271
See also: Predator–prey equations 44–49 ■ Non-consumptive effects of predators on their prey 76–77 ■ Human activity and
biodiversity 92–95 ■ The food chain 132–133 ■ The ecosystem 134–137 ■ Chaotic population change 184landed at Botany Bay from Britain,
to establish the first Australian
penal colony. On board the “First
Fleet,” along with more than 1,000
people, including convicts and
emigrants, were six European
rabbits, brought along for food.
By the 1840s, rabbits had
become a staple food in Australia,
and were contained within stone
enclosures. All this changed
in 1859 when a settler, Thomas
Austin, imported 12 pairs of
European rabbits and released
them on his estate near Geelong in
Victoria. Twenty years later, rabbits
had migrated to South Australia
and Queensland, and then in the
next two decades to Western
Australia. By 1920, the rabbit
population was 10 billion.
Rabbits appear to be innocuous
creatures, but they have wreaked
havoc on Australia’s native species,
competing with them for resources
such as grass, herbs, roots, and
seeds, and degrading the land.
They become particularly
troublesome during a drought,
when they eat anything they
can find in order to stay alive.There have been several attempts
to control the feral population, from
rabbit-proof fences stretching more
than 2,000 miles (3,200 km) to the
more successful introduction of the
myxoma virus and the rabbit
calicivirus, in 1950 and 1995
respectively. The resulting disease
has proved the most effective way
of controlling their numbers and
protecting native species.The secrets of success
As invasive species have spread
throughout the world, scientists
have tried to determine what
makes some of these species so
successful, and how to control themTHE HUMAN FACTOR
The harlequin ladybug is the world’s
most invasive ladybug. In the UK,
where it was first seen in 2004, it
is reportedly responsible for the decline
of seven native ladybug species.Spread of rabbits in Australia
Since their arrival
in Australia, rabbits
have spread throughout
the country. They have
contributed to the decline
of many native plants and
animals, and may have
caused several small
mammals to go extinct.without accidentally introducing
additional ecosystem problems.
Despite being hampered by the
lack of comparative data on those
invasive species that fail to
succeed, scientists have developed
a number of theories to explain the
success of certain species in
nonnative environments, including
the resource availability hypothesis,
the evolution of increased
competitive ability hypothesis, and
the enemy release hypothesis.
In general, species success
depends on a variety of genetic,
ecological, and demographic
factors. The resource availability
hypothesis, first proposed in 1985 ❯❯< 1870 1900–1910
1870–1880 1910–1920
1880–1890 > 1920
1890–1900 Not included in analysisKEYUS_270-273_Invasive_species.indd 271 12/11/18 6:25 PM