POPULATION DYNAMICS OF THE BIG BROWN BAT (EPTESICUS FUSCUS) IN SOUTHWESTERN OHIO
RICHARD S. MILLS, GARY "V. BARRETT, AND MICHAEL P. FARRELL
ABSTRACT.-Population dynamics of the big brown bat (Eptesicus fuscus) were studied for four years (1969-1972) in southwestern Ohio. Data were col· Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 Jected from 10,761 banded bats located in 81 summer nursery colonies and five winter hibcrnacuJa. Of 4506 immature big brown bats captured during the study period, 2223 (49.3 percent) were females. Contrary to previous studies, adult females outnumbered males in three of five winter hibernacula. Tooth wear of known age hats predicted population age class structure, but was a poor indicator of a specific age of a given individual. Survivorship curves for female bats were constructed from the percentage of banded individuals which were recaptured in subsequent years within the nursel}' colonies. Annual female mortality rate values for two large bat populations were 68.1, 28.7, and 72.0 percent and 89.5, 30.0, and 42.9 percent, respectively. Big brown bats recaptured at distances greater than 8 kilometers (km) (5 miles, mi) from the home colony were found to move in a southerly direction. In two instances record natural movements of 250 km and 290 km (155 and 180 mi) were recorded for E. fusctts. Larger populations of Eptesicus were located in the unglaciated region of the study area. Efficiency of young production per adult female was found to decrease with a corresponding increase in nursery population size. Merits of this inverse correlation efficiency as a potential population regulatol}' mechanism are dis cussed.
Several studies of the big browll bat (Eptesicus fuscus fuscus Beauvais) have been conducted; however, most of these have been limited either to a single season, a single colony or hibernacula, or to a restricted geographical area (for example, Phillips, 1966; Christian, 1956; Brenner, 1968; Davis et aI., 1968; Kunz, 1974). To date, the population ecology of this species remains poorly understood (Barbour and Davis, 1969), Eptesicus fuscus is relatively uncommon in southwestern Ohio, accounting for only 22 percent of all bats captured between 1969 and 1972 by mist netting over streams within the study area. Nevertheless, 10,761 big brown bats were banded and released by personnel of the Dayton Museum of Natural History in the four-year study. Data from winter studies of the big brown bat conducted from 1964 to 1973 by personnel of the Joseph Moore :Museum at Earlham College, Richmond, Indiana, were also used. It was the object of the present study to analyze the long-term population dynamics of the big brown bat under natural environmental conditions in southwestern Ohio. METHODS AXD MATERIALS Eighty-one summer nursel}' colonies and two winter hibernacula of big brown bats in southwestern Ohio were studied (Fig. 1). Three winter hibernacula in southern Indiana were also sampled during this period. Colonies were located by posting 591 592 JOURNAL OF MAMMALOGY Vol. 56, No.3
I 1______, __ I IT-- I Hardin I : Auglaize 1 : Mercer I Marion . i __ J_____ I • I ---,~--'---, I r------I 1<2 ~ " , I f-- Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 ie I I I Logan I " : ir_J I I D .~-----·-~I Shelby I 81 I elaware " 13 ,I • J I Da rke I • 1______• ,I Union : i _L __ ----
O. 1:'•
Ross
Pike
, ! Scioto
Kentucky ...... __.. Maximum Wisconsin glacial stage advance
FIG. I.-Map of study area in southwestern Ohio. Numbered black dots indicate the approximate locations of big brown bat nursery colonies. August 1975 MILLS ET AL.-BIG BROWN BAT IN OHIO 593
"bats wanted" signs, an extensive newspaper campaign, radio and television appeals to the public, and by communications with extennination agents, game wardens, and others. In most instances population estimates were made upon entrance to a nursery struc· ture by visual observation. Evening flight counts were used when it was considered undesirable to disturb the bats and to substantiate our visual observations. This method has been used successfully by many researchers as summarized by Humphrey
(1971). Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 Populations were sampled by hand with long forceps and nets. A bee smoker was sometimes used to drive bats out to where they could be captured. Mist nets were placed over streams and cave entrances to capture bats outside the colonies. Bats were aged, by examination of the cartilaginous areas of the finger joints (Barbour and Davis, 1969), sexed, reproductive condition determined, classified by tooth wear, banded with Fish and Wildlife Service bat bands and released near the site of capture. Nurseries were visited infrequently during the height of parturition in order to avoid disturbance to the population at this critical time. Relationships between population size and latitude, longitude, altitude, and distance of the nursery to water were evaluated by Pearson's simple correlation coefficients, while differences in population size between glaciated (Wisconsin stage advance) and unglaciated areas (Fig. 1) were tested by a Student's t-test. Tooth wear for 208 bats of known age was estimated to establish an age class tooth wear relationship. The upper canine teeth of known age bats were classified as follows; 0 to 10 percent worn; 11 to 25 percent worn; 26 to 50 percent worn; 51 to 75 percent worn; 76 to 100 percent worn. These classifications were easily used in the field and allowed the processing of large numbers of hats in a relatively short period of time. Survivorship curves for female big brown bats from two different colonies were plotted from cohort data based on the number of banded bats recaptured at the home colonies in years subsequent to banding. Most recaptures of banded bats away from the maternity colonies were made by citizens who reported the hand number to the Fish and Wildlife Service. The test statistic Z of the Rayleigh test and the test statistic U of the V test as described by Durand and Greenwood (1958) and Batschelet (1972) were used to test for a nonrandom distribution and for movement in a predicted direc tion, respectively, for those bats captured away from the maternity colonies. Although some bats were recaptured at distances less than 40 km (25 mi), 80 km (50 mi), or 120 km (75 mi) from the release point, it was assumed for analysis that bats would have continued on the same course and crossed the nearest radii at the angle from the release point at which they were recaptured. A "dummy variable" multiple regression analysis was used to evaluate the predictive relationships among the ability of females to rear volant young successfully, nursery population size, and sample year.
RESULTS AND DISCUSSION Summer Nursery Colonies Eighty-one summer nurseries of the big brown bat were located in man-made structures such as attics of houses, barns, and churches in southwestern Ohio (see Fig. 1). Small nursery colonies « 100 individuals) were sometimes located in open barns, under signs and shutters, or under the eaves on the exterior of buildings. In one case, several females and their young took up temporalY residence in a hollow tree on the grounds of the Dayton Museum of Natural History, a five mile displacement from their nursery. This par ticular and unique residency has been previously summarized by Davis (1969). 594 JOURNAL OF MAMMALOGY Vol. 56, No.3
Nursery colonies of the big brown bat were twice located in the same building with nurseries of the little brown bat, Myotis lucifugus (sites 13 and 57, Fig. 1). In one case the two species occupied roosts at opposite ends of a tobacco shed. In the other instance big brown bats moved into the attic of a church already colonized by 600 little brown bats. No big brown bats had been observed in the attic in 1969 or 1970. By July 1971, an estimated Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 20 big brown bats occupied the attic. This colony increased to 50 individuals by August 1972. The number of little brown bats, meanwhile, decreased to approximately 150. The reason for this decline in population density of the little brown bat is unknown. However, because roost space was apparently abundant, differential resource utilization (for example, Kunz, 1974) may have influenced the decline in the little brown bat population density. Eighty-nine percent of the populations located were within 0.8 km (0.5 mi) of water. The greatest distance of any nursery to water was 1.8 km (1.1 mi). However, those populations located nearer water were not significantly larger than other populations (r = 0.01, P > 0.95). Also, no significant correlation was found between population size and latitude (r = -0.07, P > 0.53), longitude (r ~ -0.15, P > 0.13), and altitude (r ~ --0.07, P > 0.50). Significantly larger populations of big brown bats were found in the un glaciated portion (mean = 220, SD ± 201) of the smdy area than were found in the glaciated part (mean = 128, SD ± 129) of the Wisconsin stage advance (t == 2.78, df ~ 105, P':;; O,ol). Humphrey and Cope (1974) also reported greater numbers of Myotis IUcifugus from the unglaciated portion of Indiana. This difference may be attributed to (a) more hibemacula present in the hilly topography, (b) more nursery structures available in the form of vacant houses and farm buildings, or (c) less use of pesticides and, perhaps, a more abundant insect food source due to a difference in farming activities between the two areas. Nursery colonies in thc study area ranged in size from eight to 700 with a mean of 154 (SD ± 157) individuals. The median for these data was 90. Rysgaard (1942) reported a colony of big brown bats with a population size of 400, and Barbour and Davis (1969) found populations ranging from 20 to 300 individuals in Kenmcky. The larger nursery population densities located in this study exceed those previously reported. Observations at several colonies indicated that at least a few big brown bats remained within the nursery colony structure throughout the winter. Most females appeared at the nurseries about 1 May. Young were born over a period of at least a month beginning near 1 June. For example, 107 young were counted in the Sinking Springs nursery (nursery 34, Fig. 1) on 11 June 1972 and two newborn young were found at \Vinchester (nursery 2) as late as 15 July 1969. Our findings substantiate the wide variation in reproductive time as reported by Smith and Goodpaster (1963) and Kunz (1974). Of 74 adult females examined during late June and early July 1971, 67 (92 percent) were either pregnant or lactating. Two young per female were observed in August 1975 MILLS ET AL.-BIG BROWN BAT IN OHIO 595
all cases. Of 4506 immature big brown bats captured between June 1969 and September 1972, 2223 (49.3 percent) were females. Observations by Gates (1937), Griffin (1940), Reynolds (1941), Cagle and Cockrum (1943), Hitchcock (1949), and Kunz (1974) also suggest that the ratio of male to female young should approach 1:l.
Male big brown bats comprised less than two percent of the nursery Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 population in the spring and early summer. In late summer (August-Septem ber) adult males moved into the nurseries, but never constihlted more than 10 percent of the total population. On the basis of these observations, we assume that most males roosted outside the nursery structure either singly or in small groups (Barbour and Davis, 1969). A few solitary males were located in mortise joints of bam beams, under shutters, in wood piles, and in the attics of houses not containing nursery colonies. A male was observed daily during July and August of 1969 roosting between the logs on the front porch of a cabin ncar Dayton, Ohio. This bat usually returned to the same roost indicating that roost site fidelity may be characteristic of solitary males.
Winter Populations Most long-term studies of the big brown bat in hibernation show that males outnumber females and that such colonies are usually located in caves, tunnels, or sewers (Rysgaard, 1942; Mohr,' 1945; Beer, 1955; Beer and Richards, 1956; Mumford, 1958; Davis, 1963; Hitchcock, 1965; Phillips, 1966; Goehring, 1972). Although hibernation in buildings has been reported for the big brown bat (Toner, 1935; Swanson and Evans, 1936; Wetmore; 1936; Whclden, 1941; Goehring, 1972), such accounts arc considered to be rare and are based on a small (1-30 individual) sample size. ,,,jntering populations of the big brown bat in southwestern Ohio were small in number and not easily located. Winter roosting sites for the majority of the population are not known. However, two wintering populations located and investigated from this area (near nursery sites 70 and 81, Fig. 1) were exceptional because females outnumbered males (Fig. 2) and because they were both associated with buildings. Of 85 big brown bats captured in a cave at Cave Lake, Pike County, Ohio, 25 (29 pcrcent) had been previously banded in nearby unheated buildings containing summer nursery colonies (nurseries 34 and 70, Fig. 1). Twenty of the recaptures were females. The proximity of the cave to these nurseries may account for the large number of females in this winter popula tion. Also, a school building near Bellefountain, Logan County, Ohio (nursery 81), was heated and some bats remained in the attic all year, perhaps ac counting for the abundance of females in this winter population (see Fig. 2), Of three winter populations located in Indiana by personnel from the Joseph Moore Museum at Earlham College, Richmond, Indiana, one (\Vyun dotte Cave, sec Fig. 2) had significantly fewer males than females (x~ = 8.72, df = 1, P ~ .01). Personnel of the Joseph Moore Museum have also studied 596 JOUR~AL OF MA1'IMALOGY Vol. 56, No.3
100
% FEMALE 80 ~ Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 Z Q ~ D 60 0'" ~ ~ 0 u
~ 40 Z w U ~ w ~ 20
b z d ~ Ci...... ~ ~'" ~U~ . .n
Age", 0.16(PTW)-o.OOl (PTW2)
6 R2=O.90
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2
20 40 60 so Tooth wear c%) FIG. 3.-A comparison of the percent wear on the upper canine teeth of known age bats. Area between the dotted lines represents 95 percent of all individuals sampled. PTW equals percent tooth wear.
Tooth wear of bats has been studied by Twente (\955), Christian (\956), and Stegeman (1956) in efforts to find an effective means of aging bats. These studies have been criticized because bats of a known age were not used (Hall et al., 1957; Barbour and Davis, 1969). It is apparent from the present study that tooth wear is useful for indicating the relative age structure of a population (Fig. 3). Such an aging criterion would be valuable because productivity, dispersal, and mortality are age specific parameters. Tooth wear, however, was found to be less useful for indicating the specific age of individual big brown bats due to the wide variation between individual mem· bers of the population (Fig. 3).
Survivorship Fig. 4 shows survivorship curves for llO female big brown bats from the Sinking Springs colony (nursery 70, Fig. 1) and for 142 female big brown bats from the \Vinchester colony (nursery 2). These bats were banded as volant immatures, and the survival curves were based on the actual number of banded bats which were recaptured in the nurseries in years subsequent to banding. Because it was impossible to capture the entire colony, the re· suIting survivorship curve is probably somewhat lower and indicates higher mortality than was actually the case. Female bats from Sinking Springs showed annual mortality rates of 68.1 percent for the first year, 28.7 percent for the second year, and 72.0 percent for the third year. Females from 'Vin· 598 JOURNAL OF MAMMALOCY Vol. 56, No .. 3
1000 Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021
<" > 100 > "~ 00
x "L.______,
AGE IN YEARS FIG. 4.-SUI'viVOfShip curves for female E. fuscus banded as volant young in nurseries at Winchester, Adams County, Ohio (closed circles) and Sinking Springs, Pike County, Ohio (X). chester showed annual mortality rates of 89.5 percent for the first year, 30.0 percent for the second year, and 42.9 percent for the third year after banding. These percentages represent the number of marked females returning to the colony each year. These data do not account for those individuals which may have survived but failed to rehun to the natal roost. It should be pointed out that the overall population of the Sinking Springs nursery decreased ap~ proximately 88 percent, and that of the \'Vinchester population decreased approximately 60 percent during the study period, perhaps the result of disturbance brought about by our study (Constantine, 1970). A larger per centage of the cohort would presumably have survived to subsequent years in an undisturbed, stable population. Beer (1955) calculated mortality rates of 62, 33, and 23 percent, respec tively, for three years following banding for unaged Eptesicus fuscus captured during the winter. Beer's mortality rates are somewhat lower than those obtained in this study, perhaps due to a greater number of older individuals within his populations. His populations suffered a 60 percent decrease dur ing the study period. Studies by Goehring (1958, 1972) indicate first year mortality rates of greater than 50 percent. Studies of Mohr (1945) and Beer ( 1955) indicate little difference in mortality between sexes.
M ovemellt Patterns The big brown bat seldom moves far from its natal colony (Beer, 195:5; Davis et al., 1968; Barbour and Davis, 1969). Of the 10,761 big brown bats August 1975 MILLS ET AL.-BIG BROWN BAT IN OHIO 599
NORTH = MEAN VECTOR x =RELEASE POINT • =RECAPTURE POINT Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021
WEST EAST
• • •
• • SOUTH
FIG. 5.-Directional movement of big brown bats released at the home nursery and recaptured at distances greater than 8.0 km (5 mil from home. banded in the four years of study, 265 males and 1677 females were later recaptured at the banding site. Interestingly, no males and only seven fe males were recaptured in summer nurseries other than the ones in which they were originally banded. Three females moved from Cave Lake (nursery 70, Fig. 1) 8.0 km (5 mi) to Sinking Springs (nursery 34), one moved from Germantown (nursery 64) 102.4 km (64 mi) to Cave Lake, one moved from a nursery in Scipio, Indiana, 51.5 km (32 mi) to the Germantown nursery, one flew from Winchester (nursery 2) 25.6 km (16 mi) to Cave Lake, and one banded in Higginsport (nursery 5) was recaptured 62.4 km (39 mi) away at Cave Lake. \Ve have no way of knowing how much of this move ment was caused by our disturbance of the nurseries or how many bats emigrated to unknown colonies. Natural movement for both sexes of over 80.0 km (50 mi) were recorded nine times. The longest movement was made by an immature female-from Kettering, Ohio, to Danville, Illinois, a distance of 288.0 km (ISO mi). An immature male moved from Dayton, Ohio, to Goshen, Indiana, a distance of 600 JOURNAL OF MAMMALOGY Vol. 56, No.3
248.0 km (155 mi). These movements exceed the previously recorded natural movement of 227.2 km (142 mi) for this species (Mumford, 1958), Natural movements of greater than 8.0 km (5 mi) were plotted on a circle diagram (Fig. 5) with the nursery-release point as center. The Z-tcst and U-test were used to test for nonrandom distribution and for movement in a predicted direction, respectively. Movement was found to be significant Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 (P '" .05) for the 40 km (25 mil. 80 km (50 mil and 120 km (75 mil radii. Bats moved in a nonrandom southerly direction (Z25 := 5.44, U 2" = 3.24;
Z5Q = 4.33, U 50 = 2.94; Zt5 := 3.09, U.5 = 2.33, respectively) from the release point. Small sample size (N = 3) precluded the analysis of movement at distances greater than 120 km (75 mi). Southerly movement for this species may be due to vestigial migratory behavior although movement was recorded for all months of the year. The number of recorded monthly movements for the 25 bats that moved greater than 8.0 km from January through December was 2, 2, 3, 1, 4, 1, 1, 4, 1, 2, 2, and 2, respectively. Migration, although not characteristic of this species (Smith and Goodpaster, 1958), may persist in some individuals. Fall migra tion south to a warmer climate may have been of survival value prior to human habitations which presently serve as winter hibernacu1a.
Population Regulation Sixty-six colonies of varying size were compared for reproductive success. It was assumed that each female had an annual reproductive potential of two young (Davis et al., 1968). Reproductive success was calculated as a ratio of the number of lactating and postlactating adult females to the number of volant young for those nurseries sampled between 15 July and 15 August, 1969 to 1972. Samples taken after 15 August were not used in order to avoid any bias due to early autumn nursery emigration. A log-log "dummy variable" regression analysis, as described by Draper and Smith (1966), was used to compare rearing efficiency to population size, and a significant relationship (P ~ 0.01) was found for all years (Table 1). Thus, at higher population densities the number of young reared by each female decreased. Although this relationship is significant, the low R2 value obtained indicates a considerable variation unaccounted for by population size. A partial explanation for this variation was obtained by comparing data gathered in years 1970 to 1972 with data obtained in the arbitrarily selected "base year" of 1969. The year 1972 differed significantly (P ~ .01) from the base year (Table 1). Crowding has been shown to reduce the reproductive success of some small mammal populations (Rowe et al., 1964; Christian, 1960). This crowd ing effect has not been shown for bats, and it has been assumed that coloniza tion is advantageous because of thermoregulation (Twente, 1955, 1956; Herreid, 1963). It does appear, based on the results of this study, that there is a density-dependent factor or set of factors operating within each August 1975 MILLS ET AL-BIG BROWN BAT IN OHIO 601
TABLE l.-"Dummy" variable multiple regression aTUllysis of the effect of sampling year OIJ the relationship between population size and the ratio of young bats to adult females. Significance (*.) = p ~ .01, NS = not significant.
Analy~is of variance Source DF EMS F R'
Regression 4 1.5565 8.00** .36 Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 Error 56 0.1948
Regression coefficients and statistics of fit Soun·c regression codficient, t value ------~--- Intercept 1.4817 5.02** "Dummy" variable' (1970 ) -0.2427 -1.45 NS ( 1971) --0.0537 -0041 NS (1972 ) --0.8981 -3.30** Log," (Pop. size) -0.2237 -3.65**
--.--c-----;-~~~~~~~~~~~~~- , lflo9 was us"d a'i hase y"ar.
Eptesicus fuscus population which helps to maintain an optimum population size. Further studies are needed to outline the details of this regulatory mechanism. Nurseries were infrequently examine:d during the peak of parturition to avoid unnecessary disturbance of the population. Consequently it is not known if fewer young are born to females in larger colonies, as is true for other small mammals (Rowe et al., 1964; Sadlier, 1965). Few young were found on the floors of nurseries. However, this may be because predators consume dead and dying bats or because dying immature move outside the structure or into secluded comers. In large colonies young bats may have trouble competing with adults for a limited food supply, or adults may have difficulty feeding both themselves and their young. This would be especially true in years during which insect populations were reduced or irregular. The big brown bat's diet is mostly comprised of Coleoptera and Hymenoptera (Hamilton, 1933; Whitaker, 1972). Although food has not been shown to be a limiting factor for bats, other studies have shown that it limits fecundity in insectivorous birds (Nice, 1937; Lack and Lack, 1951), The summer of 1972 was characterized by exceptionally low temperatures. Monthly lows of 4.4° C, 6.7 0 C, and 7.3 0 C were recorded during the months of June, July, and August, respectively. These temperatures are considerably below the average lows of 13.5° C, 17.9° C, and 15.5° C recorded for these months in other years (temperature data were obtained from the Cox Munic~ ipal Airport, Vandalia, Ohio). Temperature has been shown to affect greatly the development and time of maturation of insects (Lack and Lack, 1951; Bursell, 1964) and bats (Racey, 1969). A reduced or irregular insect emer gence due to decreased temperatures is one possible explanation for the 602 JOUR~AL OF MAMMALOGY Vol. 56, No.3
reduced young rearing efficiency of the big brown bat observed in the summer of 1972. It is hoped that follow-up studies will answer many of the questions raised by this study, and that other similar long-term studies will be carried out with this and related species in other geographical areas. Only through long
term studies of this nature will the ecology of the big brown bat become Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 better understood.
ACKNOWLEDGMENTS We thank the personnel of the Dayton Museum of Natural History and the Joseph :\foore Museum at Earlham College for support of the field work. We express our gratitude to Drs. Douglas H. Taylor, Miami University, Roger W. Barbour, University of Kentucky, Stephen R. Humphrey, Florida State Museum, W. Wilson Baker, Tall Timbers Research Station, and James B. Cope, Earlham College, for their constructive criticism of the manuscript. Thanks are also due the Mammal Section of the Bird and Mammal LaboratOlies, National Museum of Natural History, for bat bands and for use of recapture data.
LITERATURE CITED BARBOUR, R. W., AXD W. H. DAVIS. 1969. Bats of America. Univ. Press Kentucky, Lexington, 286 pp. BATSCHELET, E. 1972. Recent statistical methods for orientation data. Pp. 61-91, in Animal orientation and navigation (S. R. Galler, K. Schmidt-Koenig, G. J. Jacobs, and R. E. Belleville, cds.), National Aeronautics and Space Adminis tration, NASA SP-262, 606 pp. B~En, J. R. 1955. Survival and movements of banded big brown bats. J. Mamm., 36:242-248. BEER, J. R., A::-J"D A. G. RICHARDS. 1956. Hibernation of the big brown bat. J. Mamm., 37,31-41. Bm:.'-"ER, F. J. 1968. A three year study of two breeding colonies of the big brown bat, EptesiclIs fuscus . .T. Mamm., 49:775-778. BUHSELL, E. 1964. Temperature and humidity relations. Pp. 323-361, in Physiology of Insecta II (M. Rockstein, ed.), Academic Press, ~ew York, 640 pp. CAGLE, F. R, A::-J"D L. Cockrum. 1943. Notes on a summer colony of Myotis lllcifuglls lucifugus. J. Mamm., 24:474-492. CHRISTIAN, J. J. 1956. The natural history of a summer aggregation of the big brown bat Eptesicus fuscus fuscus. Amer. Midland Nat., 55:66-95. 1960. Endocrine adaptive mechanism and the physiologic regulation of popu lation growth. Nav. Med. Res. Inst. Lect., Res. Series, 49:60-62. CO.'1STANTlKE, D. G. 1970. Bats in relation to thc health, welfare and economy of man. Pp. 319-449, in Biology of bats, Vol. 2 (W. Wimsatt, ed.), Academic Press, New York, 477 pp. COPE, J. B., AND R. S. :MILLS. 1970. Big brown bat (Eptesicus fllscus) movement in Tunnel Cave, Clifty Falls State Park, Indiana. Proc. Indiana Acad. Sci., 79;439. DAVIS, W. H. 1963. Sex ratios of hibernating bats. A. S. B. Bull., 10:26. ~~-. 1969. Here and there. Bat Res. News, 10:38. DAVIS, W. H., R W. BARBOUR, AND M. D. HASSELL. 1968. Colonial behavior of Eptesicus fllscus. J. Mamm., 49;44-50. DRAPEH, N. R, A~D H. S~IITH. 1966. Applied regression analysis. John Wiley and Sons, Inc., i\"cw York, 134-142 pp. August 1975 MILLS ET AL.-BIG BROWN BAT IN OHIO 603
DURAND, D., AXD J. A. GIIEE:- 201-206. Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 GlUFF!!\!, D. R. 1940. Notes on life histories of New England cave bats. J. Mamm., 21:181-187. HA:\ULTON, W. J., JR. 1933. The insect food of the big brown bat. J. "Mamm., 14: 155-156. HALL, J. S., R. J. CLOUTIER, ASD D. R. GRIFFI"'. 1957, Longevity records and notes on tooth wear of bats. J. Mamm., 38:407-409. HERREID, C. F. II. 1963. Temperature regulation of Mexican free-tailed bats in cave habitats. J. Mamm., 44:560-573. HITCHCOCK, H. B. 1949. Hibernation of bats in south-east Ontario and adjacent Quebec. Canadian Field Nat., 63:47-59. 1965. Twenty-three years of bat banding in Ontario and Quebec. Canadian Field Nat., 79:4-14. HtJMPHHEY, S. R. 1971. Photographic estimation of population size of the Mexican free-tailed bat (Tadarida brasiliensis). Amer. 1-lidland Nat. 86:220-22.3. HUMPHREY, S. R., AND J. B. COPE. 1974. Population ecology of the little brown bat Myotis lucifu{.!us in Indiana and north-central Kentucky. Spec. Pub!., Amer. Soc. Mamm., in press. Ku"iz, T. H. 1974. Reprod\lction, growth, and mortality of the vespertilionid bat, Eptesicus fllseus, in Kansas. J. Mamm., 55:1-13. LACK, D., A:- STEGEMAN, L. C. 1956. Tooth development and wear in Myotk J. Mamm., 37: 58-£3. SWANSO:-'-, C., AND C, EVANS. 1936. The hibernation of certain bats in southern Minnesota. J. Mamm., 17:39-43. TO:-lER, C. C. 1935. A note on Eptesicus fUscus. J. Mamm., 16:147. TWENTE, ]. W., In. 1955. Aspects of a population study of cavern-dwelling bats. J. Mamm., 36:379-390. Downloaded from https://academic.oup.com/jmammal/article/56/3/591/848889 by guest on 01 October 2021 1956. Ecological observations on a colony of Tadarida mexicana. }. Marum., 37,42--47. WHELDEN, R. M. 1941. Hibernation of Eptesicus fuseus in a New Hampshire building. J. Mamm" 22;203. WETMORE, A. 1936. Hibernation of the brown bat. J. Mamm., 17:130-13l. WHITAKER, J. O. 1972. Food habits of bats from Indiana. Canadian J. Zool., 50:877- 883. Department of Zoology, Miami University, Oxford, Ohio 45056 (present address of Mills.' Aullwood Audubon Center, 1000 Aullwood Road, Dayton, Ohio 45414). Sub~ mitted 9 August 1974. Accepted 12 Febmary 1975.