Since their introduction into Victoria in the 1870’s, foxes have adapted well to the Australian environment and now infest almost all habitats except the far tropical north of the continent. Their range and density may still be increasing.
Foxes are highly effective predators and thrive by killing a great number of Australian native animals. Small mammals and ground nesting native birds are at special risk. Many species have become extinct due to the relentless predation pressure from foxes.
Apart from their massive impact on wildlife and lamb production, foxes are known to spread weeds such as blackberries and olives via their scats.
Foxes are also responsible for major economic losses of newborn lambs and goat kids. These predation losses can reach more than 20% of lambs born, so effective fox control programs commonly result in significant increases in marking rates.
Perhaps even more importantly, foxes carry and spread parasites, bacteria and viruses that affect working and pet dogs as well as native wildlife (mange, worms, distemper, hepatitis and parvovirus). Foxes would transmit rabies, should this virus enter Australia.
An important first step is to understand the true size of the fox problem.
Most areas have between 1 and 4 foxes/Km2. Some areas, such as swamps or some periurban areas, can harbour even greater local densities in excess of 10/Km2.
At a density of 4 foxes/Km2, there may be hundreds of foxes within a 10 Km radius. A common error of fox managers is to seriously underestimate fox numbers and to use too few baits or not run a baiting program for sufficient time to achieve good levels of control.
Foxes have scent-marked home ranges where they spend most of their time. These can vary from 3 to 400 ha) but foxes are known to make sporadic transient forays of up to 10 Km outside their normal home ranges.
In uncontrolled areas, foxes have been shown to cause lamb losses of 10% to 30%. Under extreme conditions, predation on lambs can be as high as 50%. Fox predation has also been reported on calves, cows in birth difficulty, deer, ostrich and emu chicks, and free-range poultry.
They have a diverse diet that includes meat and plant items including fruits. They can spread seeds of pest plants like blackberries and olives.
Foxes are agile, can climb reasonably well and can travel a kilometre in just a few minutes.
The national cost of direct fox predation of lambs is estimated at more than A$100 million annually.
If lamb marking in a 500ha farm increases from a typical figure of 80% to nearly 100% (i.e. 100 lambs marked per 100 ewes mated), as has been shown in the field, then the gross return to the farmer could be 20 to 50 times the investment in a fox control programme.
Foxes mate in late winter and give birth to about 4 cubs per female in spring, after a 5 week gestation. Fox cubs stay in natal dens for the first month or two of life then start to forage for food with parental assistance. In late summer the sub-adult cubs leave the parental location to establish their own territories. This is known as dispersal, when young foxes can move long distances to reinfiltrate any area of low fox abundance. Thus, control should be conducted on an annual basis, or more often if possible.
Fox density is estimated to be about 1 to 4 foxes/Km2. Therefore a state like Victoria (approx. 250,000 Km2) harbours up to 1 million foxes. Half are female and each female raises about 4 cubs/yr. The production rate is thus about 2 million new foxes per year.
Foxes have a high risk of failing in their first year of life. Only about half of the newborn foxes make it to one year old. The death rate continues at about 30% of each age group, each year, throughout the 5 year natural lifespan. Contrary to common opinion, most foxes are young and fewer than 10% of foxes reach 4 or 5 years old. All foxes can damage stock and wildlife. It is not just a “few old rogues” that need to be controlled.
The adult fox weighs 5 to 7kg. It has excellent sight, smell, and hearing for skilled hunting. Foxes also possess canine teeth, speed, agility (including limited climbing ability) and wide dietary adaptability.
Foxes naturally cache food and mark the sites of food caches by defecating or urinating nearby. This is not hiding of food, as other foxes can easily find and dig up the food. The buried baiting strategy simply mimics the natural behaviour of the fox. Even after a bait has been taken, other foxes will visit the site, so bait replacement during a program over several weeks is wise. A single bait round will not control all foxes in an area.
Animal Control Technologies (Australia) Pty Ltd
46-50 Freight Drive
Somerton, Victoria, 3062
Telephone +61 3 9308 9688
Fax +61 3 9308 9622