Volume 38
Issue 1

An hour north of Houston lies the town of Huntsville: population 38,000home to the Texas Department of Criminal Justice (TDCJ), Sam Houston State University and over 750,000 Mexican free-tailed bats.

In the heart of downtown Huntsville stands the Texas State Penitentiary at Huntsville; known locally as the Walls Unit, it is the oldest prison in the state. At any one time, nearly 1,700 inmates may reside within the facility. During spring and summer months, these residents may witness a river of bats bursting from the derelict Depression-era cotton warehouse located across the street. It is a spectacular sightnearly 750,000 bats streaming out to feed on insects, including pest species that plague corn and cotton fields.

Walls Colony Emergence
Courtesy of Dan Jones/TPWD

Once a storage unit and dormitory for prison guards, the warehouse now sits abandoned. The roof appears to be burdened under the weight of dense vegetation, and its structural integrity has been compromised with age. With no use for the building, and fearing its impending collapse, TDCJ sought to demolish the structure.

Problem is, the old warehouse provides the perfect microclimate for bats to flourish. And bats being bats, once they found a home they liked, they kept on coming. In fact, the colony has now grown to become one of the largest urban bat populations in Texas. If the warehouse were to collapse or be demolished without a conscious effort to relocate the roosting sites, hundreds of thousands of bats would be forced to find new homeslikely in the eaves and attics of the nearby residential neighborhood.

Even though there are many older buildings in town, there are no other structures anywhere in the Huntsville area that could house the colony now that it has grown so large, says Monte Thies, Sam Houston State University Professor, Department of Biological Sciences. One of our fears is that the colony would be disrupted by demolition of the building, thereby forcing homeless bats to relocate into one or more of the area churches and schools. Having numerous bats trying to relocate into spaces occupied by people would not be healthy for any involved, neither people nor bats.

In Texas it is unlawful to demolish a vacant building containing a bat colony. And while most of the colony migrates south in the cooler months, about 10 percent of the bats occupy the building year-round.

Several groups, including Bat Conservation International, Sam Houston State University, City of Huntsville, Huntsville Audubon Society, Austin Bat Refuge and Texas Parks and Wildlife Department (TPWD), have voiced their concerns about TDCJ demolishing the warehouse without an adequate plan to prevent displacing the bats. In March of 2017, members of TDCJ staff and a stakeholder working group proposed a plan for the construction of large bat houses, dubbed bat condos. The idea was that inmates learning carpentry skills through TDCJs Windham School District vocational education program would build these bat condos to house the colony. Construction began in early 2018.

Over 50,000 bats live in the old warehouse year-round.
Courtesy of Jonathan Alonzo

Unfortunately, the plans used by the prison system to build the bat condos were not consistent with the designs provided by the stakeholder group, resulting in new roosts that wouldnt be able to accommodate all the potentially displaced bats. In fact, each new bat condo would only house about 50,000-75,000 batsleaving over 500,000 bats to find new roosts in less desirable locations throughout Huntsville.

Relocating a bat colony of this size is a challenge, says Dan Jones of Texas Parks and Wildlife Department. That is why the stakeholder working group was formed to assist the prison system in this effort, with the resulting plan based on input from numerous experts with relevant experience.

In September 2018, TDCJ requested a meeting with the stakeholder group to discuss the demolition of the warehouse building and plausible plan for coaxing the bats into the newly constructed structures.

A compromise was reached. TDCJ would address the issues with the bat houses while the majority of the resident bat population had migrated south for the winter. And under the auspice of TPWD, bat relocation would commence in the spring and take place in stages, incentivizing the migrating population to utilize the upgraded bat condos. The remaining 50,000 year-round resident bats would not be relocated until all the bat condos were updated to accommodate the whole population. All this would be great news for the prison, the town, and the bats.

Our hope is that the colony can be encouraged to relocate into the bat condos over the next 34 years as additional structures are built, says Thies. It would be a definite win-win situation for TDCJ, the City of Huntsville and most importantly, the bats, if we can encourage them to utilize the bat condos.