Author Institution: Biology Department, Grove City CollegeA hibernating colony of Myolis lucijugus was studied for a five-year period. The members of the colony exhibited movement within the cave system during the winter months. The expectancy of finding a bat present in the cave was approximately two-and-a-half years after banding. The average distance of bats recaptured was 25±5 miles from the banding site

Brenner, Fred J.

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A FIVE-YEAR STUDY OF A HIBERNATING COLONYOF MY OTIS LUCIFUGUS1FRED J. BRENNERBiology Department, Grove City College, Grove City, Pa. 16127ABSTRACTA hibernating colony of Myolis lucijugus was studied for a five-year period. Themembers of the colony exhibited movement within the cave system during the wintermonths. The expectancy of finding a bat present in the cave was approximately two- and-a-half years after banding. The average distance of bats recaptured was 25±5 milesfrom the banding site.The availability of banding records has enabled investigators to study thebehavior and structure of hibernating bat colonies. In spite of the large numberof bats banded annually, numerous questions remain unanswered regarding thebehavior, ecology, and structure of these colonies. The problem of insufficientband returns, in addition to the problem of individual bats changing their hiber-nating site from year to year, continually plagues investigators. Furthermore,the annual variability within a colony may be too great to justify the time andexpense in the exact precision estimate in prediction of population numbers.Davis (1960) indicated that life expectancy can be calculated from the probabilityof survival as long as the age or the date of breeding is clearly defined and thepopulation size at each interval is known. Since the determination of the exactage of an individual at banding may be exceedingly difficult, the life expectancymay be more clearly defined as the length of time that a segment of the populationis present in a colony in subsequent years following banding.Another problem that confronts investigators involves the local movements ofindividuals within the cave system or the existence of movement between coloniesas suggested by Hall (1962) and Daan and Wichers (1968). Moreover, theanalysis of banding records and populations suggests that this may be a commonphenomena among bat populations. This study involves the analysis of fiveyears of banding records as prediction of behavior and structure of a bat population.METHODSThe study was initiated in 1965 with the colony being visited once or twice ayear for five years. Laurel Caverns is a commercial cave located seven-and-one-half miles southeast of Uniontown, Fayette County, Pennsylvania. Commer-cialization of the cave began in 1963 and the caverns were opened to the public inthe summer of 1964. The section of the cave inhabited by bats remained in anatural state, consisting of three large rooms connected by narrow passages. Allthe bats observed in rooms one and three could be collected without difficulty, butthe high ceilings in room two prevented the collection of between 50 and 75 batsthat inhabited the inaccessible portions of the room (fig. 1). Bats were collectedin each room, banded and released. The cave was visited during November andFebruary in 1966, 1967, 1968 and 1969 to determine the movement of bats withinthe cave as well to obtain a population estimate. The relative humidity andambient and substrate temperatures were determined at the end of the commercialarea and in the areas inhabited by the bats.The length of time that members of a population would be expected to remainin a colony was calculated from the population of banded individuals present in thepopulation in years subsequent to banding referred to as the probability of survivalby Davis (1960). The starting date of an age class was November and the lifexManuscript received March 7, 1973 (73-18).THE OHIO JOURNAL OF SCIENCE 74(4): 239, July, 1974240 FRED J. BRENNER Vol. 74expectancy was calculated by a method described by Davis (1960): where lc =the time interval in years; lx = the number alive at each time interval; Lx = anapproximation to the average alive during the time interval and is strictly the( L )average of initial and final population or . Tx is the cummulated total2of live individuals from the end of the column Lx, which is the total number ofyears that a bat may be expected to be present in the colony by Lx individuals.FIGURE 1. The hibernation of Myotis lucifugus in Laurel Caverns during November and Feb-ruary. Each circle represents ten individuals and the clear and solid circlesrepresent November and February, respectively. (A = air temperature; S = sub-strate temperature).From this: Ex is Tx/lx where Ex is the life expectancy or length of time that themembers of each age class can be expected to be present in the population. Onlyage group four and five were combined because of the low number of returnspresent in the fourth and fifth years following banding. These values may notbe an exact life expectancy but an indication of the length of time that an indi-vidual would be present in a colony. The movement of bats from the hibernatingcolony was determined by bands returned to the U.S. Fish and Wildlife ServiceBat Banding Office.RESULTS AND DISCUSSIONA total of 2,914 bats were banded during the five years of study. The popula-tion was estimated by the mark and recapture method in the winters of 1966through 1969. In this three-year period, the number of bats visiting the cavewas estimated to vary between 3,000 and 6,000 individuals. However, in thesesame three years between 788 and 892 individuals were captured (table 1) and allbut 50 to 100 of the bats observed in the cave accounted for 11 to 14 percent ofthe estimated population visiting the cave during the winter (table 1). Theproportion of males in the population varied between 62 and 83 percent and didnot appear to change seasonally except with the possibility of February 1969(table 2).Numerous other investigators have reported disproportionate sex ratios amonghibernating bat colonies in the eastern United States (Griffin, 1940; Mohr, 1945;No. 4 HIBERNATING MYOTIS LUCIFUGUS 241TABLE 1Estimated population size of Myotis lucifugus in Laurel Caverns,Pennsylvania from 1966 through 1969.Population estimate % of estimatedpopulation observedYear Male Female in colony1966-67 3100 ±230 2500 ±360 14.11067-68 2400 ±710 800 ±230 28.01968-69 3900 ±1000 2300 ±500 11.3Hitchcock, 1949; Hitchcock and Davis, 1964; and Davis, 1959). These studiesindicated that males comprise between 60 and 80 percent of hibernating coloniesof Myotis sp. Eptesicus fuscus and Pipistrellus subflavus. However, considerablevariations have been shown to exist in the sex ratios from one cave to another, aswell as in different geographical areas.TABLE 2The number of Myotis lucifugus banded and the proportion of males present inLaurel Caverns during a five-year period.NovemberFebruaryN1271965c?61.5N2155731966-67cf67.568.6N3944981967-6872.072.0N2083841968-69&76.982.5N515197072.5Bats were observed in greater numbers during November in Room One andapparently aggregated in Room Three in February (fig. 1). This apparent move-ment was supported by the observation that bats banded in room one duringNovember were recovered in room two and three in February, while bats taggedin room two and three during November were recaptured in these rooms in February(table 3). These movements might have been due in part to the disturbancesTABLE 3The movement of Myotis lucifugus banded in November and recapturedduring February in Laurel Caverns.Room123Total bandedin November -41423233Percent recaptured in FebruaryRoom 1oo oO O CDRoom2.04.82.92 Room 32.70.05.8resulting from banding, but since all bats were released at a central locations andapproximately the same amount of time was spent in each room, these activitieswere probably not a major contributing factor to the relocation of bats. Batswere apparently present in slightly larger numbers in February than in November(table 2). This aggregation of bats did not appear to be in response to temperaturesince the air and substrate temperatures were approximately the same in both242 FRED J. BRENNER Vol. 74rooms one and three. However, the lack of a large number of bats in room twomay be related to the cooler substrate temperatures. The relative humidity wasapproximately 68% in all three rooms. Therefore, the distribution of bats wasprobably related, at least in part, to temperature but not to relative humidity.The probability of finding a bat in a cave following banding was greater formales than for females. However, the length of time that an individual bat couldbe expected to be present in the population (table 4) was similar for both sexes.TABLE 4Life expectancy and survival rates of bats in Laurel Caverns basedon band recoveries.Age groupX0123401234lx*100074625329100026221411Lx*537685841155132418136MaleTx*7191821145615Female5746137196Ex*0.722.461.841.060.520.572.541.181.350.55*lx = number alive at each time interval.Lx = average of initial and final population.Tx = cumulated total of live individuals.Ex = life expectancy of members of each age class.For example, if a bat survives the first year after banding, these individuals maybe expected to be present in the population for approximately two-and-a-halfyears. Humphrey (1971) stated that the highest minimum survival, calculatedfrom 71,706 banded M. lucifugus were relatively low in the first year after bandingbut were relatively constant in subsequent years. Therefore, this expectancyestimate may be a useful figure in determining the length of time that a particularsegment of a population would remain in the hibernacula following banding.Furthermore, since it is possible to obtain this estimate from relatively few returns,this could eliminate unnecessary time and expense in banding large numbers ofbats. The proportion of banded bats present in the population from previousyears was 17.6 percent in November and 14.6 percent in February for males, whilefor females it was 9.0 percent and 9.4 percent for November and February, respec-tively. Hence, the number of unhanded individuals accounted for approximately84 percent of the male members and 91 percent of the female members of thepopulation. A recruitment of this magnitude could not be accounted for byreproduction; hence, some immigration must occur from other populations.Bats were recaptured at distances varying from approximately 9 to 90 milesaway from the hibernating colony. The average distance for the 21 bats re-captured was 25 ="=5 miles from the banding site (fig. 2). The sexes of the batsrecaptured consisted of 17 males and 2 females. The largest number of returnsNo. 4 HIBERNATING MYOTIS LUCIFUGUS 243was during the month of July with eight, and four returns each month were ob-tained during September and November, respectively. One returned during Mayand two in June. The majority of the returns were from locations northwest ofthe hibernating site in close proximity to the course of the Monongahela River andoccurred during the late summer and early fall, indicating that they were probablyreturning to the hibernating colony. This migratory movement was not due tothe break-up of maternity colonies, since the majority of the returns were malesand these results are consistent with those of Hall and Brenner (1968).L A K E ERIEFIGURE 2. The dispersal of bats from Laurel Caverns as calculated from bands returned tothe U.S. Fish and Wildlife Service.By capturing bats with mist nets at the entrance of Aiken Cave in Penn-sylvania, it was found that Myotis lucifugus began to visit caves beginning inearly July and continued throughout the remaining summer and early fall. InHall and Brenner's (1968) study, 571 and 485 bats were captured and bandedduring the summers of 1964 and 1965, respectively. However, the followingwinters, 14.3 percent and 11.1 percent, respectively, of the summer visitors weremembers of the hibernating colony. Hall and Brenner (1968) stated that theserecoveries indicated that the summer population was approximately 3980 and 4370in 1964 and 1965, respectively. The winter colony of Aiken Cave consisted of 15percent of the summer transients. This transient movement of bats indicatedthat a large number of bats visit a cave system but hibernate elsewhere. Further-more, Hall (1962) states that females tend to change their cave of hibernationmore than males, and Tinkle and Patterson (1965) and Daan and Wichers (1968)indicated that various species of bats tend to change their hibernation site fromyear to year as well as periodically during the same winter.This movement of bats between caves and/or within a cave system complicates244 FRED J. BRENNER Vol. 47the calculation of a precise estimate of bats present in a hibernating colony. Theestimated population based on banding returns suggests that many more batsare present in the cave than were observed during any visit. Moreover, the num-ber of banded individuals observed in Laurel Caverns in subsequent years follow-ing banding suggests that movement occurs between caves and/or within a cavesystem. These movements may account in part for the disproportionate sexratios that have been observed, since females may tend to change their hibernationsite more than males.LITERATURE CITEDDaan, S. and H. J.Wichers. 1968. Habitat selection of bats hibernating in a limestone cave.Zeit. Saugetierk. 33: 262-287.Davis, D. E. 1960. A chart for estimation of life expectancy. J. Wildl. Mgmt. 24: 344-348.Davis, W. H. 1959. Disproportionate sex ratios in hibernating bats. J. Mammal. 40: 16-19.Griffin, D. R. 1940. Notes on the life history of New England cave bats. J. Mammal. 21:181-187.Hall, J. S. 1962. A life history and taxonomic study of the Indiana Bat, Myotis sodalis. Read-ing Museum and Art Gallery Pub. No. 12. 68 pp.Hall, J. S. and F. J. Brenner. 1968. Summer netting of bats at a cave in Pennsylvania. J.Mammal. 49: 779-781.Hitchcock, H. B. 1949. Hibernation of bats in southeastern Ontario and adjacent Quebec.Can. Field. Nat. 63: 47-59.Hitchcock, H. B. and W. H. Davis. 1964. Notes on sex ratios of hibernating bats. J. Mammal.45: 475-476.Humphrey, S. R. 1971. Population ecology of the little brown bat, Myotis lucifugus, in Indianaand North-central Kentucky. Unpub. Ph.D. Thesis. Okla State Univ. 149 pp.Mohr, C. E. 1945. Sex ratios of bats in Pennsylvania. Proc. Penn. Acad. Sci. 19: 65-69.Tinkle, D. W. and I. G. Patterson. 1965. A study of hibernating populations of Myotis velifcrvelifer in northeastern Texas. J. Mammal. 46: 612-633.Tropical Macrofungi—Some Common Species. M. H. Zoberi. Hafner Publishing CompanyInc., New York, 1972. xvi + 158 p., 46 figs., 4 color pi. $16.95.This very expensive little book represents a systematic account of 104 species of tropicalmacrofungi, about half of which are cosmopolitan; several are either rare or infrequently en-countered. Contrary to the title, which conveys the impression of a worldwide compilation,emphasis is placed on species collected and described by the author in West Africa. Forty-sixof these are figured as line drawings by the author's wife and 16 by full-color photographs on 4plates.The book, according to the author, was designed as an aid for identifying some of the at-tractive macrofungi one might find in the tropics and, at the same time, as a contribution to anarea of mycology almost totally barren of such literature. The author is to be complimented onboth objectives, although neither is completely achieved in this work. The greatest fault isprobably not that of the author, but largely of the publishing company itself. At $16.95 thisbook is out of reach for most students in tropical countries and to those in other parts of theworld as well. One must seriously question, therefore, the value of this contribution if it isgenerally unavailable to those for which it was specifically intended.There are a number of misprints throughout the text. The diagnoses are inconsistent withrespect to the details included and in some cases include cumbersome and irrelevant details.The compilations are, however, accurate. The line drawings are realistic in form, but lackmagnifications, captions, and specific morphological characteristics. The color photographs areof little use in making specific or generic determinations and could have been omitted, thusreducing publishing costs.Having used this manual in the tropics, I find the lack of keys to species a serious handicapto the user. As a result, one must in many cases plod through many lengthy descriptions beforefinding the correct species or discovering that it is not even included in the book.There is a great need for manuals dealing with fleshy fungi of the tropics. The author shouldbe encouraged to continue his endeavors, but with more consideration given to the cost and scopeof subsequent publications.ROLAND SEYMOUR

A Five-Year Study of a Hibernating Colony of Myotis Lucifugus

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A Five-Year Study of a Hibernating Colony of Myotis Lucifugus

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