Habitat associations of bats in Northern Ireland: implications for conservation

Agricultural intensification in Northern Ireland has brought about large-scale changes to the landscape with a detrimental effect on biodiversity. Between 1996 and 1998, we surveyed a stratified random sample of 1 km squares for bats using a spot-sample technique and time expansion bat detector to establish linear and area habitat associations. Bats strongly selected water bodies with bankside vegetation, treelines, and deciduous and mixed woodland edge, avoiding open areas such as upland/unimproved grassland and improved grassland. Of three sympatric pipistrelle species (Pipistrellus pipistrellus, P. pygmaeus and P. nathusii), two were shown to forage in different habitats; P. pipistrellus being more of a ‘generalist’, foraging in a wider variety of habitats than P. pygmaeus, a ‘specialist’ which foraged in a smaller range of habitats. Nyctalus leisleri selected parkland/amenity grassland, deciduous woodland edge and rivers/canals and avoided improved grassland, hedgerows, whilst Myotis spp. selected deciduous woodland centre, lake/reservoir margins and rivers/canals. Reduction in area and quality of inland water, deciduous woodlands and field boundaries in Northern Ireland may impact on bat populations. Habitat management should focus on improving those habitats which are selected by bats, including the maintenance and enhancement of connecting linear habitats.     

The effects of illuminating the roost entrance on the emergence behaviour of Pipistrellus pygmaeus

In an attempt to increase the accuracy of roost emergence counts for a monitoring programme, the exits of two Pipistrellus pygmaeus roosts were illuminated with light of different colours and intensities. Light intensity affected bat emergence more than light colour. At one roost there was no significant difference in the bat emergence pattern between when the roost exit received no illumination and when it was illuminated with red light. The use of the latter is proposed to increase the accuracy of bat roost emergence counts.     

Influence of temperature in roost selection by Pipistrellus pygmaeus (Chiroptera): relevance for the design of bat boxes

The soprano pipistrelle (Pipistrellus pygmaeus) is a house-dwelling bat, whose maternity colonies are often affected by exclusion from buildings in southern Europe. Bat boxes with a suitable thermal behaviour can provide alternative roosts. However, this is particularly difficult to achieve in hot climates, where boxes may overheat. We studied roost temperatures and roost thermal preferences of this bat in attics and roofs in a Mediterranean region. Roosts reached high temperatures, experienced great thermal fluctuations and had wide spatial thermal ranges. Bats preferred the warmest locations within roosts, indicating that they are a heat tolerant species. However, they avoided temperatures of 40 °C and above, suggesting that this is the upper limit of the species thermally neutral zone. The study of experimental sets of white, grey and black boxes demonstrated that the latter were the ones that most often reached the temperatures observed in roosts in buildings. They were also the ones occupied by larger numbers of bats. These results suggest that, even in hot Mediterranean climates, black boxes are the best option as alternative roosts for evicted colonies. However, on particularly hot days, bats left them, suggesting that black boxes could be improved by creating a wider thermal range.     

The value of bat-boxes in the conservation of Pipistrellus pygmaeus in wetland rice paddies

Wetlands with rice paddies are key habitats in the conservation of biodiversity in the Mediterranean Region and are potentially suitable habitats for foraging bats, since they provide food (insects) and drinking places; nevertheless, many wetlands lack natural roosting sites. A bat-box program designed to ascertain bat-box preferences was initiated in 1999 in the Ebro Delta (NE Spain), one of the most important wetlands in Europe. A total of 69 bat-boxes of two types (single and double compartment) were placed on three supports (trees, houses, and posts) facing east or west. Pipistrellus pygmaeus occupancy rates and the number of individuals per box were monitored on 16 occasions from July 2000 to February 2004. Bat-box preferences were only detected during the breeding season. Bat abundance was higher in east-facing boxes, in double-compartment boxes, and in boxes placed on posts and houses. Boxes on natural supports (trees) were avoided. Bat-box occupancy rates were higher during the breeding season (95.6%, spring-summer) due to the formation of maternity colonies. The number of individuals in bat-boxes during the breeding season increased as the study period progressed (from summer 2000 to summer 2003), suggesting a high degree of acceptance by maternity colonies of these alternative locations. Occupancy rates observed were the highest ever reported in bat-box scientific literature. This study highlights the role of bat-box programs as useful alternative management tools for the conservation of bat populations in highly productive wetland habitats where few natural roost sites are available.     

Relating bat species presence to simple habitat measures in a central Appalachian forest

We actively sampled the bat community at 63 sites using detection and non-detection metrics on the Fernow Experimental Forest (FEF) in the central Appalachians of West Virginia using Anabat acoustical equipment May-June 2001-2003 to relate species presence to simple habitat measures such as proximity to riparian areas, forest canopy cover, forest canopy gap width, and forest canopy height. We acoustically detected eight species on the FEF, including the endangered Myotis sodalis. The presence of Lasiurus cinereus, M. lucifugus, M. sodalis, and Pipistrellus subflavus was associated more with riparian areas than upland areas. Both univariate comparisons and multiple logistic regression modeling showed that the probability that clutter-adapted foraging species such as M. septentrionalis and M. sodalis would be detected was greater as forest canopy cover increased or forest canopy gap size decreased, whereas the opposite was true for open-adapted foraging species such as Eptesicus fuscus and L. cinereus. The overall proportion of unidentifiable bat echolocation sequences to those identified to species was related to upland sites with increasing forest canopy cover indicating some sampling bias between cluttered and uncluttered habitats. However, given sufficient sample points, bat community surveys using acoustical detection show the ability to quickly develop generalized habitat associations for rugged areas such as the central Appalachians where traditional mist-net survey efforts often are logistically difficult and are lacking in scope. Moreover, these acoustical surveys also could lend themselves to species-specific predictive mapping of foraging habitat as well as allowing researchers to formulate testable hypotheses about detailed bat habitat relationships to be definitively tested with radio-telemetry techniques.     

Improving the biodiversity benefits of hedgerows: How physical characteristics and the proximity of foraging habitat affect the use of linear features by bats

Within agricultural landscapes, linear features such as hedgerows and tree-lines provide valuable habitat for many species. We use data from 315 transects, completed as part of a national acoustic survey of bat distribution, to examine the incidence of four bat species adjacent to linear features in rural areas. The use of linear features was assessed in relation to hedgerow width, tree density, the presence of water and woodland proximity. To examine the effect of tree density, linear features were classified as either hedgerows without trees, hedgerows with sparse trees (comprising <50% tree canopy) or tree-lines (>50% tree canopy). The use of linear features by Pipistrellus pipstrellus was not affected by tree density; linear features of all types were associated with a similar increase in P. pipistrellus incidence. The use of linear features by Pipistrellus pygmaeus was dependent on both tree density and the proximity of woodland; only linear features containing trees provided an increase in P. pygmaeus incidence regardless of woodland proximity. P. pipistrellus and P. pygmaeus incidence was not affected by hedgerow width or the presence of water. Incidence of Nyctalus noctula and Eptesicus serotinus was unaffected by the density of linear features of any type. Many agri-environment schemes offer financial incentives for the creation and management of hedgerows. Optimising the biodiversity gain provided by linear features will maximise the effectiveness of these schemes. Agri-environment measures that encourage the provision and retention of hedgerow trees will benefit bats in agricultural landscapes.     

Location of roosts of the lesser long-eared bat Nyctophilus geoffroyi and Gould's wattled bat Chalinolobus gouldii in a fragmented landscape in south-eastern Australia

The location of roosts of two species of vespertilionid bats, the lesser long-eared bat (Nyctophilus geoffroyi) and Gould’s wattled bat (Chalinolobus gouldii), was investigated in a remnant vegetation-farmland mosaic and adjacent floodplain forest in south-eastern Australia. A total of 45 individuals of N. geoffroyi and 27 C. gouldii were fitted with radio transmitters, which resulted in the location of 139 and 89 roosts respectively. Selection of roosting habitat showed both inter- and intra-specific differences. At the landscape level, locations of roosts used by male and female N. geoffroyi differed markedly. Most males roosted in the farmland mosaic within 3 km (mean 1.9±2.9 km) of where they were captured while foraging in remnant vegetation. In contrast, roost sites of females were predominantly in the floodplain forest, 6-12 km from their capture site in farmland (mean for all females, 6.7±2.9 km). All maternity roosts were in the extensive floodplain forest, 4-10 km from foraging areas. Distances moved by this species were greater than previously recorded and further than predicted by flight morphology. Most C. gouldii roosted in the floodplain forest, 4-10 km from their capture site (6.9±1.6 km). Within the floodplain forest, both species roosted in areas that had higher densities of hollow-bearing trees than generally available; dead hollow-bearing trees for N. geoffroyi and large, live trees for C. gouldii. The scale of movements undertaken by these species means that they can obtain resources from multiple landscape elements. Both species used different habitats for roosting and foraging despite the energetic costs of commuting relatively large distances. Conservation of bat populations in rural environments needs to be considered at the landscape scale, with particular attention to identifying landscape elements that provide key resources.     

Bat activity affected by sewage effluent in Irish rivers

Bat activity and benthic macroinvertebrates were sampled at nine paired sites, upstream and downstream from sewage effluent discharges into Irish rivers. Bat activity was measured using broadband acoustic detectors and macroinvertebrates by three 30-s standard benthic kick samples per site. Biological indices of water quality were significantly lower downstream from sewage outfalls, relative to upstream. The soprano pipistrelle (Pipistrellus pygmaeus) was significantly more active (as measured by bat passes per unit time) at downstream sites, while Daubenton’s bat (Myotis daubentonii) was less active. These results contrast with those of a similar study in England, where P. pygmaeus were less active, and Myotis spp. were more active downstream from sewage outfalls. We suggest that P. pygmaeus were more active downstream in our study because of a preference for preying on small orthocladiinid Chironomidae (non-biting midges), which were significantly more abundant downstream. M. daubentonii may prefer Trichoptera (caddis fly), which were significantly more abundant upstream. Organic pollution may then affect bats, but its effect appears to be more complex than previously implied. Implications of changing nutrient levels in freshwaters for populations of M. daubentonii and P. pygmaeus may be different from what is currently suggested in the literature.     

Sex differences in population genetics, home range size and habitat use of the parti-colored bat (Vespertilio murinus, Linnaeus 1758) in Switzerland and their consequences for conservation

When habitats are declining, niche segregation by demographic groups, such as the two sexes, can have a profound impact on the extinction risk of a species as a whole. Thus, differences in the requirements of demographic groups are of importance in conservation. We combined behavioural and genetic data to investigate whether the sexually segregated parti-colored bat (Vespertilio murinus) exhibits sex-specific niche partitioning. We use our data to evaluate implications for conservation of this potentially vulnerable species in Switzerland, the western boundary of its range. Using radio-telemetry, we found sex-specific differences in habitat use. Foraging females strongly relied on lakes while foraging males displayed more flexibility in their habitat use. Moreover, males covered significantly larger foraging areas than females. Sequencing 341 base pairs of the mitochondrial D-loop of 247 individuals revealed sex-specific differences in the genetic structure of colonies, but no such difference was observed for three nuclear micro-satellite markers. We found high mtDNA diversity in two Swiss male colonies and one German female colony, but low mtDNA diversity in two Swiss female colonies. Our genetic data suggest that considerable gene flow occurs via male dispersal and mating. At the same time immigration of females into the existing female colonies in Switzerland is rare compared to the immigration of new males into male colonies. Since we found the sexes in Vespertilio murinus to differ markedly in their ecology, population genetics, and behaviour, we conclude that sex-specific conservation plans are required to protect this species efficiently.     

Habitat selection by the pale-headed brush-finch (Atlapetes pallidiceps) in southern Ecuador: implications for conservation

The pale-headed brush-finch (Atlapetes pallidiceps) is threatened with extinction due to habitat loss, but very little is known about its ecological requirements. We used multiple logistic regression to study habitat selection of this species at landscape, territory, and nest site scales in order to make recommendations about effective management. Habitat selection by the sympatric stripe-headed brush-finch (Buarremon torquatus) was examined with the same methods in order to analyse interspecific resource partitioning and potential competition. The pale-headed brush-finch selected semi-open habitat types with intermediate scrub heights, and avoided forests. Nest sites depended on the presence of vines or bamboo. By contrast, the stripe-headed brush-finch chose dense habitat with low ground cover under tall vegetation and avoided semi-open habitat. The two species had overlapping territories but differed significantly in microhabitat use and the use of vegetation strata. We found no convincing evidence that the stripe-headed brush-finch displaces the pale-headed brush-finch from optimal habitat. The preservation of semi-open scrubland maintained by low-intensity grazing is suggested for future conservation of the pale-headed brush-finch.     

Scale-independent significance of river and riparian zones on three sympatric Myotis species in an agricultural landscape

Conserving biodiversity in agricultural landscapes is an urgent issue. The effective conservation of biodiversity requires plans based on species’ habitat preferences at multiple spatial scales. We examined how the foraging habitat selection of bats varied with grain size (50, 150, 250, and 350 m) and how habitat selection in the home range differed from that in the foraging habitat in an agricultural landscape. Focusing on three sympatric Myotis species (Myotis petax, Myotis gracilis, and Myotis frater), we radio-tracked 10 individuals of each species for 121 nights in Hokkaido, northern Japan. Rivers and broadleaved riparian forests were commonly preferred at multiple scales, although the preferred land-cover type was dependent on both extent and grain size for most species. The best grain sizes for predicting the foraging-habitat use of M. petax and M. gracilis were 50 and 150 m. By contrast, M. frater showed no tendency across the grain sizes. Our results indicate that it is necessary to consider both extent and grain size to understand the habitat selection of bats. Our findings also suggest that focusing primarily on preferred land-cover types at multiple scales is effective for conservation planning, given the limited resources in terms of time, manpower, and finances. Although arable did not negatively affect the selection of foraging habitats and home ranges in these bat species, preventing the loss of rivers and forests should be prioritized over preventing arable land expansion.     

Protecting more than the wetland: The importance of biased sex ratios and habitat segregation for conservation of the Hine’s emerald dragonfly, Somatochlora hineana Williamson

Within species habitat use may depend on age, season or sex of an individual. The distribution of males and females may vary both temporally and spatially due to differences in the costs of reproduction and the distribution of critical resources. Conservation of a species requires knowledge of the habitat use of both sexes in order to predict the population size and protect all habitats that a species requires. Adult dragonfly populations often have highly male-biased sex ratios at the breeding habitat. This bias has been attributed to females using alternative habitats to avoid male harassment, or to high female mortality. We monitored adult Hine’s emerald dragonfly (Somatochlora hineana Williamson) populations, in breeding and non-breeding habitats in Door County, Wisconsin and found significant differences in habitat use between males and females. Males primarily used wetland habitats, while females primarily used dry meadows and marginal breeding habitats, only coming into wetlands to lay-eggs or find mates. We assessed food resources in the different habitats and found that high quality insect prey (primarily adult Diptera) were more available in the wetland habitat, indicating that these areas were likely a more productive foraging area for adult dragonflies. The fact that females appear to avoid the wetland habitat is consistent with the hypothesis that male harassment alters female distribution patterns. Consideration of the patterns of habitat use by S. hineana indicates the need to develop a broader understanding of the importance of non-wetland areas in the conservation of wetland species.     

Effects of landscape-scale broadleaved woodland configuration and extent on roost location for six bat species across the UK

Although forest fragmentation can greatly affect biodiversity, responses to landscape-scale measures of woodland configuration in Europe have been examined for only a limited range of taxa. Almost all European bat species utilise woodland, however little is known about how they are affected by the spatial arrangement of woodland patches. Here we quantify landscape structure surrounding 1129 roosts of six bat species and a corresponding number of control locations across the UK, to examine associations between roost location and landscape composition, woodland proximity and the size of the nearest broadleaved woodland patch. Analyses are performed at two spatial scales: within 1 km of the roost and within a radius equivalent to the colony home-range (3–7 km). For four species, models at the 1 km scale were better able to predict roost occurrence than those at the home-range scale, although this difference was only significant for Pipistrellus pipistrellus. For all species roost location was positively associated with either the extent or proximity of broadleaved woodland, with the greatest effect of increasing woodland extent seen between 0% and 20% woodland cover. P. pipistrellus, Pipistrellus pygmaeus, Rhinolophus hipposideros, Eptesicus serotinus and Myotis nattereri all selected roosts closer to broadleaved woodland than expected by chance, with 90% of roosts located within 440 m of broadleaved woodland. Roost location was not affected by the size of the nearest broadleaved patch (patches ranged from 0.06–2798 ha ± 126 SD). These findings suggest that the bat species assessed here will benefit from the creation of an extensive network of woodland patches, including small patches, in landscapes with little existing woodland cover.     

Factors maintaining species diversity in satoyama, a traditional agricultural landscape of Japan

Satoyama is a traditional agricultural landscape in Japan. It contains many kinds of organisms, including endangered species. Satoyama is composed of several habitat types, including paddy fields, secondary forests, secondary grasslands, ponds, and streams. High species richness has been sustained in most habitats by anthropogenic disturbances of intermediate impact, mainly activities related to agriculture. The variety of habitats and connectivity among them have contributed to the high species diversity within satoyama. These factors allow organisms to move among habitats and use different habitat types to obtain different resources. The connectivity among habitats is often more vulnerable than the specific habitats themselves under anthropogenic influences. In satoyama, species that require connectivity among habitats (e.g., grey-faced buzzard [Butastur indicus] and Genji firefly [Luciola cruciata]) have tended to decrease. The grey-faced buzzard is categorized as a “vulnerable” species in the Japanese Red List. It usually nests in forest trees and forages in habitats such as paddy fields, grasslands, and forests. Its foraging locations shift seasonally depending on food availability. It is thought that the degradation of either paddy fields or forests in a landscape may result in the disappearance of this species. The Genji firefly spends its larval period in stream water, pupates underground along streams, and flies near streams after emergence. This species requires not only the integrity of streams and nearby areas, but also connectivity between these areas. The ecology of these species suggests that the variety of habitats and connectivity among them are critical factors for their survival.     

Mitochondrial DNA sequence, morphology and ecology yield contrasting conservation implications for two threatened buckmoths (Hemileuca: Saturniidae)

Taxa of conservation interest are frequently identified using morphological or ecological characters. These characters are assumed to represent evolutionary importance, population structure and/or phylogenetic relationships in such organisms. We tested this assumption using two species complexes of the moth genus Hemileuca (Saturniidae). Both have populations threatened by habitat loss and need conservation protection. Legislation protects one taxon with apparent ecological differences. We sequenced 624 base pairs of mtDNA from the COI gene for geographically distant populations of the Hemileuca maia species complex and the H. electra species complex. Resultant phylogenies contradict prior assumptions about relationships in both species complexes. The legislatively protected Bog Buckmoth is paraphyletic with widespread H. maia, and its use of a novel hostplant seems to be a local adaptation. Divergent morphology and hostplant use among H. electra subspecies are associated with modest genetic divergence (0.48%). However, a group of unrecognized populations that are morphologically similar and geographically close to H. electra electra have mtDNA that is divergent by an average of 4.1%. There is disagreement regarding prioritization of ecological divergence over neutral genetic distance in conservation. We place ecological variation in a phylogenetic context and recommend that exploration of genetic relationships be undertaken when populations are threatened. Adaptive ecological variation should be evaluated in a phylogenetic context to understand its conservation importance. This study illustrates the importance both of phylogenetic context and the use of independent characters in assessing biodiversity for conservation prioritization.     

Influence of prey variables, food supply, and river restoration on the foraging activity of Daubenton’s bat (Myotis daubentonii) in the Shibetsu River, a large lowland river in Japan

To conserve the foraging habitat of Daubenton’s bat (Myotis daubentonii) in a large lowland river, we investigated the influence on this bat of prey variables (number or biomass) and insect origin (aquatic or terrestrial). We tested the hypothesis that river restoration (re-meandering) conducted in the Shibetsu River, northern Japan, enhances foraging habitat quality by increasing the abundance of aquatic insects. From June to September 2004, flying insects were collected using Malaise traps in restored and channelised reaches in the Shibetsu River. Bat activity was recorded by bat detectors placed near the Malaise traps in each of the two reaches. Foraging activity of Daubenton’s bat was more strongly related to the number of insects than to biomass, and to adult aquatic insects than to terrestrial insects. The high dependence of Daubenton’s bat on aquatic prey was attributed to the fact that aquatic insect numbers were always higher than those of terrestrial insects. Contrary to the hypothesis, Daubenton’s bat was more active in the channelised reach than the restored reach in all months except June, and it synchronized its foraging activity with the seasonal distribution of adult aquatic insects. However, the study was undertaken just two years after restoration and the riparian vegetation had not yet established itself. Our results demonstrate the importance of aquatic insect abundance for Daubenton’s bat throughout the seasons in large lowland rivers. A further decrease in aquatic insects, associated with progressive anthropogenic alteration of river environments, undoubtedly exerts a harmful influence on the conservation of this species.     

Patterns of roost use by bats in a neotropical savanna: implications for conservation

Neotropic bats comprise a highly species-rich group and are considered important regulators of complex ecological processes. Resource partitioning of roosts and food is considered a key element in shaping bat communities. In this paper we examine the roosting patterns of 10 bat species belonging to a neotropical bat community in a Bolivian savanna. Roosts were more common in open woodlands than in forest islands and human settlements. In open woodlands, Tabebuia heptaphylla comprised the largest proportion of roosting trees, whereas in forest islands, Gallesia integrifolia was the most important roosting tree for phyllostomid bats. By comparing active roosts with control holes in Tabebuia heptaphylla, we found that roost site selection by Noctilio albiventris was mainly based on tree diameter and inner width of the cavities. The earlier results are discussed in view of resource partitioning within savanna bat communities and their practical conservation.     

Habitat use and conservation of bumblebees (Bombus spp.) under different grassland management regimes

Declines in the natural populations of several bumblebee species across Britain and Europe are an increasing cause for concern. In this study the habitat use of bumblebees was investigated on Salisbury Plain Training Area, the largest remaining area of unimproved chalk grassland in north-west Europe. Habitat characteristics influencing the overall abundance, species richness and foraging activity of bumblebees included the diversity and abundance of flowering plant species (particularly of favoured forage plants such as Trifolium pratense), vegetation structure and height. It is suggested that different Bombus species respond to these habitat characteristics depending on their specific foraging and nesting requirements, the case of Bombus humilis being especially relevant. The effects of several grassland management practices were considered in terms of their suitability for the conservation of bumblebee habitats. Cattle grazing was shown to be preferable to both sheep grazing and the absence of any management, although the timing and intensity of such grazing was important. Small-scale disturbances caused by vehicle activity were also of value in producing locally abundant forage resources in less intensively managed grasslands.     

Habitat selection by the Mediterranean horseshoe bat, Rhinolophus euryale (Chiroptera: Rhinolophidae) in a rural area of southern Italy and implications for conservation

We studied habitat selection by Rhinolophus euryale in a rural area of southern Italy in 1998-2000 by radio-tracking. Two comparisons were carried out, one between habitat occurrence within individual home ranges and within the study area, the other between time spent in each foraging habitat and habitat occurrence within the home range. The first analysis showed that olive groves and conifer plantations were, respectively, the most and the least important habitats. The second analysis highlighted the importance of woodland for R. euryale, while urban sites, open areas and conifer plantations were avoided. We recommend that clearing of continuous, large areas of woodland for tree harvesting should be avoided. Conifers should not be used for reforestation. Urbanisation should be limited in the areas of greatest importance for the species, and linear landscape elements such as tree lines and hedgerows should be maintained.