# Rattlesnake — Facts, Threats & Conservation

*Genera Crotalus and Sistrurus — ~36 species in the Americas*

> Rattlesnakes are American pit vipers (~36 species) with tail rattles and heat-sensing pits — venomous rodent controllers whose status varies from Least Concern to Endangered.

**IUCN status:** Varies by species (Least Concern to Endangered)  ·  **WARN range:** Americas — United States, Mexico, Central and South America

## Quick facts
| Fact | Value |
| --- | --- |
| Species | ~36 in Americas |
| Rattle | Keratin segments added each shed |
| Heat pits | Detect infrared from prey |
| Reproduction | Live young (ovoviviparous) |
| Venom | Haemotoxic; some neurotoxic |
| Largest | Eastern diamondback — up to ~2.4 m |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Reptilia
- **Order:** Squamata
- **Family:** Viperidae
- **Subfamily:** Crotalinae (pit vipers)
- **Genera:** Crotalus, Sistrurus

## Conservation status
- **Status:** Varies by species. Most widespread species Least Concern; island and range-restricted species Endangered or Critically Endangered.
- **Population:** Unknown for most; local declines from roadkill and roundups
- **Trend:** Decreasing for several species with restricted ranges
- **Assessed:** Varies by species
- **CITES:** Not listed as a group; international pet trade minimal
- Road mortality is a major source of adult death near human development.

## Key facts: Rattlesnake
- The rattle is a warning device — added segment each shed; silent rattlesnakes still bite.
- Pit organs detect infrared radiation from warm-blooded prey.
- Most US snakebite fatalities involve rattlesnakes, yet deaths remain rare with care.
- Rattlesnake roundups in some US states harvest wild snakes controversially.
- Brazil and Colombia host relatives in the wider pit viper radiation — not true Crotalus.
- Freeze-dried rattles and novelty products drive minor trade; habitat loss is the main threat.

## Pit vipers and the rattle
Rattlesnakes belong to Viperidae subfamily Crotalinae — pit vipers sharing heat-detecting loreal pits with copperheads and bushmasters. The rattle comprises interlocking keratin segments clicking when vibrated — an honest signal reducing surprise encounters.

Triangular heads house venom glands; vertical pupils aid nocturnal hunting. Colour patterns — diamonds, bands, blotches — camouflage against local substrate from desert sand to forest floor.

Juveniles born with pre-button shed into first rattle segment within days. Adults may retain multiple segments or break them in brush.

## Venom, bite and medical care
Rattlesnake venom mixes haemotoxins damaging tissue and blood clotting with neurotoxins in some species — Mojave rattlesnake famously. Bites cause pain, swelling and systemic effects requiring hospital monitoring.

First aid emphasises immobilisation, removal of tight jewellery and urgent medical care — not tourniquets, cutting or suction. Antivenom availability in US and Mexican hospitals keeps mortality low despite thousands of bites yearly.

Dry bites without envenomation occur — snakes meter venom for prey, not always wasting it on defensive strikes.

## Ecology and roundups
Rattlesnakes consume rodents, rabbits and ground birds, reducing hantavirus and crop damage vectors. They are prey for roadrunners, kingsnakes, hogs and raptors.

Spring denning aggregations in northern climates concentrate hundreds overwintering — vulnerable to development and deliberate destruction. Texas and Oklahoma roundups collect thousands annually for meat and entertainment, debated for sustainability and cruelty.

Several species are range-restricted: eastern massasauga Endangered in Canada; Santa Catalina rattlesnake Critically Endangered on one Mexican island.

## Rattlesnakes and people
Hikers prevent bites by watching foot placement, avoiding hand holds in crevices and giving space when rattling is heard. Boots and trekking poles reduce risk in snake country.

In Brazil and Colombia, pit vipers such as fer-de-lance cause more medical cases than any true rattlesnake — different genera, similar caution. WARN education promotes regional snake awareness without universal fear.

Never collect wild rattlesnakes as pets. Secure property reduces rodent attraction that draws snakes near homes.

## Related WARN guides
Rattlesnakes are pit vipers — read WARN's cobra guide for elapids, python page for constrictors, and snake hub for overview.

Gecko and monitor lizard pages cover other North American reptiles.

Coexistence beats roundup slaughter — rattlesnakes control rodent populations.

## What WARN does
WARN educates readers in Brazil and Colombia — nations with diverse pit vipers — alongside US-focused rattlesnake searchers. Free guides promote coexistence and habitat stewardship across partner countries.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

## Frequently asked questions: Rattlesnake
### How many rattlesnake species are there?
About 36 species in genera Crotalus and Sistrurus, found only in the Americas from Canada to Argentina.

### Why do rattlesnakes rattle?
The tail rattle warns predators and people to stay back — an honest signal that reduces defensive bites when heeded.

### Are rattlesnake bites fatal?
Rarely with modern antivenom. Untreated bites can cause serious injury or death. All rattlesnake bites need emergency medical care.

### Do rattlesnakes lay eggs?
No. They are ovoviviparous — females bear live young, sometimes dozens in a litter, fully formed and venomous from birth.

### Are there rattlesnakes in Brazil?
True rattlesnakes (Crotalus) occur in the Americas including South America. Brazil has Crotalus durissus; many Brazilian pit vipers are related but not rattlesnakes.

### What should I do if bitten?
Stay calm, immobilise the limb, remove rings, and seek hospital care immediately. Do not cut, suck or apply tourniquets.

## Sources
- [IUCN Red List — Crotalus assessments](https://www.iucnredlist.org/search?query=Crotalus)
- [Smithsonian National Zoo — rattlesnake](https://nationalzoo.si.edu/animals/reptiles)
- [Encyclopaedia Britannica — rattlesnake](https://www.britannica.com/animal/rattlesnake)
- [Wikipedia — Rattlesnake](https://en.wikipedia.org/wiki/Rattlesnake)

---
Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/rattlesnake