Lecture on Invasive Species in Australia and the United States

Introduction

• Discussion of the impact of invasive species on natural landscapes and agriculture.

Invasive Species in Australia

Feral Rabbits

• 287 million feral rabbits causing significant damage.

Other Invasive Species

• Feral goats, wild boars, feral camels, European red foxes.
• Introduced by European explorers and settlers in the 17th and 18th centuries for hunting and food.
• Escaped or released animals bred and formed invasive populations.

Control Measures

• Similar to the U.S., hunting and trapping are allowed.
• Economically valuable species are collected and sold by farmers.

Feral Goats in Australia

Introduction

• Brought by British workers and miners in 1788 as pets and food.
• Established wild populations after escaping or being released.

Current Population

• About 2.3 million wild goats.
• Mainly in semi-arid or hilly areas (Western New South Wales, South Australia, Western Australia, Queensland).

Environmental and Agricultural Impact

• Compete with native wildlife and livestock for resources.
• Overgrazing, damaging crops, reducing farmer profits.
• Estimated $25 million annual cost to agriculture.
• Main cause of foot and mouth disease in cattle.

Economic Exploitation

• Industry worth $29 million.
• Mustering and selling goats is essential for many farmers.
• Hunting and trapping are used to control populations.
• 39% of wild goat population exterminated annually.
• Population doubles every 1.6 years if unchecked.

Wild Camels in Australia

Introduction

• First brought in 1840s by British for exploration.
• Population peaked at 3.1 million in early 2000s.
• Reduced by hunting, trapping, and mustering.

Current Population

• About 1.3 million wild camels (2022).
• Present in 53% of Australia's grassland ecosystems.

Environmental and Agricultural Impact

• Destroy fences, vegetation, deplete water reservoirs.
• Aggressive towards livestock, estimated $17 million annual economic loss.
• Common control methods: aerial hunting, mustering, unlimited hunting by people.
• Estimated 103,000 wild camels culled annually, with control measures costing $19 million.
• Population doubles every 7-9 years if unchecked.

Invasive Species in the United States

Common Invasive Species

• Wild boar, white-tailed deer, coyotes, swamp rats, Canadian geese, beavers, raccoons, wild turkeys, wild horses.
• Control measures: habitat destruction, trapping, hunting.

Canadian Geese

Population and Breeding

• Estimated 7.3 million in the U.S.
• Nest and lay eggs near water bodies from March to May.
• Female lays around 5 eggs, incubation by both parents.

Environmental and Agricultural Impact

• Feed on grasslands, causing pollution and destruction.
• Poop frequently, causing pollution in parks and lakes.
• Dangerous for flights, causing around 1200 plane crashes annually.
• Control measures: hunting, drones to scare off geese.

Swamp Rats (Nutria) in Louisiana

Population and Breeding

• Large rodents, widespread in Southern U.S.
• Eat plant roots in swamps, causing ecological damage.
• Can give birth to 40-60 young per year.

Control Measures

• Trapping and hunting encouraged by $6 reward per swamp rat killed.
• Authorities encourage chefs to use swamp rat meat in menus.

Wild Horses in the United States

Population Growth

• Grow at 18-20% per year.
• Overgrazing and competing with cattle for resources.

Control Measures

• Bureau of Land Management gathers and removes horses.
• Contraception used to slow population growth.