Year Round Residents
Bats are one of the most common mammals at Jewel Cave National Monument. Thousands of bats, of nine species, take advantage of the monument's habitat. Five species of Myotis and one species of Corynorhinus use the limestone caves throughout the year. Eptesicus fuscus (Big brown bats) are found at Jewel Cave during the summer months, and a few will hibernate here during the winter.
In late spring, pregnant Myotis are found at the monument, forming nursery colonies in ponderosa pine snags, rock crevices, and sometimes buildings. Several hundred Myotis and Corynorhinus hibernate inside Jewel Cave during the colder months, accessing the cave through the historic entrance.
Each year, the monument conducts a mid-winter bat count in order to monitor population levels. In January 2011, 1,164 bats were counted. There were 620 Corynorhinus, 542 Myotis, and 2 Eptesicus. Click here to download the 2011 bat count report (358 kb PDF).
Fair Weather Friends
Two 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. They form nursery colonies in cavities created by woodpeckers and under loose, peeling bark. When the weather turns cold, the hoary and silver-haired bats migrate to the southern United States and Mexico.
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.
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. They also eat cockroaches, termites, crickets, katydids, cicadas, and night-flying ants. A single little brown bat (M. lucifugus) can catch hundreds of mosquitoes in an hour. Cucumber and June beetles, stink bugs, and leafhoppers, all well-known pests, are just a few of the many insects known to be consumed by bats. 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 be long-lived (a little brown bat was documented at 36 years of age), but the average life span of a bat that reaches adulthood is ten years.
Bats sometimes form large colonies, which makes them susceptible to disturbance. A significant portion of a colony can be put at risk each time the colony is disturbed. Because of their reproductive and colony-forming characteristics, bats do not bounce back quickly after significant disturbance.
During winter, many bats enter hibernation, a state characterized by a 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 bat biologists and park managers.
Homeowners who attempt to evict bats from nursery sites might cause the adult females to abandon their young before the young are capable of flying and capturing food. This can result in starvation and the loss of a generation of bats. To avoid affecting the colony, bat exclusion should be accomplished before the bats arrive, or after they leave the roosts in late summer. Homeowners should provide alternate bat roosting sites near their buildings before excluding bats.
Bats are also threatened by predators. They are a food source for owls, hawks, falcons, raccoons, domestic and feral cats, and snakes. A single feral cat once waited outside the historic entrance of Jewel Cave and killed more than 200 bats! If you see a cat anywhere in the monument, report it at the visitor center. Park staff will trap the cat and bring it to a shelter.
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 at relatively low levels, and are tolerant of 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. The gate 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, and in the evening. The monument 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 Lantern Tour, you may even see bats inside the cave.
Monument Bat List
Eptesicus fuscus (Big brown bat)
Myotis lucifugus (Little brown myotis)
Myotis volans (Long-legged myotis)
Myotis ciliolabrum (Western small-footed myotis)
Myotis septentrionalis (Northern myotis)
Myotis thysanodes pahasapensis (Black Hills fringed-tail myotis)
Corynorhinus townsendii (Townsend's big-eared bat)
Lasionycteris noctivagans (Silver-haired bat)
Lasiurus cinereus (Hoary bat)
Several of these species have been given special designations. Four species have been designated species of concern by the U.S. Fish and Wildlife Service: M. thysanodes, M. volans, M. ciliolabrum and C. townsendii. Four species are monitored by the South Dakota Natural Heritage Program: M. thysanodes pahasapensis, L. noctivagans, M. septentrionalis, and C.townsendii.
For additional information on bats, contact:
P.O. Box 162603,
Austin, TX 78716
(512) 327- 9721