introduced predators

A Crest-tailed Mulgara, a small carnivorous marsupial known only from fossilised bone fragments and presumed extinct in NSW for more than century, has been discovered in Sturt National Park north-west of Tibooburra.

A team from the UNSW Sydney Wild Deserts project made the unexpected discovery during recent scientific monitoring.

UNSW scientist and Wild Deserts ecologist Dr Rebecca West, said it was particularly exciting to find a Crest-tailed Mulgara alive for the first time in NSW.

“The Crest-tailed Mulgara was once widely distributed across sandy desert environments in inland Australia, but declined due to the effects of rabbits, cats and foxes.
“The species weighs around 150 grams and has pale blonde fur and a thick tail with a distinctive black crest,” Dr West said.

"The discovery comes at a great time," said UNSW scientist and Wild Deserts project co-ordinator Reece Pedler.

“Next year we are due to begin introduced predator and rabbit eradication from a large area, which will no doubt help the Mulgara,” Mr Pedler said.

“The Wild Deserts project is contributing to the NSW Government’s Saving our Species conservation program (SOS),” said National Parks and wildlife Service area manager Jaymie Norris. “The aim of this project is to return mammal species not seen in their natural habitat for over 90 years in Sturt National Park. “Rabbits, cats and foxes will be eradicated from two 20-square-kilometre fenced exclosures in Sturt National Park, before locally extinct mammals are reintroduced."

"Reintroduced native mammal species will include greater bilby, burrowing bettong, western quoll and western barred bandicoot,” Mr Norris said.

The Wild Deserts project is a partnership between UNSW and Ecological Horizons, in collaboration with Taronga Conservation Society Australia. Wild Deserts has been contracted by the NSW Office of Environment and Heritage to restore and promote desert ecosystems in Sturt National Park. Previous work in South Australia by Wild Deserts team members suggests that the Crest-tailed Mulgara has been recovering in numbers and expanding its range. Reduced rabbit populations during the last 20 years due to release of rabbit calicivirus is thought to have benefited the species by leading to increases in ground cover. Reductions in populations of introduced predators such as cats and foxes has also increased the numbers of small rodents for Mulgara to prey on. In recent years, Crest-tailed Mulgara have expanded their distribution in the Strzelecki Desert over the border in South Australia.

Currently there are attempts to demonstrate pro or contra the attribution of blame on possums for some cases of tree damage. Relatedly, there has also been discussion about the value of introduced predators in keeping the numbers of possums down. Currently Mt Eliza Council has hired Ecology Australia to study this matter. Their final results will be published at the completion of their study early in 2014. This article reviews the results of completed studies regarding tree dieoff and possum predators.

Earlier studies have not even mentioned native animals as having a role in causing tree damage, yet appear satisfied with a wide range of other causes.

"Patches of dead and dying eucalypts have been recorded in Victoria for many years and may be caused by both biotic agents (fungi, insects etc) and/or abiotic agents (drought, water logging, fire, herbicides etc.)." See /files/Survey of tree dieback on the Mornington Peninsula Smith Smith and Clements 2006.pdf (Draft copy).

Below we reproduce the results of a number of scat [droppings] content studies for owls and foxes.[1] These show that possum numbers are much less affected by fox presence than the presence of owls, their natural predators. Owl scats carried signs of digested possum in 90% of cases; foxes only in 11% of cases. The effectiveness of fox predation on possums shows that foxes make only a minimal impact on possum numbers. Cats prey less on Brush-tail possums than foxes but possibly more on ringtail possums than foxes. The table below shows the results of fox predation on mammals in various reserves, based on the percentage of scats containing possum remains.

Considering that one possum would produce several scats, the above figures appear relatively too high.

The other 82% of mammalian remains in the scats consist of Sugar Gliders, Bandicoots, Swamp Rats, Bush Rats, Marsupial Mice, Dunnarts and introduced species. This scenario can be compared with the cane toad which does much more damage to other species than to the intendant ones. It is therefor unacceptable to relay on foxes and cats to reduce possum numbers. Beside mammals, both foxes and cats are also serious predators on birds, lizards,frogs and insects.

The ideal predator on possums may well be the powerful owl. This species is declared endangered in Victoria and it feeds almost entirely on both species of possums. Owl pellets collected less that 200m from a residential area at Hastings contained a high 90% of possum remains.

Probably the most drastic reduction in possum numbers occurs during the more and more frequent heat waves that we experience where thousands of possums die from heat exhaustion. We may ask, is there a need for the reduction of possums?

Then comes the big question, what are all the other reasons that are the cause of tree dieback? In an article:

“Survey of tree dieback on the Mornington Peninsula, Victoria” by I.W. Smith, D.I. Smith and P.A. Clements of Melbourne University, several other other reasons were given that cause tree dieback.

They include:

- Root disease (Phytophtora sinnamomi)

- Armilla luteobubalina (fungal pathogen)

- Defoliaters (Bell miners associated dieback)

- Other insect defoliaters (6 species)

- Mycpherella Leaf disease (several mycpherella species)

- Vertebrates (Possums and Koalas)

- Bark and wood borers (Longicorn beetles)

- Abiotic (Mundulla Yellows)

- Salt (Salt spray)

- Drought

In their recommendations for each reserve, possum control (by tree banding) was only once mentioned and this was in the Mt. Martha reserve. Are possums really such a problem?

** Finally, why don’t we remove the thousands of pines and replace them with eucalypts?

NOTES

These zoological studies reflect situations when fewer humans impacted on the areas in question and there were more trees. Arguably they therefore represent a more normal environment than today's.

Sherbrook Forest Park:

“Fox Scat Analysis in a Forest park in South-eastern Australia”

Hans Brunner, John W. Lloyd and Brian J. Coman, 1975, Aust. Wildl. Reseach

Dandenong Valley:

“The Vertebrate fauna of Dandenong Valley Metropolitan Park”

Robert R.L. Wallis, Peter R. Brown, Hans Brunner and Anna M. Andrasek.

A Report Prepared for the Melbourne and metropolitan Board of Works, Waterways and

Park Division, May, 1990

Currawong Reserve:

“Diet of Red Foxes and Cats;” The impact on Fauna Living in Parks Near Melbourne.

R.L. Wallis, H. Brunner and J. H. Seebeck. Vic. Nat. Vol. 113, 1996

One Tree Hill Reserve:

Vic. Nat. Vol. 113, 1996

Dandenong Ranges:

Vic,. Nat. Vol. 113, 1996

Seaford Wetland:

Flora and Fauna Surveys of Seaford Wetlands by Hans Brunner & Bev Courtney,.

Report to Frankston Council, 1999

The Briars:

Vic. Nat. Vol. 113, 1996

Dartmouth Reservoir A&B:

“The diet of Dingoes and foxes in the Dartmouth Reservoir Area” Technical Report

based on”The Use of Predator Scat Analysis in a Mammal Survey at Dartmouth in

Northern Victoria” H. Brunner, R. L. Amor and P.L. Steven, Aust. Wilsl. Res. 1976