Dr. Charles Campbell: Bat House Pioneer

Mark Kiser

The first known bat houses were built exactly a century ago. In his 1925 book, Bats, Mosquitoes, and Dollars, Dr. Charles A. Campbell, a physician in San Antonio, Texas, described his decades of work designing and testing artificial bat roosts to combat malaria-spreading mosquitoes. While his claims that bats eliminated malaria from the Mitchell Lake area near San Antonio are open to debate [BATS, Summer 1989], Dr. Campbell proved for the first time that bats can be attracted to artificial roosts.

By studying bats’ natural roosts, Dr. Campbell contended, he could “build a home for bats in a scientific manner to meet the requirements of their most singular habits.” He quickly discovered, however, that this was no easy task. Although details of his earliest bat houses are not given, he reports that “quite a number of boxes of different sizes and construction were lined [with cheese cloth saturated with bat guano from a nearby cave] and placed on trees in different localities” around San Antonio in 1902. Boxes were also placed in old buildings, under bridges, and in large warehouses and stables. Although bats did move into two boxes placed in a stable, Dr. Campbell considered his first round of experiments “a most dismal failure.” He concluded that bats preferred larger structures where they could roost high above the ground, and he set to work designing a new type of roost: a “bat tower.”

With $500.00 of his own money, Dr. Campbell built his first bat tower in 1909 at the United States Experiment Farm near San Antonio. The pyramid-shaped tower itself was approximately 20 feet (6.1 meters) tall and mounted on four stout posts about 10 feet (3 meters) high. The roost was 12 feet (3.7 meters) square at the base and about 6 feet (1.8 meters) square at the top. Inside, a series of inclined roosting “shelves” that ran the height of the tower were designed to shunt guano into a central chamber where it would collect in a hopper. “Seeing room for improvement,” he modified the tower inside and out in 1910, but no bats ever came. The tower, which attracted only exotic House Sparrows, was eventually dismantled and sold for scrap.

Rather than giving up, Dr. Campbell closed his medical practice so he could devote all his time to studying bats. After comparing Texas caves that were favored versus ignored by bats, he concluded that one of the biggest flaws of his original tower was its location. In April 1911, he built a new and improved roost at Mitchell Lake, 10 miles (16 kilometers) south of San Antonio, where mosquitoes were abundant. Less than three months later, free-tailed bats had moved into his “Malaria-Eradicating, Guano-Producing Bat Roost.” Estimates of bats in the roost ranged from thousands to hundreds of thousands, and 4,000 to 4,558 pounds (1,814 to 2,067 kilograms) of bat guano were removed each year from 1918 to 1923. A viewing area was added to handle the spectators who came to watch the bats emerge from the tower. Bats kept using the tower long after Dr. Campbell’s death in 1931, and an heir received royalty checks from guano sales until at least 1948. Sadly, the historic Mitchell Lake roost no longer exists.

Only three of the 16 Campbell towers built in the U.S. and Italy still survive, two on private land in Texas and one in Florida. Some of the towers were vandalized or burned in the 1950s, during a period of rabies hysteria, while others apparently succumbed to age. A tower owned by the Steves family in Comfort, Texas, was restored in the late 1980s and is still used by small numbers of cave myotis (Myotis velifer) and Mexican free-tailed bats during migration and as a night roost in summer. Built in 1918, it is a registered landmark with the Texas Historical Commission. Hidden by trees and overgrowth, the bat tower in Orange, Texas, is largely forgotten and badly deteriorated, but might be restored in the near future.

The third tower, and the only one accessible to the public, is on Sugarloaf Key, Florida. Built for R.C. Perky in 1929, it was stocked with bats imported from Texas or Cuba (accounts vary). Those bats promptly flew away and the tower never actually attracted any new bats. It is, nonetheless, a well-known tourist destination and a registered National Historical Landmark.

While many of Dr. Campbell’s claims in Bats, Mosquitoes, and Dollars werecontroversial, his work with artificial roosts sparked interest around the world. One hundred years later, Dr. Campbell’s contributions to bat house research endure.

This 84-year-old bat tower in Comfort, Texas, is still being used by Mexican free-tailed bats and cave myotis. Only three of the 16 towers designed by Dr. Charles Campbell survive.