Behavioural Variation in Echolocation Pulses of the Northern Bat,Eptesicus nilssoni

17 northern bats, comprising a maternity colony, were observed and recorded in their natural feeding habitat in southern Sweden. They searched for insects in more or less open habitats, 2–50 m above ground, and usually established individual feeding territories, which were patrolled in straight or slightly curved flight paths at rather constant altitudes. Duration, bandwidth, amplitude, repetition rate and, to a lesser extent, terminal frequency of the echolocation pulses varied according to feeding habitat and situation. In general, long (13.0–17.7 ms), loud, shallow frequency-modulated (FM) signals were used during search flight near treetop level (15 m) or above. At lower altitudes, steep FM-components were added, and the terminal shallow-sweep portions were shortened. These pulses were 6.3–13.4 ms long. Steep FM-signals of short (0.4–8.4 ms) duration and relatively low amplitude were used in the vicinity of obstacles or targets.     

Influence of night length on home range size in the northern bat Eptesicus nilssonii

The northern bat Eptesicus nilssonii is widespread in Fennoscandia, with breeding populations well above the Arctic Circle. I studied this species at its extreme northern limit, at 69°N in Norway. I radio-tracked 17 bats from 2 maternity roosts during 2003–2006 to study the influence of the midnight sun and increasing lengths of darkness on activity (time spent out of roost) and home range size. Activity and home range was highly correlated with night length (light intensity); both increasing progressively with season. Bats were classified into 3 groups based on the time of the season they were tracked (basically July, August and September–October); short activity (average 1.57 h) and small home range (average 0.91 km²), medium activity (3.69 h) and medium-sized home range (4.58 km²), and long activity (4.80 h) and large home range (17.2 km²). Bats visited roosts several times during the night, and the duration of roost visits increased significantly by group. The number of periods out of roost increased from the first to the second group (1.45 vs. 2.36 flight periods per night), but insignificantly to the third group (2.37 flights). The most significant increase in activity and home range was associated with the first flight of juveniles in early August. These bats appeared to have a threshold level of around 1700 lux for activity out of roost, with little difference between light levels at emergence and return (the second group returned in significantly poorer light than they emerged in). Although the northern bat at this extreme latitude had adapted to the ambient light conditions, the bright nights under the midnight sun and the short season strongly reduced their window of opportunity for activity and may possibly reduce survival and reproductive success.     

Seasonal Changes in Body Mass and Activity of Digestive Enzymes in Eptesicus nilssonii (Mammalia: Chiroptera: Vespertilionidae) during Hibernation

Journal of Evolutionary Biochemistry and Physiology - Hibernation can be considered as a circannual cycle of feeding and fasting. During winter, the absence of dietary substrates in fat-storing...     

Northern bats, Eptesicus nilssonii, use vision but not flutter-detection when searching for prey in clutter

We investigated the detection cues used by the aerial-hawking bat Eptesicus nilssonii foraging in a cluttered environment. The bats can detect and attack rapidly moving targets within the clutter, i.e. below grass panicles, by using prey motion as a cue. Stationary objects are attacked only above the grass, but still within the clutter overlap zone. To test if the bats were guided by flutter from moth wings or by vision when searching for stationary targets, they were presented with male ghost swifts mounted on top of steel wires. There was no difference in attack frequency on live, fluttering moths compared to dead and spread ones. However, when comparing white and dark moths, we found a significantly higher attack frequency on white ones. As the attacks always were guided by echolocation calls, we hypothesize that northern bats, at least in the initial search phase, use visual cues as a complement to detect stationary ghost swifts.     

Variation in body composition of female big brown bats (Eptesicus fuscus) during lactation

Most small mammals support the nutritional requirements of milk production by increasing food intake. However, when nutrient intake is low, maternal body reserves may be mobilized to maintain adequate milk output. We examined patterns of body composition, including dry matter, fat, protein, and mineral content in big brown bats, Eptesicus fuscus, during lactation. Concentrations of fat and phosphorus were markedly lower in lactating mothers during week three of lactation than during the first two weeks, but these constituents rebounded to previous levels in the fourth and fifth week. Rapid recovery from fat depletion suggests that females are able to adjust to changes in demands for energy. The decrease in phosphorus during mid-lactation suggests bone demineralization, but an interspecific comparison of adult concentrations of minerals prevalent in bone suggests that mineral concentrations may never reach critically low levels in reproductively active females.     

Ectoparasites in an urban population of big brown bats (Eptesicus fuscus) in Colorado

Ectoparasites of an urban population of big brown bats (Eptesicus fuscus) in Fort Collins, Colorado, were investigated during summers 2002, 2003, and 2004. Eleven species of ectoparasites were found (the macronyssid mite Steatonyssus occidentalis, the wing mite Spinturnix bakeri, the myobiid mites Acanthophthirius caudata and Pteracarus aculeus, the chirodiscid mite Alabidocarpus eptesicus, the demodicid mite Demodex sp., the chigger Leptotrombidium myotis, the soft tick Carios kelleyi, the batfly Basilia forcipata, the batbug Cimex pilosellus, and the flea Myodopsylla borealis). Five species were analyzed by prevalence and intensity (C. pilosellus, M. borealis, L. myotis, S. bakeri, and S. occidentalis) based on 2161 counts of 1702 marked individual bats over the 3 summer study periods. We investigated 4 factors potentially influencing prevalence and intensity: age class of the host, reproductive status of adult female hosts, roosts in which the hosts were found, and abiotic conditions during the year sampled. The macronyssid mite, S. occidentalis, was the most prevalent and abundant ectoparasite. Adult big brown bats had more ectoparasites than volant juveniles for most of the species analyzed. In a sample of known age bats at 1 large colony, bats of 4 yr of age or greater had higher ectoparasite loads of S. occidentalis and S. bakeri when compared with younger bats. Lactating female bats had the highest prevalence and intensities of most ectoparasites. Annual differences in ectoparasite prevalence and intensity were related to temperature and humidity, which can affect the nidicolous species of ectoparasites. Residents of 2 buildings sprayed insecticides in response to Cimex sp., and this appeared to reduce ectoparasitism of S. occidentalis and C. pilosellus present at these buildings. Intensity of S. occidentalis had no influence on annual survival of big brown bats.     

Length and Sequence Variation in Evening Bat D-Loop Mtdna

Length variation in D-loop mitochondrial DNA was observed after amplification with the polymerase chain reaction (PCR) in 28% of 195 evening bats, Nycticeius humeralis, from seven colonies. Nucleotide sequences of PCR products show that this heteroplasmy is characterized by an 81-bp region which is tandemly repeated five to eight times. Southern blots using PCR products as probes on HaeIII genomic digests confirm the presence of heteroplasmy. Furthermore, densitometry of electrophoresed PCR products from 109 mother-offspring pairs indicate that heteroplasmy is stably transmitted from mother to offspring with one exception: a heteroplasmic offspring had a homoplastic mother and sib. Nucleotide sequences from this family reveal that a repeat duplication and deletion occurred. The observed mutation rate per generation, mu, for length polymorphism is comparable to an independent estimate, mu = 10(-2), based on hierarchical diversity statistics. With the exception of the repeat nearest the proline tRNA gene, sequence similarities between repeats within bats are consistent with a model of concerted evolution due to unidirectional replication slippage. Selection is inferred to act on the first repeat because in comparison to other repeats it has the least sequence divergence among bats, the fewest transversions, and the lowest minimum free energy associated with folding.     

Bat casualties by road traffic (Brno-Vienna)

We studied the impact of road E461, Brno-Vienna, on bat mortality, with the goal to predict this impact after the road has been reconstructed and turned into highway, R52. In the Czech territory, two proposed road sections of E461 were selected, 3.5 and 4.5 km long, and divided into segments 100 m in length. Bat carcasses were picked up from emergency stopping lanes, and bat activity was recorded by ultrasound detectors along the road and 100 m away on both sides from the central strip. From May to October 2007, 25 checks of bat mortality performed at weekly intervals revealed 119 bat carcasses representing 11 or 12 species.Pipistrellus nathusii, P. pygmaeus andMyotis daubentonii were the most frequent traffic casualties. The greatest mortality was documented from early July to mid-October, with a peak in September. Monitoring bat activity by ultrasound detectors (one night per month in May, June and September) yielded 12 bat species and 3 species couples (Myotis mystacinus/brandtii, M. emarginatus/alcathoe, Plecotus auritus/austriacus), mostly the same taxa as found dead on the road. Significantly greater bat numbers were revealed in the section where the road was situated between two artificial lakes, as compared to a road section without any lakes directly adjacent to the road. In the former section, significant correlation was found between the number of carcasses found and the activity detected, according to road segments.     

Bat and hummingbird pollination of an AUTOTETRAPLOID COLUMNAR CACTUS,Weberbauerocereus weberbaueri (Cactaceae)

I present data on flower morphology, pollination, breeding system, and genetic diversity of the columnar cactus Weber-bauerocereus weberbaueri at 2500 m elevation in southwestern Peru. Weberbauerocereus weberbaueri is a self-compatible columnar cactus that is visited and pollinated by one species of rare endemic bat, Platalina genovensium, and two species of hummingbirds, Patagona gigas and Rhodopis vesper. W. weberbaueri exhibits pronounced interplant variation in floral color and size, and flowers exhibit traits corresponding to both bat and hummingbird pollination syndromes. Starch-gel electrophoresis of flower bud tissue indicated that W. weberbaueri is an autotetraploid and that genetic diversity (Hep = 0.257) of the study population was high relative to diploid plants but similar to other tetraploid species. Initial fruit set from pollinator exclusion experiments conducted in 1991 and 1993, at the onset of and after a drought associated with the El Niño event of 1991–1992, revealed that bats were the most important pollinators in 1991, but that hummingbirds and diurnal insects were most important in 1993. In both years, however, autogamy and lepidopteran larval infestation of fruits reduced differences in mature fruit production among pollinator exclusion treatments so that differences in mature fruit set were not statistically significant. Reduced bat pollination in 1993 is attributed to the reduced abundance of bats at the study site during a drought caused by El Niño. I hypothesize that interaction among several factors, including tetraploidy, autogamy, larval infestation of developing fruits, and variation in pollinator abundance, may not result in strong selection for a bat vs. hummingbird floral morph, thus allowing the persistence of floral variation in this cactus.     

Bat community structure in an urban park

In summer 1990, we mist-netted bats on 35 net-nights, for 4 h each night, along tributaries of the River Rouge in surburban Detroit, Michigan, USA The floodplains of these nvers are preserved as parkland We compared elements of bat community structure in these urbanized park areas to that of rural areas For the rural data set, we used mist-netting data obtained previously on 53 net-nights in southern Michigan using a similar protocol Mean number of bats captured per night was lower in urban compared to rural areas (13 vs 46) Species diversity (Simpson Index) was lower in the city (0.53 vs 0.28) as was species evenness (0.66 vs 0.36) The big brown bat Eptesicus fuscus made up 65% of the catch m rural areas but 83% in the city The red bat Lasirus borealis represented 18% of all bats m rural areas and 13% in the city The proportion of sites where the big brown bat was captured was significantly lower in the city (51% vs 74%) The proportion of sites that yielded red bats also declined, from 52% along rural nvers to only 14% in the city Sex ratio of adult big brown bats did not differ between urban (43% male) and rural (32% male) sites The ratio of juvenile big brown bats to adult females was significantly lower in the city (1.21 vs 30.77) Our data suggest that urbanization is a threat to insectivorous bat communities and leads to decreased overall abundance, decreased species diversity, and possibly lower reproductive success of those that are present     

Population Genetic Structure Within and among Seasonal Site Types in the Little Brown Bat (Myotis lucifugus) and the Northern Long-Eared Bat (M. septentrionalis)

During late summer and early autumn, temperate bats migrate from their summering sites to swarming sites, where mating likely occurs. However, the extent to which individuals of a single summering site migrate to the same swarming site, and vice versa, is not known. We examined the migratory connectivity between summering and swarming sites in two temperate, North American, bat species, the little brown bat (Myotis lucifugus) and the northern long-eared bat (Myotis septentrionalis). Using mitochondrial and microsatellite DNA markers, we examined population structuring within and among summering and swarming sites. Both species exhibited moderate degrees of mitochondrial DNA differentiation (little brown bat: F_ST(SWARMING)= 0.093, F_ST(SWARMING)= 0.052; northern long-eared bat: F_ST(SWARMING)= 0.117, F_ST(SWARMING)= 0.043) and little microsatellite DNA differentiation among summering and among swarming sites. Haplotype diversity was significantly higher at swarming sites than summering sites, supporting the idea that swarming sites are comprised of individuals from various summering sites. Further, pairwise analyses suggest that swarming sites are not necessarily comprised of only individuals from the most proximal summering colonies.     

Experimental rabies virus infection of big brown bats (Eptesicus fuscus)

A captive colony of adult Big Brown Bats (Eptesicus fuscus) was experimentally infected with a rabies virus (RABV) variant isolated from the salivary glands of a naturally infected Big Brown Bat and passaged once through murine neuroblastoma cell culture. Bats were divided into 11 groups, which were composed of one to three noninfected and one to three infected individuals each. Twenty of 38 animals were infected intramuscularly into both left and right masseter muscles; they received a total of 10(3.2) median mouse intracerebral lethal dose (MICLD50) of Big Brown Bat RABV variant. Experimental outcome after viral exposure was followed in the bats for 140 days postinoculation (PI). Of 20 infected bats, 16 developed clinical rabies, and the mean incubation period was 24 days (range: 13-52 days). Three infected bats never seroconverted and succumbed early to infection (13 days). Four infected bats that survived until the end of the experiment without any signs of disease maintained detectable antibody titers until the third month PI, peaking between days 13 and 43, and consequent drop-off below the threshold for detection occurred by day 140. Limited excretion of virus in saliva of infected bats during the clinical course of disease was observed in two individuals on days 13 and 15 PI (<24 hr prior to onset of clinical illness). No bat-to-bat transmission of RABV to noninfected bats was detected.     

Spatial unmasking in the echolocating Big Brown Bat, <Emphasis Type="Italic">Eptesicus fuscus</Emphasis>

Masking affects the ability of echolocating bats to detect a target in the presence of clutter targets. It can be reduced by spatially separating the targets. Spatial unmasking was measured in a two-alternative-forced-choice detection experiment with four Big Brown Bats detecting a wire at 1 m distance. Depth dependent spatial unmasking was investigated by the bats detecting a wire with a diameter of 1.2 mm in front of a masker with a threshold distance of 11 cm behind the wire. For angle dependent spatial unmasking the masker was turned laterally, starting from its threshold position at 11 cm. With increasing masker angles the bats could detect thinner wires with diameters decreasing from 1.2 mm (target strength −36.8 dB) at 0° to 0.2 mm (target strength −63.0 dB) at 22°. Without masker, the bats detected wire diameters of 0.16 mm (target strength −66.2 dB), reached with masker positions beyond 23° (complete masking release). Analysis of the sonar signals indicated strategies in the echolocation behavior. The bats enhanced the second harmonics of their signals. This may improve the spatial separation between wire and masker due to frequency-dependent directionality increase of sound emission and echo reception.     

Handedness in the echolocating Schreiber's Long-Fingered Bat (Miniopterus schreibersii)

Bats, in terms of variety of species and their absolute numbers, are the most successful mammals on earth. The anatomical and functional peculiarities of Microchiroptera are not confined only to the auditory system; the wings (hands) of bats are unique both from an anatomical point of view as from a sensorial one. They are much thinner than those of birds and their bony structure is much more similar to a primate hand than to the forelimb of other mammals of the bat's size; the thumb, is very small and on its distal end there is a little claw that bats use for crawling and manipulating food. However, despite this very frequent use of the hands for food catching and for walking, nothing is known about the existence of a preferential use of the hands in Microchiroptera. The present study investigates the existence of handedness in the Schreiber's Long-Fingered Bat by recording the preferential use of the hand while climbing the walls of a plastic cylinder. This bat species is lateralized at population level and shows a left forelimb bias when using hands for climbing/grasping. This result is the first evidence of population-level handedness in an echolocating bat species.     

Food habits of northern (Eptesicus nilssoni) and brown long-eared (Plecotus auritus) bats in Sweden

Food habits of sympatric northern and brown long-eared bats were examined by analysis of droppings collected in six maternity roosts of each species. Relatively large, nocturnal flying insects such as moths (Lepidoptera), June-beetles (Coleoptera: Scarabaeidae), crane-flies (Diptera: Tipulidae) and caddis-flies (Trichoptera), were eaten by both bat species, representing 47% (by volume) of the northern and 57% of the long-eared bat's diet. Small dipterans were important food items for the northern bat (47% of the diet) but not for the long-eared bat, which instead consumed large amounts of diurnal or predominantly non-flying taxa such as blow-flies (Diptera: Calliphoridae), earwigs (Dermaptera), spiders (Araneae) and harvestmen (Opiliones) (40% of the diet). The difference in food selection by the two species is probably due to the different foraging strategies used.     

GABAergic inhibition and the effect of sound direction on rate-intensity functions of inferior collicular neurons of the big brown Bat,Eptesicus fuscus

GABAergic inhibition shapes many auditory response properties of neurons in the inferior colliculus of the big brown bat, Eptesicus fuscus. This study examined the role of GABAergic inhibition on direction-dependent rate-intensity functions of bat inferior collicular neurons. When plotted at three sound directions (60 degrees contralateral, 0 degrees and 60 degrees ipsilateral relative to recording site), most collicular neurons had nonmonotonic and saturated rate-intensity functions at 60 degrees contralateral and 0 degrees but had monotonic rate-intensity functions at 60 degrees ipsilateral. The dynamic range of rate-intensity functions of majority (>90%) of collicular neurons significantly decreased as the sound direction changed from 60 degrees contralateral to 60 degrees ipsilateral. Bicuculline application increased or decreased the dynamic range of IC neurons in different degrees with sound direction and abolished direction-dependent intensity sensitivity of these IC neurons. Possible mechanisms for these observations are discussed.