FERAL CATS OF AUSTRALIA
By Guro Moira Oma
1. INTRODUCTION 2
1.1 Introduction 2
2. HISTORY OF FERAL CATS 2
2.1 A historic perspective 2
2.2 Growth of Feral Cats 3
3. THE PROBLEMS WITH FERAL CATS 3
3.1 Problem Issues 3
3.2 Effects on Bio-diversity 4
4. ADDRESSING THE PROBLEMS 5
4.1 Addressing the heart of the problem 5
4.2 Effective Countermeasures 6
5. CONCLUSION 6
5.1 Conclusion 6
6. SOURCES 7
6.1 Links and sources 7
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1. INTRODUCTION
1.1 Introduction
It is speculated that the fast growing populations of feral cats in Australia are responsible for the great decline and extinction of unique species in its native fauna.
In this assignment I have investigated the consequences of the introduction and growth of the feral cat population. Although measures have been taken to approach the problem, none have proven to be too effective, and discussions have arisen between different interest groups. The impact of feral cats on native fauna has not been critically investigated, but historical and circumstantial accounts suggest that cats can have great deleterious effects. Using information from various interest groups I will present the different points of view as objectively as possible.
What impact does the feral cat population in Australia really have on the local wildlife, and would its removal simply introduce other problems?
2. HISTORY OF FERAL CATS
2.1 A historic perspective
The domestic cat (Felis Catus), may have derived from the African or Arabian
wild cat, Felis Sylvestris lybica, and that domestication began around
8000 BC in the eastern Mediterranean. Eighteenth Dynasty sculptures and
paintings reveal that cats were fully domesticated and lived in close
association with people of Egypt by 3600 BC. In the last 2000 years, cats
have been actively transported on sailing vessels to most parts of the
world either as a source of food, as pets, or for their ability to control
ship borne rodents (vermin control). The domestic cat is now the most
widely distributed felid.
The first recorded instance of domestic cats brought to Australia is by
English settlers in the 18th century. Cats may have arrived earlier, in
the 17th century, escaping shipwrecks, via trading routes from South East
Asia or visits by European ships from the west coast. In the 19th century,
cats were deliberately released into the wild to control rabbits and mice.
Feral cats are now found in all habitats, except some of the wettest rainforests,
from Torres Strait across the breadth of the mainland.(Australian Government,
Depertment og Enviromental Heritage,http://www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/introduction.html)
2.2 Growth of Feral Cats
Cats are grouped into three categories according to how and where they
live. The first group consists of domesticated cats, owned and dependant
on humans. The second group are the stray cats, found in cities, towns
and rural properties. They depend partially on humans, but are not owned.
The last group are the feral cats, which are those that live and reproduce
in the wild, surviving by hunting or scavenging. Humans satisfy none of
their needs.(Australian Government, Department of Enviromental Heritage,
www.deh.au/biodiversity/threatened/tap/cats/3.html)
Initially, cats were brought to Australia for the purpose of pest control.
Naturally, cats managed to escape into the wild from time to time or were
abandoned, and degenerated into feral cats. The need for cats in the wild
was also welcomed, more cats were imported during the 1800s in order to
eliminate large number of rats, mice and rabbits which endangered crop
yields. Cats were released at gold digs in southeastern and western Australia
to control mice, and also in order to combat plague caused mainly by rabbits
and rats.(Australian Government, Department of Enviromental Heritage,
www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/introduction.html).
A female cat becomes sexually mature after one year, and is capable of
having two litters a year, but may have as many as four, each of which
the average is four kittens. It has been estimated that two cats producing
eight kittens a year, could be the progenitors of 174,760 cats over the
course of seven years even if each cat could only reproduce for one year.
This effectively means that 88% of all feral cats would have to be spayed
in order to maintain zero population growth.(Australian Government, Department
of Enviromental Heritage). A single pair og breeding cats, which can have
two or more litters a year, can exponentially produce 420,000 offspring
over a seven year period.(www.messybeast.com/TED-feralcats.htm).
Cats also created the dilemma at hand, how fragile the native Australian
wildlife is, being easy prey for the highly successful feline predators,
by presenting excellent breeding grounds for them.
This fantastic reproduction capacity, coupled with the abundance of easy
food sources served as a catalyst to an uncontrollable feline population
boom. It was estimated in 1996 that the feral cat population of Australia
was above 12 million. In comparison, the United States had a cat population
of an estimated 60 million, and Great Britain 1 million the same year.(www.messybeast.com/TED-feralcats.htm)
3. THE PROBLEMS WITH FERAL CATS
3.1 Problem Issues
The main problem that has been brought fourth in regards to feral cats
is their impact on the native fauna, as previously mentioned.
A large proportion of Australia?s native animal species exist nowhere
else in the world. Of Australia?s animal species, it is estimated that
84 percent of mammals, 89 percent of reptiles, 93 percent of frogs, and
45 percent of birds are endemic. Scientists estimate that 19 land mammals
and 20 birds have become extinct (that is, not sighted in the wild for
at least 50 years) since European settlement. The World Conservation Monitoring
Centre classifies 63 mammals, 37 birds, 38 reptiles, and 35 amphibians
as threatened?.(Encarta Encyclopedia, http://encarta.msn.com/encyclopedia_761568792_2/Australia.html#p29)
It is important to understand the fragility of the native Australian fauna,
since it evolved in isolation, not being influenced by the competition
elsewhere in the world. Until European colonisation of the Pacific region;
Australia, New Zealand, Antarctica and the many Pacific islands, contained
no species of the cat family, Felidae. Thus the arrival of the domestic
cat probably represented an important ecological event. The indigenous
specious of the native fauna did not evolve with the capacity to defend
themselves against cats, making cats disproportionately successful killers.(Australian
Government, Department of Enviromental Heritage, www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/introduction.html).
On the mainland, the continued survival of native species is thought to
be threatened by the predation of feral cats. Feral cats are being accused
of contributing, if not directly, causing the extinction of species of
wildlife indigenous to Australia. The feral cats are eager hunters, killing
more food than they could possibly eat. In Australia they tend to prey
on mammals weighing up to 2kg and birds weighing up to 3.5kg, though most
prey comprises smaller species weighing less than 220g. For the most part,
feral cats feed on rabbits, mice and rats, so called ?pests?. When these
species are lacking, the feral cat will attack and feed on any animal
in its size range. (Australian Government, Department of Enviromental
Heritage, http://www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/feral.html)
Mammals comprise the major prey of feral cats. Rabbits and house mice
predominate in semi-arid and some arid habitats, whereas marsupials are
predominant in temperate forest, urban and suburban habitats. Possums
are the main prey in temperate forests and suburban habitats. Smaller
native species such as brown antechinus, bush and swamp rats are caught
in temperate forests as well. In areas where rabbits do not occur, native
wildlife becomes the natural prey.
Small birds such as galahs, robins, thornbills, and magpies are frequently
hunted.
Several reptiles are also preyed upon, such as skinks, geckos and lizards.
In total, 38 species of mammals, 47 species of birds, 48 species of reptiles
and 3 amphibian species have been recorded in the diet of feral cats.(Australian
Government, Department of Enviromental Heritage, http://www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/feral.html#4-2)
Another important issue, are the number of pathogens and diseases the
cat?s have brought with them. Some, such as Toxoplasma gondii are suspected
to have caused population declines in several native species of mammals.
Rabies has also been a source of concern.(Australian Government, Department
of Enviromental Heritage,http://www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/feral.html#4-3)
3.2 Effects on Bio-diversity
When the highly specialized animals from Eurasia and Africa, evolved through millions of years of competition and were introduced to the secluded continent of Australia, they arrive with great advantages. They have evolved to be able to out-compete the less hardy native wildlife.
Direct predation by feral cats is the most dominant problem on the native bio diversity.
Another concern is that feral cats share the same feeding grounds and habitats as native wildlife, such as quolls. This will put the less adaptable quolls at a disadvantage, and unless it is able to find a new niche it will decline in numbers. (http://www.deh.gov.au/biodiversity/invasive/ferals/cat/impacts/feral.html#4-1)
Feral cats, coupled with other introduced species, diseases, and not
to mention humans themselves may have been too much for several species,
leading to their extinction or decline in populations.
4. ADDRESSING THE PROBLEMS
4.1 Addressing the heart of the problem
Obviously, the observed problem is the great decline in native wildlife, some even becoming extinct. However, there are a lot of mixed opinions about what the cause of this is. We live in a society where the cat is man?s second best friend. Appointing feral cats as a major source of the problem and taking the means to address the problem will naturally cause a lot of emotional debate.
However, even though mankind is naturally the main source of the problem, ignoring the impact a skilled predator such as the cat has on the Australian wildlife is ludicrous. As previously mentioned, we have seen the fantastic reproduction capabilities of the cat, which shows why the growing feral cat population is a big problem.
Several methods of denting their growing numbers have been tried, and none have had any significant success.
In 1996 Richard Evans of the Australian Parliament called for ?total eradication of cats from Australia?.(www.messybeast.com/TED-feralcats.htm)) His views were viewed by many as extreme, but perhaps it is the only solution. Can we afford to take the chance of letting the feral cats be, at the cost of perhaps even more native wildlife, or would it be better to remove a non-native species?
Past attempts at regional extermination has not met with any success, as feral cats from surrounding areas quickly migrate to the now open areas and multiply quickly. Reducing their number would only be a temporary solution. On Marion Island outside South Africa, the deliberate infection with feline enteritis killed around 65% of the population, and the remainders developed immunity. The remaining cats were exterminated by hunting. (http://www.deh.gov.au/biodiversity/threatened/tap/cats/3.html) Nevertheless, it showed how difficult it was on an extremely small scale, and proved beyond any doubt that such method would never work in Australia. Poison, hunting, trapping, ?Trap-neuter-release? programs, anaesthesia, surgical procedures have all been tried with limited success. (www.feralcat.com/michelle.html/www.feralcat.com/sarah2.html)
4.2 Effective Countermeasures
The feral cat problem is worldwide, and has now found its way into research laboratories. At Virginia-Maryland Regional College of Veterinary Medicine, microbiologist Dr. Stephen Boyle and theriogenologist Dr. Beverly Purswell are developing an oral, feline-specific, immunocontraceptive vaccine.
Great advances have already been made when it comes to reproductive controls for pets, few which have proven efficiently to control the overpopulation of feral animals. Using antigens to inhibit fertilization is a new humane, cost-effective route to a dramatic reduction of the feral cat population. With spays costing around 100 US dollars each, an oral vaccine will prove to be a fraction of the cost, and further reduce the need for euthanasia.
The glycoprotein layer Zona Pellucida surrounds the female egg cell and is responsible for the binding of the sperm to the egg during fertilization. The animal will produce antibodies if taken from one species and injected into another, and attachment of the sperm will be impossible. The challenge of developing an oral vaccine affecting only the fertility of cats is now researchers greatest task.
The oral form of a vaccine would not only be practical, but also financially affordable opposed to the proven financially impossible trapping and injecting of vaccines, which is simply ineffective. A cost-effective oral vaccine can change the way veterinarians approach spaying pets on a day-to-day basis.
New technology that can help keep feral cat population in check is our best hope for the future and the native fauna of Australia.(www.vetmed.vt.edu/ACCD/spotlight.htm)
5. CONCLUSION
5.1 Conclusion
It has become quite obvious that the feral cat problem is a complex and delicate matter. That feral cats harm the indigenous wildlife in Australia is an unquestionable fact, and the question at hand is how far we are willing to go to preserve it.
Animal organizations like to state that humans put the blame on the cats, but the facts speak for themselves, the feral cats are predators, and they are reproducing rapidly. They are obviously receiving their meals from somewhere. As stated previously, the thought of killing cats causes a lot of emotions, but it is nonetheless important to keep a clear view of the problem; the harm they are causing the native wildlife.
If new technology can be effectively used, perhaps both sides can meet in unison. Only time will tell.
6. SOURCES
6.1 Links and sources
www.deh.gov.au Main Source:(Australian Government, Department of Environmental Heritage)
www.feralcat.com
www.messybeast.com
www.vetmed.vt.edu/ACCD/spotlight.htm
(The alliance of contraception in cats and dogs)
http://encarta.msn.com/encyclopedia_761568792_2/Australia.html#p29
(Encarta Encyclopedia)