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| Fox Baiting ProgramSee also:
The Fox Eradication Branch has been set a difficult task – to find and eradicate what is most likely to be an extremely low-density population of foxes. The Fox Eradication Branch and its scientific advisers suspect, from evidence and collective knowledge, that the density of a Tasmanian fox population might be as low as one fox per 500 km2.
The location of baits is marked by flagging tape.
 | Research in other parts of the world shows that once foxes are at a density of one per 25 km2 they are almost impossible to find, and once at one per 40 km2 the chances of finding them virtually collapse. The scenario in Tasmania, therefore, is extremely unusual and presents many new challenges for any eradication efforts.
Even if the Fox Eradication Branch is unable to find individual foxes, it is their brief to put all foxes that are present in the state at risk from the eradication methods that are employed. Therefore, it was decided to lay baits on a scale that made it highly likely that foxes would be able find them.
Of course, it was also important to establish a baiting regime that endangered foxes but not Tasmanian devils, quolls or any of our other unique wildlife.
To achieve this, the Fox Eradication Branch chose 40g pieces of dried kangaroo meat (DKM) as bait. This is very hard for most wildlife (including quolls) to eat while dry.
During trials in Victoria baits were buried to minimise interference from birds, to take advantage of foxes expertise in finding buried baits and the relative inability of quolls and devils to do likewise. Foxes have evolved to survive harsh winters when most food is hidden by snow whereas devils and quolls never encountered such severe conditions, and therefore never needed to develop this skill.
Through these trials, the Fox Eradication Branch quickly confirmed that foxes start taking such baits as soon as they are laid and also discovered that Tasmanian devils and eastern quolls find few baits, until the baits rot (and smell). Eastern quolls seemed especially unaware of buried baits.
A lot of work has been done on bait-take by Spotted-tailed quolls in Victoria and NSW, and the Fox Eradication Branch did more. The Fox Eradication Branch confirmed that these marsupials are not very interested in dry DKM. This difference between foxes immediately taking baits, and devils and quolls rarely taking them until rotting (usually starting at 1-2 weeks in the ground) provided a practical means of protecting wildlife while endangering foxes.
The poison 1080 is used because of its different toxicity to different species, and because of its biodegradability. This poison has a poor reputation in the state but it is extremely important that the Tasmanian public has access to accurate information about the use of 1080 in fox baits, which differs greatly to the levels and processes used against native browsing animals in other operations.
The active ingredients of 1080 are found in some Australian plants as a natural chemical defence against browsing, and long-term exposure to these plants has resulted in Australian native animals having some resistance levels. This includes native carnivores.
Foxes, on the other hand, evolved in habitats where there is no 1080 in plants, making them super-sensitive to the poison in comparison to devils and quolls, which are among the most resistant of all mammals to it.
A species’ sensitivity is usually described as its 'LD50', a measure of relative sensitivity defined as the level of poison that needs to be ingested by a species for it to have a 50% likelihood of fatality.
The LD50 for red foxes is 0.14 mg per kilogram of its body weight. This compares to Tasmanian devils, which have an LD50 of 4.24 mg per kilogram, Eastern quolls - 3.7 mg per kilogram, and Spotted-tailed quolls - 1.85 mg per kilogram. Put simply, kilo for kilo, devils are over 30 times as resistant as foxes, Eastern quolls over 26 times and Spotted-tailed quolls about 13 times.
Another factor to remember is that 1080 breaks down quite rapidly in moist conditions due to fungal and microbe activity. Therefore, its persistence is dependent upon local soils and rainfall. Experiments showed that between the kangaroo meat being dosed and actual use, Fox Eradication Branch baits lost about 10% of their 1080. Breakdown is then rapid, with only 43.3% of the original 1080 being left after one day in the ground, 28.2% after five days, 19.7% after 10 days and only 11.6% after two weeks. In wet conditions breakdown was even greater, less in very dry conditions.
The Fox Eradication Branch chose 2.5 mg of 1080 per bait as the original dose, but quickly moved to 3 mg since the breakdown of 1080 was so rapid. At that level, most animals need multiple baits in a short time to have any problem. Foxes on the other hand usually only need a small part of one bait. In brief, this means by the time devils and quolls can easily find and eat DKM, it has levels of 1080 relatively safe for them.
Research has turned up further safeguards for our native carnivores. Although odourless and tasteless to people, it turns out that some species can detect 1080 in some bait types and therefore avoid eating them. This was observed with Spotted-tailed quoll in NSW but has not been seen for foxes.
Careful research was conducted before the specific baiting regime for the Tasmanian eradication program was decided upon. The Fox Eradication Branch follows strict procedures ensuring that the permission of property owners is granted and all neighbours are fully aware that the program is taking place before the baits are actually laid in the ground.
The first step taken is to contact landowners to discuss the program about to take place, and to ensure agreements to bait with 1080 on the property are signed. An important part of this process is to ensure that the dates for baiting the property are convenient for the landowner – for example, consideration needs to be made for when lambing might be taking place.
When Fox Eradication Branch officers lay baits, each bait is marked by flagging tape and the position recorded on a GPS. The baits are spaced between 200 to 250 metres apart, depending on such factors as the lay of the land or whether there are potential 'wildlife corridors' in the area. The officers are also careful to stay away from roads, houses and certain other landscape features.
Letters known as 'Neighbour Notifications' are also sent to all homes in the area of the property being baited to ensure that all persons in the vicinity can take due precautions during the period of baiting. Contact details for the Fox Eradication Branch are also included so that any questions neighbours may have can be personally answered.
Baits are retrieved after 14-28 days, and taken back to the Fox Eradication Branch storage facility at Prospect until contractors collect them for appropriate disposal.
Contact: Fox Eradication General EnquiriesFox Eradication Program
167 Westbury Road
PROSPECT TAS 7250
Phone: 03 6336 5320
Fax: 03 6336 5453
Email: Fox.Enquiries@dpipwe.tas.gov.au
Media enquiries should be directed to 03 6233 3625; 0438042610.
Report fox sightings and other evidence to the FOX HOTLINE 1300 FOX OUT (1300 369 688) | |
