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.
Highlights
Koalas (Phascolarctos cinereus) are arboreal folivores that occur in the eucalypt forests of eastern Australia
Koala density ranged from 0.404 ha21 to zero koalas ha21 (Fig. 2; Fig. 3)
The second highest density of 0.29760.036 koalas ha21 was recorded in mixed eucalypt woodland, which includes 2233 hectares or 45% of the island and supports 80% of the island’s koala population
Summary
Koalas (Phascolarctos cinereus) are arboreal folivores that occur in the eucalypt forests of eastern Australia Their current distribution is widespread, covering approximately one million square kilometers and 30 biogeographical regions, from the tropical forests of northern Queensland to the temperate forests of the Victoria coast [1], [2]. Their distribution is not continuous, but patchy, composed of many separate populations isolated from other groups by unsuitable habitat [3] This is primarily a reflection of forest fragmentation [4] as the distribution and density of koalas is limited by the presence of Eucalyptus and Corymbia species that comprise the koala diet [3], [5]. This combination of factors makes estimating koala abundance difficult and costly [6,7,8], and has resulted in a limited number of estimates at regional, state and national levels [6], [9], [10]
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