Do Opossums Kill Snakes and Are They Immune to Venom?

Opossums do kill and eat snakes, and venomous ones are on the menu. Their protection is strong resistance to one family of snakes, not immunity to every venom.1Toxicon. Resistance of the opossum (Didelphis virginiana) to envenomation by snakes of the family Crotalidae That resistance is built into the opossum’s blood, which is why scientists are studying it as a possible snakebite treatment for people.2National Geographic. Opossums Could Hold the Key to Saving Snakebite Victims

Which Snakes Opossums Eat

Several opossum species are known to prey on venomous snakes.3PubMed. Snake-venom resistance as a mammalian trophic adaptation: lessons from didelphid marsupials They share the habit with a short list of mammals, including some hedgehogs, mongooses, weasel relatives and skunks.4PubMed. Snake-venom resistance as a mammalian trophic adaptation: lessons from didelphid marsupials A common opossum has even been seen eating a terciopelo, one of the most dangerous pit vipers in Central America.5Reptiles & Amphibians. Catching the Predator? A Common Opossum, Didelphis marsupialis (Mammalia: Didelphidae), Eating a Terciopelo, Bothrops asper (Reptilia: Viperidae), in Costa Rica Pit vipers are the group that includes rattlesnakes, copperheads and cottonmouths, named for the heat-sensing pits on their faces.

Snakes are an opportunistic meal, not a specialty. Opossums are omnivores that eat insects, slugs, rodents, toads, snakes and dead animals.6The National Wildlife Federation Blog. Opossums and Gardening: A Few Things to Know Venom resistance may have developed in larger opossums, over about 500 grams, partly as an adaptation for eating venomous snakes.7Reptiles & Amphibians. Catching the Predator? A Common Opossum, Didelphis marsupialis (Mammalia: Didelphidae), Eating a Terciopelo, Bothrops asper (Reptilia: Viperidae), in Costa Rica

When a snake does turn up for a backyard Virginia opossum, a harmless garter snake is far easier prey than a rattlesnake. You rarely see an opossum eating a snake, simply because they feed after dark.

It also works the other way around. Some tropical pit vipers eat opossums, especially young or small ones. A large adult opossum is the hunter, while a juvenile can be the meal.

An opossum doesn’t stalk snakes the way a cat stalks birds. It forages by smell and touch along fences, brush and woodpiles, and a snake it bumps into becomes a possible meal. A snake that is cold, sluggish or resting in a hiding spot is much easier to catch than one that is warm and alert, so the odds shift with the weather and the time of night.

How an Opossum Kills a Snake

Opossums subdue snakes by biting the head or neck, and they begin eating from that same end, head first.8Studies on Neotropical Fauna and Environment. Predatory Behavior of the Opossum Didelphis albiventris on the Pitviper Bothrops jararaca Their attack style changes depending on how the snake fights back.9Current Herpetology. Predation by the Opossum Didelphis marsupialis on the Rattlesnake Crotalus durissus A snake that coils and strikes forces the opossum to deal with the fangs first, while one that tries to flee can be seized and held.

A snake’s head is its weapon, so disabling the head or neck is the quickest way to stop it from striking. A crushing bite suits the job, and opossums have 50 teeth, more than any other North American land mammal. The opossum’s resistance helps it survive any bites it does take.

Fights usually happen at night and are quick. If you do come across one, don’t try to separate the two animals.

Which Venoms Opossums Survive and Which Kill Them

Virginia opossums survived the venom of these pit vipers:

The venoms that were not survived:

The line falls where it does because pit viper venom mainly destroys tissue and blood, while cobra and coral snake venom mainly attacks the nerves. The opossum’s protective blood factor doesn’t neutralize nerve-attacking venoms like cobra.18PubMed Central. Opossum peptide that can neutralize rattlesnake venom is expressed in Escherichia coli In the U.S., that makes the coral snake, with its nerve-attacking venom, the main native venomous snake known to still kill an opossum.

Resistance means a bite that would kill a similar-sized animal usually doesn’t kill the opossum. It doesn’t mean the venom does nothing. A very large dose, or a bite in a vulnerable spot, could still harm one, and even bites it survives may cause pain or swelling.

What in Their Blood Stops the Venom

Opossum blood carries proteins that latch onto the venom enzymes that break down tissue and cause bleeding.19PubMed. Structural and functional analyses of DM43, a snake venom metalloproteinase inhibitor from Didelphis marsupialis serum Each blood protein binds one venom enzyme in a stable pair, switching it off.20PubMed. Structural and functional analyses of DM43, a snake venom metalloproteinase inhibitor from Didelphis marsupialis serum A similar protein from another opossum species stopped the bleeding and tissue damage those enzymes cause.21PubMed. PO41, a snake venom metalloproteinase inhibitor isolated from Philander opossum serum In the Virginia opossum, one such protein is called lethal toxin neutralizing factor, or LTNF.22PubMed Central. Process for production and purification of Lethal Toxin Neutralizing Factor (LTNF) from E. coli and its economic analysis

A second defense works on clotting. Some pit viper venoms make blood platelets clump by acting on a clotting protein in the blood. Virginia opossum platelets did not clump with two such venom compounds and only partly with a third.23PubMed Central. Resistance of South American opossums to vWF-binding venom C-type lectins This clotting protein has evolved unusually fast in snake-eating opossums.24PubMed Central. Adaptive Evolution of the Venom-Targeted vWF Protein in Opossums that Eat Pitvipers Both defenses are built in from birth; the opossum doesn’t have to survive earlier bites to earn them.

An Arms Race Between Opossums and Snakes

The fast-changing clotting protein is the first known case of rapid evolution in a molecule that venom targets.25PubMed Central. Adaptive Evolution of the Venom-Targeted vWF Protein in Opossums that Eat Pitvipers In snake-eating opossums, venom is the likely pressure driving that change, which is why researchers see an ongoing contest and not a one-time adaptation.

Venom is usually thought of as a tool for catching prey, but if opossums eat snakes, it also works as a defense. Snakes may therefore be evolving venom to protect themselves from opossums, not just to catch prey.26PubMed Central. Adaptive Evolution of the Venom-Targeted vWF Protein in Opossums that Eat Pitvipers

The back-and-forth works like this. If a venom changes, opossums whose blood happens to resist the new version survive and pass that trait on. As resistant opossums become common, snakes with slightly altered venom gain an edge and pass that on in turn. Reconstructing ancestral versions of the protein shows this long pattern between opossums and their snake prey.27Molecular Biology and Evolution. Ancestrally Reconstructed von Willebrand Factor Reveals Evidence for Trench Warfare Coevolution between Opossums and Pit Vipers

It also explains something odd: resistance is matched to the snakes opossums historically met. Cobras are absent from the Americas, so opossums never had reason to evolve a defense against them, and cobra venom still kills them.

Can Opossum Blood Help People Bitten by Snakes

The protective activity of LTNF sits in a short piece at one end of the protein.28PubMed Central. Process for production and purification of Lethal Toxin Neutralizing Factor (LTNF) from E. coli and its economic analysis Researchers therefore didn’t need to copy the whole thing. They made lab versions just 10 and 15 building blocks long.29Toxin Reviews. PART 2: CONVERSION OF THE ACTIVE DOMAIN OF NATURAL OPOSSUM LETHAL TOXIN NEUTRALIZING FACTOR TO A SYNTHETIC PEPTIDE, LT-10 These short versions prevented death in mice given lethal doses of animal, plant and bacterial toxins.30Toxin Reviews. PART 2: CONVERSION OF THE ACTIVE DOMAIN OF NATURAL OPOSSUM LETHAL TOXIN NEUTRALIZING FACTOR TO A SYNTHETIC PEPTIDE, LT-10 A synthetic version saved mice exposed to rattlesnake venom,31SJSU ScholarWorks. Construction of Bacterial Strains Containing a Plasmid Producing an Opossum-Based Anti-Venom Peptide for Low Cost Production of the Peptide32National Geographic. Opossums Could Hold the Key to Saving Snakebite Victims

The natural opossum factor also neutralized scorpion and bee venoms in lab tests.33Journal of Venomous Animals and Toxins. ANTI-LETHAL FACTOR FROM OPOSSUM SERUM IS A POTENT ANTIDOTE FOR ANIMAL, PLANT AND BACTERIAL TOXINS But one short lab version did not neutralize cobra venom,34PubMed Central. Opossum peptide that can neutralize rattlesnake venom is expressed in Escherichia coli so it wouldn’t be a cure-all for every bite. The peptide can be made cheaply in bacteria, which could matter for poorer regions where costly treatments are hard to get.35PubMed Central. Process for production and purification of Lethal Toxin Neutralizing Factor (LTNF) from E. coli and its economic analysis

Still, this is evidence from animals, not proof it would work in a person. Human trials have to test safety and dosing, many promising lab compounds fail at that stage, and approval would take years. It remains a research lead, not something available to snakebite victims.

If you or a pet is bitten today, antivenom is the proven treatment. Call 911 or get to an emergency room, keep still, and keep the bitten limb at heart level. Don’t cut, suck or ice the wound, and don’t use a tourniquet. For a pet, go straight to an emergency vet.

Will Opossums Keep Snakes Out of Your Yard

Opossums in gardens eat insect pests, slugs, rodents and dead animals.36The National Wildlife Federation Blog. Opossums and Gardening: A Few Things to Know By eating rodents, they may reduce what attracts snakes in the first place. But since snakes are only an occasional meal, you can’t count on an opossum to find and eat the ones in your yard. Opossums also wander and rarely stay in one yard long, so one that visits tonight may be gone next week.

To discourage snakes directly, remove woodpiles, tall grass and debris where they hide. Control the rodents that draw them in, and seal gaps under sheds and porches.

A yard opossum is easy to live with. They are usually shy and prefer to avoid people. Playing dead, or hissing with an open mouth, is a bluff and a defense, not aggression. Securing trash and pet food keeps them from settling close to the house. Don’t handle one, since like any wild mammal it can carry disease and may bite if grabbed.