California is not home to the highly toxic “poison dart frogs” found in tropical regions. However, some native amphibians possess natural defensive toxins. These substances deter predators, making the amphibians unpalatable or harmful if ingested. The risk these toxins pose to humans is low, but understanding which species carry them and how they are transferred helps ensure safe interactions with California’s diverse amphibian populations.
Understanding Toxicity: Poison vs. Venom
The terms “poisonous” and “venomous” describe distinct mechanisms of toxin delivery. An animal is venomous if it actively injects toxins, typically through a bite or sting, like a snake or a bee. In contrast, a poisonous animal releases toxins when touched or ingested. Amphibians are almost always poisonous because their defensive chemicals are secreted onto their skin, requiring contact or consumption to cause harm.
California’s Frogs and Their Defenses
Many common frogs in California, such as the Pacific Tree Frog (Pseudacris regilla), are not poisonous. While their skin may carry bacteria like Salmonella, posing a risk if hands are not washed, they do not produce toxins as a defense. However, some native toad species do secrete defensive compounds.
The Western Toad (Anaxyrus boreas), including the California Toad subspecies (Anaxyrus boreas halophilus), is widespread and produces a mild toxin called bufotoxin. This substance is secreted from glands, notably the large parotoid glands behind their eyes, and is also present in their eggs. While not dangerous to humans upon casual contact, bufotoxin can irritate eyes or mucous membranes. It can also be harmful, even fatal, to smaller predators if ingested.
Another species, the Colorado River Toad, also known as the Sonoran Desert Toad (Incilius alvarius), is found in southeastern California. This large toad secretes a more potent bufotoxin from its parotoid glands and skin. If ingested, its toxins can cause severe reactions in animals, affecting the nervous and cardiovascular systems.
Safe Interactions with Wild Frogs
Observing wild amphibians from a distance is best. It is advisable to avoid handling wild frogs and toads whenever possible. Amphibian skin is highly permeable, meaning oils, salts, and chemicals on human hands can be absorbed and harm the animal. Handling can also stress the animal or transfer pathogens.
If handling is unavoidable, such as to move an amphibian out of harm’s way, wash hands thoroughly with soap and water beforehand, and keep them wet during contact. Wearing non-powdered vinyl gloves can also protect both the amphibian and handler. Always wash hands thoroughly immediately after touching any wild amphibian, even if gloves were worn, to prevent the spread of bacteria like Salmonella.
Pet owners should be cautious, especially if dogs are prone to mouthing objects. If a pet licks a toad, particularly a larger species, symptoms like excessive drooling, pawing at the mouth, vomiting, or seizures may occur. Promptly rinse the pet’s mouth with cool water, being careful not to force water down their throat, and seek immediate veterinary attention.