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Quite regularly we hear of plans to kill animals when their population expands or someone considers them a nuisance. For example:

• About 500 kangaroos were killed on Defence Department land in Canberra in 2008.

• There were plans to kill around 5000 wild horses by helicopter shooting on Lake Gregory station in northern WA. This was plan B after the apalling plan A, to transport the wild horses 3000km to Peterborough in SA to be slaughtered, was rejected. However, plan B was also scrapped due to public outcry.

• A nursing home in Adelaide employed a shooter to shoot pigeons roosting on the roof, to the great distress of residents.

• In 2009 about 40 wood ducks were shot on Belair golf course in Adelaide because they pooed on the greens. Local people protested against the killing.

• Koalas on Kangaroo Island SA escaped death because of public opposition, especially from overseas tourists, and were sterilised instead.

Considering how much native habitat has been destroyed, some populations do need to be kept in check so that they don't degrade their limited environment and end up starving. However, killing is not the answer. Not only are killing methods cruel, but the killing has to be carried out every few years as the population builds up again.

 

 

Wildlife managers should not wait until a population builds up and then use cruel methods to reduce animal numbers.

Some deterrent methods

In the case of nuisance, there are usually other ways to deter animals without hurting them. Here are some examples:

• Some councils south of Adelaide have used hand-raised and trained birds of prey to scare flocks of corellas from town centres as an alternative to killing them.

• Pigeons can be deterred by putting up spikes where they want to land and roost. These are metal strips with long, blunt spikes that the pigeons never come in contact with, they just stop them landing. This is the approach recommended by the Royal Society for the Protection of Birds 

• Areas can be fenced or netted to exclude unwanted animals.

• There are spray deterrents available (see for example ReJex-iT) to protect new seedlings or golf greens from browsing animals or birds. The products don't kill the animals but are very unappetising, so they go elsewhere to feed.

The cruelty of killing

Muster and lethal injection

In the ACT, kangaroos were rounded up into pens, where they were tranquillised with darts, and then given a lethal injection. The problem is that kangaroos are highly strung wild animals, and being rounded up is extremely stressful. Some kangaroos were seen to jump the high pen fences in panic (Sydney Morning Herald, 18 May 2008). Kangaroos are susceptible to capture myopathy which can cause them to collapse and die.

 Helicopter shooting

Fortunately a plan in northern WA is to shoot unwanted horses from helicopters has been abandoned. There are 2 main problems with this method:

• when terrified animals run at high speed through rough country, there is always the danger of injuries such as broken legs;

• when a marksman is shooting a moving target from a moving vehicle (the helicopter) there is always the danger of wounding animals.

Shooting through the head with a high-powered rifle by an expert marksman on the ground is an instant way to kill an animal. However, in the case of marsupials such as kangaroos there may be pouch joeys who also have to be killed, and joeys at foot who will probably die without their mother. In Tasmania wallabies are shot with shotguns, which are cruel and ineffective weapons. They spray 100-200 small pellets that are more likely to injure than kill animals.

Traps set for dingoes are very cruel. Even if rubber jaw traps or steel jaw traps with strychnine rags are used, that won't stop many other animals being caught, such as the kangaroo joey.

Traps

Traps may be set for dingoes/wild dogs, foxes, cats and rabbits. The traps inflict terrible pain on these target animals, as well as many non-target animals.

Queensland has no restrictions on traps, while in SA and WA steel jaw traps may only be used for dingoes/wild dogs along the dingo fence and must be wrapped in rags soaked in strychnine to kill the trapped animals. Other states allow only traps with rubber jaws. While these padded traps cause less horrific injuries than steel jaw traps, they are not humane. Studies have show that substantial numbers of trapped animals still have broken bones, swelling, tendon and ligament damage, cuts and injuries such as broken teeth, bleeding mouth and self-inflicted injuries. Carnivores bite the trap and their own leg when they suffer the pain and fear of being trapped. For more details go to Further Information on Wildlife Management

Unintended animals caught in traps, even padded traps, are usually too severely injured to survive. For example, in Queensland, black striped wallabies often have broken bones from the trap or dislocated joints from their own frantic struggling.

Wrapping strychnine soaked rags around traps to kill animals is also not humane. The poison enters the victim's system either through the leg wound caused by the trap, or when the victim chews the trap in trying to escape. Strychnine causes violent convulsions and painful muscle contractions before the animal dies. An RSPCA (UK) official described "the obvious severe pain and distress caused by this poison which leaves animals fully conscious while their limbs and body jerk with uncontrollable tonic extensor spasms " The Feral Animal Search Conference in Canberra in 1991 recommended that the sale and use of strychnine be banned.

 In addition to the obvious physical injury and suffering, RSPCA Australia has also noted: “The use of any other type of live trap can also cause suffering if the captured animal: (a) injures itself when attempting to escape; (b) is rendered vulnerable to attack from other animals; (c) is restrained for a long period without food or water.”

All traps catch unintended animals such as the wallaby and wombat. Although steel jaw traps inflict particularly awful injuries, like the snapped leg bone in this wallaby, padded traps also injure animals.

Poisons

1080 is the most commonly used poison for a variety of animals. The poison is added to meat baits for carnivores, and to grain or carrots for vegetarians. As with all poisons, it is not a humane way to kill animals, and non-target species can eat the baits and die. “RSPCA Australia believes that the available evidence indicates that, in general, the effect of 1080 on animals is not humane.”

Studies have been done on just about every wild animal in Australia to see what symptoms they show before they die of 1080 poisoning. Symptoms include convulsions, struggling for breath, trembling and vomiting. Animals take many hours to die. For more details go to Further Information on Wildlife Management

Authorities should control animal populations humanely and wherever possible without killing.

Fertility control

Surgery is one way to stop animals breeding. Koalas on Kangaroo Island were caught and surgically sterilised. Male kangaroos at Government House in Canberra and Sanctuary Cover resort in Queensland have been given vasectomies. Colonies of cats have been surgically desexed to successfully reduce their populations in a housing estate in Battersea, UK, on the large grounds of a hospital in Louisiana, and on the campuses of the Texas A&M University and the University of Central Florida. Go to Further Information on Wildlife Management and the website of Cats Assistance to Sterilise (CATS).

While surgery works, it isn't practical for large numbers of wild animals. It requires anaesthetic, a vet to perform the operation, and some post-operative care. Chemical alternatives being considered include:

• hormonal contraceptives such as Deslorelin/Suplorelin and Levonorgestrel, which prevent the body from reaching a breeding hormonal state

• immunocontraceptive vaccines, such as GonaCon and SpayVac, which cause the body to produce antibodies that prevent reproduction.

Levonorgestrel implants are the most common method used in zoos to stop animals breeding. The implant is inserted under the skin and no surgery is needed.

Immunocontraceptive vaccines in horses and deer

In the US, a number of programs have shown that immunocontraceptive vaccines are an effective way to control the populations of wild horses and white-tailed deer. These programs do not cause the public outrage that killing produces. Some examples include:

• Immunocontraception has been used for 13 years to control a wild horse population on Assateague Island. Zero population growth was achieved after only 2 years and by year 11 the population had declined by almost one quarter in spite of the fact that treated mares were living longer.

• Immunocontraceptive vaccine was used to control white-tailed deer on Fire Island National Seashore. The program started in 1993, and after 13 years the population had declined to less than half its peak density, without any killing.

• When a group of wild mares was vaccinated, there was 100% infertility in the first year, and still 83% in year 4 without further treatment.

• When an improved vaccine was tested on white-tailed deer, infertility was 100% for 2 years and still 80% after 5 years. So, after 5 years 80% of the deer were still not producing offspring.

For more information, go to Further Information on Wildlife Management

Fertility control in marsupials

Contraceptive methods are not specific to particular species. Marsupials respond to the same methods as placental mammals. For example:

• Immunocontraceptive vaccine produced infertility in tammar wallabies for at least 18 months

• In several studies, contraceptive implants (Deslorelin) resulted in an average 18-21 months without pouch young in tammar wallabies.

• The same type of contraceptive implants were used to control brushtail possum populations around Perth zoo. At the end of the program, 80% of the possums trapped had not reproduced, with an average of more than a year without young.

• Slow-release levonorgestrol implants in koalas prevented births for at least 4 years.

• In humans, levonorgestrol implants can prevent conception for up to 6 years, and in both tammar wallabies and grey kangaroos implants prevented breeding for the duration of the studies (2 and 3 years, respectively).

• Levonorgestrol implants in 2 free ranging kangaroo populations in Victoria successfully reduced the birth rate. After 4 years at one site only about one-third of the treated kangaroos were breeding and at the other site only half were breeding after 5 years.

It is possible to control populations humanely. Research is continuing on contraceptive methods, particularly to make them longer-lasting and to deliver them in a food bait.