European Rabbit Invasive Species Assessment
A dangerous pest, the European rabbit also known as the Oryctolagus cuniculus, was originally brought from England but was native to several other countries. These include the Iberian Peninsula (Spain and Portugal), the Gibraltar (France), Africa (Morocco and Algeria). The immense impacts of the rabbits were immediately apparent and caused great havoc. Although only a small number of rabbits were imported to Australia, they quickly spread throughout one of the world’s fastest reproduction rates. The spreading of the species was also aided by the existing animal burrows, habitat modification for farming and by intentional introduction of meat/hunting.
After a gestation period determined by rainfall of 28- 30 days, the female, adult rabbit gives birth to hairless and blind rabbits, that are helpless for the first two weeks. In less than a month (approximately 18-25 days) they are ready to forage on their own, and once they are six months old, they can breed. A healthy female, adult rabbit can breed six times a year on yards filled with foods. They often live to 9 years, both in captivity and in the wild. Diet is crucial to reproduction and maintenance. It consists of 40% fibre, 10-12% protein for maintenance and 14% protein for reproduction. Australia is a perfect breeding ground for the rabbits as there is food: shoots, herbs, grains, grasses, leaf buds and vines readily available, good ground cover and a small number of predators.
The European rabbit’s origins began when the first fleet arrived had arrived in Australia in 1788. Aboard this ship was the cuddly yet chaotic European rabbit. Whilst, Andrew Miller, the head commissioner of the First Fleet initially listed 5 rabbits, most likely silver greys to transport to Australia, they did not become a major pest until they were released in Victoria. After arriving, they’re moral purpose was to serve as the settler’s companions. However, they failed to survive in the Australia Bush. More than a century later, on Christmas Day, 1879 a man by the name of Thomas Austin had released 24 rabbits onto his property in Winchelsea, Barwon Park, Victoria. They had been sent to him by a relative in Europe as a form of entertainment. This is because wealthy settlers would shoot the rabbits as a hunting game. On the first day that they were released, only 7 rabbits were shot. Shortly later, in 1866 approximately 14,253 rabbits were shot.
Habitat is a major influence on the rabbit’s lifestyle. They are able to thrive in both urban and coastal areas; however they prefer low vegetation, well drained, deep sandy soil locations. This is because these locations are easy to dig and allow the rabbit to easily build warrens. In Brisbane the rabbits populate Ipswich and urban areas of South Australia and places, such as Granite Belt, south-western Darling Downs, Maranoa, southern Warrego and the far south-west with the largest populations, north-western Darling Downs and north Burnett with modern populations and the rest of Queensland with low numbers.
Impacts on the Ecosystem
The impact that European rabbits have had on Australian ecosystems include loss of plant biodiversity and animals due to the overgrazing of land. According Pestsmart Australia it only takes one rabbit per hectare to prevent the successful regeneration of many native trees and plants’. This is because the European rabbit mainly consumes local seeds and shrubs which are in critical stages of development. Due to this the inhibition of these plants are prevented. Not only do these native plants suffer, but they are often replaced with invasive weeds. The destruction of vegetation caused by the European rabbit’s warrens has resulted in degradation and erosion. This is because, the removal/loss of plants makes the soil prone to the open air which can lead to soil fertility and siltation of dams. Furthermore, the European Rabbit poses a great threat to native animals. They are currently competing with other animals for food and shelter. Especially during the drought and bushfire season, the European Rabbit often scavenges and consumes whatever food is available. This is because they have altered the habitat of native animals, reduced supply of food, attracted predators (e.g fox) and displaced small animals from burrows. The European Rabbit has caused several species to decrease in number including the greater bilby (Macrotis Lagotis) and the pig footed bandicoot (Chaeropus ecaudatus).
Several mechanisms such as mechanical, chemical biological controls have been applied to European rabbit infested areas to reduce the detrimental effects. Before managing the pest, the person be fully aware of the European’s rabbits’ behaviours, density of population, and distribution. These strategies include warren ripping which is done using explosives, fencing, fumigation and shooting. This is the process of interline ripping and ensuring by cross ripping at a 90-degree angle to the original rip. The depth is approximately 70cm and the deeper the ripping is the better the result.
Additionally, fumigation of warrens is a great control as a fumigant, often aluminium phosphide comes in a tablet form which seals the warren by releasing a poisonous phosphine gas when activated by moisture. This flushes the rabbits out as it cuts the entrance off, reducing the possibility of the rabbit appearing again. Exclusion fencing is another mechanical mechanism of constructing fences consisting of a minimum of 17cm wire framing beneath the ground, securely attached to pegs, rocks or timber.
Additional mesh is added to support the main fence. This strategy is particularly effective, when well built, however one concern is that it prevents the movement of native animals. Baiting can be completed in several ways including trail baiting, perishable carrot bait, and shelf stable oat bait. All these methods involve sodium flouroacetate (1080). To eliminate the rabbit, a pressure fumigation or a diffusion fumigation including toxins such as chloropicrin and carbon monoxide is used. Poisoning can also be completed through the Myxomatosis Virus. These strategies are not particularly effective as they always require the rabbit to be inside the warren, consistent monitoring, the rabbits have developed resistance against the poison and are not time or money efficient.
Contribution of Science to Impacts
Scientist have created a vaccine to decrease the population of European rabbits in Australia. It is commonly known as RHDV (Rabbit Haemorrhagic Disease Virus). Its purpose is to inoculate the haemorrhagic disease into the blood stream, which is done through an intramuscular injection.
RHDV is a very deadly, and once the rabbits start displaying symptoms, there is not much there can be done to save it. Currently, there are no treatments or cures available. The disease is transmitted quite easily, resulting in a significant decrease of population. Although RHDV has effectively reduced the impact of rabbits across many parts of Australia, it is unlikely to keep populations down over time.
One challenge is if rabbits start returning will be the wage and income of Australians, especially farmers. Before the release of RHDV, when rabbits were a very common pest in QLD, production losses in agriculture were around 120 million, every year. It is estimated that decreasing rabbit populations would increase profits by $600 million.
Another challenge is that although scientists created the RHDV vaccine to protect Australia and its wildlife, it is doing the opposite When another animal predates on a rabbit with RHDV, it too will have the virus. These predators could be animals such as foxes, owls and dingos.
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