Pests within Australia 2

Another disaster of similar proportion to the prickly pear of my previous post was the introduction of European rabbits to Australia.

This innocent, almost cute looking animal, the European Rabbit, has cost the Australian agricultural industry and our environment billions of dollars over the past 150 years.

The history of the rabbit in Australia demonstrates that people can be really stupid. In 1859, a farmer introduced 24 grey rabbits to remind him of home. At the time, the man wrote:

"The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting."

By 1900, the rabbits had reached plague proportions and were causing extreme environmental damage. They ring-barked trees, ate fields to oblivion and caused massive soil erosion by digging burrows.



During my youth sights like this were fairly common for those of us who lived outside of the cities or who chose to go rabbit hunting/shooting/trapping or ferreting for them, I undertook all of these past-times as a teenager and at a conservative estimate probably accounted for several thousand of them over a 6 to 8 year period, my efforts and those of hundreds more like me did not even dent the rabbit population.

Rabbits are extremely prolific creatures, and spread rapidly across the southern parts of the country. Australia had ideal conditions for a rabbit population explosion. With mild winters, rabbits were able to breed the entire year. With widespread farming, areas that may have been desert, scrub, or woodlands were instead turned into vast areas with low vegetations, creating ideal habitat for rabbits. Humans are directly responsible for the initial release of the rabbits, and indirectly responsible for modifying the Australian landscape for ideal rabbit survival.

There have been inroads made by science that have been used to temporarily eliminate rabbits from various ecosystems. The first is the CSIRO's myxomatosis virus. When it was first introduced in the 1950s, the virus killed up to 99 per cent of rabbits without infecting any other species. On the downside, it was a short-sighted solution that pushed the ecosystem into imbalance. In less than 50 years, the kill rate has dropped to 50 per cent and within another 50 years almost all rabbits will be immune. Basically, all the virus did was interfere with the ecosystem's adaptation to the presence of rabbits. Unfortunately, it interfered in a way that was helpful for rabbits. Because rabbits are very fast breeders, a cycle of population explosions followed by population collapses has been helpful for the rabbits moving towards complete domination of the ecosystem.

1080 poison.

1080 is a synthetically produced substance that is a replication of a naturally occurring poison found in plant species such as poison bush. Although native animals can eat the foliage, seeds and flowers of the plants with no ill effect, it is deadly on the feral animals that have not evolved alongside it.

1080 is a slightly better control method than a virus because as well as rabbits being killed, so can cat foxes and cats. In this way, both predators and rabbits can be removed. Nevertheless, it is still results in a shock to the ecosystem and only temporarily removes the ferals until more migrate in to take their place. Furthermore, not all native animals have been exposed to poison bush thus 1080 can kill native animals as well.

The most recent control measure undertaken a few years ago was;
The introduction of Rabbit Haemorrhagic Disease or Rabbit Calicivirus (RHDV or RCD) also helped control populations, especially in arid areas, but again, rapid resistance to RCD has left rabbits as one of Australia's most formidable pests.

Rabbit biology

Rabbits are territorial animals with a well defined hierarchy or 'pecking order'.

Rabbit territories and areas where they feed are commonly defined by piles of scats or faeces or by a scented exudate from glands under the chin.

Rabbits will rarely feed outside these designated areas unless seasonal feed shortages force them to forage further afield. This is one of the key determinants in the success of a baiting program, as it is crucial to lay the trail where the rabbits are feeding. This area may not be where the warrens are located.

Breeding

A dominant male or 'buck' mates with most does within the group's territory. Dominant females can prevent lesser females in the group from breeding.

The gestation period of a rabbit is 28-30 days, with the average litter size between three and four kittens, depending on the age of the doe. Young does may have as few as two kittens, yet mature does may have eight or more. Five to six litters are possible in a good season.

Given excellent seasonal conditions, a mature doe is capable of mating again within hours of giving birth, while young does can start to breed at four months of age.

As you can see this puts a whole new light on the saying "The Buck Stops Here"