Australia imported 2,400 toads to save its crops – now 200 million of them are an unstoppable disaster

The post Australia imported 2,400 toads to save its crops – now 200 million of them are an unstoppable disaster appeared first on AZ Animals.

Quick pick up
Cane frogs were introduced to Australia in 1935 to control sugarcane beetles, but toads ignore bug while decimating the ecosystem they were supposed to protect.
Instead, they became one very toxic invasive species no natural predators.
Cane frogs threaten many native reptiles, mammals, birds and amphibians.
Despite decades of effort, large-scale control of cane toads remains nearly impossible.

In 1935, native beetles were wreaking havoc on Australian sugar cane crops in Queensland. The beetle larvae lived in the soil and chewed the sugarcane roots, stunting growth or killing the plants. Looking for a natural solution to kill the grubs, the Australian government imported cane toads from Hawaii, with the hope that the toads would eat the grubs and save the sugar cane. Unfortunately, the worst case scenario happened. The frogs did not keep the cockroach populations in check. Instead, they have become one of Australia’s most destructive invasive species and an ecological disaster.

History of Australia’s Disastrous Cane Frog Introduction

Sugarcane had become a key crop in Queensland by the late 1800s. Settlers found that Queensland’s hot, humid climate was ideal for growing the plant. However, farmers faced a struggle with the larvae of native beetles, especially the gray cane beetle (Dermolepida albohirtum), as the larvae ate the sugarcane roots and decimated the crops. To help farmers, the government established the Queensland Bureau of Sugar Experiment Stations (BSES) in 1900.

Entomologists working for BSES studied multiple methods of beetle control, eventually arriving at a relatively new science: biological control. At the time, entomologists were experimenting with the new idea of ​​bringing in natural predators to control pests. Thus the cane toad entered.

Cane toads to the rescue

cane toads (Rhinella marina) they are the largest toads in the world. They are opportunistic predators and eat a diet of insects, small animals, plants and even pet food and garbage. Cane frogs grow up to 10 inches long and weigh up to 4 pounds. These massive toads are also highly poisonous, even as eggs and tadpoles. Toads secrete a toxic substance called bufotoxin, which can kill animals that try to eat them and can irritate the skin or burn the eyes of humans who handle them.

As you can imagine, the introduction of cane toads to Queensland has brought more problems than it has solved. Cane frogs are native to Central and South America. However, in the 1920s and 30s, they were introduced around the world to control pests. Today, they are considered invasive species in Australia, the Caribbean islands, Hawaii and Florida.

In August 1935, the BSES released 2,400 cane toads into the sugarcane plantations of Gordonvale, North Queensland. This was not a well thought out plan. According to the National Museum of Australia, “Remarkably, no studies have been carried out into the potential environmental impact. Nor has the Bureau of Sugar Experiment Stations even determined whether the toad will actually eat the cane beetles.”

Cane frogs thrived in the warm environment. However, they did nothing to control the cockroaches. Today, beetle larvae are controlled in sugar cane farms with soil insecticides.

What species are most affected by cane toads?

By 1950, the Australian government declared the cane toad an invasive predator. Dangers posed by toads include poisoning their prey, competing with native species for resources, and their voracious appetites.

According to the Queensland government, 75 species of Australian crocodiles, lizards and freshwater turtles are threatened by toads. Some of the animals that are in danger of dying after eating a cane frog include Australian lizards, quolls, tiger snakes and freshwater crocodiles. Many of these animals are designated as threatened species.

A research study has shown that native tadpoles suffered mass mortality shortly after the frogs were introduced to Queensland. The study found that 1,300 tadpoles from 10 different species died in a single season. Birds are also affected by toads. For example, cane toads eat the eggs and young of the rainbow bird. Research has shown that cane toads have caused a third of bee nests to fail.

Finally, cane frogs have an indirect effect on native species by changing the ecosystem when they arrive in an area. Toads have large appetites and eat many insects. Eventually, the population of invertebrates begins to decline, which reduces the amount of resources for other species. These cascading changes can have broad implications for complex food webs.

Why cane toads are so difficult to control

By 2010, the Australian government announced, “It is unlikely that there will ever be a large-scale method available to control cane toads throughout Australia.” What was introduced as a benefit to sugarcane farmers has become a plague that is rapidly spreading across the continent. Scientists estimate that the cane frog’s range is expanding at a rate of 25 to nearly 40 miles per year.

Cane frogs have no natural predators or diseases that threaten them in Australia. In Central and South America, they are kept in check by the natural predators that have evolved with them. For example, many South American snakes are either immune or have some level of immunity to cane toad bufotoxin.

Cane frogs are also opportunistic feeders and will eat almost anything, even pet food and people’s garbage. They breed opportunistically, usually in warm and humid conditions, and may breed several times a year. Females lay between 8,000 and 30,000 eggs at a time. To understand how cane toad populations can explode, consider that most native Australian toads lay between 1,000 and 2,000 eggs in an entire year.

Cane toad control efforts continue

Experts offer ways to control cane frogs if they are found in a small area or small pond. They suggest collecting and removing cane toad eggs from the water or humane disposal of adult toads. Community groups provide information on how to recognize adult cane toads and humanely remove them from the environment. However, these control measures are only feasible for small areas and cannot be applied to large cane toad populations.

Despite the challenges, researchers are looking for new ways to control toads. Scientists have discovered they can edit the DNA of a cane toad egg to prevent it from growing beyond the tadpole. If scientists can find a way to genetically modify large numbers of eggs, they may have found a solution to controlling the growth of the cane toad population.

In another study, scientists were successful in conditioned taste aversion (CTA) in freshwater crocodiles. Some crocodile populations in Australia have declined by over 70% due to poisoning from ingesting cane toads. In the study, researchers placed cane toad carcasses with the toxin removed, but a nausea-inducing chemical was added. While the crocodiles in the control sites continued to eat and get sick from the poisoned cane frogs, those in the treatment sites stopped trying to eat the cane frogs.

Another project that began as a citizen science initiative involves a tadpole trap design that can catch thousands of tadpoles. And in an effort to protect the Pilbara from invasive hoppers, scientists are looking at ways to prevent the frogs from accessing the water. Cane frogs cannot survive more than a few days without access to water.

The post Australia imported 2,400 toads to save its crops – now 200 million of them are an unstoppable disaster appeared first on AZ Animals.