Volume 25
Issue 1

Millions of bats are finding safe – and often celebrated – homes in bridges around the United States and other countries because a civil engineer named Mark Bloschock encountered a biologist named Merlin Tuttle nearly 20 years ago. Bloschock worked for the Texas Department of Transportation (TxDOT), and he became the nation’s leading expert and most vigorous proponent of making bridges welcoming for bats. He has been an invaluable partner to Bat Conservation International.

Bloschock was a key player with BCI in studying bats’ use of bridges and highway culverts, in designing simple, low-cost modifications that add bat roosts to new and existing bridges – and in demonstrating the value of doing so. He has spread that message through countless lectures to highway engineers around the nation and abroad. Many of those engineers took the lesson to heart, and bat-friendly bridges have been and still are appearing all over the landscape.

For his contributions to bat conservation around the world, Bloschock was honored with BCI’s Distinguished Service Award in 2001.

Now Mark Bloschock is retiring after more than 28 years with the Texas Department of Transportation. Here he retraces for BCI members the path that turned him into “The Batman of TxDOT” and the challenges and successes he encountered along the way.

by Mark J. Bloschock

At a bat conservation meeting several years ago, I was introduced as a “bat biologist.” I promptly corrected the introduction, explaining that I am a structural engineer by training and experience, and my only exposure to biology was one class in high school. I later recounted that story to Merlin Tuttle, who replied that I probably knew more about bat biology than any other structural engineer in the world.

That statement remains a source of great pride, and I am grateful for all the knowledge that real bat biologists have shared with me for more than a decade. It has been a fascinating journey down a path I never anticipated.

I was a field engineer for TxDOT during reconstruction of the Congress Avenue Bridge in Austin, Texas, from mid-1978 through 1979. Although it is a city-owned bridge, TxDOT was responsible for inspections and, as a young engineer eager for construction experience, I volunteered for the job. I soon moved on to another project, but retained a sense of ownership in the bridge – what we engineers call “bonding with the structure.”

During the early 1980s, when bats by the hundreds of thousands discovered that crevices in the bottom of the bridge made ideal roosts, I watched as unreasoning fear greeted their growing numbers. Then, in 1986, Tuttle and his young organization, Bat Conservation International, showed up in Austin and began explaining the many benefits of having a bat colony downtown. Many Texans thought he was a nut, but his quiet leadership style and careful marshalling of the facts eventually convinced city officials – facing strident demands that the colony be eradicated – to investigate the situation before acting.

Today, of course, the 1.5 million Mexican free-tailed bats that spend their summers under the Congress Avenue Bridge are a source of municipal pride and a tourist attraction that pours millions of dollars a year into the local economy.

While involved in planning a 1994 TxDOT Bridge Designers Conference in Austin, I proposed inviting Merlin Tuttle to speak about issues surrounding bats roosting at the Congress Avenue Bridge and also the Foster Street Bridge in San Angelo. My suggestion was rejected as irrelevant to bridge design.

When I was asked to plan the 1995 conference, I skipped the asking-permission step, invited Merlin to speak and added his name to the agenda. He gave a stellar performance, which softened the field for planting.

The seeds went into the ground later that year. I envisioned a study of bats and bridges under the aegis of TxDOT’s highly influential research program, which affects transportation and highway engineering nationally and internationally. (With about 50,000 bridges and bridge-length culverts, TxDOT oversees more bridges than any other state and more than many countries.) But 12 years ago, such a notion seemed so far-fetched that it would surely die by committee vote. TxDOT, however, had just appointed a new executive director with an “open-door policy,” and I took advantage of this new management concept by sending a well-researched proposal to him personally. He approved it, providing $55,000 in discretionary funding for a one-year study of bats in Texas bridges, and we partnered with BCI.

BCI’s lead biologist for the Texas Bats and Bridges project was Brian Keeley, whose diligence and attention to detail were remarkable and an inspiration to everyone involved in the research.

This was a banner year for me and bats. During the research project, I received a BCI scholarship to attend a Bat Conservation and Management Workshop in Portal, Arizona. In addition to learning a great deal about bats at this workshop, we also developed the initial design for incorporating bat roosts in new highway culverts. The design, field-tested near Laredo, Texas, earned TxDOT a Design for Transportation National Award from the U.S. Department of Transportation in 2000.

The Texas Bats and Bridges Study included examination of the impact of bats’ use of bridges on the health and safety of workers and the public; the effects on bridge structures and associated water quality; and the significance of bridges to bat populations and the conditions bats require.

This state study was – and remains – an important milestone. We learned of many more bridge-bat colonies around the state. We also began to affect public opinion about bat colonies through frequent appearances in newspapers, television and such major publications as National Geographic.

This media attention, plus the presentations I made to DOT engineers in a number of states, generated keen interest in taking the research to the national level. Funding was obtained and the National Bats and Bridges Project was undertaken in 1998-99. Transportation departments of various states contributed research funds and I oversaw the national project as the TxDOT representative. BCI’s Brian Keeley was the researcher.

Brian spent the first year visiting DOT offices, bridges and culverts in the Eastern United States, and traveled through the West during the second year. He covered some 10,000 miles and gathered mountains of data and excellent photos. Brian discovered bats and bat sign in many bridges near sea level and even in highway snow sheds above 10,000 feet in Colorado.

The final report for this project remains the gold standard for research on bats and bridges. The BCI publication that resulted, Bats in American Bridges (available on BCI’s website), describes the research findings, strategies for incorporating bat habitat in new bridges and designs for retrofitting existing ones.

An unexpected side-benefit of my work with BCI has nothing to do with bridges. I learned that at least two species of yellow bats roost year-round in the dead fronds – called “beards” – of palm trees in south Texas. Countless palm trees grow on TxDOT rights-of-way, I found anecdotal evidence that our maintenance crews were unknowingly feeding trimmed palm fronds through shredders with flightless bat pups still in the foliage.

Armed with documentation from BCI Science Officer Barbara French, I met with the local TxDOT authorities in Pharr, Texas, who immediately wrote a new palm tree trimming policy that excludes any trimming from April to November. This change seems to preserve more habitat for yellow bats and to sharply reduce – and possibly eliminate – the destruction of bats during palm-tree-trimming. It also saves Texas taxpayers about $100,000 a year.

I have been honored to discuss bats and bridges with audiences of engineers, conservationists and many others around the United States and in a number of other countries. Newspaper and television reporters often wrote about our work and the importance of bats. But the most significant thing I’ve learned has not been about bats but about humans.

So many people whom I’ve met have offered to help in any way they can to dispel myths and provide accurate information about bats. Folks have tackled this chore with great enthusiasm, often achieving remarkable successes. The military call this phenomenon a “force-multiplier effect.” I’m not really sure what it is about bats that inspires people to want to help, but they do.

Engineering is almost always a team effort. No one person is irreplaceable, and the work goes on. So as I retire and go in search of other opportunities, I’m sure the force-multiplier effect will come into play. Someone will make new things happen at TxDOT or some other DOT. The Bats and Bridges effort will continue.

Texas Bridge Bats

While bats roost in only a relatively small number of Texas bridges, these colonies are often quite large: the Congress Avenue Bridge in Austin hosts an estimated 1.5 million bats; the McNeil Road Bridge north of Austin has almost as many; the Foster Street overpass in San Angelo, 500,000; Seco Creek Bridge near Uvalde, up to 1 million; the Salado Culvert near Waco, 500,000.

Bats in smaller numbers also use other bridges and culverts around the state. Some of the sites are used only as temporary stopovers, but quite a few shelter nursery colonies. Many of the colonies are “happy accidents” in which bridges or culverts just happened to have features that fit the needs of bats. Increasingly, though, Texas bridges in appropriate areas are being specifically designed to attract bats.

TxDOT considers public and worker safety its paramount concern, and the Bats and Bridges program has allowed us to conserve and protect bat colonies in our bridges and culverts in a responsible manner that’s worthy of public scrutiny – and replication.