Volume 4 • Issue 10 • October 2010

Management and Cave Protection for the Ozark Big-eared Bat and Gray Bat in Oklahoma

Another Endangered Species Project

All North American bats that are endangered or threatened can be classified as cave-dwelling species or subspecies and 13 are cave-dwellers year-round.  Two cave-dwelling species, the gray bat (Myotis grisescens) and Indiana bat (Myotis sodalis), and one subspecies, the Ozark big-eared bat (Corynorhinus townsendii ingens), are of particular concern to recovery biologists because each is federally listed as endangered.  

Human disturbance at caves has caused population declines of many cave bats.  As a result, cave gating has been used widely by governmental and private organizations to protect these sensitive ecosystems.  Such management activities are immediate and long-term deterrents to human access at critical bat roosts and have become necessary to minimize ongoing human impacts.  Populations of bats presently are protected with internal gate systems throughout the United States including 31 entrances to caves in northeastern Oklahoma.  Seven of those caves have been inhabited historically by colonies of endangered gray bats.  The remaining caves are inhabited by populations of endangered Ozark big-eared bats, big brown bats, tri-colored bat (formerly known as the Eastern pipstrelle), northern long-eared bats and a single location for hibernation of endangered Indiana bats.  Four caves that contain populations of either Ozark cavefish and/or Ozark cave crayfish also are protected from human entry by internal gates.  Population estimates of bats at each of these caves prior to installation of gates beginning in 1981 and post-installation estimates from 1999 and 2000 show that each cave continues to be used by stable populations of resident bats.

The Ozark big-eared bat is a federally endangered species. Photo by Richard Stark, USFWS.
In other parts of their ranges, populations of gray bats and endangered Virginia big-eared bats do not respond favorably to gated cave passages with prolonged, stable populations like those in Oklahoma; in fact, gating cave passages often is discouraged or prohibited.  Nevertheless, little empirical evidence exists to suggest that these species will not accept fully gated cave passages, and experiments elsewhere have shown that appropriately placed gates within cave passages will not impede flight.

Recent studies have shown that relative to flight, populations of cave-dwelling bats are not adversely affected by appropriately placed gates in twilight or “dark zones” within cave passages, which are intended to restrict human access to bat roosts and colonies.  Minimal effects of appropriately manipulated passages and entrances are further substantiated by the presence of stable populations of gray bats and Ozark big-eared bats in such caves in Oklahoma

Procedures during this project were conducted in Adair, Cherokee, Delaware, and Ottawa counties of northeastern Oklahoma in the western limit of the Boston Mountains of the Ozark Plateau.  The Plateau covers about 50,000 square miles in the central United States.  The Plateau is comprised of alternating layers of limestone, flint and sandstone that are conducive to cave formation.  Caves in this region may serve as refuge from severe winters for cave-dwelling species.  The vegetation on mountain slopes is predominantly blackjack oak, post oak, black hickory and winged elm.  Coralberry and sassafras comprise the sparse shrubby understory.  Riparian areas are dominated by silver maple, river birch, American elm, cottonwood, sycamore, and various oak species.  Sporadic openings of managed grasslands were used for various types of agriculture.  

The objectives of this project were to identify caves that were considered critical habitat for Ozark big-eared bat and gray bat colonies in northeastern Oklahoma. Management and protection plans for these caves were developed and implemented during the project year as funding and time allowed.  These management and protection plans were coordinated with the landowners and included posting a warning sign at cave entrances, placing human restrictive structures at or within caves such as fencing around the cave entrance or a gate/grill structure within the cave’s passage.  Caves also were monitored to determine the effectiveness of restrictive management plans, particularly gated caves, to determine the impact of these structures or other protection measures implemented at the site.  As problems were identified with the cave protection plans, they were corrected.

Written by Dr. Keith Martin from Rogers State University. Dr. Martin is the Principle Investigator for this Endangered Species Act project.

The Regal Fritillary

Quite Uncommon

The regal fritillary (Speyeria idalia) is one of Oklahoma’s rarest butterflies and is an icon of the northern tallgrass prairies.  The regal fritillary is a large, predominantly orange butterfly with many bold silver spots on the under surface of its wings.  It can be distinguished from the other four fritillary species in Oklahoma by the dark, almost black, margin of the hind wing.  Regal fritillaries are found in the extensive landscapes of native tallgrass prairie, and most of the state’s population is found in the Flint Hills region of Osage County.  A few other records come from the remnant tallgrass prairies in the Osage Plains of Rogers, Nowata and Craig counties.

The Regal Fritillary is uncommon in Oklahoma. Photo by Northern Prairie Wildlife Research Center of the USGS.
Adult Regal Fritillaries feed on the nectar of a wide range of prairie wild flowers including ironweed, blazing-star, milkweed and thistles, but their caterpillars have a very specialized diet and feed only on violets – primarily birdsfoot, prairie and lanceleaf violets.   The adult female fritillary lays her eggs in scattered locations at the bases of flowering plants in the late summer.   The eggs hatch shortly afterward and the velvety-black caterpillars hibernate through the winter in leaf litter, often without feeding because the violets upon which they depend have gone dormant.  The following spring, the caterpillars move onto violets and begin to grow rapidly.  They complete their development in early summer when they build their cocoons and emerge as adult butterflies about three weeks later.  The now adult butterflies live through the summer, reproduce and then die before the fall.  Thus there is only one generation of regal fritillaries each year. 

The regal fritillary is dependent upon the botanically rich tallgrass prairie ecosystem.  Its range once extended from New England to North Carolina and across the country to Oklahoma and the Dakotas.  As tallgrass prairies have been converted to fescue and bluegrass pastures, crop fields and housing developments, the Regal Fritillary has lost habitat and become less common.  In Oklahoma, the most reliable place to see this rare butterfly is on The Nature Conservancy’s Tallgrass Prairie Preserve near Pawhuska. 

Written by Mark Howery. Mark is a wildlife diversity biologist with the Oklahoma Department of Wildlife Conservation.

Winterizing Your Wildscape

This is the second of a three-part series on getting your Wildscape ready for winter

Winter Shelter for Wildlife:     Fall and winter is a good time to prune some trees and shrubs in your yard.  Instead of hauling the cut limbs away, construct a brush pile!     Certain construction specifications, however, will increase the value of the brush pile.  First, loosen the dirt to a depth of about eight inches.  Starting with some good-sized logs, lay out a wagon wheel design over the loosened dirt to make a base.  This will create tunnels and openings in the pile.   Next, add the brush, starting with larger limbs first and then gradually adding smaller limbs.   Box turtles utilize the loose dirt underneath these brush piles as a place to hibernate.  Rabbits and songbirds use brush piles as nighttime shelter and cover from predators.  And don’t forget your Christmas tree.  Place the cut boughs from the tree on top of the pile.

Questions concerning the effectiveness of butterfly hibernation boxes have become more prevalent.  The purpose of the hibernation box is to provide crevices for butterflies to overwinter. In nature, butterflies use cracks in logs, fence posts, loose boards or tree bark.   Butterflies that commonly overwinter as adults in Oklahoma include the mourning cloak, goatweed, question mark, hackberry emperor and the red admiral.  To possibly increase the effectiveness of your hibernation box,  loosely fill the inside of the hibernation box to the roof with large pieces of bark.  This creates lots of crevices and deters wasps from constructing their nests on the inside of the roof during the spring and summer months.  To create more natural shelters for butterflies you can build a butterfly logpile by crisscrossing logs.  Place each layer of logs perpendicular to the previous one and build a stack of logs three to five feet high.  Cover the top with a tarp and anchor the tarp with a final layer of logs.  Another method is to tack rough cedar boards or large slabs of bark in protected places on fences or on the side of the house or garage. Place the boards or slabs vertically, leaving one side not completely nailed down, with a crack where the butterfly can wedge itself inside.

What would autumn be like without the task of raking leaves? After you have completed the traditional “jumping into the pile of leaves” (don’t even try to deny it!), spread the leaves around your trees and shrubs.  Deep leaf litter under your trees and shrubs creates habitat for insects eaten by wrens, towhees and fox sparrows.  Leaf litter also provides protection for moth and butterfly pupa.  And did you know that the gray treefrog hibernates in deep leaf litter?

Next month:  Winterizing the wildlife-friendly water garden.

Written by Melynda Hickman. Melynda is a wildlife diversity biologist with the Oklahoma Department of Wildlife Conservation.

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