Researchers studying the ability of toads to ingest prickly, venomous scorpions have captured the precise moment on video, proving just how much fun science can be.
In recent years, the most populated parts of Brazil have been experiencing an “alarming” increase in scorpion accidents, also known as scorpionism, mainly caused by the yellow scorpion (Tityus serrulatus), or “escorpiao amarelo” in Portuguese. Considered particularly dangerous to humans, officials have responded by developing scorpion killing policies that include the use of toxic chemicals. But a much more simple solution may be lurking in the city outskirts, report researchers in the journal Toxicon.
Scientists believe that the increase in scorpion populations is largely due to a decrease in their predators. Cue Rhinella icterica, a “repugnant” brown toad that deserves more credit than it is currently given.
“[The] predatory behavior of toads upon scorpions was unknown because scorpionism was not before considered a public health problem. At this moment it is important to gather the most information we can about scorpions, including what animals are their predators,” study author Carlos Jared told IFLScience.
To shed light on the predatory habits of toads, specifically on scorpions, researches placed 10 toads in plastic boxes and offered the amphibians individual scorpions. Video captured by the team shows seven of the toads chowing down on the arachnid within five seconds of noticing it – all without even flinching. Toads were even seen manipulating the limbs of the scorpions for a smoother swallow. Slow-motion footage shows that the toads were likely stung in the mouth, but did not exhibit any symptoms. Shortly after, the toads ate cockroaches presented as dessert, which indicates that they were left relatively unscathed by scorpion ingestion.
Toads were also injected with venom equivalent to 10 scorpions, the lethal dose for mice, and a venomous amount to humans. They did not exhibit any adverse symptoms.
“The scorpion sting mainly causes pain [in humans]. Moderate symptoms can cause nausea, vomiting, increased heart rate, sweating, nausea, difficulty in breathing and pressure drop,” explained Jared. “In severe cases, more frequent in children, vomiting can be abundant, as well as sweat. Other symptoms include agitation, uncoordinated movements, drowsiness, mental confusion, tremors, and spasms.”
For toads, yellow scorpions appear to be nothing more than a “real treat”.
Jared adds that his team is not proposing a reintroduction of toads in cities for scorpion control. However, he notes that the work suggests the decline – or extinction – of scorpion predators, including toads, is one of the main reasons for the uptick in urban scorpionism. Even so, human relationships with toads have led largely to their decline in urban areas and the amphibian’s ability to keep scorpion populations at check has been overlooked.
“The poor toads are seen as 'ugly' and 'disgusting' by the rural people in general,” said Jared, who adds that the main contributor to the toads’ decline is destruction to their local habitat.
Jared says that his team hopes to continue its work by determining how the toads’ resistance or immunity occurs, whether or not there are protective molecules in the blood or other tissues, or if the resistance is of a physiological origin.