I had a bucket list day on halloween. I was over in the US for a family wedding in Florida, and one of the big aims of the trip was for my brother Gaz and I to take my dad away for a few days. My incredible sister in law evidently went into full research mode, and arranged for a trip to Austin. We took the 2 hour flight from Orlando (It was the first flight I’d taken with my dad since I was about 12 – we both hate flying, so spent the flight calming each other down!) and checked into our hotel.
What has the city of Austin got to do with halloween? Well, for bat workers, Austin, Texas is a bit of a bat Mecca, as it is home to a colony of 1.5 million Mexican Free-tailed bats which spend their days roosting under the Congress Avenue bridge, emerging and swarming each summer night.
Once we had checked into the hotel, we took a walk down to the bridge as a bit of a recce for bat-watching later that night. I wasn’t expecting to see anything, but it was a lovely walk along the Colorado River. Within a few minutes I noticed a sign with a bat silhouette, and as I approached the bridge I could hear a high-pitched chattering noise coming from the underside of the bridge!
I was, needless to say, extremely excited – and I did a quick video in which (if you turn the volume up) you can hear the sound of the bats!
I did a bit of searching for guano, but the gaps above the path itself had, understandably, been filled up, I assume in an effort to stop walkers and cyclists on the path from getting guano in their hair! Eventually I found a single dropping on the river bank. I wonder if there is a significant nutrient increase in the water downstream of the bridge? Having seen how much a single bat deposits, 1.5 million is a lot of fertiliser!
After an amazing afternoon and a bit of trick-or-treating with my neice (AKA Doc McStuffins) we headed back to the bridge for sunset to watch the bat emergence.
Because we were there in October, bat emergence took place after it was fully dark, whereas in the early summer you get to see the bats swarming against a light sky. But there was a good view under the bridge of some bats flitting about prior to emergence swarming:
I did my very best to get some photos and videos that show you just how incredible the sight was. It was without a doubt the most impressive natural phenomenon I’ve seen in my life.
The Mexican Free-tailed Bat (AKA Brazilian Free-tailed Bat –Tadarida brasiliensis) is an insectivorous species, a bit bigger than some of our Myotis bats here in the UK – MFTs weigh in at around 12 grams (1 MFT = two fat pipistrelles). Below are some pics of the one that I got to meet a few years ago at the Florida Bat Conservancy. You can see where the ‘free-tailed’ part comes from, as unlike our UK species, the tail membrane (patagium) doesn’t join onto the bat’s tail at its tip, but instead the tail itself extends past the edge of the membrane. The are famous for the enormous size of their roosts.
The cool thing is that these bats don’t hibernate like all of our UK species – they migrate to Mexico instead! By the middle of November the bats are gone from the bridge, not to return until spring. Alas, I cannot migrate to Mexico, but must instead endure the British winter, hopefully with some wintery wildlife adventures coming your way shortly…
JT Bear had a great time, too! JT Travels the world raising money for the Sarcoidosis and Interstitial Lung Association and the British Lung Foundation. Last year he walked across Scotland! Please follow the links to each of these charities if you’d like to donate!