Amphibians are remarkably resilient creatures. In the 300 million years they’ve been around, they have survived mass extinctions, ecological upheavals and persistent threats from predators—not least of which includes human demand for their psychedelic compound. In the process of evolving, many amphibians, like toads, have developed strange but highly efficient defense mechanisms against predation.
Some are brightly colored to warn other animals of their toxicity, a strategy known as aposematism. However, others, like the Sonoran Desert Toad (which happen to be North America’s largest native species of toad) could easily be mistaken as harmless due to their more subdued coloration and inconspicuous appearance.
When threatened, many such toads belonging to the Bufonidae family, including the Sonoran Desert Toad, secrete a potent cocktail of poisonous toxins. These secretions originate from skin glands such as the parotoid glands, found around the back or neck region of the animal. This is the primary defense mechanism for a toad that is otherwise physically incapable of defending itself from the likes of raccoons, skunks, snakes or birds of prey, like eagles.
How Does The Toad Use These Compounds In The Real World?
The parotoid glands of the Sonoran Desert Toad produce two toxins, among others, that are of interest: 5-MeO-DMT and Bufotenine (a toxic DMT analog).
Both these compounds have powerful hallucinogenic properties that can incapacitate predators, allowing the toad to escape, relatively unharmed. Bufotenine goes a step further. In high enough concentrations, it can lead to severe physiological reactions. These reactions may include respiratory arrest, cardiac dysfunction and extreme changes in blood pressure, which can be fatal for the predator.
A landmark 1956 study in Herpetologica found that these toxins, combined with a defensive posture and inflated size of adults, could ward off predators quite effectively.
Because ethical considerations in research were less stringent during this time, the researchers were able to forcibly apply the toad’s toxins directly into a three-month-old dog’s mouth. For the 30 minutes that followed, the dog was physically incapacitated (although it made a full recovery later):
- It frothed at the mouth
- It had persistent convulsions
- It lost control of its bladder
- Its coordination was “extremely poor”
To observe how the toxins would function in a real-world scenario, the researchers then placed a skunk and a Sonoran Desert Toad in a cage. The toad, under threat, assumed a defensive posture:
- It exposed its back and neck region (where the parotoid glands are)
- It inflated its size by drawing in air
- It hissed loudly as it slowly forced the air out of its lungs
This aggressive stance, combined with the taste and smell of the toxins, visibly deterred the skunk from pursuing its attack.
When the researchers observed that similarly sized, non-toxic toads were attacked and consumed by the skunk, while Sonoran Desert Toads were ignored, they reached the conclusion that the skunk had decided not to pursue these toxic toads.
However, it is important to remember that this is the story of one skunk. As a species, they seem to have learned how to prey on these toads safely.
Is The Sonoran Desert Toad Ever Vulnerable?
Historical accounts, such as a 1930 article in Copeia, vividly illustrate the dangers of preying on these toads:
- A fox terrier, having bitten into one of these toads, succumbed within minutes
- A German shepherd, after merely touching its nose to the toad, was paralyzed, though it eventually recovered
Such incidents underscore the toad’s formidable defense and highlight the fine line predators must walk when encountering this amphibian. Interestingly, there isn’t evidence to suggest that any known predator has developed a physiological resistance to the amphibian’s toxins. This doesn’t mean that the toad isn’t eaten, but that preying on these creatures, in most cases, would result in a great deal of discomfort or even death.
The most effective solution to successfully preying on the toad was reported in a 1966 article published in Herpetologica. A raccoon in the Sierra Bacadéhuachi mountain range in Sonora, Mexico was observed employing a clever tactic to avoid the toad’s toxic secretions.
It preyed upon the toads by flipping them onto their backs and attacking through the abdomen, steering clear of the glands known for their poison. This behavior suggests that mammalian predators, including skunks, ringtails, coatis, bobcats and gray foxes, may have similarly adapted their hunting techniques to circumvent the toxic defenses of the Sonoran Desert Toad, pointing to a remarkable example of predatory innovation and adaptation in the face of potent chemical defenses.
The saga of the Sonoran Desert Toad and its predators exemplifies the dynamic of evolutionary adaptation. With its potent defensive toxins, the toad has crafted a near-perfect deterrent, yet the relentless march of natural selection empowers certain predators to find and exploit a critical weakness. This interplay ensures that the balance of survival never stagnates, as each evolutionary innovation prompts a countermove in the complex chess game of predator-prey relationships.