Marcus Butler
14 April 2015: Wildlife scientists and managers are regularly asked to give a number for the population of a certain species, especially feral animals, but researchers with the Institute for Applied Ecology (IAE) and the Invasive Animals Cooperative Research Centre (CRC), both at the University of Canberra, have found that often there is very little data to provide any response.
Providing an answer to the question of, "how many are there?" can be fraught with pitfalls, particularly if the figure is a guess, an extrapolation or even just the larger number in a range.
-
Feral cats pose a risk of Australian native wildlife, but just how many are there at large? Photo: Andrew Cooke
Researchers, Professor Jim Hone from IAE and Dr Tony Buckmaster with the Invasive Animals CRC, both at the University of Canberra, have found that when it comes to feral animals, such as feral cats and feral pigs, some publications and programs, policies and eradication programs are based on questionable population figures.
Their research has been published in the scientific journal, Wildlife Research.
Through an extensive review of scientific journal articles and papers on the abundance of feral cats, feral pigs and other mentions dating as far back as the 1950s, they found many of the figures which circulate through the media and scientific and management publications are outdated or even wild guesses.
Dr Buckmaster said that scientists and managers need to be more open when there isn't data available and say we don't know, rather than making a well-intentioned guess.
"People get hung up on the numbers game. Unless needed for an eradication program or commercial purposes, knowing the exact numbers of these animals is not really important. It is much more useful to focus on the damage caused," Dr Buckmaster said.
"Managers and scientists use figures for feral animal populations to plan conservation, pest control and sustainable use of wildlife, but sometimes these numbers are based on small samples and are scaled up to reflect the whole of the Australian landmass," he said.
The number of feral cats has been quoted and published to be up to 18 million animals, but previously there was no known source for this figure. The researchers propose a source which was simple extrapolation to the whole of Australia from one study in a part of Victoria.
Professor Hone said when dealing with feral animal populations, everyone from journalists to policy-makers wants a hard number to base their work on, but it seems people are often using unreliable figures, with no factual basis.
"We have found that with some native wildlife, such as red kangaroos, there is much better data. We need reliable, robust data and good science with strong evidence to get a more accurate picture of feral animal numbers."
"Since numbers are often used for planning wildlife management programs for many species, it is important to evaluate the evidence and reliability of the available data, rather than doing guesswork," Professor Hone said.
