Parks and Monuments have the tricky task of balancing visitor
access with protecting the wildlife and landscapes those visitors
wish to see.
Parks and Monuments have the tricky task of balancing visitor access with protecting the wildlife and landscapes those visitors wish to see.
Pinnacles National Monument had an unfortunate firsthand experience Labor Day weekend when a maternity colony of Townsend’s Big-eared Bats moved from their normal nursery area in the Bear Gulch Cave, which is closed to public access, to a lower cave open to visitors. Park officials are not sure what caused the disturbance. However, Pinnacles Wildlife Biologist Jim Peterson suspects a park visitor may have cut through fencing and entered the bat cave.
Green fencing around the site restricts access to the upper chamber of the cave where the maternity colony roosts and protects their newborn pups. There are also heavy steel gates to close off visitor access from the lower cave to the upper cave.
“It’s hard to say because there were some green sections that had been cut,” Peterson said.
Park officials want to continue to keep areas of the tallus cave, a boulder filled gulch with many crevices, openings and caves, open to the public, but are concerned about the health of the bat colony.
“We could have closed the entire cave and said ‘forget it,'” said Paul Johnson, a Pinnacles wildlife biologist. “But we didn’t. We’re letting them in as much as we can.”
If disturbed, mother bats may abandon their pups and leave the cave entirely, Johnson said. This would be detrimental to the park’s efforts to build and sustain the Townsend’s Big-eared Bat colony’s population.
Townsend’s Big-eared Bats often seek out mines and caves with only two openings for hibernation, breeding and roosting. However, the creatures prefer the Bear Gulch Cave because it is cold in the winter and hot in the summer, Johnson said. Park officials discovered the bats only a decade ago.
When the roosting season ends and the bats leave the cave in October, the public will have access to the entire cave system. Access will again be restricted when the bats return for the winter to hibernate in what is called the hibernaculum.
The cool winter temperatures allow the mouse-sized bats, one of the 14 species of bats found at Pinnacles, to regulate and cool their body temperatures. If disturbed the bats have to expend valuable energy stored in the form of brown fat to wake from their slumber.
“They essentially have to build a fire inside and raise their body temperature from 45 degrees to 100 degrees,” Peterson said.
If disturbed too often, the bats can starve.
Once the winter season is over and the cave is too humid for the bats, Pinnacles reopens the cave to the public, usually in March. Park officials quietly enter the cave to count the bats and when fewer than 20 bats remain, the cave is opened.
In mid-May the cave is once again closed as the bats enter their breeding, roosting and nursing cycle for the summer.
Closing the Big Gulch Cave for five years helped park officials figure out the natural behavior patterns of the colony without human interference, Johnson said. As long as the public respects restricted areas, visitors will continue to have access to the cave during certain months and seasons.
“I think people are really cooperative,” Johnson said. “But it only takes one person to disturb the maternity colony and possibly cause the bats to leave and abandon their young.”
The cave will open fully to the public some time next month. Park officials will consider restricting access further if the bats continue to be disturbed.
Michael Van Cassell covers public safety and agriculture for the Free Lance. He can be reached at (831)637-5566 ext. 335
