The Toad Invaders

The most human deaths happening today are because of an animal who is just the size of a small LED, the name of this animal is a mosquito. But this blog is not about mosquitos, it is just an example of how even one of the smallest animals can cause a havoc for everyone.

This blog is about an animal known as a Cane Toad. Who thought that the toad of the size of a tea cup will become one of the major threats to a nation’s native wildlife and in all one of the worst invasive species on the entire planet. No doubt that they are magnificent animals but they are spreading to the wrong parts of the planet, where they are not meant to be and are causing a disaster for the environment.

About Cane Toad

Cane Toads (Rhinella marina) or Giant Toads or Marine Toads are the largest species of terrestrial toads found in South and Mainland of Central America. They can typically reach up to 10 to 15 cm with the maximum size of 24 cm and can live up to 10 to 15 years in the wild and around 35 years in captivity. Their natural diet includes small rodents, reptiles, some amphibians, birds, bats and invertebrates. Back in the days, Cane Toads were transported to different countries to be used to eradicate pests from sugar cane plantations thus giving them the common name they have today. And today this is the reason why they are an invasive species in around 20 countries around the globe.

Now lets talk about the famous and feared defence mechanism of the Cane Toads. Upon being threatened their parotid glands situated behind the eyes secrete a white milky fluid known as Bufotoxin. Bufotoxin is a poison, if ingested by humans leads to hypersalivation, vomiting, diarrhea, weakness, pulmonary edema (A condition caused by excessive fluid in lungs which collects in numerous air sacs in the lungs) and seizures. Coma and death can occur within 30 minutes of ingesting the poison (Here many of you might confuse the word poison with venom. In the most simplified language, venom is something that adversely affects you when it is injected in you and poison is something that adversely affects you when it is ingested by you). Apart from releasing Bufotoxin through their glands, Cane Toads puff up their lungs and lift up their body off the ground to look larger in front of their predator.

There have been cases of human and animal deaths because of the consumption of Cane Toads. One of the main threats are to the domestic pets like dogs because if they lick or bite a Cane Toad they can be poisoned and potentially die a painful death.

But how did they become a major threat in so many countries ?

Cane Toads were released in many countries for agricultural pest control. However they did not succeed with removing pests but became successful in establishing themselves as a dominant invasive species. Two prime reasons for them flourishing in almost very country they are introduced are adaptability and fast reproduction mechanism.

Cane Toads are highly adaptable and hardy animals. They can be found in varied areas like mangrove swamps, dunes, coastal grasslands and even rainforests. They have also been seen surviving temperatures between 5 °C to 40 °C. The second reason is that Cane Toads are prolific breeders. Once fertilized, female Cane Toads lay anywhere between 8,000 to 30,000 eggs twice an year. These eggs hatch within 1-3 days. The females lay these eggs in long stripes in small freshwater bodies like a pond.

Case Study: How Cane Toads are affecting the native wildlife of Australia ?

Back in the days, Cane Toads were artificially introduced in sugar plantations in different countries to get rid off pests destroying the plantations. After being successful in Puerto Rico, Australia planned on doing the same thing. In August 1935, Australia brought Cane Toads from Hawaii where Cane Toads had been used for the same purpose and introduced 102 adult Cane Toads in the sugarcane fields of Queensland. The Commonwealth Department of Health decided to ban any introduction of Cane Toads till the study was conducted to notice their feeding habits.

The ban was lifted in 1936 and a batch of 62,000 toadlets were released into the wild in March 1937. Soon this started to prove one of the worst decision ever taken by the concerned authorities of Australia. Soon they started to reproduce and spread to Northern Territory and New South Wales. Along with the problem of population explosion it was noted that the Toads failed to control the population of the Grey Backed Cane Beetles (Dermolepida albohirtum) because the beetles were found high on top of the sugar canes whereas Cane Toads are not good climbers. Therefore they started eating whatever could fit in their mouth except the animals they were brought in to remove.

In Central America where Cane Toads are found, their predators like Caimans, certain snakes, eels and fishes find them to be a tasty snack. Some of their predators in their natural range are immune to their poison whereas some have developed ways to eat them by avoiding most of the poisonous parts and tolerate even if they ingest some.

Just like any native animal is not accustomed to an invasive species, similarly the native wildlife of Australia is not accustomed to a non-native species like the Cane Toads. The native predators of Australia are neither immune to the poison secreted by the Cane Toads nor are aware on how to hunt them without ingesting any poison or poisonous part. Native predators that have died after eating, or attempting to eat, cane toads include goannas, freshwater crocodiles, tiger snakes, red-bellied black snakes, death adders, dingoes and quolls. Today the population of the Cane Toads has increased from 102 individuals to around 200 million individuals. An animal introduced to eradicate a pest has become a pest itself. They are not only harming the native wildlife by endangering their lives but also by outcompeting them for resources like food and breeding habitat.

It has been almost 80 years since Cane Toads were introduced in Queensland and so they have adapted themselves really well in the ecosystem and therefore it does not seem very possible to eradicate them all at once. On top of it, they have spent a lot of time in Australia’s ecosystem and if they suddenly perish, it can lead to imbalance in the ecosystem. Therefore the common citizens of Australia along with the concerned authorities are trying to control their population locally by disposing off long stripes of eggs in freshwater bodies and maintaining hygiene around them.

World Wildlife Fund-Australia is working with the Cane Toad Coalition to train their native predators like the northern quolls to recognize and avoid hunting Cane Toads. This is called the taste aversion training. During the training the trainers bait the animal with a Cane Toad sausage or very small Cane Toads possessing a very small quantity of the poison, making them a bit ill but surely not enough to kill them. Slowly the animal starts to understand that this is not good for its body. Thus when they encounter larger Cane Toads in the wild, they will know to avoid it. This technique has worked with great success in a part of Kimberley and is being planned to implement in other parts of Australia, where Cane Toads are going to spread and also where they are causing a menace.

This instance is one the greatest example as to what can be the consequences of tampering with nature and wildlife. These are the instances that has opened the eyes of many people but it is important for the rest to understand as well. And this shouldn’t be by experimentation, it should be by education and learning from the mistakes of the others. In this way we will ensure a better future for the wildlife as well as ourselves.