Threats to koalas | Redland City Council

Threats to koalas

Redlands Coast is part of the wider South East Queensland Koala Coast. The Queensland Government first began monitoring Koala Coast koala populations in 1996. A survey in 2008 showed an estimated 64 per cent decline in koala populations throughout this coastal region. 

A follow-up study in 2015 showed an estimated 80 per cent decline in koala populations between 1996 and 2014. The largest declines occurred in bushland areas, as a flow-on effect from habitat loss and mortality in urban areas.

The main threats to koalas include habitat loss and fragmentation, road mortality, dog attacks, disease, backyards and climate change.

Key threats


Several diseases are a threat to the resilience of koala populations. The two most common are:

  • chlamydiosis – symptoms include reduced fertility rates, blindness and ultimately death 
  • koala retrovirus (KoRV) – an immunodeficiency that can be genetically transmitted between koalas and from parent to offspring.

High levels of infertility have been found in many koala populations, with levels of more than 50% previously recorded in Queensland. This can lead to population decline.

For more information on sick or injured koalas download the fact sheet -  how to spot an sick or injured koala.

Habitat loss and fragmentation

Koala habitat can be lost through: 

  • clearing for urban development
  • broad-scale clearing in rural and peri-urban areas
  • bushland degradation from poor management, fire, or pest and weed infestations.

Fragmentation happens when development creates barriers to movement, including the loss of stepping stone trees in the urban landscape. Habitat loss and fragmentation affect the genetics of koala populations by reducing genetic variation and gene flow.


Death or injury from being hit by a moving vehicle is the second most significant threat to koalas. Although koalas spend most of their time in trees, they need to move between trees within their home range. 

This movement usually happens at night, but koalas can be active at any time. It’s also more common during breeding and dispersal season (July to December) when koalas are moving around more.


Dog attacks have historically been the third most significant impact on koalas. These deaths are usually caused by domestic dogs, generally in suburban backyards.

Attacks are more likely to happen during July to September, at the peak of breeding season when koalas are moving around more. It's also common in areas with a higher density of dog ownership and the risk to koalas increases if there is more than one dog in a yard. 

Dog attacks occur with healthy koalas as much as sick ones. Even friendly and curious dogs can unintentionally harm a koala through play or stressing the koala. 


When koalas in urban areas are moving around their home range, or travelling through new areas during dispersal and breeding season, backyards can pose a serious threat. Fences that are not wildlife friendly can make it difficult for koalas to escape an enclosed yard, or an aggressive or over-enthusiastic pet. Pools are also a danger to koalas as they can quickly drown if they accidentally fall in and cannot escape.

Climate change

Climate change predictions for koalas include an increase in drought frequency and high fire-danger weather in many parts of Australia. This may force koalas to move more frequently in search of water or new habitats, increasing their vulnerability to predators and vehicles.

It has also been predicted that increasing atmospheric CO2 levels will reduce the nutritional quality of eucalyptus leaves, which would compromise the ability of koalas to find enough nutrients to survive. 

Predictions also suggest South East Queensland may become increasingly important to the long-term survival of Queensland's koala population, as the climate in other parts of Queensland becomes more hostile to their survival.

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