Home North America Mexico 11 Most Toxic and Dangerous Animals in Mexico

11 Most Toxic and Dangerous Animals in Mexico

Photo by Andrés Sanz on Unsplash

The much-loved bottom of North America ain’t all tacos, tequila, and tamales, you know. This list reveals 11 of the most dangerous animals in Mexico, some of which also happen to be among the most dangerous on the whole planet (fer-de-lance snake, we’re looking at you!). Yep, from the lush jungles of the Yucatan to the dusty canyons of the Sonora Desert, the wave-lashing Pacific coast to the paradise isles of the Quintana Roo Caribbean, there are all sorts of critters you need to know about…

Of course, that’s not to say that you 100% will meet one of these less-than-savory beasts. In fact, the chances you’ll cross paths with a beaded lizard or a fer-de-lance snake are pretty minimal. But it’s still a good idea to know what’s lurking out there when you go trekking into the Sierra Madre or diving in the Sea of Cortez, don’t you think?

So,whether you’re lounging on the beaches of Cancun or browsing the street markets in Nogales, enjoying the fizz of life in Mexico City or chasing tequila shots on the Riviera Nayarit, this list of the most dangerous animals in Mexico is sensible reading for anyone who’s bound for the home of sombreros and mariachi. Let’s go…

Mexican beaded lizard

A Mexican beaded lizard sunning itself in a desert habitat
Image from Wiki Commons
  • Latin name: Heloderma horridum
  • Attacks: Venomous bite that can cause respiratory failure
  • Treatment: Thorough cleaning and medical attention if side effects persist
  • Where you find them: Desert, tropical deciduous forests and thorn scrub forests across Mexico
  • Conservation status: Least concern

The Mexican beaded lizard is one of two venomous lizards found across Mexico. When fully grown, these guys can range from 57 to 91 cm (22 to 36 inches) in length – that’s almost a meter for the biggest of the bunch! The descriptive name comes from the fact that they have hard and touch outer scales that have the appearance of large beads running from head to tail. Other identifying marks include a black base color, yellow spots or bands, and a trademark forked tongue.

Mexican beaded lizards are venomous. Each tooth is pumped with venom from glands located in the lower jaw. However, the reptiles rarely attack humans and the venom is not considered lethal. In some cases, an accidental bite can be enough to cause serious respiratory failure. Other common side effects of Mexican beaded lizard bites include swelling, weakness, sweating, and a rapid fall in blood pressure.

There’s a whole load of folklore surrounding the beaded lizard in Mexico. Pregnant women won’t make eye contact with them, for example, because they’re thought to cause miscarriages. It’s much more likely that this species holds some medical breakthroughs, though. Scientists are currently examining the lizards venom for compounds that are thought might help in the treatment of  Alzheimer’s and HIV.

Kissing bug

Photo from Wiki Commons
  • Latin name: Triatominae
  • Attacks: Carrier of a parasitic, systemic, and chronic disease – Chagas disease
  • Treatment: Urgent medical assistance, treated with Benznidazole and also Nifurtimox
  • Where you find them: Active at night and common around muddier areas
  • Conservation status: Not evaluated

Triatomines, commonly known as kissing bugs, also deserve a place among the most dangerous animals in Mexico. Similar to mosquitoes, these insects can be carriers of a nasty parasite that causes Chagas disease. Not to be confused with arthritis or chikungunya, this chronic ailment has irreversible consequences for the nervous system, digestive system, and heart.

Kissing bugs are around 0.5-1 inch (1.27-2.5cm) in length, have a coned-shaped head, and a long, oval body. They are brown in color and usually have some yellow or orange markings on the back. They’re most notable for the stretched, nose-like protrusion at the front and the ochre-tinted orange legs that sprawl out ahead.

These are nocturnal insects, so most bites happen while the victim is blissfully unaware and sleeping. Not every bite results in Chagas. However, it’s thought that the disease still causes a whopping 12,000 deaths per year worldwide. Symptoms of a parasitic bite include fever, headache, cough, abdominal pains and swelling. It’s important to seek urgent medical care if you experience any of those. Treatment is available and effective in curing the disease, but it needs to be administered ASAP.

As with mozzies, prevention is better than the cure with kissing bugs. Use insecticide-coated nets around your bed when sleeping and put on strong repellents throughout the day. It’s also a good idea to cover up vulnerable areas – the ankles, the wrist, the neck – in high-risk zones.

Botflies

The botfly is one of the most dangerous animals in Mexico
Photo from Wiki Commons
  • Latin name: Dermatobia hominis
  • Attacks: Parasite larvae left under the victims skin after a bite
  • Treatment: Immediate medical treatment for extraction of larvae
  • Where you find them: Tropical forest areas
  • Conservation status: No special status

Next up on our list of the most dangerous animals in Mexico is another disease-carrying insect: The botfly. Also known as warble flies and gadflies, these are small but dangerous bugs that use their victims as a host to carry eggs. When a botfly bites, it injects its larvae into the flesh. Ultimately, that leads to maggots developing under the skin. Urgh!

Because lots of big mammals can now recognize the approach of a botfly, these guys have adapted to use to mosquitoes or ticks to insert their parasitic larvae by proxy. Once the larvae have been deposited, they instantly burrow under the skin of the victim to incubate and grow. An extreme case of that is known as myiasis. It’s caused when the maggots burrow further down into the flesh than required, leading to severe swelling and raised lumps at the point of contact.

Botfly larvae won’t kill a human, which makes these guys a true parasite. However, being burrowed through by mini worms is never going to be a pleasant experience, right? So, if you think you might have been bitten and are showing signs of myiasis, be sure to seek medical advice either in Mexico or back home immediately after your travels. Doctors can treat parasitic myiasis in several way, including with antiparasitic oral medication, an iodine flush, and extractor syringes. Top travel tips for Mexico always recommend using insect repellent to prevent bites in the first place.

Mexican green rattler

Photo from Envato Elements by sergeyskleznev
  • Latin name: Crotalus basiliscus
  • Attacks: Strong venom in its bite
  • Treatment: Antivenin from a medical professional
  • Where you find them: West coast of Mexico in dry and arid environments
  • Conservation status: Least concern

The Mexican green rattler is one of the largest endemic species of snake found in Mexico. It has an incredibly potent venom and typically grows up to 5 feet – but some are reported to be over 6 feet in length! The camouflaged coloring hides these rattlesnakes against the ground even when in plain view, especially in the canyon-carved and heavily forested coastal plains of Sinaloa and the Rivera Nayarit (their main stomping ground).

Luckily, these snakes don’t hunt humans. They prefer to eat small rodents and birds. In fact, rattlers usually prefer to steer clear of conflict with people entirely. They’ll even give us a warning before they attack – using their trademark percussion attached to the end of the tail. You’ll be able to tell a green rattler apart from other snakes because of the clear olive green coloring and the diamond dorsal pattern. The young of this species tend to have a redder color.

Although the most common effects of the strong venom are blistering and pain around the bite, the green rattler is a potential killer. A bite from one of these could lead to serious neurological damage similar to those from the formidable US Mojave rattlesnake. Symptoms include blurred vision, confusion, and eventual shutdown of the nervous system.

Rattlesnakes are found along the west coast of Mexico and are mostly restricted to the coastal plains. They are most active in the rainy summer months and often hunt during the night.

Coral snake

Photo from Wiki Commons
  • Latin name: Micrurus fulvius
  • Attacks: Strong venom delivered through a chewing motion, rather than a bite
  • Treatment: Antivenin from a medical professional
  • Where you find them: Under rocks, leaf piles, or in underground burrows across the dry deserts of Mexico
  • Conservation status: Least concern

Next up is the coral snake. This is the second most venomous snake in the world after the black mamba. That’s the bad news. The good news is that coral snakes tend to be far less confrontational than other sorts of serpents, so attacks aren’t as common. What’s more, they lack an effective poison delivery system, so they’re technically less dangerous than rattlesnakes (see above).

Coral snakes average 18-20 inches (45-50cm) in length, and they have non-retractable fangs. That actually makes their teeth weaker than mos, so the chances of them penetrating human skin is unlikely (but it’s not unheard of). Most coral snakes will only attack when people try to pick them up. It delivers the venom through a chewing motion that’s effective on frogs, but not so much on grown adults. Antivenin is nonetheless strongly recommended to avoid any severe reactions, like cardiac arrest.

Bright colors make coral snakes fairly easy to spot. However, the red and yellow bands can be easily misidentified for a nonvenomous counterpart. It’ll serve you well to learn a common rhyme to help identify coral snakes: Red and yellow, can kill a fellow; Red and black, friend of Jack.

Coral snakes can be found under rocks and leaf piles among the scrub of the Mexican desert. They burrow underground for a secretive and reclusive habitat. Most sightings are in spring or fall when coral snakes are at their most active.

Black widow

Photo from Wiki Commons
  • Latin name: Latrodectus
  • Attacks: Extremely strong venom that can cause cramps and spasms
  • Treatment: Seek medical attention and anti-venom
  • Where you find them: Dry and dark spaces, like under window sills and under rocks
  • Conservation status: Least concern

Black widow spiders are prevalent throughout South America, but are also common across the globe – they are found on every continent bar Antarctica. Widows are one of only three venomous species of spiders found in Mexico, the others being the brown recluse and the hobo spider. While their venom doesn’t often result in death, a bite is still extremely painful and can cause severe muscle pain, abdominal cramps, heavy sweating, heart palpitations, and muscle spasms. Not nice at all…

Against popular belief, this spider is not aggressive. Attacks on humans often come when the spider has been disturbed accidentally or is caught defending its nest. They like to hide away in cool, dark places. Be conscious of that when walking in the forest, and picking up sticks or rocks along your treks. Anti-venom is always a good idea if you are bitten by one of these spiders. Identifying a black widow should be relatively easy. Most are shiny black with a red or white marking clearly striking down the center of the body.

Gila monster lizard

Photo from Wiki Commons
  • Latin name: Heloderma suspectum
  • Attacks: Neurotoxin and strong jaw
  • Treatment: Seek medical attention
  • Where you find them: Dry and arid environments across Mexico
  • Conservation status: Near threatened

Closely related to the Mexican beaded lizard, the Gila monster is another venomous species found in Mexico and in the southern parts of America. It is significantly smaller than its beaded counterpart (see above). These guys only average around 2 feet in length when fully grown. However, they are stocky lizards, with heavy set claws and wide bodies, so they certainly look like a tough cookie!

Gila monsters are typically found in dry and arid settings. So keep an eye out for them if you are exploring the deserts and canyons throughout northern Mexico, especially in Sonora. Unfortunately, their numbers are in decline, largely because of hunting and illegal killings. The chances of seeing them in the wild are rapidly decreasing.

Despite the venom, these lizards have a similar delivery system to coral snakes – they chew their prey to pass the venom deep into the tissue and flesh. They are also slow-moving and fairly docile. That all adds up to make a serious attack very unlikely. But it’s not impossible, so always have your wits about you around one of these prehistoric beasts.

A bite from one of these is extremely painful. It will leave a nasty mark and some may even have a bad reaction to the neurotoxin. That said, there are currently no known reported deaths from a Gila monster bite. If bitten, still seek medical assistance from a hospital or a local doctor.

Fer-de-lance snake

The fer de lance snake is one of the most dangerous animals in Mexico
Photo from Wiki Commons
  • Latin name: Bothrops asper
  • Attacks: Extremely toxic poison that causes organ failure and necrosis
  • Treatment: Anti venom and possible amputation depending on how severe the reaction
  • Where you find them: Gulf of Mexico in lowland areas
  • Conservation status: Least concern

The Cuatro Narices, commonly known as the fer-de-lance snake, is a highly venomous pit viper species found across the southern regions of Mexico and northern parts of South America to boot. It lives predominantly in lowland habitats and often around residential areas and towns. In fact, the fer-de-lance snake is one of the most dangerous animals in Mexico precisely because it often comes into direct contact with humans (fer-de-lances are the main contributors to snake bites in Mexico, being accountable for almost a third of all hospitalizations).

But that’s not the only reason…These guys are also incredibly defensive and aggressive. What’s more, their toxic venom is extremely fast-acting. With each bite, 150mg is delivered (50mg is enough to be fatal to most adults). Effects include local pain, severe blistering, numbness, necrosis of the flesh, vomiting – the list goes on! Immediate medical attention is recommended if you’re unfortunate enough to experience firsthand the hemotoxin from the fer-de-lance snake’s large fangs. If left untreated, organs will begin to fail and severe cell and tissue damage will occur rapidly.

These snakes vary in length. Females are often larger and can grow up to 6 feet in length, weighing up to 13 lbs. They have very typical snake coloring; dark browns and blacks, with clear yellow undersides. They are found around the Gulf of Mexico, from southern Tamaulipas to Yucatán and Chiapas. So, if you are planning your trip to any of those, be careful where you step!

Box jellyfish

A box jellyfish swimming in the Gulf is one of the most dangerous animals in Mexico
Photo from Wiki Commons
  • Latin name: Chiropsalmus quadrumanus
  • Attacks: Long tentacles with a powerful sting
  • Treatment: Antivenom and vinegar wash
  • Where you find them: Gulf of Mexico between March and June
  • Conservation status: Not evaluated IUCN

The most dangerous animals in Mexico are not restricted only to the land. Box jellyfish are found in the western Atlantic Ocean, the Pacific Ocean, and the Gulf of Mexico. However, they are seasonal, so avoiding the swarms is easily done. And trust us, avoiding these bad boys is essential! Their sting is highly venomous and dangerous to humans, especially children.

Jellyfish season around Cancun and the Riviera Maya is between March and June. After heavy rainfall, the currents bring them into the Gulf of Mexico in swarms. The water becomes saturated and swimming is risky. Many divers or snorkelers wear stinger-suits (1mm wetsuits) as a precaution.

Most reactions to box jellyfish stings include a long-lasting rash, severe pain, and possibly even cardiac dysfunction. In extreme cases, people have been resuscitated on the beach after an encounter. Antivenom helps reduce the pain and brings down the rash faster.

Box jellyfish are extremely hard to see in the water as they are translucent. They are only around 14cm in diameter, but the tentacles can reach up to 4 meters in length! And it’s the tentacles that are the dangerous part…

Stonefish

Photo from Wiki Commons
  • Latin name: Synanceia
  • Attacks: Thirteen dorsal fin spines loaded with venom
  • Treatment: Antivenom from a medical professional
  • Where you find them: Gulf of Mexico, on rocky reefs and the ocean floor
  • Conservation status: Least concern

The stonefish, also known as the scorpionfish, is the world’s most venomous fish. This aquatic creature can produce enough venom to kill a human. It’s incredibly camouflaged against the ocean floor and is often mistaken for a rock (hence the name).

Most incidents happen by complete accident, when swimmers step on the stonefish thinking it’s part of the natural reef. The dorsal fin spines easily penetrate the foot and inject strong venom deep into the victim. Stings from stonefish can result in severe pain, swelling, necrosis, and potentially even death.

But don’t let these fish stop you from going in for a dip in bath-warm Mexicana waters. Stonefish are not aggressive. They don’t actively seek out humans to attack. You’ll just need to be wary of them when diving and snorkeling, and be extremely careful where you place your feet as a swimmer. You could also:

  • Wear water shoes. Nope, they aren’t the most attractive footwear for beach days, but they do protect to the soles of your feet when snorkeling and exploring the Gulf.
  • Look where you are walking. It’s bad practice to walk on the reef regardless of if there is a dangerous animal about or not!
  • Shuffle instead of stepping. This warns stonefish and other marine life, like stingrays, that you are approaching and allows them to move to a safer place. You’ll also avoid stepping directly onto the fish by shuffling across the bottom.

Mosquito

Mosquitoes are one of the most dangerous animals in Mexico because of the diseases they could carry
Photo from Envanto Elements
  • Latin name: Stegomyia albopicta and Aedes aegypti
  • Attacks: Infectious bite
  • Treatment: Monitor for severe side affects, seek medical attention if feverish
  • Where you find them: Everywhere! But especially around water supply, rainforests, and most outdoor areas
  • Conservation status: Least concern

Mosquitoes are found in almost every corner of our planet. However, they breed faster and have bigger populations in warmer tropical climates. Cue the home of tacos…Mexico has a pretty clear mosquito season running from April to November. Southern Mexico has a higher density than the northern territories during these months. So, depending on when you choose to travel to Mexico, you may need more protection against these fliers.

Many travelers underestimate the dangers that come with these small and annoying insects. While they buzz around and avoid your swots, they could also be carrying some of the nastiest diseases in Mexico. We’re talking the likes of zika, dengue, and malaria. All of the above are potentially life-threatening (worldwide malaria fatalities alone were estimated at 409,000 in 2019!).

Dealing with mosquitoes in Mexico is the same as anywhere in the world. A reliable and strong insect repellent keeps them away during the day. Sleeping with a net around the bed is highly advised to avoid getting bitten while you sleep during the night. You should also get into the habit of covering arms and legs at dusk and dawn – times when the mozzies are at their most active.

If you have been bitten by a mosquito and experience symptoms such as dizziness, a loss of appetite, rash, fever, headaches, or diarrhea, seek urgent medical care.

FAQ

What is the most dangerous animal in Mexico?

The most dangerous animal in Mexico is the fer-de-lance snake. Also known as the bothrops asper, it’s a feared pit viper that has very strong venom capable of causing severe tissue necrosis. It’s thought to be responsible for over 50% of snakebites in key regions of Mexico like the Yucatan, and is the most common snakebite in a number of other Latin American countries besides.

Are there any poisonous snakes in Mexico?

Poisonous snakes can be found across Mexico. Rattlesnakes, coral snakes, and fer-de-lance snakes are the most deadly and are often seen on the drier west coast. Yellow bellied sea snakes also pack a powerful bite, however, their jaws don’t open wide enough to attack humans.

Are there venomous spiders in Mexico?

There are three venomous spiders in Mexico: The black widow, the brown recluse spider, and the hobo spider. However, despite the bad rep that spiders get, none of those are overly aggressive and will not typically actively attack humans. Most encounters and spider bites are accidental, usually occurring when humans threaten the nests.

What is the deadliest snake in Mexico?

The fer-de-lance is the deadliest snake in Mexico, largely because there’s a lot of habitat crossover with humans. They are accountable for a large proportion of snake bites. A bite from a fer-de-lance snake results in swelling, severe pain, necrosis, and possibly even death.

Can scorpions in Mexico kill you?

The scorpions found in Mexico are not as dangerous as those in the Middle East. One of the most dangerous species of scorpion found in Mexico is the bark scorpion. While the sting is uncomfortable, it’s highly unlikely to kill you.