Notes on the least brown bat Myotis subulatus leibii.

NOTES ON THE LEAST BROWN BAT: MYOTIS SUBULATUS LEIBII Author(s): Charles E. Mohr Source: Proceedings of the Pennsylvania Academy of Science , 1936, Vol. 10 (1936), pp. 62-65 Published by: Penn State University Press Stable URL: https://www.jstor.org/stable/44108904 JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at https://about.jstor.org/terms Penn State University Press is collaborating with JSTOR to digitize, preserve and extend access to Proceedings of the Pennsylvania Academy of Science This content downloaded from 216.73.253.237 on Wed, 26 May 2021 17:09:03 UTC All use subject to https://about.jstor.org/terms 62 PENNSYLVANIA ACADEMY OF SCIENCE NOTES ON THE LEAST BROWN BAT MYOTIS SUBULATUS LEIBII By Charles E. Mohr Reading Public Museum In January, 1931, I checked through Miller and Allen's bulletin on "The American Bats of the Genus Myotis and Pizonyx" in an effort to learn just what bats might be expected to occur in Pennsylvania. I was surprised to find that a newly-described species, Myotis sodalis, had been "taken in February from a cave in Center County, Pa." Communication with Vernon Bailey, the collector, led me to believe the locality was Woodward Cave. Accordingly, on January 28, 1931, I visited that cave, collected a dozen or so bats and brought them back to the zoology laboratory at Bucknell University. Hasty examination indicated that there were no Myotis sodalis among them. In the press of work the bats were neglected, several died, and later the mummified skins were carried along to the Heading Museum. There Earl L. Poole, assistant director, in looking over them recognized one of them as Myotis subulatus leibii, the Least Brown Bat, which, with the exception of a western Pipistrellus, is the smallest bat in North America. This was the first record for Pennsylvania, añd at the time of the report on its discovery,1 the ninth specimen recorded in the literature.2 In 1933, I made a careful check on museum and private collections, and although this species has been known since 1842, I learned of the existence of only 18 specimens.3 Since then Vernon Bailey has reported finding it in Colossal Cave, in the Mammoth Cave area,4 but has only a single specimen. This apparent scarcity over the rather extensive range shown in Map 1 is in marked contrast with its abundance in a small area in Centre and Mifflin counties, in central Pennsylvania, where during the last five winters I have collected, or marked and released, 124 specimens. As can be seen from the map, this area lies close to the geographical center of the Least Brown Bat's known range. 1 Mohr, Charles E., Myotis subulatus leibii and Myotis sodalis in Pennsylvania. Jour, of Mamm., XIII, 2, pp. 160-161, 1932. , 2 Miller, Gerrit S., Jr., and Allen, Glover M., The American bats of the genera 1 Myotis and Pizonyx, U. S. Nat. Bull. 144, p. 172, 1928. 3 Mohr, Charles E., Pennsylvania bats of the genus Myotis. Proc. Pa. Acad. Sci., VII, p. 42, 1933. 4 Bailey, Vernon, Cave life of Kentucky. American Midland Naturalist, XIV, 5, p. 462, 1933. This content downloaded from 216.73.253.237 on Wed, 26 May 2021 17:09:03 UTC All use subject to https://about.jstor.org/terms PENNSYLVANIA ACADEMY OF SCIENCE 63 Map 1. Distribution of Myotis s. leibii in U. S. Map 2. Distribution of Myotis s. leibii in Pa. As soon as it became apparent that the Least bat might be found with some regularity, I determined to mark individual bats. I used bird bands and ear tags* the first year; but finding tags superior I have used them exclusively since then.5 In the past five winters I have marked 84 bats, of which I have retaken 17, and of these, seven were observed more than once, one of them four times. Observations made at the time of collecting or marking bats, and upon recovering marked bats, lead to some interesting conclusions regarding the Least Brown Bat. In the first place, its range in Pennsylvania seems remarkably restricted. Although I have visited almost 100 caves in Pennsylvania and West Virginia in winter, returning to most of them at least once, I have found the Least Brown Bat in only seven caves. With the exception of Dulaney Cave, where a single specimen has been taken, all these caves are located in Centre and Mifflin counties. Map 2 shows the proximity of five of them, Woodward, Stover, Rossman, Aitkin, and Little Aitkin caves. Indeed a circle with a diameter of about 22 miles would include the five. These caves harbored 120 specimens. The two Aitkin caves and Stover Cave, which together contained over 100 Least bats, are located in heavy hemlock forests in the foothills of mountains which rise to 2000 feet. The other caves occupied are very s Mohr, Charles E., Marking bats for later recognition. Proc. Pa. Acad. Sci., VIII, pp. 26-30, 1934. This content downloaded from 216.73.253.237 on Wed, 26 May 2021 17:09:03 UTC All use subject to https://about.jstor.org/terms 64 PENNSYLVANIA ACADEMY OF SCIENCE close to such areas. The caves are usually small, and in the more extensive caves the Least bats are found close to the entrances. The Least Brown Bat is rivalled only by the Big Brown Bat, Eptesicus f. fuscus, in its ability to withstand severe weather, and by its almost continuous activity throughout the winter. Although my cave visits in late fall have been comparatively infrequent, I am convinced that few Least bats enter caves before the end of November, while other bats have been there for a month or more. December 1, 1935, is my earliest record. In the same way they have departed from the caves while the colonies of Myotis sodalis and M, I. lucifugus are still quite torpid. April 9, 1936, is my latest record for the Least Brown Bat ; other species remain in the caves for several more weeks. Their rarity at certain times in midwinter, and their abundance at other times only two or three weeks apart suggests that they may wander outside of the caves during moderately warm winter weather, returning when it becomes colder. For instance, on March 8, 1936, after six weeks of unusually severe weather, I found about 25 Least bats in Stover Cave, concentrated largely in the most sheltered portions of this rather open cave. In Aitkin Cave also, the Least bats were farther back than usual, it being surprising to find them much more than 100 feet from the entrance. The Least Brown Bat, along with other bats/ shows a definite homing sense. Marked bats occur in the same cave in different seasons, or if removed to another, they return to their original cave. For instance, #293 was captured and banded at Aitkin Cave on March 19, 1933, but released in Little Aitkin Cave, a quarter mile away. During the following winter I recovered it three times, each time back in Aitéin Cave. The history of #310 is somewhat different. It was captured and tagged in Little Aitkin Cave on February 25, 1934, and retaken there in March and April. On December 30, 1934, I visited Aitkin Cave on a hurried night trip and to my surprise found #310 there. It was not until February, after I had found it again, that I learned that the entrance of Little Aitkin Cave had been completely closed by a rock slide which occurred during the previous November. Deprived of its winter roost, #310 hibernated in the nearest accessible cave, which happened to be Aitkin Cave. Little has been learned regarding the breeding habits of this species. It is a solitary species, only once have I observed a cluster, and that contained only three individuals. The sexes are equally divided. Of the bats examined 60 have been males, 64 females; of those tagged, 33 were This content downloaded from 216.73.253.237 on Wed, 26 May 2021 17:09:03 UTC All use subject to https://about.jstor.org/terms PENNSYLVANIA ACADEMY OF SCIENCE 65 malés, 31 females. The fact that six males, but eleven females have been recovered might be interpreted as an indication that the females are less active and possibly stay nearer to the caves in summer. The only known summer records are from Sing Sing, N. Y., Plummer Island, Maryland, the Mammoth Cave area, Kentucky, and Mt. Bridges, Ontario. Only the last was a female. Exactly half of the Least bats found in Pennsylvania, 62, have been found in Stover Cave. This cave is unique in the respect that in it the Least bats usually outnumber all other species. Solitary Eptesicus /. fuscus, Pipistrellus s. subflavus, Myotis sodalis, M. I. lucifugus, and rarely M. keenii septenrionalis occur, but seldom as many as half a dozen of any one species. In other caves where the Least Brown Bat occurs regularly there are large colonies of Myotis I. lucifugus or M. sodalis . A study of Stover Cave6 leads one to the belief that the cave does not offer sufficient shelter for the social species, but provides enough protection for the hardy Least Brown Bat even in the coldest weather. The cave is just about 100 feet in extent, 15 to 30 feet wide, 6 to 20 feet high, and descends at about a 45° angle. It is rumored that the cave was once quite extensive but the fact that the bats are most numerous in severe weather indicates that they cannot retreat beyond the known passages. The observations here presented permit the following tentative conclusions : 1. The Least Brown Bat is limited in its winter range to very definite ecological situations. 2. Ecological conditions being favorable, this bat may occur in considerable numbers. 3. This species spreads out during summer, down from the mountains and the caves in which it hibernates. 4. Even in winter the Least Brown Bat shows considerable activity, besides showing its hardiness by entering the caves late and leaving them early. 5. Individuals of this species winter in the same cave year after year, as shown by the recovery of marked specimens. e Stone, Ralph W., Pennsylvania caves, 2nd edition. Topographic and Geologic Survey, Harrisburg, 1932. pp. 46-47. This content downloaded from 216.73.253.237 on Wed, 26 May 2021 17:09:03 UTC All use subject to https://about.jstor.org/terms