, Doi 10.1371/journal.pone.0166941
