Crotalus oreganus
Silhouette: Bill Bouton (source photo) & T. Michael Keesey (vectorization) · PhyloPic
In 3 days ~10% in a week ~20%
Crotalus oreganus, commonly known as the Western rattlesnake or northern Pacific rattlesnake, is a venomous pit viper species found in western North America from the Baja California Peninsula to the southern interior of British Columbia.
The size of this species varies greatly, with some populations being stunted and others growing very large. The species also varies in size in relation to its migration routes as individuals with longer and more linear paths tend to have more mass. The C. oreganus is classified with 6 subspecies with 3 of them being present within the state of California.
This species, in its various forms, shows considerable ontogenetic variation. Juveniles usually have more or less distinct patterns, but these fade as the animals mature. The color of the iris often matches the ground color, which may be bronze, gold, or different shades of tan, pink, or gray.
The habitat and/or the substrate of the Crotalus oreganus determines their coloration. The color pattern of the typical form, C. o. oreganus, has... Wikipedia →
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Canada · 2023
© Julia Carr · iNaturalist · CC BY-NC 4.0
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Canada · 2021
© Leah Ramsay · iNaturalist · CC BY-NC 4.0
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Canada · 2026
© Nathan Earley · iNaturalist · CC BY-NC 4.0
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Sequoia and Kings Canyon National Parks | 🇺🇸 United States | |
| 2 | Zion National Park | 🇺🇸 United States | |
| 3 | Yosemite National Park | 🇺🇸 United States | |
| 4 | Grand Canyon National Park | 🇺🇸 United States | |
| 5 | Joshua Tree National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Sacramento | 🇺🇸 United States | |
| 2 | Tijuana | 🇲🇽 México | |
| 3 | San Diego | 🇺🇸 United States | |
| 4 | Los Angeles | 🇺🇸 United States | |
| 5 | Salt Lake City | 🇺🇸 United States | |
| 6 | San Francisco | 🇺🇸 United States |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | San Diego Zoo | 🇺🇸 United States | |
| 2 | Living Desert Zoo and Gardens | 🇺🇸 United States | |
| 3 | Bronx Zoo | 🇺🇸 United States | |
| 4 | Los Angeles Zoo | 🇺🇸 United States | |
| 5 | Phoenix Zoo | 🇺🇸 United States | |
| 6 | Fresno Chaffee Zoo | 🇺🇸 United States | |
| 7 | Hogle Zoo | 🇺🇸 United States | |
| 8 | California Living Museum | 🇺🇸 United States | |
| 9 | Santa Barbara Zoo | 🇺🇸 United States | |
| 10 | Reptile Gardens | 🇺🇸 United States | |
| 11 | Sacramento Zoo | 🇺🇸 United States | |
| 12 | Turtle Bay Exploration Park | 🇺🇸 United States | |
| 13 | Staten Island Zoo | 🇺🇸 United States | |
| 14 | Orange County Zoo | 🇺🇸 United States | |
| 15 | Siam Serpentarium | 🇹🇭 Thailand | |
| 16 | Lindsay Wildlife Experience | 🇺🇸 United States | |
| 17 | The Reptile Zoo | 🇺🇸 United States | |
| 18 | CuriOdyssey | 🇺🇸 United States |
No species of the same family or order lives in San Francisco, so these are its closest relatives here: other reptiles.
Rare
Under 5% of wildlife watchers report a Western Rattlesnake sighting in San Francisco on a given day, based on 42 verified sightings from GBIF citizen-science data. It is the 14th most-seen of the 21 reptiles we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Western Rattlesnake in San Francisco on a given day, so our monthly data shows no clear season.
Between 8 and 11 am
Across all the parks we cover, that three-hour window holds the most Western Rattlesnake sightings with a recorded time, and about 6 in 10 of them come between 6 am and 6 pm: it is seen both by day and at night.
6th of 6
Of the 6 cities where we can rate Western Rattlesnake sightings, San Francisco ranks 6th at under 5%. The best odds are in Sacramento (United States, about 20%), Tijuana (México, about 10%) and San Diego (United States, about 10%).
GBIF citizen-science records
It is estimated from how often the Western Rattlesnake is recorded against all the reptiles logged in San Francisco (42 verified sightings), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
