Threats to Koalas

The Koala Recovery Partnership are working with Fire Management Agencies to try to improve fire management, and post-fire animal rescue responses in key koala habitat. Fire is a natural part of many Australian ecosystems and has a major role in the ecosystem functioning of the eucalypt-dominated vegetation types preferred by koalas. Because koala’s habitat comprises eucalypt forests, they live in some of the most fire-prone environments in the world. Inappropriate fire management is a major risk to koalas. Fires that burn the eucalypt canopy are particularly devastating resulting in a loss of koala food and causing direct mortality and injury to koalas through burns and smoke inhalation. Devastating wildfires can even cause local extinction or otherwise a population ‘bottleneck’ which can reduce genetic diversity. A lack of fire can also be a risk as fire is important for the recruitment of many eucalypt species that need sunlight (via canopy gaps) and exposure of bare soil for germination. An absence of fire can therefore result in a ‘monoculture’ of old trees and eventually a loss of koala food. Furthermore, some studies have reported declining eucalypt health (and eucalypt leaf nutrient content) in the absence of fire. This effects canopy vigour and thus the quantity and quality of koala food resources. This process is likely mediated by the interplay with mycorrhizal fungi and other microbial communities. An absence of fire in certain areas can even result in the transition of koala habitat towards rainforest species. The high abundance of regenerating rainforest shrubs can strip nutrients from the eucalypt canopy and prevent the regeneration of eucalypts- ensuring that koala habitat is being lost with time. A complete absence of fire can also increase the risk of catastrophic fires later due to the accumulated fuel load. In contrast, too frequent fire can also reduce koala food supply in the short-term but also in the longer-term as regenerating eucalypts are burnt before reaching a resilient age. How fire affects koala populations depends on factors such as the extent of habitat fragmentation, the proximity of source populations (i.e. other koalas), the intensity and extent of the fire, seasonal and climatic factors and the degree of other threats operating in the landscape. Factors such as the availability of ‘mesic refuge’ areas (such as drainage lines which may support less flammable species), rainfall events following a fire and free-standing water availability may all be factors that affect koala survival during, and after, a wildfire. Hazard reduction burning is an important technique to reduce koala mortality by reducing the extent, intensity and frequency of wildfires but nonetheless, even hazard reduction burns may result in koala injury and death if the canopy is scorched.

Post-fire koala rescue can reduce localised extinctions
After a devastatingly hot fire in koala habitat
Dog Attack Hot Spot Mapping

The Koala Recovery Partnership, the NSW State Government and human behavioural experts are working together, using real-world data and examples, to solve the issue of dog attacks on koalas

Across eastern Australia, many housing estates exist within, or adjoining, areas of koala habitat. As a result, many suburban homes have remnant koala populations surrounding their house and may have backyards with trees that koalas may visit. Koalas may enter suburban yards either to access feed trees or may simply be moving about their home range. Koalas have an amazing spatial memory of where feed trees are located within their home range, and so frequently still come looking for them- even after they have been removed. Unfortunately, when koalas enter suburban yards, dog attacks (even by friendly family dogs) are all too common. Data from the Port Macquarie Koala Hospital shows that 90% of koalas die following dog attacks and that the number of annual koala fatalities from this cause is significant. Some housing estates prevent dog ownership, but many people choose to ignore this rule. Many new housing estates now try to discourage koalas from entering the urban context through koala exclusion fencing and the removal of all koala food trees. Roaming individual dogs and dog packs also impact koalas. It is a responsibility of all dog owners to restrain their dogs when outside their properties and not allow dogs to roam, particularly at night.

Thor Aaso fits a camera in a road underpass

The Koala Recovery Partnership are investigating ways to solve road strike issues. These cameras monitor koala, and other animal, use of road underpasses through key koala habitat.

Road strike (koalas getting hit by motor vehicles) is a major cause of koala decline. In excess of 150 koalas are struck each year by cars within the Hastings-Macleay Area. Research by the Koala Recovery Partnership has revealed the existence of road strike ‘hotspots’ across the region where busy arterial roads with higher speed zones now cut through important areas of koala habitat or wildlife corridors. Additionally, koala deaths from motor vehicle strike also occur diffusely across the region and can occur even on urban streetscapes. Unfortunately, research has shown that road signage is ineffective to change driver behaviour (reduce driver speed). Road strike solutions such as ‘fauna fencing’ and ‘underpasses’ are typically only applied to major highways due to their high expense and maintenance requirements. Fauna fencing can also sever areas of koala habitat, if underpasses are not used or are not accessible to koalas. Also some individual animals may not use underpasses (one study for example revealed that while some koalas will use underpasses, other individuals did not over the course of the study). More appropriate road location and design is required to reduce the incidence of road strike or populations will continued to decline in and around these areas.

Plantings are Important to Offset Habitat Loss

The Koala Recovery Partnership are looking closely at ways that existing habitat can be provided and additional habitat created for koalas in the Hastings-Macleay Region.

Habitat loss and fragmentation is the number one cause of decline in koala populations. Not all ‘bush’ is koala habitat. Koalas need the right combination and amount of eucalypt tree species and fertile soils rich in nutrients to occur in suitable abundances for self-sustaining populations. Fertile soils are important as the nutrient content of the soils is reflected in the nutrient content of eucalypt leaves (hence determining whether they are a food source or not). Unfortunately, the flat, fertile areas along the east coast of Australia are those most favoured for coastal development. Of the c. 70 Eucalypt species present within the Hastings-Macleay Region, only around 6 species are used extensively and regularly by koalas as food trees. These include Forest Red Gum (Eucalyptus tereticornis), Swamp Mahogany (Eucalyptus robusta), Tallowood (Eucalyptus microcorys), Small-fruited Grey Gum (Eucalyptus propinqua), White Stringybark (Eucalyptus globoidea) and Scribbly Gum (Eucalyptus signata). Other species are occasionally used, often dependent on seasonal factors and soil type. Such species include Red Mahogany (Eucalyptus resinifera) and Broad-leafed Paperbark (Melaleuca quinqueflora), Koala food trees are sometimes referred to as “Primary” or “Secondary” food trees, reflecting their overall importance. In some cases, tree size is also a determinant of its status as a koala food tree, with large trees being preferentially used. Removing koala food trees, such as through selective logging practices that target larger trees of certain species, can therefore have detrimental impacts to koala habitat (even if standing bush remains). There is also increasing recognition by koala ecologists that areas that may not support large quantities of koala food trees may still comprise important areas of a koala’s home range or habitat. These notably include linking corridors and ‘mesic refuge areas’ (cool, shady parts of the landscape which are often wetter and support paperbarks or rainforest species and provide important refuges during heat events, droughts or fires). Furthermore, habitat establishment plantings take time to grow and reach an age whereby koalas can use them (c. 10-15 years for some species). As such, habitat establishment has a time lag and therefore is not an immediate replacement for removing occupied koala habitat.

A Koala Gets a Health Check

The Koala Recovery Partnership work closely with the Koala Hospital and other researchers, to examine the incidence and treatment of disease in the Hastings-Macleay region.

Koalas suffer from many diseases, perhaps the two most prevalent being the Koala Retrovirus (KoRV) and Chlamydia. These diseases can either kill koalas directly, cause infertility or blindness or leave koalas more prone to other diseases, such as cancer. Some koala diseases are likely to have always been a background factor in koala populations but may be becoming increasingly more prevalent as koalas are placed under increasing stress from a range of factors (such as increasing prolonged hot weather and drought, loss of high quality habitat and stress from urban environments). Scientists are working hard to better understand koala disease and to examine cures and vaccines, but this is costly and takes time. Facilities such as the Port Macquarie Koala Hospital provide care and rehabilitation of koalas suffering disease. This is a costly process for a facility run mainly by volunteers.

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