AZ, NM, W. TX, NV, southern UT/CA desert — Peak snake activity at dawn/dusk in warmer months; snakes shelter midday.
| Species | Type | Risk | Tell |
|---|---|---|---|
| Western Diamondback | snake | High | Diamond blotches; black-and-white banded tail above the rattle. |
| Black Widow | spider | Moderate | Glossy black body with a red hourglass on the underside; webs in woodpiles, sheds, and undisturbed corners. |
| Arizona Bark Scorpion | scorpion | Moderate | Slender, pale tan, often found climbing walls or hiding in shoes and bedding. |
| Gila Monster | lizard | Moderate | Thick-bodied, black-and-orange beaded skin; slow-moving and rarely bites unless handled. |
| Mountain Lion | mammal | Low (rare encounters) | Tan, unspotted coat; long tail with a dark tip. Sightings are usually brief, at a distance, near dawn or dusk. |
| Culex Mosquito | mosquito | Moderate | Common brown mosquito, active mainly at dusk and after dark; breeds in any standing water. |
| Mojave Rattlesnake | snake | High | Green-tinged rattlesnake with a well-defined diamond pattern and a white-banded tail; neurotoxic venom unlike most rattlers. |
| Sidewinder | snake | Moderate | Small horned rattlesnake that moves sideways across sand; horn-like scales over the eyes. |
| American Black Bear | mammal | Moderate | Straight facial profile, no shoulder hump, short claws; color ranges from black to cinnamon. |
| Yellowjacket | insect | Moderate | Bright yellow-and-black wasp; nests in the ground or in cavities. Attracted to food and drinks at camps. |
| Aedes Mosquito | mosquito | Moderate | Black-and-white striped legs; aggressive daytime biter, often around standing water in containers. |
| Deer Mouse | rodent | Moderate | Bicolored tail, white belly, large ears; common in cabins, woodpiles, and trail shelters. |
| Africanized Honey Bee | insect | High | Looks like a European honey bee; the difference is behavior — large numbers defending a nest aggressively. |
| Anopheles Mosquito | mosquito | Low (rare encounters) | Rests with tail tilted up; the historic malaria vector, still present in the southern US. |
Poison Control: 1-800-222-1222. Emergency: 911. General reference only, not medical advice.
A field reference for rattlesnakes, ticks, spiders, bears, poisonous plants, and large-predator hazards — filtered to what is in season in your region.
Peak snake activity at dawn/dusk in warmer months; snakes shelter midday.
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Trail Watch doesn't run its own live disease-tracking feed — for real-time and county-level surveillance, go straight to the CDC's own public resources.
Crotalus atrox
Diamond blotches; black-and-white banded tail above the rattle.
Active March–November, most seen in spring and fall; dens communally through winter.
Latrodectus mactans
Glossy black body with a red hourglass on the underside; webs in woodpiles, sheds, and undisturbed corners.
Neurotoxic venom can cause muscle cramping and pain; rarely fatal to healthy adults.
Most active spring through fall; can persist indoors or in sheltered structures year-round.
Centruroides sculpturatus
Slender, pale tan, often found climbing walls or hiding in shoes and bedding.
Most venomous scorpion in the US; sting causes intense localized pain and numbness.
Most active at night, spring through fall; shelters in cool, dark spaces by day.
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Heloderma suspectum
Thick-bodied, black-and-orange beaded skin; slow-moving and rarely bites unless handled.
One of the few venomous lizards in the world; bite is painful but rarely life-threatening.
Active March through November; spends most of its life underground or in burrows.
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Puma concolor
Tan, unspotted coat; long tail with a dark tip. Sightings are usually brief, at a distance, near dawn or dusk.
Not venomous — included as a trail hazard, not a bite/sting risk.
Active year-round, mostly at dawn and dusk (crepuscular).
Culex spp.
Common brown mosquito, active mainly at dusk and after dark; breeds in any standing water.
Primary US vector for West Nile virus; most bites cause no illness.
Active late spring through fall, mainly from dusk through night.
Crotalus scutulatus
Green-tinged rattlesnake with a well-defined diamond pattern and a white-banded tail; neurotoxic venom unlike most rattlers.
Venom can be highly neurotoxic; do not wait for swelling — seek emergency care immediately.
Active April–October; most dangerous rattlesnake in the Mojave and Sonoran deserts.
Crotalus cerastes
Small horned rattlesnake that moves sideways across sand; horn-like scales over the eyes.
Nocturnal in summer heat; more diurnal in spring and fall.
Ursus americanus
Straight facial profile, no shoulder hump, short claws; color ranges from black to cinnamon.
Usually avoid people; most incidents involve food-conditioned bears. Fight back if attacked.
Most active spring through fall; may den in winter depending on latitude.
Vespula spp.
Bright yellow-and-black wasp; nests in the ground or in cavities. Attracted to food and drinks at camps.
Multiple stings and allergic reactions can be life-threatening. Ground nests are easy to step on.
Peak late summer and early fall when colonies are largest and most aggressive.
Aedes spp.
Black-and-white striped legs; aggressive daytime biter, often around standing water in containers.
Can transmit dengue, Zika, chikungunya in the southern US and territories; also a nuisance biter.
Warm months; some species active year-round in South Florida and the Gulf Coast.
Peromyscus maniculatus
Bicolored tail, white belly, large ears; common in cabins, woodpiles, and trail shelters.
Primary reservoir of hantavirus (Sin Nombre). Do not sweep dry mouse droppings in enclosed shelters.
Year-round; indoor encounters increase when weather turns cold.
Apis mellifera scutellata
Looks like a European honey bee; the difference is behavior — large numbers defending a nest aggressively.
Run in a straight line to shelter or a vehicle; do not jump in water. Call 911 for multiple stings or breathing difficulty.
Year-round in the low desert; most defensive in warm months.
Anopheles spp.
Rests with tail tilted up; the historic malaria vector, still present in the southern US.
Local malaria transmission is rare but has occurred in the US in recent years.
Warm months near still freshwater.
These are the same field steps as on your printable trail card. They are general reference, not a substitute for 911 or Poison Control.
One-page card for a specific park: in-season hazards, weather, first aid. First one each month is free.
Generate briefingTweezers, permethrin, bear spray — the tools named in the protocols, not a merch dump.
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