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Koala threats

Koala Threats

As urban expansion continues, koalas face ever-increasing threats to their survival. These include:

Destruction and degradation of habitat

The greatest threat facing koala populations today is destruction of suitable habitat.

Since European settlement of Australia, more than 50 per cent of koala habitat has been destroyed and much of what remains has been degraded and fragmented.

Degradation of habitat can occur through factors such as selective logging of preferred koala food trees, weed invasion and inappropriate fire regimes. Fragmentation of habitat can lead to isolation of individuals and populations.

Barriers to movement

Fences, roads and cleared land can all create barriers to koala movement. This alters population dynamics, impedes gene flow and limits the ability for populations to recover.

Road fatalities

Due to habitat fragmentation effects, koalas often need to regularly cross busy roads to access food and shelter resources. Road fatalities contribute to a significant number of koala deaths each year. 

Dog attacks

Domestic dogs can cause death and injury to koalas. This can occur either when koalas enter yards that contain dogs or when dogs are allowed to roam into nearby bushland. More information about koalas and dogs can be found in the Koalas and domestic dogs on the Gold Coast fact sheet.

Fires

Fire events, including some controlled burns for fuel reduction and wild fires, can kill and injure koalas and destroy their habitat.

Disease

Chlamydial disease is a common bacterial infection in koalas, and most wild koala populations (though not all) are infected. Chlamydia can cause a variety of clinical symptoms in koalas including:

  • eye infections in both male and female koalas, which can lead to conjunctivitis and blindness in severe cases
  • urogenital infections in female koalas, which can lead to 'wet bottom' or 'dirty tail' (a brown discoloured rump caused by dripping urine), cystitis and infertility
  • respiratory infections (including nasal discharge) leading to pneumonia in some cases.

Chlamydial disease can be a significant issue for the conservation of wild koala populations, although koalas in more-healthy populations may display relatively few clinical symptoms.

When koalas are subject to high levels of stress such as caused by social dissolution or nutritional deficiency due to habitat loss, their immune system is likely to be suppressed, making them more susceptible to disease.

Researchers are currently attempting to gain a better understanding of Chlamydia in koalas in order to create an effective vaccine for potential use to assist the recovery of highly threatened populations.

Most koalas in Queensland are also believed to be infected with Koala retrovirus (or KoRV). This retrovirus may cause suppression of the immune system in koalas, leukaemia and lymphoma.

Research also suggests that KoRV may lead to increased prevalence of disease symptoms due to Chlamydia (Tarlinton et al. 2005).

The combination of Chlamydial disease and KoRV infection together with cumulative impacts of habitat loss and other threats associated with urban development means that many koala populations are under significant threat of collapse, particularly in South East Queensland and northern New South Wales.

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