Crotalus ornatus
Silhouette: Bill Bouton (source photo) & T. Michael Keesey (vectorization) · PhyloPic
In 3 days ~70% in a week ~90%
The black-tailed rattlesnake (Crotalus molossus) is a venomous pit viper species found in the southwestern United States and Mexico. Four subspecies are currently recognized, including the nominate subspecies described here.
A 2012 revision showed that eastern populations from Texas and central and eastern New Mexico form a distinct species separate from C. molossus: Crotalus ornatus Hallowell 1854. Alternate common names are green rattler, and Northern black-tailed rattlesnake.
This medium-sized species averages from 76 to 107 cm (30 to 42 in) in length. The females tend to be larger than the males. They range in color from yellows and olive greens to browns and black. As their name implies, one of their most distinguishing features is, despite variations in body color, entirely black tail scales. Often, this rattlesnake has a black band across its eyes extending diagonally down to the corners of its mouth... Wikipedia →
Recording0:13
United States · 2024
© Bob Nieman · iNaturalist · CC BY 4.0
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Big Bend National Park | 🇺🇸 United States | |
| 2 | Guadalupe Mountains National Park | 🇺🇸 United States | |
| 3 | Cumbres de Monterrey National Park | 🇲🇽 Mexico |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Oklahoma City Zoo and Botanical Garden | 🇺🇸 United States | |
| 2 | Arizona-Sonora Desert Museum | 🇺🇸 United States | |
| 3 | Philadelphia Zoo | 🇺🇸 United States | |
| 4 | El Paso Zoo | 🇺🇸 United States | |
| 5 | Riverbanks Zoo | 🇺🇸 United States | |
| 6 | Tula Exotarium | 🇷🇺 Russia |
Possible
About 30% of wildlife watchers report an Eastern Black-tailed Rattlesnake sighting in Big Bend National Park on a given day, based on 102 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 8th most-seen of the 48 reptiles we can rate there. Over three days the chance rises to about 70%, and over a week to about 90%, if each day is a fresh chance.
August
In that month about 60% of wildlife watchers report an Eastern Black-tailed Rattlesnake in Big Bend National Park on a given day, against under 5% in January, the lowest month. That is one of Big Bend National Park's wettest months, with about 45 mm of rain against 10 mm in April.
Between 8 and 11 pm
Across all the parks we cover, that three-hour window holds the most Eastern Black-tailed Rattlesnake sightings with a recorded time, and about half of them come between 6 pm and 6 am: it is seen both by day and at night.
Yes
Of the 3 parks where we can rate Eastern Black-tailed Rattlesnake sightings, Big Bend National Park has the highest daily chance: about 30%. Next come Guadalupe Mountains National Park (United States, about 30%) and Cumbres de Monterrey National Park (Mexico, about 10%).
Same genus: Crotalus
The closest relatives of the Eastern Black-tailed Rattlesnake that you can see in Big Bend National Park (genus Crotalus, Rattlesnakes) are Western Diamondback Rattlesnake (about 40%), Mohave Rattlesnake (about 10%) and Rock Rattlesnake (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Eastern Black-tailed Rattlesnake is recorded against all the reptiles logged in Big Bend National Park (102 verified sightings from 2019 to 2026), 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.
