Natrix helvetica
Silhouette: Danny S. · PhyloPic
In 3 days ~30% in a week ~60%
The barred grass snake (Natrix helvetica) is a non-venomous colubrid snake from Western Europe, typically living in and close to water. It was included within the grass snake species, Natrix natrix, until August 2017, when genetic analysis led to its reclassification as a separate species.
There are currently five subspecies of Natrix helvetica recognized (having been formerly classified as subspecies of N. natrix): N. helvetica helvetica (syn. N. natrix helvetica) – most of range N. helvetica cetti (syn. N. natrix cetti) – Sardinia
N. helvetica corsa (syn. N. natrix corsa) – Corsica N. helvetica lanzai (syn. N. natrix lanzai) – mainland Italy, but not south N. helvetica sicula (syn. N. natrix sicula) – Calabria and Sicily The barred grass snake has a dark grey-green upper body with distinctive black markings in the form of bars running along its sides. Its underside is pale. Like the grass snake, it has a distinctive yellow and black collar around its neck. It can grow to over a metre in length.
The species is found in Great Britain as far north as southern Scotland, and in the Netherlands, western Germany, Switzerland, Italy... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 2 | Cévennes National Park | 🇫🇷 France | |
| 3 | Mercantour National Park | 🇫🇷 France | |
| 4 | Pyrénées National Park | 🇫🇷 France |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | British Wildlife Centre | 🇬🇧 United Kingdom | |
| 2 | Alpenzoo Innsbruck | 🇦🇹 Austria |
With luck
About 10% of wildlife watchers report a barred grass snake sighting in London on a given day, based on 108 verified sightings from GBIF citizen-science data. It is the 3rd most-seen of the 6 reptiles we can rate there. Over three days the chance rises to about 30%, and over a week to about 60%, if each day is a fresh chance.
May, July and October
In those months about 20% of wildlife watchers report a barred grass snake in London on a given day, against under 5% in December to February, the lowest months.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most barred grass snake sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 5 cities where we can rate barred grass snake sightings, London has the highest daily chance: about 10%. Next come Milan (Italy, about 10%) and Paris (France, about 10%).
GBIF citizen-science records
It is estimated from how often the barred grass snake is recorded against all the reptiles logged in London (108 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.
