WYOMING – Wyoming Game and Fish reminded the public recently about the upcoming seasonal closure of a popular cave in the Bighorns.
Tongue River Cave on the Bighorn National Forest just west of Dayton is one of four caves (Big Piney, Cliff Dweller’s, Eaton’s, Tongue River) that are closed every year from October 15 through April 15 to protect hibernating bats from disturbance. When hibernating bats are roused, they fly around expending energy they need to survive the winter at a time when bats can’t find insects to eat to replenish their strength.
Experts believe at least six, and as many as 10 different species, use Tongue River Cave at any given time. Bats play important roles in the earth’s ecosystems by eating insects, pollinating plants, and dispersing seeds to regenerate forests.
Bats are having a hard time of late. The fungus that causes white-nose syndrome (WNS) is spreading throughout the northeastern United States and has now been found in 36 states (including Wyoming) and seven Canadian provinces. Since 2006, WNS has killed more than five million bats in the US.
Concern for bats as well as the cave itself resulted in the Forest Service closing the cave in July 2010. Tongue River Cave is notable for a wide variety of rare cave formations and animal species, but the cave has suffered in recent decades from unrestricted traffic, vandalism, and the theft of many of the cave’s speleothems.
The cave since has reopened to the public with a new signup process in now in place.
Registration through the Forest Service and a commitment to follow decontamination procedures is required to enter the cave. Decontamination involves cleaning clothing and equipment to prevent accidentally spreading the fungus that causes white-nose syndrome (WNS) from one site to another.
A new bat-friendly gate was recently built and installed by WGFD personnel to protect hibernating bats from human disturbance during the winter.
The Hole-In-The-Wall Grotto will be helping the Forest Service clear the cave of people, as well as trash, before the gate will be closed and locked on the afternoon of Sunday, October 14.
Tongue River Cave background
Tongue River Cave is in the Madison Limestone. Mapped in 1969 by the National Speleological Society, Tongue River Cave is 106 feet deep and contains 1.23 miles of passages. It’s composed primarily of two separate river channels, one abandoned and the other active.
The active stream passage is an underground portion of the Little Tongue River which resurges farther east down the Tongue River Canyon. The active and abandoned river channels intersect approximately 1/2 mile into the cave in a large chamber known as the Boulder Room.
The upper channel is mostly dry and sandy, ending in a sand-filled chamber. The lower, active stream passage begins in a sump and ends in a narrow fissure. Attempts have been made to explore the cave’s underwater portion, but low water temperatures and the difficulty of hauling adequate scuba equipment through tight passages have hampered the success of such efforts.
In October 1974, fluorescent dye injected into surface waters of the Little Tongue River 2.6 miles to the south of the cave appeared inside the cave’s river, verifying speculation that The Little Tongue River is the source of the cave’s stream passage.
Waterfalls exist in places of rapid erosion and softer stone within Tongue River Cave, including a 24-foot drop at the cave’s Big Falls. Surface rain and snowmelt contribute to the river’s level inside the cave, with rapid increases in water level possible even days after the surface event which triggered the increase occurred. Flash floods in the cave are a rare occurrence.
The cave’s temperature remains a constant 50 degrees Fahrenheit with near 100% humidity. Approximately 750 feet into the cave, the main passage constricts into a narrow crawl where barometric equalization of the cave’s atmosphere with that of the outside generates significant winds. Near the cave’s entrance, condensation resulting from the meeting of the subterranean and surface air masses results in the cave’s Rain Room where water droplets fall in constant succession from the chamber’s ceiling.
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