Are Snakes Immune to Their Own Venom?

Despite a sketchy reputation, venomous snakes in the United States aren’t prone to going on biting sprees. Only about 8,000 people are attacked every year, with an average of five victims fatally succumbing to the toxins deployed via puncture wounds.

But what happens when two snakes face off against one another? Can their venom induce the same hemorrhaging and necrosis it does in their prey, or do they have a built-in immunity to their own flesh-tenderizing enzymes and paralyzing neurotoxins?

“The conventional wisdom is that they have circulating antibodies in their blood,” says Stephen Mackessy, Ph.D., a Professor of Biological Sciences at the University of Northern Colorado and an expert in venomous snakes. “This would protect them from their own venom, as well of venom from another snake in their own species.”

Hypothetically, if a speckled rattlesnake bit another speckled rattlesnake, the immunity they’ve built from being exposed to low levels of their own venom—kept in glands behind their eyes and secreted when they bite—would protect them from a fatal wound. (Even though the glands are closed, they still contain blood vessels that allow the venom to circulate in their system, causing mild exposure, Mackessy says.) But a speckled rattlesnake that meets up with a cobra might have a different day entirely.

“The more distantly related the species, the more probability it would be toxic,” Mackessy says. “If a rattlesnake and cobra bit one another, without prior exposure to their venoms to build immunity, they would probably kill each other.”

Because organized snake fights to the death are frowned upon in scientific circles, there isn’t likely to be a definitive answer on just how much immunity they have—just that there’s likely enough to ward off attacks from close relatives or self-contamination. “It makes sense,” Mackessy says. “If you have something dangerous you’re injecting, you want to be protected from injecting yourself.”