Hedgehogs are neither poisonous nor venomous in the traditional biological sense. Confusion about their potential toxicity stems from an unusual and visually dramatic behavior these small mammals exhibit. This action makes the animal appear to be covering its body with a toxic substance, leading many to incorrectly assume it is applying a poison for defense.
Defining Poisonous Versus Venomous
The classification of a toxic animal depends entirely on how the toxin is delivered. A poisonous organism contains a toxin that is passively transferred, typically when the substance is absorbed through the skin or ingested, such as with a poison dart frog. The organism does not actively inject the harmful substance into a victim.
In contrast, a venomous organism actively injects its toxin into another creature, usually through specialized structures like fangs, stingers, or barbs, as seen in snakes or wasps. Hedgehogs lack any mechanism for injecting a toxin and do not secrete natural poisons from their skin or tissues. Therefore, they are neither venomous nor poisonous.
The Unique Behavior of Self-Anointing
The widespread belief that hedgehogs are toxic is likely due to a bizarre, well-documented behavior called “self-anointing.” This process is triggered when the hedgehog encounters a strong, novel scent or taste in its environment. The stimulating substance can be anything from a food item, a cleaning product, or even a toxic substance like toad skin or tobacco.
Upon encountering the novel item, the hedgehog begins to chew and lick it, generating a large amount of frothy saliva. The animal then contorts its body into awkward positions, bending its head back until it touches its quills. Using its tongue, the hedgehog spreads the saliva-substance mixture over its spines, coating them in the foam.
Scientists have proposed multiple theories for the purpose of this ritual, though none are definitively proven. One hypothesis suggests that coating themselves in the new scent creates olfactory camouflage to mask their own scent from predators. Another theory posits that if the hedgehog chews a naturally irritating or toxic substance, it may be using the external chemicals to enhance the defensive capability of its spines. Studies have shown that spines coated with toxins from a specific toad can cause irritation upon contact.
Actual Health and Safety Risks
While a hedgehog’s spines are not inherently toxic, handling the animal presents health hazards, primarily involving zoonotic diseases. The greatest health concern is the risk of contracting Salmonella infection, which hedgehogs carry asymptomatically in their feces. The bacteria can easily contaminate the hedgehog’s body, habitat, and anything it touches.
Infection in humans, known as salmonellosis, typically occurs through the fecal-oral route, such as by touching the animal or its environment and then touching one’s mouth. Symptoms usually include diarrhea, fever, and stomach cramps. Infection can be more severe in young children, the elderly, or those with compromised immune systems. Even healthy hedgehogs can shed the bacteria, making diligent hygiene practices necessary.
The risk of disease transmission emphasizes the need for preventative measures, specifically thorough hand washing with soap and warm water immediately after handling the hedgehog, its food, or its enclosure. Physical injury is a secondary concern, as the animal’s sharp spines are its primary defense mechanism. Hedgehogs defensively roll into a tight ball when startled, and they may bite if they feel threatened or are mishandled.