Phrynosoma modestum
Silhouette: Jose Carlos Arenas-Monroy · PhyloPic
In 3 days ~40% in a week ~70%
The roundtail horned lizard (Phrynosoma modestum) is a species of lizard in the family Phrynosomatidae. It is one of the smaller species of the horned lizards (genus Phrynosoma). The specific epithet, modestum, is Latin, meaning "modest" or "calm". The species is native to the United States, in western Texas, New Mexico, eastern Arizona, and southeastern Colorado; and eight states in northcentral Mexico, where it is referred to as tapayaxtin.
The roundtail horned lizard prefers rocky and sandy, semiarid habitat with sparse vegetation, near harvester ant or especially honeypot ant colonies, which are its primary diet. The coloration of the roundtail horned lizard usually reflects the color of the soil in its native habitat. Most specimens are uniformly gray in color, but can also be light brown, or even a pale yellow. Often, darker-colored regions occur around the neck and groin, and sometimes striping on the tail.
Phrynosoma modestum is a short, flat, round-bodied lizard with short limbs, and a small head, which has a distinctive crest of nearly equal-length horns. Unlike other horned lizards, it lacks a fringe of lateral scales and does not seek to... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Guadalupe Mountains National Park | 🇺🇸 United States | |
| 2 | Big Bend National Park | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Roundtail Horned Lizard sighting in Big Bend National Park on a given day, based on 32 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 25th most-seen of the 48 reptiles we can rate there. Over three days the chance rises to about 40%, and over a week to about 70%, if each day is a fresh chance.
July
In that month about 40% of wildlife watchers report a Roundtail Horned Lizard in Big Bend National Park on a given day, against under 5% in August and October–February, the lowest months.
Between 8 and 11 am
Across all the parks we cover, that three-hour window holds the most Roundtail Horned Lizard sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
2nd of 2
Of the 2 parks where we can rate Roundtail Horned Lizard sightings, Big Bend National Park ranks 2nd at about 10%. The best odds are in Guadalupe Mountains National Park (United States, about 30%).
Same family: Phrynosomatidae
The closest relatives of the Roundtail Horned Lizard that you can see in Big Bend National Park (family Phrynosomatidae, Phrynosomatid Lizards) are Greater Earless Lizard (about 60%), Canyon Lizard (about 30%) and Common Side-blotched Lizard (about 30%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Roundtail Horned Lizard is recorded against all the reptiles logged in Big Bend National Park (32 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.
