Tadarida brasiliensis
Silhouette: T. Michael Keesey · PhyloPic
In 3 days ~10% in a week ~20%
The Mexican free-tailed bat or Brazilian free-tailed bat (Tadarida brasiliensis) is a medium-sized bat native to North, Central, and South America and the Caribbean, so named because its tail can be almost half its total length and is not attached to its uropatagium. It has been claimed to have the fastest horizontal speed of any animal, reaching level flight speed of up to 99 mph (160 km/h). It also flies the highest among bats, at altitudes around 3,300 m (10,800 ft).
It is regarded as one of the most abundant mammals in North America. Its proclivity towards roosting in huge numbers at relatively few locations makes it vulnerable to habitat destruction in spite of its abundance. For instance, up to 1.5 million bats reside under just one bridge in Austin. The Texas Legislature recognized the Mexican free-tailed bat as the "Official Flying Mammal" of the State of Texas in 1995.
The Mexican free-tailed bat was described as a new species in 1824 by French zoologist Isidore Geoffroy Saint-Hilaire. Geoffroy placed it in the now-defunct genus Nyctinomus with a binomial name of Nyctinomus brasiliensis.
The holotype had been collected in Brazil. Molecular sequence data indicate... Wikipedia →
Recording0:12
United States · 2025
© Ashley Fruhwirth · iNaturalist · CC BY-NC 4.0
Recording0:17
United States · 2023
© Nicholas Canino · iNaturalist · CC BY-NC 4.0
Recording0:19
United States · 2025
© Debiani · iNaturalist · CC BY-NC 4.0
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Big Cypress National Preserve | 🇺🇸 United States | |
| 2 | Death Valley National Park | 🇺🇸 United States | |
| 3 | Everglades National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Santiago | 🇨🇱 Chile | |
| 2 | Rosario | 🇦🇷 Argentina | |
| 3 | León | 🇲🇽 México | |
| 4 | Austin | 🇺🇸 United States | |
| 5 | Montevideo | 🇺🇾 Uruguay | |
| 6 | Sacramento | 🇺🇸 United States | |
| 7 | Houston | 🇺🇸 United States | |
| 8 | Phoenix | 🇺🇸 United States | |
| 9 | San Antonio | 🇺🇸 United States | |
| 10 | Buenos Aires | 🇦🇷 Argentina |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | California Academy of Sciences | 🇺🇸 United States | |
| 2 | Turtle Bay Exploration Park | 🇺🇸 United States | |
| 3 | Bat World Sanctuary | 🇺🇸 United States |
Rare
Under 5% of wildlife watchers report a Mexican Free-tailed Bat sighting in San Francisco on a given day, based on 13 verified sightings from GBIF citizen-science data. It is the 30th most-seen of the 38 mammals we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Mexican Free-tailed Bat in San Francisco on a given day, so our monthly data shows no clear season.
Between 7 and 10 pm
Across all the parks we cover, that three-hour window holds the most Mexican Free-tailed Bat sightings with a recorded time, and about 6 in 10 of them come between 6 pm and 6 am: it is seen both by day and at night.
19th of 19
Of the 19 cities where we can rate Mexican Free-tailed Bat sightings, San Francisco ranks 19th at under 5%. The best odds are in Santiago (Chile, about 20%), Rosario (Argentina, about 20%) and León (México, about 10%).
GBIF citizen-science records
It is estimated from how often the Mexican Free-tailed Bat is recorded against all the mammals logged in San Francisco (13 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.
