Abstract
Koala populations are in catastrophic decline in certain eastern Australian regions. Spanning from 1997–2013, a database derived from wildlife hospitals in southeast Queensland with N = 20,250 entries was classified by causes of morbidity and mortality. A total of 11 aetiologies were identified, with chlamydiosis, trauma, and wasting being most common. The clinical diagnosis at submission varied significantly over the observation period. Combinations of aetiologies were observed in 39% of koalas submitted, with chlamydiosis frequently co-occurring. Urogenital (cystitis 26.8%, bursitis 13.5%) and ocular (conjunctivitis 17.2%) chlamydiosis were the most frequently diagnosed representations of the infection. Approximately 26% of submissions comprised koalas involved in vehicle accidents that were otherwise healthy. Age and sex of the koala as well as season and submission period were compared for the case outcomes of ‘dead on arrival’, ‘euthanized’, or ‘released’ for the four most common clinical diagnoses using multinomial logistic regression models. Exploratory space-time permutation scans were performed and overlapping space-time clusters for chlamydiosis, motor vehicle traumas and wasting unveiled high risk areas for koala disease and injury. Our results suggest that these aetiologies are acting jointly as multifactorial determinants for the continuing decline of koalas.
Highlights
Marsupials have declined substantially in Australia: 25% of their original range has been cleared and 24 marsupial species have been declared extinct[3]
Their occurrence was previously considered common in SEQLD, where there is certainty from surveys conducted on urban koalas[23] and where current estimates have warned about declining subpopulations since the mid-1990s14,15
This data is difficult to extrapolate to adjacent bioregions as different ecosystems face dissimilar threats, it does provide an overall picture of how future koala conservation and expanding urbanization would interplay
Summary
Marsupials have declined substantially in Australia: 25% of their original range has been cleared and 24 marsupial species have been declared extinct[3]. Previous reports estimate in QLD koala presence is segmented and rather uncommon, persisting only where ideal habitat occurs[22] Their occurrence was previously considered common in SEQLD, where there is certainty from surveys conducted on urban koalas[23] and where current estimates have warned about declining subpopulations since the mid-1990s14,15. It is paramount to determine cause-specific morbidity and mortality risk factors to facilitate urgent conservation measures, ensuring the survival and the long-term preservation of the koala These measures should include preservation of viable habitat, informed local and federal government management policies, and the successful rehabilitation of animals in care. The aims of the present study are to 1) identify the major causes of morbidity and mortality in SEQLD koalas from 1997–2013; 2) for each cause determine demographic, seasonal and temporal risk factors associated with koalas classified as ‘dead on arrival’, needed to be ‘euthanized’ or ‘released’; and 3) identify spatial-temporal clusters of causes of koala morbidity and mortality
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