Celebrating the future and appreciating the past
Protecting the Indiana bat for three decades
July 17, 2017
Rock outcroppings at Pilot Knob National Wildlife Refuge. Photo by USFWS.
Happy 30th birthday to Pilot Knob National Wildlife Refuge in Missouri! For three decades, this refuge has quietly gone about the business of protecting a large hibernacula of Indiana bats and today we’d like to take a moment to recognize this special place.
Like many national wildlife refuges, Pilot Knob has a rich cultural history. That history is written into the landscape itself, since it was mined for iron ore from 1830s until 1980. This 90-acre refuge was donated to the U.S. Fish and Wildlife Service by the Pilot Knob Ore Company in 1987 and is managed by staff at Mingo National Wildlife Refuge. The donation was authorized under the Endangered Species Act as critical habitat, not because of the sparse forest and rock outcroppings above ground, but because of the habitat underground.
At one time, more than 100,000 Indiana bats utilized the abandoned iron mine shafts in the mountain. This huge number of bats accounted for about one third of the world population of Indiana bats at the time the refuge was established.
In addition to providing important bat habitat, the refuge is also geologically significant. Part of the Saint Francis Mountains, Pilot Knob Mountain is an igneous rock formation deposited 1.5 billion years ago. The mountain provides geologists with a rare opportunity to study base rock in the Midwest. The extreme heat, pressure, and magma created mineral deposits with very small crystal structures. The unique deposits of iron, mica, and quartz attract roughly 100 petrology students from universities throughout the Midwest every year. In an area known as the upper cut, very rare ripple marks and mud cracks are easily seen as well.
Interested in learning about Pilot Knob’s geology and mining history yourself? Take a hike! Along with the special university classes, refuge staff also lead at least two interpretive hikes open to the public every year. These hikes give visitors the opportunity to explore geology and learn how mining has changed the landscape over time, while also creating habitat for endangered hibernating bats. We generally keep the numbers of participants to approximately 25 hikers per trip.
The refuge has been a draw to people since the earliest European settlements in the Ozarks. Pilot Knob National Wildlife Refuge is located in the Arcadia Valley, a popular recreational area in Iron County, Missouri. There are several state parks and other attractions in the county and the number of visitors can crest 500,000 annually!
Bat population and a changing landscape
As we opened the story, Pilot Knob Mountain was an active iron ore mining site for decades. Abandoned iron mine shafts excavated in the mid-1800s provide an important home for these federally-endangered bats from September through April each year. While staff used to do annual census work in the mine to assess population levels, several of the mine shafts become unstable over time and collapsed, making the area unsafe for people. In this unsafe condition, we can no longer make population estimates from inside. Instead, along with support from the Missouri Department of Conservation staff, we monitor the bat population by conducting exit counts and trapping bats with harp nets.
More recent counts have shown that populations have decreased substantially since the refuge was established 30 years ago. The 2016 count estimated the that population is between 5,000 and 7,000 bats. This decline was primarily thought to be due to the changing air flow from the collapsed portions of the mine, but in 2013, we realized that the decline was more complicated. At that point, bat biologists discovered evidence of white-nose syndrome in the mine and those variables changed.
White-nose syndrome is a disease affecting hibernating bats. Named for the white fungus that appears on the muzzle and other parts of hibernating bats, it is associated with extensive mortality of bats in eastern North America and continues to impact hibernating bats that overwinter at the mine.
The Civil War history of Pilot Knob
The first large mine was built in 1838 and operated through the Civil War. The mining operations were important to the Union Army, with Fort Davidson being built at the base of the mountain in 1863. On September 26, 1864 Confederate General Sterling Price attacked the Arcadia Valley. During the battle of Pilot Knob, Fort Davidson was attacked repeatedly before the Union blew up their own fort. During that battle, the Union Army had a defensive skirmish line of approximately 100 troops posted on what is the refuge today. According to historians, the Confederate Army passed near the bottom of the Pilot Knob Mountain.