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Slide 1
Case Study: Becoming a Pest -Rabbits and Cane Toads Part
3-Lesson 1
Slide 2
Introduction A pest can be defined a number of ways but for us,
it is a non-native plant or animal that disrupts or has the
capacity to disrupt or alter the natural ecosystem function,
composition and diversity of the site it occupies.
Slide 3
Introduction If an organism is brought into a new environment
with a lack of predators, competitors and has other members of the
same species to mate with, it has the potential to become a pest.
The relative importance of each of these factors depends on the
nature of the organism and the habitat.
Slide 4
Rabbits European wild rabbits have had the greatest effect on
the Australian environment of any introduced species. They first
arrived in Sydney in 1788 with Governor Phillips fleet. The rabbits
were brought as a source of fresh food and often released when the
ships arrive at their desired location.
Slide 5
Rabbits Its believed that the first really successful release
of rabbits was in 1859 by Thomas Austin on his property near
Geelong in Victoria. He brought 24 wild rabbits from England and
set them free with the intention of hunting them for sport.
Slide 6
Rabbits Six years after he released the 24 rabbits he had
estimated he had killed 20,000 and had over 10,000 left. In 1866
14,000 were shot on his property.
Slide 7
Rabbits Rabbits spread very quickly across the country. The
spread was referred to as a grey blanket because of the huge number
that covered the land. They migrated to NSW by 1870, Southern
Queensland by 1890 and Western Australia and the Northern Territory
by 1900.
Slide 8
Rabbits At one stage there was said to be 100 rabbits for ever
man, woman and child in Australia. Rabbits ate everything; bushes,
shrubs, grasses and bark. Their effect on the country was
devastating.
Slide 9
Rabbits There was nothing left for grazing animals.The rabbits
ate down grasses so far that they killed the roots leaving the soil
bare. This affected the native animals and increased rates of
erosion. How do you think this affected the economy of the
time?
Slide 10
Rabbits Below is a list of reasons why rabbits were so
successful: Were able to adapt to the climates easily Able to adapt
to the habitats easily as many were found in their natural
environments Abundant sandy soil for warrens Could bread unnoticed
because of the shear size of Australian properties Little
competition for food Prolific breading animals Few natural
predators Need little water as they absorb most of what they need
from their food
Slide 11
Rabbits Rabbits were declared vermin in the late 1800s. The
government set a bounty on their tails which led to them being
hunted, trapped and poisoned in large numbers. A 3200 kilometre
rabbit proof fence was built between 1902 and 1907 to try and keep
them from entering the cereal growing areas of the south west.
Slide 12
Rabbits The first successful control program involved the
release of a virus called Myoxmatosis which is endemic in South
American rabbits and is transmitted by parasites (fleas and
mosquitoes). It was released in 1950 and had a 99% mortality rate.
The virus reduced the population from 600 million to 100 million in
2 years.
Slide 13
Rabbits Rabbit calicivirus disease (RCD) AKA: haemorrhagic
disease, is another method of biological control that has been
trialled in recent years. This disease is transferred by contact
between infected and non-infected rabbits as well as through the
faeces of birds which prey on rabbits.
Slide 14
Rabbits This virus escaped from an island off the coast of
South Australia and in 1995 was subsequently approved as a
biological control. It was released in Western Australia in 1996
and its success is yet to be fully evaluated.
Slide 15
Rabbits Many people made a living out of rabbit hunting during
the Great Depression of the 1930s. They also provided a cheap meal
for many Australians.
Slide 16
Cane Toads The cane toad (Bufo marinus) was introduced into
Australia in 1935 in attempt to biologically control the greyback
cane and frenchi beetles, pests of sugar cane crops. Cane toads are
native to South America and was introduced into Puerto Rico to hold
cane pests in check, which allegedly worked pretty well.
Slide 17
Cane Toads 102 toads collected in Hawaii, where it had been
introdced three years previously, were brought to Australia to a
special breeding facility in north Queensland. They were bred and
released into the surrounding cane-growing districts.
Slide 18
Cane Toads By the next year over 40,000 baby toads had been
released around Cairns, Gordonvale, Innisfail and Tully. It was
soon apparent that the cane toad was having little effect on the
beetles.
Slide 19
Cane Toads The greyback beetle live high on sugarcane and
rarely come down. Cane toads cannot climb. Frenchi beetles invade
the cane fields at a time when the toads are absent because of the
lack of protective cover.
Slide 20
Cane Toads Cane toads were however eating other things
including honey bees, small reptiles, amphibians and mammals. They
rapidly spread down the coast and had reached Brisbane within 10
years of their release in Cairns. They are now the most common
vertebrate in some parts of Queensland. In some areas they were as
dense as 5000 per hectare.
Slide 21
Cane Toads They have migrated west to Kakadu and as far south
as Port Macquarie. Their distribution is only limited by the
availability of water for breeding. They can even survive in
brackish water.
Slide 22
Cane Toads Cane toads are regarded as a pest because of the
following factors: They are poisonous They grow to a large size and
can survive away from water for long periods Female toads produce a
large number of eggs and the tadpoles that hatch from them are
poisonous Have very few enemies They will eat nearly anything they
can put in their mouth
Slide 23
Cane Toads Cane toads are found in a range of habitats which
include forests, wetlands, swamps, farm dams and suburban back
yards. The control of cane toads has never been enforced. Recently
Brisbane City Council established the Cane Toad Eradication
Committee in attempt to control the population.
Slide 24
Cane Toads People have been able to benefit from the cane toad.
Universities use them for dissections and tests and their skin is a
novel type of leather for shoes, handbags and wallets.
Slide 25
Cane Toads Their impact on native ecosystems has not been
conclusively studied although it is obvious that they displace
native amphibians. They do however help some native frogs by eating
predators like snakes. The populations of three frog eating snakes:
the death adder and two black snakes have declined since their
introduction
Slide 26
Homework Read pages 197-201 HSC Spotlight Text Update
electronic vocabulary Complete DOT Point 3.1 and 3.2
Slide 27
Case Study: Becoming a Pest -European Carp, Lantana and
Salvinia Part 3-Lesson 2
Slide 28
Activity Read together pages 201-205 Prelim Spotlight Text
Compete Activity 4.14 Introduced Species: Its Impact and Control pg
206 HSC Spotlight Text
Slide 29
Homework Update electronic vocabulary Finish Activity 4.4 if
necessary Complete DOT Point 4.1-4.4