The Distribution and Abundance of an Island Population of Koalas (Phascolarctos cinereus) in the Far North of Their Geographic Range

Abstract

Koalas are an iconic species of charismatic megafauna, of substantial social and conservation significance. They are widely distributed, often at low densities, and individuals can be difficult to detect, making population surveys challenging and costly. Consequently, koala population estimates have been limited and the results inconsistent. The aims of this study were to estimate the distribution, relative abundance and population size of the koalas on Magnetic Island, far north Queensland. Population densities were estimated in 18 different vegetation types present on the island using a Fecal Standing Crop Method. Koala density ranged from 0.404 ha−1, recorded in forest red gum and bloodwood woodland, to absence from eight of the vegetation types surveyed. The second highest density of 0.297 koalas ha−1 was recorded in mixed eucalypt woodland, which covers 45% of the island. The total abundance of koalas on Magnetic Island, not including those present in urban areas, was estimated at 825±175 (SEM). The large variation in koala density across vegetation types reinforces the need for sampling stratification when calculating abundance over large areas, as uniformity of habitat quality cannot be assumed. In this context, koala populations also occur in low densities in areas generally regarded as poor quality koala habitat. These results highlight the importance of protecting vegetation communities not traditionally considered to have high conservation value to koalas, as these habitats may be essential for maintaining viable, widespread, low-density populations. The results from this study provide a baseline to assess future trends in koala distribution, density and abundance on Magnetic Island.

Nutritional Correlates of Koala Persistence in a Low-Density Population

“…Koala faecal pellets surveys have been employed as a proxy for a range of purposes from surveys of koala abundance and population distribution [93] , [94] to developing habitat categorisation for conservation management [46] , [50] , [56] , [95] . Koala faecal pellets have also been widely used to infer habitat and feed tree preferences [56] , [96] , [97] , however their reliability to draw nutritional inferences is still in debate [98] .…”

How to choose a cost‐effective indicator to trigger conservation decisions?

“…Alternatively, some indicators may be relatively easy to monitor due to well-established monitoring methods and/or availability of experts (McGregor, Kerr & Krockenberger 2013). We capture this as the feasibility of monitoring an indicator, , which is the probability that monitoring of an indicator happens.…”

When an iconic native animal is overabundant: The koala in southern Australia

“…Lack of dispersal opportunity has been touted as the primary cause of overabundance (Australian Koala Foundation, ) and this may be true on offshore islands or in habitat 'islands' surrounded by cleared landscapes on the mainland (Menkhorst, ). However, island populations also occur in the north and have not become overabundant (e.g., McGregor, Kerr, & Krockenberger, ). Furthermore, overabundance can occur at sites surrounded by other suitable koala habitat (e.g., Cape Otway, Kennett River, far south‐west Victoria, and Flinders Chase on Kangaroo Island, Table ).…”