Crotalus polystictus
Silhouette: Bill Bouton (source photo) & T. Michael Keesey (vectorization) · PhyloPic
In 3 days ~10% in a week ~30%
The Mexican lance-headed rattlesnake or lance-headed rattlesnake (Crotalus polystictus) is a venomous pit viper species found in central Mexico. No subspecies is currently recognized. Adults usually grow to a total length of 60 to 70 cm (24 to 28 in), although exceptionally large specimens may be as much as 100 cm (39 in) long.
The species is found on the plateau of central Mexico from southern Zacatecas and northeastern Colima east to east-central Veracruz. It occurs at elevations between 1,450 and 2,600 m (4,760 and 8,530 ft). The type locality given is "Table Land, Mexico", although a restriction to "Tupátaro, Guanajuanto, Mexico" was proposed by H.M. Smith and Taylor (1950).
This species is classified as Least Concern on the IUCN Red List of Threatened Species (v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was down when assessed in 2007.
Cope, E.D. 1865. Third contribution to the HERPETOLOGY... Wikipedia →
Recording0:10
Mexico · 2021
© daniie · iNaturalist · CC BY-NC 4.0
| # | Park | Country | Daily sighting probability |
|---|
More parks will be added in future updates.
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Mexico City | 🇲🇽 México |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | National Zoological Park | 🇺🇸 United States | |
| 2 | Los Angeles Zoo | 🇺🇸 United States | |
| 3 | Saint Louis Zoo | 🇺🇸 United States | |
| 4 | Fort Worth Zoo | 🇺🇸 United States | |
| 5 | San Antonio Zoo | 🇺🇸 United States | |
| 6 | Zoo Atlanta | 🇺🇸 United States | |
| 7 | Buffalo Zoo | 🇺🇸 United States | |
| 8 | Chattanooga Zoo at Warner Park | 🇺🇸 United States | |
| 9 | Reino Animal | 🇲🇽 Mexico |
Rare
Under 5% of wildlife watchers report a Mexican Lancehead Rattlesnake sighting in Mexico City on a given day, based on 34 verified sightings from GBIF citizen-science data. It is the 20th most-seen of the 37 reptiles we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
January, April and September–November
In those months about 10% of wildlife watchers report a Mexican Lancehead Rattlesnake in Mexico City on a given day, against under 5% in February–March, May–August and December, the lowest months.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Mexican Lancehead Rattlesnake sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Only Mexico City, in our data
Mexico City is the only city on Wallace's Line with enough records to rate Mexican Lancehead Rattlesnake sightings: under 5% of wildlife watchers there report one on a given day.
Same genus: Crotalus
The closest relatives of the Mexican Lancehead Rattlesnake that you can see in Mexico City (genus Crotalus, Rattlesnakes) are Western Black-tailed Rattlesnake (about 10%) and Mexican Pygmy Rattlesnake (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Mexican Lancehead Rattlesnake is recorded against all the reptiles logged in Mexico City (34 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.
