Congress Avenue Bridge Bats

Address: Congress Avenue Bridge, Austin, TX 78704
Hours: Emergence at dusk (roughly 30 min before sunset), March–November
Cost: Free

The Hook

Under the Congress Avenue Bridge lives the largest urban bat colony in North America — 1.5 million Mexican free-tailed bats that eat 10,000–30,000 pounds of insects every single night.

Key Facts

• 1.5 million Mexican free-tailed bats (Tadarida brasiliensis)
• Colony moved in after the bridge was reconstructed in 1980; expansion joints created ideal roosting crevices — by accident
• Bats arrive in March from Mexico for summer; leave in November
• Females form a maternity colony; each gives birth to a single pup in June
• A single bat can eat up to 1,000 mosquito-sized insects per hour
• Bat Conservation International is headquartered in Austin, partly because of this colony

Story / History

When the bats first moved in after the 1980 reconstruction, residents were alarmed and petitioned to have them removed. Merlin Tuttle, a bat biologist, moved to Austin and launched a public education campaign explaining that free-tailed bats are harmless insect eaters. By the late 1980s the colony had become a celebrated attraction. Austin went from trying to evict the bats to building an observation area under the bridge. It’s a rare conservation success story where public perception fully reversed.

Insider Tips

• Best viewing: south side of the bridge at water level, or Statesman Park on the east bank
• Peak colony size: August, when pups join the emergence
• Emergence time varies — check batcon.org for nightly estimates
• Wear layers; it cools down fast by the river at dusk

Logistics

• Tour stop duration: 45–60 min (arrival + wait + emergence)
• Parking: Street parking along S Congress; Rainey St area garages
• Nearby stops: South Congress Ave shops, Barton Springs (15 min drive)

Sources

• Bat Conservation International: batcon.org