Townsend's big-eared bats at Kentucky stamp mill

General bat anatomy displayed on a board in the Kentucky Mine Historic Park: the distinct Townsend's big-eared bat has horseshoe-shaped lumps on the nostrils and long ears joining at the base

The stamp mill at the Kentucky Mine Historic Park in Sierra City, California, hosts a maternity colony of Townsend's big-eared bats (Corynorhinus townsendii)—a cave-dwelling species that occasionally roosts in man-made structures. The bats of the Kentucky colony have acclimated to local conditions tolerating a certain level of disturbance such as human spectators and short exposure to stamping noise, happening for short times while demonstrating the function ore-crushing stamps to visitors.

Townsend's big-eared bats are named for their extremely long and flexible ears. But there is more in the long common name. The species name—also the shorter scientific name—commemorates the American naturalist and collector John Kirk Townsend (1809-1851), who, in the first half of the 19th century, explored the wildlife between the Rockies and the Pacific Ocean [1]. Various subspecies are found throughout western North America between British Columbia and Mexico.

Corners and crevices of the stamp mill at the historic Kentucky Mine serve as roosting sites for Townsend's big-eared bats

Corynorhinus townsendii is protected under the California Endangered Species Act [2]. Threats include habitat destruction and potential introduction of the white-nose syndrom. Although once created by humans for a noisy business, the Kentucky stamp mill is a a safe refuge for this endangered bat species. A tour guide at the mine park informed me that the “Kentucky stamp mill bats” do not migrate. Townsend's big-eared bats prey on moths but may include some other insects in their diet: They (and also other bats) offer natural pest control by eating insects that may otherwise attack crops or forest land.

Female Townsend's big-eared bats rear their young in maternity colonies. A handout provided at the Kentucky Mine Museum in the Bigelow House describes their mating and breeding cycle:

Mating begins in the fall and continues through the winter. Townsend's big-eared bats have delayed fertilization, storing sperm until ovulation occurs in the spring. In March or April the females begin to form maternity colonies, where theyr rear their young. During the maternity season, males remain solitary or form small bachelor groups. The length of gestation varies depending on the climate, but generally lasts between 56 to 100 days. Females give birth to a single young, called a pup. The babies develop rapidly: they are able to fly by three weeks, nearly grown by four weeks and weaned by six weeks. Females return to the same roost where they were raised to give birth to their own young. Males and females spend the winter together to hibernate.

References and suggested reading

[1] Bo Beolens, Michael Watkins and Michael Grayson: The Eponym Dictionary of Mammals. The Johns Hopkins University Press, Baltimore, Maryland, 2009; page 416.

[2] Noah Greenwald: Townsend's Big-eared Bat Protected Under California Endangered Species Act. Center for Biological Diversity, June 27, 2013. Link: www.biologicaldiversity.org/news/press_releases/2013/townsends-big-eared-bat-06-27-2013.html.

[3] Gary M. Feller and Elizabeth D. Pierson: Habitat Use and Foraging Behavior of Townsend's Big-Eared Bat (Corynorhinus Townsendii) in Coastal California. Journal of Mammology, February 2002, 83 (1), 167-177. Link: https://academic.oup.com/jmammal/article/83/1/167/2372774.  

Kentucky Mine Historic Park

Trestle top entrance for ore cars (and now visitors) into Kentucky Mine stamp mill

The Kentucky Mine Museum and Historic Park opened over the Memorial Day Weekend to kick off its 2018 season. I joined the Sunday morning hour-plus tour to see the inside of the stamp mill. The staircase walk down inside the stamp mill is the highlight, but during the tour one also gets access to the Kentucky Portal and a replica of a miners cabin. I really enjoyed to hear the local mining history as told by the tour guide, who also demonstrated how the displayed tools—mining as well as household tools—were used during the gold-mining days.

Kentucky Portal and replica of a miners cabin

Display sites of mining equipment and buildings are connected by paved trails or gravel paths. Next to the beginning of the trestle railway is a bench inviting you to rest awhile in memory of David Eugene Smith (1948-2013), a gold miner and storyteller. From there, you will have an excellent view of the Kentucky Portal, the miners cabin and an old trommel in the middle of the “plaza” between cabin and stamp mill.

Trommel with miners cabin in background

Our tour guide and her daughter performed snake-checks before letting us enter the portal in front of the adit and the multiple-floor stamp mill. Inside the portal, we got to see an operating pelton wheel. I was surprise how fast it was spinning and got sprinkled with water while coming close to it. The adit is connected with the upper floor of the stamp mill by rail, on which ore cars where transporting ore over the trestle into the hopper room above the grizzley to dump the rocks. From there, the downfall and downbreak of the rocks of various sizes into smaller pieces began. They were passing the jaw crusher and ending up at the bottom, where the pieces were finally powderized under stamps. Two five-stamp settings are there to do the job. We walked down the stairs, floor by floor, to explore the technical details including the well-preserved belt system, bull wheels and the cams and eccentrics that raised and dropped the stamps. The stamp system still works and was demonstrated to us by manually pulling the associated pelton wheel. The stamp mill operated during times, when mercury was still in use here to separate the gold from milled ore.

Next to the stamp tables, on which gold was separated from the crushed quartz and rocks by amalgamation (alloying), is an exit door. Before leaving the stamp mill, I looked up one more time, to spot some of the Townsend's big-eared bats roosting in corners high above wheels and belts.

Asking final questions, members of the tour group exited the mill.  Now, everyone was on his or her own again to check for snakes. Visitors not encountering a snake on the grounds may be interested in seeing the rattlesnake decorating a clampers antique hat on display in the museum.

Sign on Highway 49 for Kentucky Mine Historic Park

Museum

The small, awe-inspiring museum is part of the Bigelow House, a replica of a 19th century hotel.

Location

Find the park & museum at the end of Kentucky Mine Road, a short incline off the Golden Chain Highway (Hwy 49) between Bassetts Station and downtown Sierra City:

100 Kentucky Mine Road
Sierra City, CA 96125

$1 museum admission and $7 tour fee for adults (free for children 6 and under, $3.50 for children ages 7-17).

Kentucky Mine Stamp Mill with trestle

References and more to explore

[1] Kentucky Mine Historic Park & Museum. National Geographic - Sierra Nevada Geotourism.  Link: www.sierranevadageotourism.org/content/kentucky-mine-historic-park-amp-museum/sie9339b2a13f3daefe1.
[2] Kentucky Mine and Museum. Backcountry Explorers. Link: www.backcountryexplorers.com/kentucky-mine-museum.html.