Platypuses on Kangaroo Island may be on the road to recovery following thedevastation of the 2019-2020 bushfires, a team including researchers from UNSWhave found.
The researchers spent a week setting traps in the isolated Rocky River area ofFlinders Chase National Park in late May to assess the species’ condition andpopulation growth and trapped healthy juvenile and adult platypuses.
“The impacts of the fires were quite apparent as we were carrying out thesurveys for platypuses,” Dr Gilad Bino from the Platypus ConservationInitiative in the Centre for Ecosystem Science, at UNSW Sydney’s School ofBiological, Earth and Environmental Sciences.
“Compared to previous work in the areas, platypus numbers were lower and theirdistribution had contracted further downstream, mostly confined to deepwaterholes, which are critical refugia for platypuses and other freshwaterspecies during times of drought and extreme fires.
“Encouragingly, we trapped juvenile platypuses which indicates the capacity ofplatypuses in the river to recover.”
Dr Bino said despite the positive findings, the survey also revealed theimpact to platypuses in some areas, with no platypus caught further upstreamat the Platypus Waterholes or East Melrose Track in the Flinders ChaseNational Park which was severely impacted by the fires.
“This was likely as a result of the dry conditions upstream which preceded thefires but also longer-lasting effects of the fires on the habitat and perhapsthe platypuses,” Dr Bino said.
Dr Bino co-led the expedition with Dr Ryan Baring from Flinders University.
National Parks and Wildlife Service PWS Kangaroo Island conservation ecologistHeiri Klein said the expedition was a resounding success, but the rockyterrain posed many challenges to the small research team. “The sites where wethought the platypuses would be were quite isolated, so the team had to walkinto most of the remote trapping locations on foot, whilst towing a boatloaded with all the equipment by hand,” Ms Klein said.
“Platypuses are most active at night, so the surveys also required wading outin cold water in the pitch black to check traps for eight nights in a row.After a trying start, the researchers successfully trapped two healthyjuvenile females, two healthy juvenile males, and four mature platypus – twoof each gender. The age of the juveniles mean they would have been born afterthe 2020 fires that affected the entire Rocky River catchment, which is greatnews for the recovering Kangaroo Island platypus population.”
DNA samples taken from the platypuses will be analysed to provide anindication of the likely population size in the Rocky River system, but alsopossible genetic bottle necks that may affect the viability of the KangarooIsland population. While native to mainland South Australia, 19 platypuseswere introduced to Kangaroo Island from Victoria and Tasmania in the firsthalf of the twentieth century, following steep declines in their naturalpopulation. In South Australia, the platypus is considered functionallyextinct from its natural population range, which primarily includes the MurrayRiver system.
Dr Bino was one of the UNSW scientists who recommended the platypus be listedas a threatened species under Australia’s and NSW environmental legislationlast year.
The researchers hope to return to Kangaroo Island in September to complete thesurvey sampling to better understand the extent of the platypuses’ recovery.“There is still much to learn about the resilience and capacity of platypusesto recover from such extreme events which, unfortunately, are expected toincrease under a changing climate,” Dr Bino said.
The Kangaroo Island community and visitors to the island are being encourageto help improve knowledge of the platypuses by reporting their observationsusing the iNaturalist app. The survey was supported by South Australia’sDepartment for Environment and Water’s Science team and National Parks andWildlife Service, and crowdfunding from citizens.
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