Invasive and native carnivorous mammals in Australia

Question 1

Why have introduced predator species been successful?

Answer 1

Human mediation is a key factor: high introduction effort, assistance (provision of shelter, food)

Rapid reproduction, long reproductive lifespan, ecological flexibility

For cats and foxes - introduction of rabbits

Naivete of native species - foxes and mammals have caused extinction of ~25 native species

Environmental manipulation to favour predators, active destruction of (potential) marsupial competitors

Question 2

Feral cats definition

Answer 2

Free-living cats with minimal or no reliance on humans; populations are self-perpetuating

Domestic and ‘stray’ cats: potential for contribution to feral cat populations

Ferals are ubiquitous

Question 3

Impacts of feral cats

Answer 3

Direct and negative impacts at population level via predation - impact is greatest on small mammals

Indirect negative impacts via transmission of disease, exploitation competition, and sub-lethal effects (e.g. risk of predation)

Indirect impacts via removal of digging engineer species (e.g. woylies, bandicoots), other strongly interactive species

Positive impacts if rabbits/mice/rats suppressed
E.g. Tree nesting birds - indirect commensalism

Question 4

Reducing predator impacts

Answer 4

Culling – 1080 poison used extensively for foxes, nothing available for cats

Reproductive control – TNR, chemical neutering, immuno-contraception are all problematic

Biological control – nothing available (unless dingoes are used as control agents)

Predator-proof fences

‘Teaching’ vulnerable
prey species

Semi-permeable
exclosures

Question 5

What is an invasive species?

Answer 5

Non-native introduced species that have successfully established and spread in a new environment. They are likely to cause negative ecological and/or economic impacts and/or affect human and animal’s health.

Question 6

Alien species

Answer 6

non-native introduced species that occur outside their natural range.

Question 7

What makes a good invader

Answer 7

Niche breadth - Generalist species should be better invaders than are specialists, because the former are more likely to find appropriate resources than in a new environment

Behavioural flexibility - Species with larger brains and higher behavioural flexibility should be better invaders, because they may be behaviourally adapt to the new environment

Social Behaviour - Social species should be better invaders than solitary ones. Social foraging may be advantageous for invaders because it can increase the probability of detecting a predator, locating food and learning about new food sources. However, social species may also have difficulties

Human - commensalism - Human commensalists should be better invaders because introductions are generally carried out by human modified habitats

Lifespan - Long-lived species should show a higher probability of establishing themselves in a new habitat

Species with life histories that increase intrinsic population growth rates are expected to have a better chance of surviving as they can attain large population size faster

Herbivores can invade new habitats more easily than carnivores as competition is less intense for herbivores

Question 8

What doesn’t make a good invader?

Answer 8

Sexually selected species should have lower introduction success - may be more vulnerable to extinction, because production and maintenance costs of secondary sexual characters and their reduced effective population size

Ground nesters less likely to be successful because they are more vulnerable to predation

Question 9

Natural species dispersal

Answer 9

hardly crosses biogeographic borders and is mostly unidirectional.

Question 10

Anthropogenic

Answer 10

is enabled or facilitated directly by human activities and can be both unintentional or intentional (e.g. domestication, game species and escapes from captivity).

Question 11

Intensional species introduction

Answer 11

Human nutrition

• pigs, cattle etc
• release of mammals and birds for hunting

Beneficial or Biological control agents

Ornamental animals and pets - released back into wild

Question 12

Stages of Invasion

Answer 12

1) Transport
- barriers include: Geography, survival, detection

2) Introduction - disembarkation
3) Establishment - Individuals capable of surviving go on to reproduce
4) Spread - Dispersal into new environments

Question 13

Impacts of Invasive species

Answer 13

1) Ecological impacts: affect ecosystem structure and function leading to loss of biodiversity or unique habitats.
Predation pressure on native species

2) Social impacts: focus predominantly on human, plant and animal’s health.
- Human disease transmission
- Native species disease transmission: how invasive animals can kill wildlife without lifting a paw

3) Economic impacts: have a direct consequence to humans leading to monetary losses.
- Damage to crop systems -
- Pasture land damages
- Horticultural losses

Question 14

Camel as invasive species

Answer 14

Main impacts:

i) grazing pressure - contribute to erosion;
ii) potential carrier of exotic diseases: threat livestock;
iii) damage fences and cultural sites

Question 15

European red fox as invasive predator

Answer 15

Introduced from Europe into Australia in 1830 for hunting.

Their rapid spread was linked to the spread of the European rabbit and also assisted by human introductions.

Main impacts (estimated at AU$227 million per year):
i) threat to livestock, prey upon poultry and lambs;
ii) potential carrier of diseases to humans and pets;
iii) considered a threat to 14 species of birds, 48 mammals, 12
reptiles and 2 amphibians.

Question 16

European rabbit as invasive species

Answer 16

Introduced for hunting and meat

Main impacts:
i) agents of land degradation and soil erosion that is a threat to at least 120 species of plants;
ii) grazing pressure that prevents seedling regeneration and
reduce crop yields, increasing competition with livestock;
iii) compete with native wildlife for food and shelter.

Question 17

Carp as invasive species

Answer 17

Introduced for food and recreation

Widespread

Question 18

Common myna bird as invasive species

Answer 18

High ability to adapt to a wide range of rural and urban areas.

Main impacts:

i) on fruit and vegetable crops;
ii) compete with native species over nesting sites;
iii) spreading disease to humans and native wildlife.