Pipistrellus Research Articles

Bat Activity and Species Occurrence on the Hanford Site in Eastern Washington

Although bats are a group with high species richness in shrub-steppe areas of the Columbia Basin, limited information is available on distributions, species occurrence, and habitat use. We surveyed bat populations of the Hanford Site, which has provided a refuge for shrub-steppe flora and fauna in Washington State. We used Anabat detectors, harp traps, mist nets, and auditory-visual observations during 1997 and 1998 to document the occurrence of bat species and to compare activity levels among major habitat types on the site. Across both years, we recorded 6,470 bat calls during 302 bat detector survey-nights at 66 locations. Bats of the genus Myotis constituted 84 to 88% of total calls each year. The hoary bat (Lasiurus cinereus), silver-haired bat (Lasionycteris noctivagans), western pipistrelle (Pipistrellus hesperus), big brown bat (Eptesicusfuscus), and pallid bat (Antrozous pallidus) also were recorded. Big brown bats have not been reported previously at the Hanford Site. Detection rates were highest near potential roosting structures and riparian foraging areas, and lowest in upland shrub-steppe cover types. During 133 trap nights across both years, we captured 81 bats of 5 species: the western smallfooted myotis (Myotis ciliolabrum), little brown myotis (M. lucifugus), Yuma myotis (M. yumanensis), silver-haired bat, and pallid bat. The site supports at least 3 arid-land bats (western small-footed myotis, western pipistrelle, and pallid bat) that are near the northern edge of their species distributions. By protecting large patches of undisturbed habitat, the Hanford Site has helped maintain a diverse bat fauna in Washington's shrub-steppe. In addition, some habitat modifications at the site may have benefited bats, as evidenced by heavy use of old buildings, irrigation run-off wetlands, and planted trees.

Echolocation behavior and signal plasticity in the Neotropical bat Myotis nigricans (Schinz, 1821) (Vespertilionidae): a convergent case with European species of Pipistrellus ?

We used both field and flight cage observations to investigate the echolocation and foraging behavior of the seldom studied, small, aerial insectivorous bat Myotis nigricans (Vespertilionidae) in Panama. In contrast to its temperate congeners, M. nigricans foraged extensively in open space and showed an echolocation behavior well adapted to this foraging habitat. It broadcast narrowband echolocation signals of 7 ms duration that enhance the chance of prey detection in open space. Because of rhythmical alternations of signal amplitude from signal to signal in our sound recordings of search signals in open space, we conclude that the bats scanned their environment with head movements, thereby enlarging their search volume. In edge-and-gap situations, and in the flight cage, M. nigricans introduced an initial broadband component to its search calls. In the field and in the flight cage, M. nigricans hawked for prey in aerial catches; gleaning was never observed. M. nigricans demonstrates call structures, such as narrow bandwidth and rather long signals adapted to foraging predominantly in open space. Moreover, call structure is highly plastic, allowing M. nigricans to forage in edge-and-gap situations also. These adaptations in call structure and plasticity have evolved convergently at least twice within the genus Myotis. Finally, M. nigricans echolocation and foraging behavior parallels that of the small, aerial, insectivorous pipistrelle bats (Vespertilionidae), which are not closely related to M. nigricans but forage in similar habitats.

Mammalian reservoirs and epidemiology of rabies diagnosed in human beings in the United States, 1981-1998.

Between 1981 and 1998, 37 cases of rabies were diagnosed in human beings in the United States. Information directly linking the cause of infection to animal bite was available for only eight of these cases. Indirect incrimination of the vector by analysis of cDNA sequences obtained by reverse transcriptase polymerase chain reaction of samples indicated that for all cases (12/12) believed to have been acquired in foreign countries, variants of the rabies virus (VRVs) associated with dogs (7/12 involved known bite histories) were the cause of the rabies infections. In contrast, VRVs associated with bats (bat-associated VRVs or BAVs) were implicated as the cause of 88% (22/25) of infections believed to have been acquired within the United States (1/22 involved known bite histories). Sequence analyses revealed that a single BAV (Ln/Ps), associated with rabid silver-haired (Lasionycteris noctivagans) and Eastern pipistrelle (Pipistrellus subflavus) bats, was implicated in 73% (16/22) of bat-associated infections. Silver-haired bats are predominantly solitary and migratory. Eastern pipistrelle bats may occur individually or in small clusters. Both species are only infrequently submitted for rabies testing. Unrecognized bites and unique properties of the Ln/Ps BAV may explain its association with the majority of rabies infections in human beings in the United States.

Competition for food by expanding pipistrelle bat populations (Pipistrellus pipistrellus) might contribute to the decline of lesser horseshoe bats (Rhinolophus hipposideros)

The bat species Rhinolophus hipposideros has undergone a dramatic decline throughout much of western Europe from the 1960s. The mechanisms responsible for this phenomenon have not been conclusively identified. At the same time, some populations of Pipistrellus pipistrellus have increased substantially, possibly as a consequence of foraging upon insects attracted by street lamps. To evaluate whether there might be some ecological link between the opposite demographic trends observed in the two species, we compared the diets of two sympatric populations of R. hipposideros and P. pipistrellus in south-west Switzerland. The two bat species fed upon the same categories of prey, mainly moths and Diptera, and we were not able to recognize interspecific differences in diet composition in spring when resources were most likely to be limiting. Although using different foraging strategies, both species may visit the same or adjacent feeding grounds, therefore potentially competing for the same populations of prey. Although conclusive evidence is still needed, bat conservation policy should pay more attention to this possibility.

Rabies surveillance in the United States during 1998

During 1998, 49 states, the District of Columbia, and Puerto Rico reported 7,961 cases of rabies in nonhuman animals and 1 case in a human being to the Centers for Disease Control and Prevention, a decrease of 6.5% from 8,509 cases in nonhuman animals and 4 cases in human beings reported in 1997. More than 92% (7,358 cases) were in wild animals, whereas > 7.5% (603 cases) were in domestic species (compared with 93% in wild animals and 7% in domestic species in 1997). Decreases were evident in all of the major contributing species groups, with the exception of skunks and bats. The relative contributions of the major groups to the total reported for 1998 were raccoons (44.0%; 3,502 cases), skunks (28.5%; 2,272), bats (12.5%; 992), foxes (5.5%; 435), cats (3.5%; 282), cattle (1.5%; 116), and dogs (11.5%; 113). No further discernable westward extension of the epizootic of rabies in raccoons in Ohio was reported. Twelve of the 19 states enzootic for the raccoon variant of the rabies virus and the District of Columbia reported decreased numbers of cases of rabies during 1998, compared with 13 states and the District of Columbia that reported increases during 1997. Three states, Rhode Island (143.2%), Massachusetts (77.2%), and New Hampshire (69.4%), reported increases of > 50% during 1998, compared with totals reported for 1997. In Texas, the number of cases of rabies associated with enzootic canine variants of the rabies virus remained greatly diminished; however, overall totals of reported cases of rabies increased in Texas and 12 other states where skunks are the major terrestrial reservoir of rabies. At the national level, the total of 82 reported cases of rabies among horses and mules was greater than that reported for any year since 1981 (88 cases) and represented a 74.5% increase, compared with the total for 1997. The 992 cases of rabies reported in bats during 1998 were the greatest proportionate contribution by bats since 1990. Reported cases of rabies in cats (282), dogs (113), and cattle (116) decreased 6.0%, 10.3%, and 4.9%, respectively. One indigenously acquired case of rabies reported in a human being during 1998 was the result of infection with a rabies virus variant associated with silver-haired and eastern pipistrelle bats.

Effects of food abundance and wind on the use of tree lines by an insectivorous bat, Pipistrellus pipistrellus

We tested the hypotheses that the distance bats fly from tree lines depend on food abundance and protection from wind. We monitored the activity of pipistrelle bats (Pipistrellus pipistrellus) and measured insect abundance and wind speed and direction at fixed distances up to 50 m from tree lines. We compared bat behaviour in different situations: with and without wind and with low and high insect abundances in adjacent open areas. In all situations, pipistrelle bats' activity decreased with increasing distance from the tree line. Within nights, we found no effect of wind speed on bat activity (sound recorded per 5 min) on the leeward side of the tree lines. Between nights, however, bats concentrated their activities closer to the tree lines at high wind speeds or angles of incidence of wind from 45° to 90°. A significant relationship between bat and insect abundances was found only when the tree line was bordered by insect-rich grassland. Since wind and insect abundance only partly explained the distances bats flew from tree lines, two alternative explanations, namely predator avoidance and the use of tree lines as acoustic landmarks, are discussed. Pipistrelle bats using a double row of trees as a commuting route at dusk flew mainly between the tree lines, regardless of insect abundance or wind speed. It is argued that predator avoidance explains this behaviour, being a constraint on movements of bats at relatively high light levels. At high wind speeds and angles of incidence greater than 45°, the proportion of pipistrelle bats commuting on the leeward side of the tree lines increased.

Effect of roost size on the emergence behaviour of pipistrelle bats

We refined established methods for examining the temporal organization of behavioural events and applied them to the study of bats emerging from roost sites. Previous studies have shown that as roosting numbers of bats increase, temporal patterning (clustering) in their emergence behaviour, as measured by χ2or G statistics, also increases. Expressing the extent of temporal clustering using χ2or G, however, confounds two effects. The statistic may increase because clustering increases. However, an increase will occur, even if the amount of clustering stays constant, if the sample size of observations increases. A positive relation between emergence size and χ2orG may not necessarily reflect increased clustering. We developed a method to separate these effects using computer-modelled event streams. Using this method, we examined intra- and inter-roost variation in the temporal patterning of emergences of the pipistrelle bat, Pipistrellus pipistrellus, from four roosts in northeast Scotland. The ‘corrected’ expression of clustering decreased as roost size increased, which was opposite to the effect found with the uncorrected expression and also opposite that predicted a priori from the bottleneck hypothesis. This novel result suggests bottlenecks may disrupt clustering rather than promote it. This latter interpretation was supported by observations that clustering was significantly reduced in the middle of large emergences. Variation in clustering between roosts was significant, suggesting exit topology may have an important influence on clustering behaviour.

Influence of torpor on milk protein composition and secretion in lactating bats.

In the pipistrelle bat (Pipistrellus pipistrellus), the metabolic load of lactation is not met to any significant extent by increased food intake or mobilization of body reserves, and aerial foraging accounts for most of the animal's energy expenditure even during lactation. Energy conservation must, therefore, play a critical role in maintaining lactation. The principal mechanism for energy conservation appears to be the bat's ability to enter torpor, but this may itself interrupt milk synthesis and secretion unless the pipistrelle mammary gland is adapted to counteract its effect. The effect of torpor on mammary tissue function was studied in mammary tissue explant cultures prepared in weeks 1-3 of lactation, when milk water yield was 0.20, 0.88, and 0.30 mL/d respectively. Protein synthesis measured by incorporation of radiolabeled amino acids was 44% lower (P < 0.001) in bat tissue explants cultured at ambient temperature (22 degrees C) compared with 37 degrees C. The reduction was similar to that observed in mouse mammary tissue (57%) and was unaffected by stage of lactation. Analysis of explant protein after [35S]methionine labelling showed the majority of proteins synthesised in culture to be milk proteins; it also demonstrated that the decrease in protein synthesis at ambient temperature was a general phenomenon: synthesis of both secretory and intracellular mammary proteins was reduced at the lower culture temperature. The results suggest that bat mammary tissue has no mechanism to counteract the effect of reduced body temperature and that periods of lactational torpor are likely to cause a pronounced diurnal variation in the rate of milk secretion.

Energetic effects of sublethal exposure to lindane on pipistrelle bats ( Pipistrellus pipistrellus)

Many vespertilionid bats roost in proximity to roofing timbers and are therefore potentially exposed to organochlorines used as wood preservatives. Organochlorines elevate metabolic rate (MR) in some vertebrate species and any such effect in bats may threaten survival. The aim of this study was to determine whether sublethal exposure to lindane affected the body mass, food intake and MR of pipistrelle bats Pipistrellus pipistrellus and whether any such effects were modified by environmental conditions and the presence of co-roosting bats. Bats held indoors and receiving repeated doses of 50 μg of lindane lost mass (−0.26 g) relative to co-roosting bats receiving either 10 or 0 μg. Lindane increased the mealworm intake of bats, those with 0.45 g of body lipid increased their mealworm intake by 0.29 g DW night −1 when given lindane doses of 50 μg bat −1 3 days −1. The magnitude of this effect decreased as bats became heavier. Lindane significantly increased MR in bats and the effect was most pronounced in lean individuals. Environmental temperature and the presence of co-roosting bats altered the impact of lindane, the pesticide-mediated elevation of MR being greater under cold conditions. It was predicted that, under the environmental conditions of the experiment, exposure to 50 μg lindane bat −1 3 days −1 would increase the 24-h MR of a 7.3 g bat by 3.4 kJ (15%) and that of a 6.3 g bat by 4.8 kJ (23%). Such sublethal exposure might constitute a significant threat to free-living bats

Eimeria pipistrellus n. sp. from Pipistrellus kuhlii (Chiroptera: Vespertilionidae) in Saudi Arabia

Fecal samples from 12 Pipistrellus kuhlii captured at Shagrah, Saudi Arabia, were examined for coccidia and three (25%) found to harbor a undescribed eimerian, herein described as Eimeria pipistrellus n. sp. Sporulated oocysts were subspherical, 24.8 x 23.2 (22-27 x 20-25) microns, with a bilayered and smooth wall. The micropyle was absent, but a large oocyst residuum and a single polar granule were present. Sporocysts were ovoid, 11.6 x 8.3 (10.5-13 x 7.5-9) microns, with a prominent Stieda body, but without a substiedal body; sporozoites lay head to tail in sporocysts and contained one large posterior refractile body. Eimeria pipistrellus n. sp. is the 3rd species of the genus Eimeria found from bats of the genus Pipistrellus.

Do emerging pipistrelle bats lose control of their timing due to ‘crowd pressure’?

AbstractWhen bats emerge from colonies to feed and drink their emergence patterns deviate systematically from those expected at random (Kunz, 1974; Swift, 1980; Bullock et al., 1987; Brigham &amp; Fenton, 1986). In particular, many bats appear to group together as they emerge, and form into ‘clusters’ or ‘outbursts’ (but see McAney &amp; Fairley, 1988; Kunz &amp; Anthony, 1995 for exceptions). The function of this clustering behaviour has been the topic of recent debate, with some authors favouring the hypothesis that the behaviour is an artefact of large numbers of animals moving through a restricted space (Kalcounis &amp; Brigham, 1994) and others suggesting the behaviour has a more significant biological function such as protection from predation (Leen &amp; Novick, 1977; Speakman, Stone &amp; Kerslake, 1995) or information transfer (Wilkinson, 1992).

Do emerging pipistrelle bats lose control of their timing due to ‘crowd pressure’?

Do emerging pipistrelle bats lose control of their timing due to ‘crowd pressure’?

Roost selection in the pipistrelle bat,Pipistrellus pipistrellus(Chiroptera: Vespertilionidae), in northeast Scotland

Availability of suitable roost sites may limit bat distribution and abundance. We compared nine internal and 26 external features of 21 known roost buildings with those of 17 random buildings in northeast Scotland, U.K. (57°N) to assess whether pipistrelle bats,Pipistrellus pipistrellus(55-kHz phonotype) are selective in their use of roosts. Bats did not select roosts with specific structural attributes. Compared with random buildings, roosts were closer to a tree over 10m tall and had a greater percentage cover (of trees over 10m tall) within a radius of 50m. Trees may provide benefits by providing shelter and thus ameliorating the microclimate of the roost. Cover may also provide protection from predators so that bats are able to emerge earlier, thus increasing foraging time. Bats in the present study emerged 11min earlier from roosts with 29% cover than from roosts with 3% cover, potentially gaining as much as 10% of their daily energy requirements in this extra time. Roosts were also more likely to have linear vegetation elements leading away from them. These features may be important for navigation, foraging or predator avoidance. Compared with random buildings roosts were closer to and surrounded by a greater area of deciduous woodland within a radius of 0.5km, had a greater area of coniferous woodland within a radius of 0.5km, and were more likely to be found within 0.5km of a major river. All these factors are likely to be beneficial for foraging. A logistic regression model indicated that percentage cover within 50m of the building was the best predictor of the presence or absence of bats roosting in a building.

Nathusius' pipistrelle bats (Pipistrellus nathusii, Keyserling &amp; Blasius 1839) breeding in Ireland

AbstractWe describe the most westerly known maternity colony of Nathusius' pipistrelle bats (Pipistrellus nathusii). The bats were identified by using morphometric measurements and analysis of time‐expanded echolocation and social calls. The roost, containing approximately 150 individuals, was located in a mid 19th century farm stable block and store house situated in parkland in County Antrim, Northern Ireland. The roost was visited on 30 April, 1 May and 22 June 1997. Over this period, 11 bats were caught: one adult male, five pregnant females, four lactating females and a juvenile male. Direct observation of behaviour patterns suggests that mating groups of P. nathusii may occur in Ireland as late as May. The migratory nature of this species is discussed.

Variation in size at birth and post‐natal growth in the insectivorous bat Pipistrellus subflavus (Chiroptera: Vespertilionidae)

AbstractWe describe the size and developmental state at birth, examine factors which influence intra‐ and inter‐year variation in post‐natal growth, and derive age‐predictive equations and logistic growth parameters for the eastern pipistrelle bat, Pipistrellus subflavus. Ambient and roost temperature and insect abundance were lowest, and precipitation highest, before and during the post‐natal growth period in 1982, as compared to 1981. We found no sex differences in the size of pups at birth or in post‐natal growth rates in a given year; however, body mass and length of forearm of neonates differed significantly between years, being smaller in 1982 than in 1981. During the first two weeks of post‐natal growth in both years, the body mass and length of forearm of pups increased linearly at mean rates of 0.15 g.day−1 and 1.12 mm.day−1, respectively. Post‐natal growth rates for length of forearm and body mass were the same during the early linear phase of growth, but the intercept for body mass was less and growth trajectories were more variable in 1982. Length of forearm was the least variable and thus most reliable character for estimating age of P. subflavus pups during the first 14 days of post‐natal growth. When length of forearm was used in combination with mean changes in the length of the fourth metacarpal‐phalangeal epiphyseal gap, we derived reliable age‐estimation equations ranging from 1 to 45 days. Litter size averaged 1.96 and 1.93 at birth, but this was reduced to one by the time pups became volant. At birth, litter mass represented 44, and 54% of the post‐partum mass of females in 1981 and 1982, respectively. This maternal effort during pregnancy is among the highest reported for bats. At weaning, the body mass of pups approached 80% of adult post‐partum body mass, and the length of forearm exceeded 90% of adult female size. Our results suggest that size at birth and post‐natal growth are influenced by ambient and roost temperature, rainfall, and the quantity of insects available to pregnant and lactating females. Thus, energetic constraints on both mothers and pups can lead to inter‐year and inter‐individual differences in maternal effort and post‐natal growth of pups.

Can skull morphology be used to predict ecological relationships between bat species? A test using two cryptic species of pipistrelle.

Can ecological relationships between bat species be predicted largely on the basis of morphology? This question was addressed by investigating skull morphology of two cryptic species of the pipistrelle bat. Since 45 Pipistrellus pipistrellus apparently eats larger prey than 55 P. pipistrellus, we predicted that it would have a larger overall skull size, a larger dentary apparatus, and a larger gape. To test these predictions, variables were measured from skulls of the two cryptic species, and comparisons made between them. In accordance with our predictions, overall skull size was larger in 45 P. pipistrellus than in 55 P. pipistrellus, and 45 P. pipistrellus had a longer lower jaw and the distance between the jaws at maximum gape was larger. In addition, 45 P. pipistrellus had longer upper canines, which may allow it to pierce harder prey items than 55 P. pipistrellus. Only some aspects of dietary differences between the two cryptic species could be explained by differences in skull morphology, and we suggest that empirical data, at least on diet and habitat use, are also required to explain mechanisms of resource partitioning among species in bat communities.

Allomaternal care and recognition between mothers and young in pipistrelle bats (Pipistrellus pipistrellus)

Allomaternal care and recognition between mothers and young in pipistrelle bats (<i>Pipistrellus pipistrellus</i>)

Population dynamics of a maternity colony of the pipistrelle bat (Pipistrellus pipistrellus) in north‐east Scotland

Population dynamics of a maternity colony of the pipistrelle bat (<i>Pipistrellus pipistrellus</i>) in north‐east Scotland

A comparison of the toxicity to laboratory mice and pipistrelle bats Pipistrellus pipistrellus of exposure to remedially-treated timber

Many species of bats roost in roof spaces and can come into contact with pesticides used to treat roof timbers against rot. As part of a study to develop a test with laboratory mice which could be used to predict the likely toxicity of pesticides to bats, the toxic effects on pipistrelle bats Pipistrellus pipistrellus and laboratory mice (CFLP outbred-strain) of exposure to dieldrin-treated timber were compared. Dose (amount of dieldrin applied to the wood surface) — response (mortality) studies demonstrated that pipistrelle bats were 30 times more sensitive to dieldrin-treated wood than laboratory mice. However, dieldrin residues in the brain and liver of animals which had been poisoned were significantly higher in bats than mice. These residue data suggest that bats may be inherently less sensitive to dieldrin poisoning than mice and so it is likely that the 30-fold greater sensitivity of bats than mice to dieldrin-treated timber was a result of greater rate of uptake, per gram body weight, of the active ingredient from the wood surface and/or slower clearance from the body. The importance of differences in exposure and the reliability of residue data as an indicator of differences in inherent sensitivity to a chemical are discussed in terms of their importance when considering inter-species variation in toxic response.

Day-roosting activity budgets of the eastern pipistrelle bat, Pipistrellus subflavus (Chiroptera: Vespertilionidae)

Daily and seasonal activity budgets of adult female eastern pipistrelle bats, Pipistrellus subflavus, were quantified at a maternity colony in eastern Massachusetts. Ambient and roost temperatures were recorded. Activities of roosting bats were monitored using an infrared-sensitive video camera. Scan sampling was used to analyze video records taken at weekly intervals from mid-May to late July 1989. Analysis of day-roosting indicates that adult females spend an average of 77% of their time at rest, 16% alert, 7% grooming, and &lt; 1% crawling. Bats were most active immediately following their morning return to the day-roost and just prior to their departure at dusk. Periodic bouts of activity throughout the day were usually associated with urination and (or) defecation, mother–pup interactions, and movements in response to changes in roost temperature. Females were significantly more active in mortise roosts than when roosting on the open ridgepole, probably because fluctuations in temperature in mortises were smaller. As the season progressed, the overall time that bats spent resting decreased from 86 to 70%, whereas time spent alert increased from 9 to 24%; weekly fluctuations in the incidence of grooming and crawling showed no consistent seasonal trends. Roost temperature, time of day, and date explained significant amounts of variation in both daily and seasonal activity budgets. Females rested significantly less and were more alert after young were born than before, although time spent grooming and crawling did not differ significantly between the pre- and post-partum periods. Our findings for P. subflavus generally corroborate activity budgets previously reported for the little brown bat (Myotis lucifugus).