Posted on 27/08/2014 by Phillip Island Nature Parks
How do you outfox one of Australia’s most wily invasive species? That’s been the question for nearly 100 years for residents and rangers on Phillip Island in Victoria.
Researchers from Phillip Island Nature Parks have just released a case study in the online version of the CSIRO journal Wildlife Research exploring the effectiveness of fox control methods. The study reveals the oftentimes ‘hit and miss’ nature of historical pest control and the importance of continual and objective evaluation.
“Our study reveals that the effectiveness of fox control on Phillip Island has been closely linked with personal and public biases towards different methods, as well as fluctuations in resource allocation,” Dr Duncan Sutherland, a co-author of the study, revealed.
Foxes were deliberately introduced into Australia in 1855 for recreational hunting, but the hunted soon became the hunters and it wasn’t long before evidence began to appear of their devastating effects on native wildlife.
Foxes first colonised Phillip Island in 1907. Attempts to control the growing fox population began in 1918 and, from the outset, control programmes were primarily motivated by a desire to protect the iconic little penguins found on the island.
“In the latter half of the 20th century, nine out of the 10 little penguin colonies on Phillip Island had been wiped out, most likely due to fox predation,” Dr Peter Dann, research manager at the Nature Parks, explained.
“One fox can kill more than 30 penguins a night.”
A bounty system was introduced in 1954 and ran for 30 years. Although popular, the bounties failed to appreciably reduce fox numbers on the island and no clear scientific data were kept or used to steer the programme. In the 1970s and 80s, penguin kills increased enormously around the world famous Penguin Parade and a fox control programme was implemented to halt the resulting decline in penguins. The control programme relied on subjective interpretations of efficacy which led to the incorrect conclusion that foxes were under control and that harvesting foxes was useful.
“Intensive fox baiting at the start of the 80s had a noticeable effect on reducing the decline of the penguin population but at the time no one was monitoring the success of the method,” Dr Dann said.
“As such, alternative methods such as hunting and trapping soon took over as they produced carcasses, which gave a measure of success. Hunting and trapping foxes also didn’t endanger domestic pets, and was a more appealing activity for participants.”
Scientific evaluation of the control programme in the early 2000s revealed the size of the fox population far surpassed the impressions commonly held, and highlighted that even a handful of foxes could have a devastating effect on many penguins. The programme was transformed in 2006, and this time the objective was eradication. Two fox control officers were employed and island-wide poison baiting was fully implemented due to its measured effectiveness elsewhere.
As a result there was a decline from the 125 penguins killed by foxes on the Summerland Peninsula in 2007/08 to five penguins killed in the next four years. The population at Phillip Island’s last remaining penguin colony has also grown from an estimated 12,000 in 1985 to 32,000 today.
In 1996 fox numbers on the island were estimated to be 200 but today fewer than a dozen are thought to remain. Foxes are nearly eradicated from Phillip Island, though the remaining few may be challenging to remove and success difficult to qualify.
“Finding the remaining foxes will be difficult but we’ve recently employed two fox detection dogs that will help locate fox scats and scent and find the foxes’ refuges,” Stuart Murphy, manager of the fox program, said.
Outfoxing the fox may be possible after all.
If successful, Phillip Island will be the largest island from which red foxes have been eradicated. Complete eradication will be a huge achievement and an exemplar for fox control or eradication across Australia and the world. The next stage would be to remain vigilant and monitor for reinvasions.
Despite the up and downs over six decades of trying to rid Phillip Island of foxes, the team behind the case study agrees that a lot can be learned from the past.
In summarising the key findings of the study, Dr Dann concluded: “A team dedicated to control programmes is absolutely essential; there is an imperative to measure the effectiveness of each method independently of personal biases; and monitoring both predator and prey populations concurrently is vital so the benefits of control can be demonstrated or management can be adapted.”
Ms Danene Jones - Communications Executive
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