Ecology of three species of myotine bats in the Ozark Plateau

(Uploaded by Plazi for the Bat Literature Project) The purpose of this study was to learn of the size of Ozark bat populations, define habitats, ascertain sex ratios and describe seasonal patterns of movement of Myotis lucifugus. Myotis sodalis. and Myotis grisescens. Over a nine year period, 50,118 bats were wing-banded. Bats were taken from caves located in the southern half of Missouri, northwestern Arkansas, northeastern Oklahoma and west-central Illinois. Large cave entrances or double entrances were selected by maternity colonies of M. grisescens and hibernating lucifugus and IL_ sodalis. Caves with vertical entrances were preferred sites of wintering M. grisescens. There was little difference in temperature and relative humidity between caves with and without bats, but caves chosen by the majority of bats showed a greater range of temperature and relative humidity at all seasons. M. lucifugus hibernated at a mean temperature of 46.5°F. and at a mean relative humidity of 89.7 %\ M^ sodalis at 46.0°F. and 82.3 %\ and lit grisescens at 47.7°F. and 83.9 %. Maternity colonies of M^ grisescens lived a means of 63.2°F. and 94.5 %• Groups of sodalis and Mj_ lucifugus as well as ones of Mj. sodalis and grisescens were often found near one another in the same hibernaculum, but grisescens and lucifugus were never taken from the same cave during the winter. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission Sex ratios of all species of adults and juveniles were nearly equal over the nine year period. Some variation was noted in sex ratios from season to season because of differences in behavior of the sexes, but no segregation by sex was found during the winter. Of the 50,118 banded bats, 12.5$ were retaken; 9.9$ at the site ■where banded and 2.6$ elsewhere. Among M^ lucifugus there was a general migration north in summer and south in winter. Average distance traveled was 93*6 miles for males and 122.8 for females. All M;. lucifugus recovered north of the hibemacula and all maternity colonies were discovered close to rivers. Five per cent of the banded lucifugus returned to areas where banded; 0.5$ were found in other locations. M. sodalis showed moderate activity; 0 . 7 $ were recovered outside the area banded while 1 6 . 1 $ returned to the original site. There was a definite trend for this species to leave hibernacula in central Missouri for secluded hibernacula in eastern Missouri where the bulk of Mj_ sodalis were found wintering. In spring most flights away from the hibernacula were less than 20 miles, but some bats flew up to 300 miles north. Of the banded grisescens. 9 . 1 $ were retaken; 5*5$ at the site of banding and 3*6$ elsewhere. The major portion of M. grisescens in the Ozarks wintered in two caves; most bats from northeast Missouri, western Illinois and central Missouri went to a cave in west-central Missouri, while most bats in southwestern and south-central Missouri, northwest Arkansas and northeast Oklahoma wintered in a cave in southwest Missouri. Smaller hibernating groups were found in five other Ozark caves. Because Reproduced with permission of the copyright owner. Further reproduction prohibited without permission -3 this species was dependent on caves for shelter at all seasons, patterns of movement of grisescens were determined by location of caves. Both sexes frequently made flights of 169 miles. Censuses of bats in the Ozarks since 1954 indicate that the population of Mj_ grisescens has remained stable, but numbers of hibernating sodalis and Mj_ lucifugus have been greatly reduced in most caves in central Missouri. These losses are attributed to the increase in human disturbance.