Seasonal changes and overwintering of endoparasites in the bat (Myotis lucifugus) in a Southeastern Wisconsin hibernaculum

Eight digenetic trematode species (Phylum Platyhelminthes, Subclass Digena), one cestode species (Phylum Platyhelminthes, Class Cestoidea) and three nematode species (Phylum Nematoda) were recovered from the little brown bat, Motis lucifu us, at the Neda Mine hibernacu1um in southeastern Wisconsin. Bats displayed a rich and diverse helminth fauna throu~hout the year. Statistically significant seasonal variation was observed for two digenetic trematodes. Mean intensities and prevalence of parasites were highest in autumn and spring and lowest in summer. Highest species diversity occurred in autumn. Greater intensity and prevalence in autumn and spring were correlated with bat swarming and emergence patterns, behavioral phenomena which would also produce a more heterogeneous assemblage of parasites during these times of year. Myotis 1ucifu us retained a large and varied population of parasites throughout eight months of hibernation. INTRODUCTION This paper summarizes ecological studies that began in 1979 and are continuing through the present time on population ecology of the parasite fauna in the little brown bat, Myotfs lucifugus, at Neda Mines. The little brown bat is the most common bat in the United States from the standpoint of distribution and abundance (Barbour and Davis 1969). Although endoparasites of !:!. lucifugus have been recorded from other midwestern states including Kansas, Nebraska and Oklahoma (Nickel and Hansen 1967) and Iowa (Blankespoor and Ulmer 1970; 1972), little is known of the helminth fauna of Wisconsin bats (Coggins, in press). Since previous reports concerning the parasite fauna of Wisconsin bats were only species descriptions (Macy 1935; Rausch 1975; Font 1978) or new host/loca1ity records (Coggins et a1. 1981 I, the present study was undertaken to determine the nature of seasonal parasite population changes in!:!. lucifugus and to assess the effect of extended host hibernation on overwintering parasites. All the parasites recovered are endoparasites. Digenetic trematodes are parasites that have two hosts. The adult lives within a vertebrate while juvenile or larval stages reside within one or more invertebrates. All digenea reported herein use arthropods as the intermediate (invertebrate) host. Most cestodes also use two hosts in their life cycle. Although few of the life histories of both digenea and the cestode reported in the present study are known, the one cestode found is thought to use coleopterans as its intermediate -2host. Nematodes ~ary widely in their 1ife histories. They may ha~e an in~erte­ brate host or direct life cycle. MATERIALS AND METHODS Bats were collected from the Neda Iron Mine located in Dodge County, Wisconsin. Although this mine produced iron ore in the late 1800's it has been abandoned for almost 70 years. There are o~er 4.8 kID of subterranean tunnels and approximately 28 openings. This mine is surrounded by extensi~e culti~ated fields and lowland marsh; entrances are located amid isolated patches of woody and old field ~egetation. A hea~y snow co~er is normally found from December through March. The property is owned and administered by the UWM Field Station. This site is the largest known bat hibernaculum in Wisconsin and also ser~es as a summer roost for a smaller number of bats. In addition to !:!.. lucifugus, by far the most abundant species, three other bat species utilize the mine: the long-eared bat, !:!.. keeni; the big brown bat, Eptesicus fuscus; and the eastern pipistrelle, Pipistrellus subfla~us. Relati~e insect abundance near the trapping site was determined by sampling with a total of four plastic cylinders, coated with a sticky substance, placed along a transect. Traps were situated at ground le~el, 1, 2, and 3 m in height. Insects were identified to order when possible and counted. The most common insects at the time of this study were, in order of decreasing biomass, dipterans, coleopterans and lepidopterans (Rupprecht 1980). During 1979 and 1980 four to fi~e acti~e bats were collected monthly by either mist net or harp trap (Tuttle 1974). lJibernating bats were remo~ed from the mine in No~ember, 1979 and February, 1980. Since the initial two-year collection period I ha~e continued to collect smaller numbers of bats during the summer months only. Animals were transported li~e to the laboratory and necropsied for internal helminth parasites. Digenetic trematodes and cestodes were relaxed in hot water, fixed in A.F.A. and stained in Semichon's acetocarmine for species identification. Nematodes were identified as temporary mounts in lactophenol and stored in 70% alcohol with glycerine. Parasite counts were 10910 Y+l transformed before analysis by a Model II ANOVA (Sokal and Rohlf 1969). Voucher specimens of all trematode and cestode species ha~e been deposited in the Uni~ersity of Nebraska State Museum, Di~ision of Parasitology, No. 2125021258. RESULTS Eight species of digenetic trematode, one species of cestode and three species of nematodes were reco~ered from 59 !:!.. lucifugus during this study (Table 1). Pre~alence (percentage of hosts infected with one or more helminths) was greatest during spring and autumn while lowest in summer (Fig. 1).