Thamnophis sirtalis
Silhouette: Alex Slavenko · PhyloPic
In 3 days ~60% in a week ~90%
The common garter snake (Thamnophis sirtalis) is a species of snake in the subfamily Natricinae of the family Colubridae. The species is indigenous to North America and found widely across the continent. There are several recognized subspecies. Most common garter snakes have a pattern of yellow stripes on a black, brown or green background, and their average total length (including tail) is about 55 cm (22 in), with a maximum total length of about 137 cm (54 in). The average body mass is 150 g (5.3 oz). The common garter snake is the state reptile of Massachusetts.
The subspecific name fitchi is in honor of the American herpetologist Henry Sheldon Fitch. The subspecific name pickeringii is in honor of the American naturalist Charles E. Pickering. Current scientific classification recognizes 12 subspecies (ordered by date):
A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Thamnophis. Common garter snakes are thin snakes. Few grow over about 4 ft (1.2 m) long, and most stay smaller. Most have longitudinal stripes in many different colors. Common... Wikipedia →
Recording0:08
Canada · 2021
© Bryce · iNaturalist · CC BY-NC 4.0
Recording0:04
Canada · 2024
© troydavis · iNaturalist · CC BY-NC 4.0
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Wood Buffalo National Park | 🇨🇦 Canada | |
| 2 | Cape Breton Highlands National Park | 🇨🇦 Canada | |
| 3 | Isle Royale National Park | 🇺🇸 United States | |
| 4 | Point Pelee National Park | 🇨🇦 Canada | |
| 5 | Voyageurs National Park | 🇺🇸 United States | |
| 6 | Acadia National Park | 🇺🇸 United States | |
| 7 | Shenandoah National Park | 🇺🇸 United States | |
| 8 | Great Smoky Mountains National Park | 🇺🇸 United States | |
| 9 | Redwood National Park | 🇺🇸 United States | |
| 10 | Pacific Rim National Park Reserve | 🇨🇦 Canada | |
| 11 | Olympic National Park | 🇺🇸 United States | |
| 12 | Big Cypress National Preserve | 🇺🇸 United States | |
| 13 | Everglades National Park | 🇺🇸 United States | |
| 14 | Great Bear Rainforest | 🇨🇦 Canada | |
| 15 | Congaree National Park | 🇺🇸 United States | |
| 16 | Merritt Island National Wildlife Refuge | 🇺🇸 United States | |
| 17 | Glacier National Park | 🇺🇸 United States | |
| 18 | Grand Teton National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Philadelphia | 🇺🇸 United States | |
| 2 | Baltimore | 🇺🇸 United States | |
| 3 | Detroit | 🇺🇸 United States | |
| 4 | Boston | 🇺🇸 United States | |
| 5 | Montreal | 🇨🇦 Canada | |
| 6 | Toronto | 🇨🇦 Canada | |
| 7 | Washington | 🇺🇸 United States | |
| 8 | Vancouver | 🇨🇦 Canada | |
| 9 | Minneapolis [Saint Paul] | 🇺🇸 United States | |
| 10 | New York City | 🇺🇸 United States |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Barcelona Zoo | 🇪🇸 Spain | |
| 2 | North Carolina Zoo | 🇺🇸 United States | |
| 3 | Ecomuseum Zoo | 🇨🇦 Canada | |
| 4 | Toledo Zoo | 🇺🇸 United States | |
| 5 | Wildlife World Zoo | 🇺🇸 United States | |
| 6 | Saint Louis Zoo | 🇺🇸 United States | |
| 7 | Dickerson Park Zoo | 🇺🇸 United States | |
| 8 | Philadelphia Zoo | 🇺🇸 United States | |
| 9 | Riverbanks Zoo | 🇺🇸 United States | |
| 10 | Aquarama Barcelona | 🇪🇸 Spain | |
| 11 | Western North Carolina Nature Center | 🇺🇸 United States | |
| 12 | Trailside Museum & Zoo | 🇺🇸 United States | |
| 13 | Cambridge Butterfly Conservatory | 🇨🇦 Canada | |
| 14 | North Carolina Aquarium at Pine Knoll Shores | 🇺🇸 United States | |
| 15 | Scales Nature Park | 🇨🇦 Canada | |
| 16 | FarmHouse Fresh Animal Sanctuary | 🇺🇸 United States | |
| 17 | Seattle Marine Aquarium | 🇺🇸 United States |
Possible
About 30% of wildlife watchers report a Common Garter Snake sighting in Philadelphia on a given day, based on 376 verified sightings from GBIF citizen-science data. It is the 2nd most-seen of the 17 reptiles we can rate there. Over three days the chance rises to about 60%, and over a week to about 90%, if each day is a fresh chance.
March and April
In those months about 40% of wildlife watchers report a Common Garter Snake in Philadelphia on a given day, against about 10% in December and January, the lowest months.
Between 2 and 5 pm
Across all the parks we cover, that three-hour window holds the most Common Garter Snake sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 18 cities where we can rate Common Garter Snake sightings, Philadelphia has the highest daily chance: about 30%. Next come Baltimore (United States, about 30%) and Detroit (United States, about 20%).
Same family: Colubridae
The closest relatives of the Common Garter Snake that you can see in Philadelphia (family Colubridae, Colubrid Snakes) are DeKay's Brownsnake (about 30%), Common Watersnake (about 10%) and Eastern/Central Ratsnake Complex (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Common Garter Snake is recorded against all the reptiles logged in Philadelphia (376 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.
