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Indiana bat Listed: 3/11/1967 Status since listing: Declined The Indiana bat (Myotis sodalis) ranges from North Carolina west to Oklahoma and north to Iowa, Michigan and Vermont [1]. They winter in caves or mines that satisfy their highly specific needs for cold (but not freezing) temperatures during hibernation [2]. In the summer, maternity colonies of 30-300 individuals with young roost in the sloughing bark of dead and dying trees and under the exfoliating bark of live trees [1]. The Indiana bat numbered somewhere between 808,505 [1] and 883,300 [3] in 1960s. It was placed on the endangered species list in 1967 and granted critical habitat in 1976 [1]. Nonetheless, it continued to decline, reaching a low point of 353,185 in 1996 [2]. Since then it has steadily increased and in 2005 was estimated at 457,374 [3]. Over 77% of hibernating bats winter in nine locations [4]. Indiana, Kentucky, and Missouri each contain three of these “Priority One” hibernacula (defined as sites where >30,000 bats hibernate), although numbers have dropped considerably below this level at some locations [2]. Currently, half of all the hibernating Indiana bats winter in Indiana where numbers decreased by 50,000 between 1960 and 1980, but rebounded somewhat in recent years [2]. In 2005, Indiana supported an estimated 206,610 Indiana bats [3]. Severe declines took place in Kentucky (where populations decreased by 180,000 between 1960 and 1997) and Missouri (where populations decreased by 250,000 between 1980 and 1997) [2]. Populations in Missouri have continued to decrease, but between 2001and 2005 populations in Kentucky increased from 50,047 to 62,380 [3]. Virtually all Indiana bats in the Northeast (>99%) hibernate in the state of New York, although they likely summer throughout a larger area within New England and perhaps into Canada [5]. Historically, 24 hibernacula were known to occur in New England, New York, and New Jersey [5]. The presence of Indiana bats has been documented at 14 of these sites (typically abandoned mines) since 1996 [5]. In 1975 the total rangewide Indiana bat population was estimated at 459,000, with the northeast region supporting only about 500 bats (<1% of the population) [5]. However, by 1995-1997, rangewide population estimates for the Indiana bat had declined to 353,000 individuals while numbers in the Northeast increased to around 30,000 (about 9% of the population) [5]. Thus the northeast is becoming increasingly important for this species continued survival [5]. Northeastern populations have continued to increase and in 2005,a population of over 56,000 bats was estimated to comprise over 12% of the total Indiana bat population [3]. The reasons for the Indiana bat's decline are not fully understood [2]. One serious cause is thought to be human disturbance of hibernating bats B if a bat is aroused from hibernation too frequently, its fat reserves can be exhausted before it is able to forage again in the spring [2]. Vandals have damaged caves and killed bats [2]. Population declines in Kentucky were largely attributable to the construction of gates and buildings at the entrances of two of the three most important hibernation sites [2]. Not only can this prevent bats from entering the cave, improper gate designs can result in changes of airflow patterns that in turn alter the cave climate [2]. [1] Currie, R.S. USFWS Federally Listed Threatened and Endangered Species of Importance to Mining in Proceedings of Bat Conservation and Mining: A Technical Interactive Forum, Airport Hilton, St. Louis, Missouri, November 14-16, 2000. |
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