In spite of the protection laws, the attitude of many farmers towards wombats is still the same: they see them as vermin to be destroyed by any means. And some of the means they use are not pleasant. The execrable steel-jawed traps are still, often illegally, set to catch wombats, but more often these days burrows are fumigated with chloropicrin or phosphine gas, in the form of Larvacide or Phostoxin, two commercial preparations used in the destruction of rabbits. Chloropicrin is also known as 'tear-gas' because it causes intense irritation of the eyes and respiratory tract. Phosphine gas is a systemic poison. Symptoms of phosphine poisoning in humans include nausea, abdominal pain, headache and convulsions with ensuing coma. It is not known whether other mammals experience similar distressing symptoms before death, but it seems likely. Death by gassing with these preparations may not be as barbarous as the slow death of the steel-jawed trap, but it is still cruel. In a review of the management techniques for the bare-nosed wombat, Clive Marks found that in cases where the destruction of individual wombats is required, burrow fumigation using carbon monoxide as the fumigant is the most humane and target-specific method.
Shooting was found to be the second most common technique used by farmers in a survey in north-east Victoria, where it was used by 68% of the 113 landholders surveyed. Whether death by shooting is humane or not depends on the skill of the shooter and the efficiency of the firearm used. Also, if the wombat is in a trap a close shot to the head may be an appropriate method of destruction, but it is less likely that a humane death can be assured if the animal is unrestrained and distant from the shooter. Spotlight shooting is considered a sport by some weekend shooters and in some areas wombats are in double jeopardy if they feed on roadsides. They not only run the risk of becoming a road kill but are considered easy prey by these 'sportsmen'.
Cage traps are occasionally recommended by wildlife authorities for the capture of wombats, which may then be shot or transferred to national parks and other forest areas away from pastoral land. It is a method open to abuse and its use by untrained persons is questionable. Cage traps have been found to cause injury to claws and noses as the wombats try to escape, and death can occur if the caged animals are exposed to heat or cold. Translocating wombats is also a doubtful practice, as unless a release site is very carefully chosen, they are likely to be severely harassed, even killed, by resident wombats.
In fairness to the farmers who consider wombats to be pests, it must be admitted that there is a need for controlling wombat numbers where they are a nuisance. In spite of the effects of myxomatosis and 1080 poisoning campaigns, rabbits remain plentiful throughout most of the wombat's range in eastern Australia, and netting fences are still used to exclude them, not only from farmland but also from young pine plantations, which are very vulnerable to attack by rabbits. A wire-netting fence, however, erected at considerable cost to keep rabbits out, presents only a temporary barrier to a wombat, which either simply pushes a hole through the netting or digs underneath it. To do this, the wombat scoops out a shallow trough under the fence, then pushes its head under the wire to lift it up so that the
broad shoulders and neck can squeeze beneath it (Figure 7.3). Then it stands up, bending the wire as it does so and making a sizeable hole under the fence, and walks through into the crop or pasture or pine plantation or vegetable garden or anywhere else that suits it. The wombat usually rambles some distance from its point of entry, so when it leaves it makes another hole.
The number of wombats using a pasture is often overestimated. As each individual wombat produces about 100 scat pellets every night, and these are usually deposited in prominent places, an area used by even just one wombat can soon be well sprinkled with wombat sign. In addition, wombat scats have a slow rate of decay, especially in cold dry weather, so that the number of scats lying in a pasture, or along a track, can give the impression that the density of wombats in a certain area is much greater than it actually is.
Although it may eat some pasture grasses, the wombat does little, if any, economic damage to pastures, crops or plantations, and it has no interest at all in vegetables; however, the holes it makes in fences not only let rabbits in but also let domestic stock out. Other animals such as wallabies, kangaroos and pests such as wild pigs can also use the holes; and if the farmer mends these holes, the wombat simply makes others somewhere else. It is not surprising that many landholders have a very low regard for wombats, but there are some who, instead of trying to destroy them, are countering the problem by installing 'wombat gates' or electric fencing.
For many years, farmers in Europe have built swinging gates that allow badgers to pass through fences. Like the badger, the wombat regularly uses the same trails and the holes in fences along these trails. If a solidly constructed gate, swung from the top, is placed at one of these holes, while at the same time other holes nearby are repaired regularly, the wombat can be trained to use the gate. The wombat can move freely in either direction, but lighter animals such as rabbits are excluded because they cannot push the heavy gate (Figure 7.4). In a management study in southern New South Wales, Philip Borchard installed wombat gates in an existing fence and installed motion sensing cameras. Over a period of a year he obtained many photographs of the wombats using the gates, and of other animals being foiled by them (Figure 7.5). It has been found that wombats will use gates placed up to 800 metres apart in preference to making new holes. However, where wombats have access to improved pasture from surrounding bushland, their numbers increase and hence the level of movement between the bush and the pasture also increases. The commitment required by the landholder to establish and maintain wombat gates is such a drawback that this method becomes impractical. Also, as many landholders want to eliminate wombats from their land, a method which allows unrestricted access is not likely to be accepted.
The installation of electric fencing is a more practical method of excluding wombats from pasture, crops, plantations or anywhere else they are not wanted. The rising cost of fencing has prompted the development and greater use of electrified fences. These have proved to be economical and effective in controlling livestock, and they are also increasingly being used in conjunction with existing netting fences in wildlife control.
Clive Marks experimented with a two-wire, earth return electric fence, constructed on the bush side of an existing netting fence that was adjacent to pasture. The electric fence was built as a free-standing structure positioned 40 centimetres from the existing netting. The lower energised wire was about 10 centimetres from the ground while the upper wire was about 20 centimetres high. Marks made visual observations of wombats interacting with the electric fence, using infrared observation equipment. He found that wombats, which had previously dug under the netting fence,
reacted immediately to contact with the energised fence by withdrawing and moving at a fast run back to a burrow in the bushland. A second, more cautious investigation of the electric fence was made by the four wombats Marks had identified in this study, with the same result - they immediately retreated to burrows in the bushland. Some wombats, after receiving a previous shock at the electric fence, attempted to charge through the fence at places where holes had previously existed, but they also retreated immediately when they received another shock. The netting fence slowed the charging wombats and kept them near the electrified wires; without this netting barrier, Marks felt that the wombats would probably succeed in charging through the electric fence. Marks found that the wombats appeared to learn rapidly to avoid contact with electric fences, and that this learned behaviour is retained for a significant period. Thirteen weeks after his study began there were no signs of digging under the electric fence.
As well as damage to fencing, some landholders also blame wombats for the erosion of creek and river banks. Occasionally, after periods of very heavy rain, low level burrows may be flooded and cave in completely, slightly altering the shape of the bank and the stream flow. However, the amount of erosion damage caused by wombats is infinitesimal compared with that caused by poor farm management - overstocking and overclearing in particular. Unfortunately, wombats will often choose to burrow where slopes such as creek or river banks have been exposed by the clearing of the natural vegetation; any resulting erosion is blamed entirely on the wombat, which has only slightly aggravated a situation originally caused by the landholder.
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