Tarantulas can indeed bite humans. While their fangs are capable of piercing human skin, a bite is not a common occurrence and is typically a last resort defense. Understanding tarantula behavior helps clarify why these spiders generally avoid confrontation. The effects of a tarantula bite are usually mild, though reactions can vary.
The Likelihood of a Bite
Tarantulas are generally not aggressive towards humans. Bites typically occur when a tarantula feels directly threatened, cornered, or mishandled. Their primary instinct is to retreat or display warning signs rather than to bite. Before biting, many species adopt a “threat posture,” raising their front legs and exposing their fangs as a warning. This display indicates distress and that the spider should be left alone.
Many tarantulas, particularly those from the New World (the Americas), also flick urticating hairs as a first line of defense before resorting to a bite. Some tarantulas deliver “dry bites,” where they bite without injecting venom, primarily as a deterrent to the perceived threat. These bites are uncommon, especially from species commonly kept as pets, which are generally docile.
What Happens After a Bite
If a tarantula does bite, the immediate sensation is often described as similar to a bee or wasp sting. The venom of most tarantulas, especially those native to North America, is considered medically insignificant for humans, causing localized symptoms rather than severe systemic reactions. Common symptoms include pain, redness, and swelling, which may last for several hours.
In rare instances, individuals might experience a more pronounced reaction due to allergic sensitivity to the venom. Allergic symptoms include widespread itching, rash, rapid heart rate, eyelid puffiness, or, in severe cases, difficulty breathing or a drop in blood pressure. While fatalities are rare, seeking medical attention is recommended if severe symptoms develop or worsen. Basic first aid involves washing the bite area with soap and water to prevent infection and applying a cold compress to reduce pain and swelling. Elevating the affected limb can also help manage swelling.
Other Defensive Behaviors
Beyond biting, tarantulas employ other defensive strategies, the most common being urticating hairs. These are specialized, barbed bristles found on the abdomen of most New World tarantula species. When threatened, a tarantula rapidly rubs its hind legs against its abdomen, dislodging and flicking these irritating hairs towards a perceived threat.
Upon contact with human skin, these hairs cause intense itching, redness, and a rash, sometimes lasting for weeks. If the hairs get into the eyes, they cause pain, irritation, and even temporary vision problems, necessitating medical attention. Inhaling these fine hairs also lead to respiratory irritation. Old World tarantula species, found in regions like Africa and Asia, typically lack these urticating hairs and may be more prone to biting as a primary defense.