Tracking the nightly emergence and migration of millions of bats across Central Texas using NOAA NEXRAD weather radar — since 2011.
NEXRAD Radar Image
Updated nightly at emergence time
When millions of bats emerge from a roost, they show up on weather radar. Austin Bat Refuge has been studying this phenomenon — called aeroecology — since 2011, tracking the nightly emergence patterns of bat colonies across the Significant Bat Area (SBA) of Central Texas.
Our data covers an enormous region — from San Angelo in the west to Round Rock in the north, New Braunfels in the south, and Del Rio in the southwest. This area includes dozens of known bat caves, bridge colonies, and migratory corridors.
The radar images capture what the naked eye cannot: the sheer scale of bat movement across the Texas sky, night after night, season after season.
Our monitoring covers the Central Texas SBA — a region defined by the density and diversity of its bat colonies.
We use the same weather radar network that forecasters use to track storms. When bats emerge in large numbers, they create distinctive "bloom" patterns on the radar — expanding rings of biological targets rising from known roost sites.
Each night during the active season, we review radar imagery centered on the Congress Avenue Bridge and surrounding Central Texas colonies. We document emergence times, colony sizes, flight directions, and weather correlations.
Our archive now spans 14 seasons of nightly data. This longitudinal record is invaluable for understanding how bat populations respond to climate change, urban development, and natural variability year over year.
Our archive contains nightly radar images going back to the program's founding in 2011. Browse by season or year to explore historical patterns.
| Season | Active Nights | Peak Emergence | Notes | Archive |
|---|---|---|---|---|
| 2025 | 183 | August 14 | Record pup count | View → |
| 2024 | 176 | July 28 | Early season arrival | View → |
| 2023 | 168 | August 3 | High storm disruption | View → |
| 2022 | 181 | August 10 | Drought conditions | View → |
| 2021 | 172 | July 22 | February freeze impact | View → |
| 2011–2020 | 10 seasons of historical data | Browse archive → | ||