How many cassowaries are there in the Wet Tropics?

An Australian research team, headed by Dr David Westcott from the CSIRO, is also helping to fill the cassowary knowledge void. They have recently concluded a National Environmental Research Program (NERP) study estimating the population size and distribution of the Southern Cassowary (Casuarius casuarius) in Australia’s Wet Tropics.

The researchers undertook a region wide cassowary census over a two year period (2012 – 2014), surveying at both regional and local scales. The survey involved documenting signs of cassowaries along a series of transects located throughout the region. Signs sought included bird sightings, feathers, footprints and dung.

The NERP survey was conducted using a similar approach to that employed by Francis Crome and Les Moore for their seminal cassowary study a couple of decades earlier (1). By using a comparative approach, Dr Westcott’s team were able to consider how cassowaries in the Wet Tropics have fared over the preceding years.

The research team analysed and extrapolated the survey data to estimate a total regional population size of over 4,000 individuals. They noted that while this is a larger figure than what is commonly reported, it is in line with previously published estimates. Subregions found to have the greatest concentrations of birds were all located in the central Wet Tropics region. They included the Tully and Russell River subregions – areas of essential cassowary habitat at low to mid elevation – and neighbouring areas of higher elevation such as Koombooloomba and Palmerston. Based on their findings and, in the absence of any apparent driver of population change, the researchers suggest that cassowary populations in the Wet Tropics have likely remained stable with little distributional change since Crome and Moore’s 1990 study.

Despite the updated population estimate, the Southern Cassowary remains a threatened species with the Wet Tropics population listed as Endangered under both Commonwealth and Queensland law. Due to its small population size, fragmented range and decreased essential habitat under expected climate change, the researchers predict that the population will decrease and become even more fragmented in the future. They urge against complacency and recommend a series of management actions to curb the predicted declines, including:

• increasing the availability and quality of cassowary habitat
• improving habitat connectivity
• establishing a regular monitoring program
• working with Traditional Owners to establish a monitoring program on Cape York Peninsula.

(1) Crome, F.H.J. & L.A. Moore (1990). Cassowaries in north-eastern Queensland: report of a survey and a review and assessment of their status and conservation and management needs. Australian Wildlife Research. 17:369-385