Corona has forced us to be creative with our spare time, since many of the things we enjoy doing simply are not doable at the moment. This has led to a significant increase in reading, DIY projects, and board and videogame sales. It has also resulted in more people pursuing unordinary pastimes. For example, in the UK people started making colourful snakes out of individually painted rocks and created pop-up zoos with ‘animals’ made from cardboard boxes, toys, and paintings. In Australia people have (of course) come up with much weirder activities – one of which involves licking or racing poisonous cane toads. At this stage you might think “damn, Australia must have been badly affected by Corona for this to happen”, but unfortunately this activity significantly precedes the pandemic.
COVID inspired family activities in the UK - rock snakes and pop-up zoos
Let’s start at the beginning – with sugar cane. Sugar cane farming has been a major industry in Australia, specifically Queensland, since the 1860s. However, soon after being established, the sugar cane plantations were ravaged by cane beetles and the losses caused began to be a serious problem in the 1880s. Plenty of good science was produced during this time to try to overcome this issue, but no solution could be found. Until one momentous day, many years later in 1935, when a government entomologist (Reginald Mungomery) suffered from a stroke of genius. He wanted to introduce cane toads, which are native to the Americas, to eat the cane beetles. Reginald was convinced this would solve the major agricultural crisis in the sugar industry, as the toads had reportedly solved similar beetle problems in Hawaii, the Philippines, and Puerto Rico.
Close up of a cane toad
Therefore, good old Reggie (he is Australian, so we need to shorten his name asap!) went to Hawaii, grabbed 101 toads, and brought them back to Australia. He bred them and on the 19th of August 1935 he released 2400 toads in Gordonvale, far north Queensland. This didn’t go without protest, also because all the cautious testing characterising the previous investigations into cane beetle control methods was completely forgotten when it came to the cane toad. No pre-release testing was done to see if the toads even ate the cane beetles. Also, the beetles that the toads were supposed to control were native Australian species, different to those causing problems in Hawaii and Puerto Rico, but no trials were carried out to see if this translated to Australian conditions. Finally, no risk assessments of potential harms from the introduced species were done. This led a fellow Australian entomologist, Walter Froggatt, to write the following to the authorities, “this great toad, immune from enemies, omnivorous in its habits, and breeding all year round, may become as great a pest as the rabbit or cactus”. Given his surname, they should have listened…
In under two months, the number of wild cane toads increased 24-fold. And as they say, the rest is history. The toads now number well into the millions, and their ever-expanding range covers thousands of square miles in north-eastern Australia.
Cane toad fact sheet and distribution
But why are cane toads so successful in Australia, when the populations of their American cousins remain manageable? The answer is co-evolution. In their native habitats, these toads have co-evolved with their environment (e.g., predators and prey) and, importantly their predators have adapted to the toads’ toxic nature. In fact, cane toads are rather poisonous and possess a cocktail of toxins that predominantly affect the functioning of the heart. It is secreted as a milky liquid from the parotoid glands located above the toad's shoulders. So, whilst in the Americas, their predators have either developed immunity or have figured out how to eat around the poison glands, the Australian predators had to start from square one. Though, impressively, we can already observe rapid adaptive evolution in native Australian species.
Cane toad poison glands secreting their toxic cocktail
The introduction of cane toads has had a devasting effect on Australian ecology, with many native species’ populations plummeting from trying to eat the toads and the toads eating or outcompeting other species. It has also led to many pet and human poisonings and whilst the former is regrettable, the latter (in the case of adults) should be classified as natural selection. This might sound cruel, but the only real way to be poisoned by cane toads is to pick one up and lick it or just eat it. Here, you might be thinking, “why would anyone ever want to do that?” Let me commend you; this is indeed an excellent question, and the answer is beautiful in its simplicity: to get high.
A component of cane toad poison is called 5-methoxy-N, N-dimethyltryptamine. This chemical binds to serotonin receptors, which then release a lot of the feel-good hormone serotonin into the body. Indeed, people who take 5-methoxy-N, N-dimethyltryptamine can experience a full-body rush and powerful hallucinations. Though it should be pointed out that these reports involve a purified substance, not some milky liquid licked off the back of a toad.
Don't lick toads, kids
As it's not much in the toad's interest to get people high, it has other molecules in its toxic arsenal as well, such as the above mentioned cardiotoxic steroids. These are very similar to the toxin produced by the foxglove plant, digitalis. Digitalis is used to treat people with irregular heartbeats, but the dosage needs to be carefully calibrated, because the difference between a therapeutic and a lethal dose is minimal. Since toads surprisingly aren’t trained pharmacologists, it is daring to rely on their cocktail mixing skills to stay safe. In fact, their version of the toxin triggers massive adrenalin; this first increases the heart rate and then causes fibrillation (i.e., irregular heartbeat). However, at high dosage, it can also cause seizures and death.
To top things off, the toads also secrete substances that weaken muscles and cause extreme nausea. So if you are ever thinking, “to lick or not to lick a toad – that is the question” and for some unknown reason opt for the licking, this is the experience you can expect: First you might have vivid hallucinations, but quickly your heart will start racing and your muscles will start being too weak to carry your constantly-vomiting body to the bathroom. Fortunately, if licking a toad isn’t your cup of tea, but you want to participate in toad-related activities, there is another option: cane toad racing.
The Australian public has been asked to help with the cane toad problem for many years now, by catching and euthanising the toads. However, one of the things I love about Australia and Australians, is that where possible, they will take a humorous approach to even the grimmest of situations. So, some people in far north Queensland have gone beyond their civil duties of removing cane toads from the wild and also started keeping them as pets (some might even call it high value investments). The reason for that is cane toad racing: a regular feature at the Iron Bar in Port Douglas (north of Cairns), at least while I was studying in Australia. For the race, a number of cane toads are put into a ring, each with their own 'jockey'. The jockeys are all provided with a party blower as their 'whip' and the winner is the 'jockey' who can race his/her toad to the edge of the ring first. Obviously, high stake bets are a must and can present life-changing opportunities. Ohhh Australia…;)
Cane toad racing at the Ironbar in Port Douglas
Klik for at opdatere samtykke
So now that you have learned all these fun facts about cane toads, you must be left with one burning question – did those damn toads at least fix the cane beetle issue? Simply put: No. In truth, they are eating them but there is no evidence that they have affected sugar cane production overall. This is likely because the toads ate some of the native predators of those beetles (ants) and fatally poisoned others (varanid lizards). There is also a myth about how they can’t eat the beetles, because the toads are ground dwelling and the beetles sit half a meter above ground on the sugar cane; whilst that does make it harder for the toads, the beetles regularly come to the ground to lay their eggs and can be eaten by the cane toads.
To end on a light note, the lessons learned from the cane toads at least played a major role in rejecting serious proposals of introducing elephants to control the previously introduced elephant grass (which grows too tall for cattle to eat) or importing the Komodo dragon from Indonesia to fill the predatory role once played in Australia by ancient giant lizards. Thus, not all is lost.
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