Bats

Recent mid-winter bat counts have found over 1400 bats hibernating in Jewel Cave.

Lydia Austin

 

Year Round Residents

Bats are one of the most common mammals at Jewel Cave National Monument. Thousands of bats, of ten species, take advantage of the monument's habitat. Five species of Myotis, one species of Eptesicus, and one species of Corynorhinus use the cave throughout the year.

Most years, the monument conducts a mid-winter bat count in order to monitor population levels. The 2018 Mid-Winter Bat Count found over 1,400 individual bats hibernating in Jewel Cave. Over half of these bats were Townsend's big-eared bats (C. townsendii), while the rest were Myotis species (Myotis sp.) and a few Big Brown bats (E. fuscus).

The most recent bat count was conducted in the winter of 2023-2024. During this survey only 602 bats were found, which is 32 more bats than the 2022-2023 survey. Despite the rising number, the number of bats was 831 individuals less than the 2018 pre-white-nose syndrome survey. Once again, the majority of the bats were Townsend's big-eared bats (C. townsendii) while the rest were Myotis species (Myotis sp.). It is unclear as to why this dramatic change in hibernating bat population occured. It could be due to white-nose syndrome or relocation to a different part of the cave.

Fair Weather Friends

Three species of bats reside at the monument only during the warm months. Hoary bats, which are the largest of the local bats, have a heavy coat of fur and roost high in the foliage of trees. Silver-haired bats take advantage of the high number of ponderosa pine snags to establish daytime roosts. Eastern red bats are the newest addition to the species observed on the monument, only being documented in the summer of 2023.

Unsolved Mystery

Jewel Cave supports one of the largest known hibernating colonies of Townsend's big-eared bats in the world. C. townsendii are not known to migrate great distances, yet only one nursery colony has been located in the Southern Black Hills, despite intensive searches. C. townsendii seem to choose inaccessible caves (and presumably mines) for giving birth and raising young, and tend to choose sites which have little disturbance from humans. A single pregnant female was located at one of the monument's water sources in 1989, suggesting a nursery colony nearby. Information leading to the location of additional nursery colonies could help protect this species.

Beneficial Predators

Vacationers and the local community benefit from the insect control provided by bats. Black Hills bats are insectivorous; they feed on beetles, moths, flies, and mosquitoes. A single little brown bat (M. lucifugus) can catch hundreds of mosquitoes in an hour. Townsend's big-eared bats are particularly adept at catching moths.

Bats at Risk

Bats are slow-growing and slow-reproducing mammals. On average, bats rear only one young per year. Some bats do not begin reproducing until they are two or more years old. Bats can live as long a thirty or more years, but the average life span is 6.5 years for the little brown bat, and 16 years for the Townsend’s big-eared bat.

During winter, many bats enter hibernation, with much lower metabolic rate and a body temperature near that of ambient air, and requiring an insulated, sheltered roosting site. Arousal of hibernating bats results in an increased metabolic rate. Numerous arousals exhaust a bat's energy reserves and might result in the bats lacking sufficient fat and water reserves to survive winter. To protect hibernating bats, no one is permitted to enter the historic entrance of Jewel Cave from October through May. The only exception is for the mid-winter bat count, which is conducted once a year by the park’s resource management staff.

Homeowners who attempt to evict bats from their property might cause the adult females to abandon their young before they are capable of flying and capturing food. This could result in starvation of the pup. When necessary, bat exclusion should be accomplished before the bats arrive, or after they leave the roosts in late summer. It’s also a good idea to provide alternate bat roosting sites nearby, before excluding bats.

Bats are also threatened by predators. They are a food source for owls, hawks, snakes, and domestic and feral cats. If you see a cat anywhere in the monument, please report it at the visitor center. Park staff will trap the cat and take it to a shelter. Another threat to bats is white-nose syndrome. This disease is caused by a fungus that was first found in New York and has spread to many caves throughout the United States. Learn more about this disease on our White-Nose Syndrome page.

Why is Jewel Cave a good hibernaculum?

The historic area of Jewel Cave has many different levels and temperature ranges. It provides a variety of suitable roosting habitats for a diversity of species. For instance, Corynorhinus hang from walls and ceilings in areas with strong airflow and notable climatic fluctuations, while M.thysanodes, M. volans, M. lucifugus and M. septentrionalis hibernate in large rooms in relatively warm and stable environments.

The gated entrance works for bats in two ways. It provides protection by preventing unauthorized access, and it has horizontal bars which allow the bats to fly through the gate easily.

Will you see bats during your visit?

You might see bats if you are visiting during the warmer months, especially in the evening. The bats hunt for insects during the evening and night hours. They have been seen flying over the visitor center parking lot and entering and exiting Jewel Cave at the historic entrance. If you take the Historic Lantern Tour, you may even see bats inside the cave.

Monument Bat List

Eptesicus fuscus (Big brown bat)

Myotis lucifugus (Little brown bat)

Myotis volans (Long-legged bat)

Myotis ciliolabrum (Western small-footed bat)

Myotis septentrionalis (Northern myotis)

Myotis thysanodes pahasapensis (Black Hills fringed-tail bat)

Corynorhinus townsendii (Townsend's big-eared bat)

Lasionycteris noctivagans (Silver-haired bat)

Lasiurus cinereus (Hoary bat)

Lasiuris borealis (Eastern red bat)

Several of these species have been given special designations. Two species have been designated species of concern by the U.S. Fish and Wildlife Service: M. septentrionalis and C. townsendii. Four species are currently monitored by the South Dakota Natural Heritage Program: M. thysanodespahasapensis, L. noctivagans, M. septentrionalis, and C.townsendii.