Bat Box Research Articles

Bat box monitoring: testing the efficacy of eDNA to confirm box use

ABSTRACT Bat boxes can be employed to provide short-term mitigation for the loss of trees with bat roost potential. Traditionally bat box utilisation (by long-tailed bats) has been difficult to confirm in NZ, partly due to a lack of published survey techniques to confirm bat box utilisation when bats are not present at the time of sampling. While environmental deoxyribonucleic acid (eDNA) has been widely applied as a biomonitoring tool, it has not been used previously in the context of bat box surveys in New Zealand. Here we present a method for collecting eDNA from bat boxes using swabs and test the efficacy of eDNA in validating bat box utilisation as confirmation of roosting. Bat boxes were deployed by the Hamilton City Council as part of the bat mitigation strategy for the Southern Links Project in southern Hamilton. The eDNA method confirmed a total of 25 boxes out of the 73 (34%) included in this study were being utilised by long-tailed bats. The results indicate that eDNA can be applied with confidence to demonstrate box use, even at very low and infrequent occupancy rates.

Bat box monitoring: comparing multiple contemporary methods

ABSTRACT Bat boxes can be employed to provide mitigation for the loss of trees with bat roost potential. Eighty bat boxes were deployed by the Hamilton City Council as part of the bat mitigation strategy for the Southern Links Project in southern Hamilton. Several contemporary methods were employed to determine bat box occupancy to ensure effective monitoring. This included visual scoring assessments (e.g. staining, wetness), endoscope surveys, thermal imaging, and eDNA. Emergence survey data were provided by the University of Waikato which provided further insight into the accuracy of the methods. Jointly the methods confirmed the use of 34 Kent style boxes (n = 70; 49%). Indicating a high success rate of box utilisation over a relatively short period (two years). Of the methods, eDNA confirmed the largest percentage of bat box use. Comparatively, thermal imaging provided an alternative and less intrusive means of surveying on-the-day bat presence. However, there were instances where survey conditions (e.g. terrain, vegetation clutter, solar irradiance, rainfall) influenced the reliability of thermal imaging. While visual assessment and thermal imaging cannot be solely relied on, they provide a supportive tool for other monitoring techniques. They can help guide the application of more definitive methods such as eDNA.

Use of artificial refuges as a strategy for the conservation of bats

One of the main problems for the conservation of bats in Colombia is ignorance about them and their ecosystem services. In this study, we aimed to contribute to the understanding and conservation of the bat fauna of the Pasuncha region (Pacho, Cundinamarca, Colombia) by making a species inventory, installing artificial shelters as a conservation strategy, and implementing education programs addressing human-bat interaction. We recorded eight species for the region: Artibeus lituratus, Carollia brevicaudum, Carollia castanea, Carollia perspicillata, Sturnira erythromos (fruit eaters); Glossophaga soricina (nectarivorous-polynivorous); Eptesicus brasliensis (insectivore), and Desmodus rotundus (sanguinivorous). We found C. brevicaudum, C. perspicillata, and G. soricina using abandoned houses as refuges and measured the basic population characteristics of the species at the Roble & Nogal reserve. Based on the biotic and abiotic information, we designed, built, and installed a bat box for fruit eaters and nectarivorous-polynivorous species. We also implemented an environmental education project focused on citizen science to encourage changes in the community’s perceptions and behavior toward bats whose results were reflected in a series of illustrative brochures produced jointly with the community.

Evaluating bat boxes: design and placement alter bioenergetic costs and overheating risk

Bat box microclimates vary spatially and temporally in temperature suitability. This heterogeneity subjects roosting bats to a variety of thermoregulatory challenges (e.g. heat and cold stress). Understanding how different bat box designs, landscape placements, weather and bat use affect temperature suitability and energy expenditure is critical to promote safe and beneficial artificial roosting habitat for species of conservation concern. From April to September 2019, we systematically deployed 480 temperature dataloggers among 40 rocket box style bat boxes of 5 designs and regularly monitored bat abundance. We used bioenergetic models to assess energy costs for endothermic and heterothermic bats and modelled the overheating risk for each box as a function of design, placement, bat abundance and weather. For endothermic bats, predicted daily energy expenditure was lower for solar-exposed placements, large group sizes and a box design with enhanced thermal mass. For heterothermic bats, shaded landscape placements were the most energetically beneficial and bat box design was not important, because all designs generally offered microclimates suitable for torpor use at some position within the box. Overheating risk was highest for solar-exposed landscape placements and for designs lacking modifications to buffer temperature, and with increasing bat abundance, increasing ambient temperature and slower wind speeds. The external water jacket design, with the greatest thermal mass, concomitantly decreased overheating risk and endothermic energy expenditure. By assessing bat box suitability from two physiological perspectives, we provide a robust method to assess the conservation value of bat box design and placement strategies. We recommend future studies examine how changing thermal mass and conductance can be used to diminish overheating risk while also enhancing the effects of social thermoregulation for bat box users.

What makes a good bat box? How box occupancy depends on box characteristics and landscape‐level variables

Abstract Bat populations are in steep decline and presently, 16% of all species are classified as ‘threatened’. One main driver identified for this decline is the loss of natural roosting opportunities, caused by the removal of natural habitats. Installation of bat boxes is one solution to compensate for the lack of natural roosting opportunities. Current recommendations for box design emphasize low maintenance costs and are rarely based on empirical evidence. We investigated occupancy of 13,634 bat boxes in northern Bavaria, Germany. In our study, boxes differed in type, age and mounting height, as well as in maximum community age, that is the length of time a group of boxes had been installed in a particular place, the size of box groups and the distance to the next box in the surrounding area, that is box isolation. Our results showed that box occupancy depended on box type and bat species. As a case study, we analysed the two most common species found within the investigated boxes, Pipistrellus pipistrellus and Myotis nattereri, in more detail. Both species showed preference to a voluminous box that had a narrow entrance (‘Gable box’ 14 mm). For P. pipistrellus, only box type affected occupancy, whereas for M. nattereri, the relationship between box type and box age was important. Older boxes and boxes in areas with higher maximum community age of boxes showed higher box occupancy by bats. Box occupancy decreased with the distance between adjacent box groups (‘box isolation’). High mounting height showed a tendency for increased box occupancy, but the effect was only weakly significant. Because of the species‐specific responses in our study, we suggest installing a combination of different box types, including at least one box type with a narrow entrance (14 mm). Boxes should be placed as box groups of three to four boxes, and there should be short distances between adjacent box groups. We also recommend installing new box groups close to areas of high maximum community age of boxes.

Methods for assessing artificial thermal refuges: Spatiotemporal analysis more informative than averages

1Thermal refuges are widely used by animals of all taxonomic groups and are critical to survival in severe weather. 2Human activities are reducing the availability of natural refuges; consequently, artificial refuges are used as conservation management tools, particularly for bats. 3Published box evaluations are generally incomplete, omitting thermal physiology and relevant thermal properties. 4Here, we compare methods for evaluating the potential utility of bat box designs for bats and present a graphical spatiotemporal method that provides more complete information. 5For illustration, we compare the original to three modified versions of the “rocket box” style bat box. 6Box internal temperatures and generalized thermal physiology models are combined in two suitability indices appropriate to the mother, and to pups. 7Results revealed that daily and seasonal averages of these indices obscured important processes and showed insignificant differences among bat box design modifications. 8In contrast, graphical analysis highlighted the presence and spatiotemporal structure of significant differences among boxes, which were most evident in sunny weather. 9Differences among boxes were sensitive to assumptions about bat thermal physiology and behavior. 10We found that an external water jacket mitigated temperature extremes and extended favorable temperatures into the night, which could enhance pup development while the mothers foraged. 11Further experiments are needed to evaluate the relation between metabolic heating by box occupants and thermal conditions within bat boxes.

Design modifications affect bat box temperatures and suitability as maternity habitat

Abstract Artificial roosting structures (e.g. bat boxes) are widely used as conservation tools for many animals, including bats. Although it is relatively easy to monitor bat box temperatures, we know little about the effect of design on temperatures within a box. Box microclimate affects energy budgets and physiological processes and, thus, suitability as a roost. Optimal temperature varies during the period when reproductive females aggregate to rear pups; warm roosts enhance pup development during gestation and lactation, while cool roosts facilitate energy savings by torpor, which is often important during post‐lactation. To better understand the relation of design to internal temperature, we simultaneously compared 20 box designs (19 variations of a rocket box and one three‐chamber flat box) in an open site, May to September 2018. We measured temperatures at the top, middle and bottom of each box and tallied counts of daytime and nighttime cool (≤30°C; TCOOL), permissive (30.1–39.9°C; TPERM) and stressful (≥40°C; TSTRS) temperature observations. We also measured temperature, solar radiation and wind speed at the site. We used generalized linear models with negative binomial distributions to test the effects of design, environmental variables and their interactions. Adding an external jacket or decreasing ventilation increased daytime and nighttime counts of TPERM. Increasing box volume (i.e. lengthening box by 50%) also positively affected daytime counts of TPERM, whereas decreasing box volume (by 50%) had the opposite effect. Adding an external water jacket was the only modification we tested that decreased counts of TCOOL at night. Counts of TSTRS were elevated by warmer, sunnier and less windy conditions outside, but these effects were lessened by increasing roof shading or reflectivity, adding ventilation or external jackets, or decreasing box volume. These results inform the development and implementation of novel bat box designs as conservation and management tools for maternal colonies of bats, with consideration for the effects of weather on internal temperatures.

Concurrent Butterfly, Bat and Small Mammal Monitoring Programmes Using Citizen Science in Catalonia (NE Spain): A Historical Review and Future Directions

The Biodiversity and Bioindicators research group (BiBIO), based at the Natural Sciences Museum of Granollers, has coordinated four long-term faunal monitoring programmes based on citizen science over more than two decades in Catalonia (NE Spain). We summarize the historical progress of these programmes, describing their main conservation outputs, the challenges overcome, and future directions. The Catalan Butterfly Monitoring Scheme (CBMS) consists of a network of nearly 200 recording sites where butterfly populations have been monitored through visual censuses along transects for nearly three decades. This programme provides accurate temporal and spatial changes in the abundance of butterflies and relates them to different environmental factors (e.g., habitat and weather conditions). The Bat Monitoring Programme has progressively evolved to include passive acoustic monitoring protocols, as well as bat box-, underground- and river-bat surveys, and community ecological indices have been developed to monitor bat responses at assemblage level to both landscape and climatic changes. The Monitoring of common small mammals in Spain (SEMICE), a common small mammal monitoring programme with almost 80 active live-trapping stations, provides information to estimate population trends and has underlined the relevance of small mammals as both prey (of several predators) and predators (of insect forest pests). The Dormouse Monitoring Programme represents the first monitoring programme in Europe using specific nest boxes for the edible dormouse, providing information about biological and demographic data of the species at the southern limit of its distribution range. The combination and complementarity of these monitoring programmes provide crucial data to land managers to improve the understanding of conservation needs and develop efficient protection laws.

First Record of a Suspected Human-Pathogenic Borrelia Species in Populations of the Bat Tick Carios vespertilionis in Sweden.

The bat tick Carios vespertilionis has been reported from Sweden to occasionally feed on humans resulting in disease symptoms. The aim of this study was to investigate C. vespertilionis as a potential vector and reservoir of Borrelia species. In 2015 and 2018 in south-central Sweden, C. vespertilionis ticks were collected from a wooden bat box harboring Soprano pipistrelle bats, Pipistrellus pygmaeus. In addition, one C. vespertilionis tick found inside a house in southern Sweden in 2019 was collected. Ticks were screened for Borrelia spp. using a genus-specific quantitative PCR assay. The Borrelia species of the positive specimens were determined by conventional PCR followed by DNA sequencing and phylogenetic analyses. A total of 24% (22 of 92) of the analyzed C. vespertilionis ticks were Borrelia-positive. Phylogenetic analyses indicate that the bacteria belong to the relapsing fever group of borreliae; some of them appear to be identical with Borrelia sp. CPB1, a spirochete only found twice before—in the United Kingdom and in France. Our results also indicate a temporal and spatial distribution of this Borrelia species. Since C. vespertilionis occasionally bites humans, and since it exhibits a high prevalence of Borrelia bacteria, it is possible that it presents a risk of human disease. Further studies are needed to characterize Borrelia sp. CPB1 to determine if it is human-pathogenic and to determine if C. vespertilionis is a vector and/or reservoir of this agent.

Using mounting, orientation, and design to improve bat box thermodynamics in a northern temperate environment

Wildlife managers design artificial structures, such as bird houses and bat boxes, to provide alternative nesting and roosting sites that aid wildlife conservation. However, artificial structures for wildlife may not be equally efficient at all sites due to varying climate or habitat characteristics influencing thermal properties. For example, bat boxes are a popular measure employed to provide compensatory or supplementary roost sites for bats and educate the public. Yet, bat boxes are often thermally unstable or too cold to fulfill reproductive females needs in northern temperate environments. To help improve the thermodynamics of bat boxes, we tested the effect of (1) three mountings, (2) four orientations, and (3) twelve bat box designs on the internal temperature of bat boxes. We recorded temperatures in bat boxes across a climate gradient at seven sites in Quebec, Canada. Bat boxes mounted on buildings had warmer microclimates at night than those on poles and those facing east warmed sooner in the morning than those facing west or south. Our best new model based on passive solar architecture (Ncube PH1) increased the time in the optimal temperature range (22–40 °C) of targeted species by up to 13% compared to the most commonly used model (Classic 4-chamber) when mounted on a building with an east orientation (other designs presented in the Supplementary Information). Based on bioenergetic models, we estimated that bats saved up to 8% of their daily energy using the Ncube PH1 compared to the Classic 4-chamber when mounted on a building with an east orientation. We demonstrate that the use of energy-saving concepts from architecture can improve the thermal performance of bat boxes and potentially other wildlife structures as well.

Activity patterns of the soprano pipistrelle Pipistrellus pygmaeus throughout the year in southern Norway

BackgroundMost temperate bats are regular hibernators in the winter. Knowledge about the length of their active season and how they adjust their nightly activity throughout the season, is critical to conservation. The characteristics of these are likely to vary with climate as well as latitude. This study investigated the flight activity of the soprano pipistrelle Pipistrellus pygmaeus in Frafjord, a small valley in the south-western corner of Norway (58° 50′N 6° 18′E) with an oceanic climate.ResultsActivity was recorded with an ultrasound recorder throughout April 2018 to June 2019 at one site, with supplemental recordings in March to June 2020, i.e., covering all months of the year. Recordings at other nearby sites were made in the summers (June–August) of 2016, 2017, 2019 and 2020, as well as some of the last days in December 2019 to the first days of January 2020. Overall, soprano pipistrelles were recorded flying in all months of the year, but very few in December–March. Regular activity was recorded from late April or early May until late October, and some recordings were also made in November. The highest numbers of recordings were made in August and September. Social calls, i.e. male song flights, were recorded from April to November, with the vast majority in August and September. Nearly all recordings were made between sunset and sunrise.ConclusionsThe soprano pipistrelle in this region showed regular activity through 6–7 months of the year. It adjusted its activity to the changing night length throughout the year, closely following sunset and sunrise. It was rarely recorded flying before sunset and almost never after sunrise. Most activity was recorded in the middle of the night, and social calls also followed this trend closely. Harems in late summer and autumn were confirmed in a bat box, which was also used for winter hibernation.

Overheating turns a bat box into a death trap

Thirty juvenile large forest bats (Vespadelus darlingtoni) were found dead in a plywood bat box. This is the first example in Australia of an overheating event in a bat box resulting in multiple mortalities. It confirms that extreme heat in poorly insulated bat boxes can result in acute hyperthermia.

The effect of group size, reproductive condition and time period on sexual segregation patterns in three vespertilionid bat species

AbstractSexual segregation is widespread across the animal kingdom, yet there is limited consensus on the factors that shape this behavioural phenomenon. Many of the existing theories are based on study species with high levels of sexual size dimorphism. Insights from studies on species with minimal sexual size dimorphism, such as vespertilionid bats, provide an opportunity to study the factors associated with segregation irrespective of body size effects. Using long‐term data pooled from multiple bat box monitoring schemes across the U.K., we investigated segregation patterns in maternity roosts of three vespertilionid bat species, Bechstein’s bat, Myotis bechsteinii, Natterer’s bat, M. nattereri and brown long‐eared bat, Plecotus auritus. We used the Sexual Segregation and Aggregation Statistic (SSAS) to evaluate temporal trends of sexual segregation of roosts over the reproductive period (divided into pre‐parturition, lactation and post‐lactation periods). Additionally, we used generalized linear mixed models and beta regression models to investigate the effect of group size on segregation patterns. Our results showed that the size of the maternity group was an important covariate of inter‐ and intra‐sexual segregation, with males and non‐breeding females typically segregated from large maternity groups across all three periods. Additionally, we demonstrate that reproductive condition and period influence segregation patterns, with breeding females segregated from non‐breeding females and males during the lactation period. Although sexual segregation may be caused by multiple mechanisms, our results show that group size, female reproductive condition and time period are key factors associated with segregation within bat roosts. These findings make a valuable contribution to the understanding of inter‐ and intra‐sexual segregation in vespertilionid bats and complement existing research on segregation in other mammalian taxa, providing further evidence that sexual size dimorphism is not a prerequisite for sexual segregation.

Novel real-time PCR species identification assays for British and Irish bats and their application to a non-invasive survey of bat roosts in Ireland

Detection and monitoring of extant bat populations are crucial for conservation success. Non-invasive genetic analysis of bat droppings collected at roosts could be very useful in this respect as a rapid, cost‐efficient monitoring tool. We developed species‐specific real-time PCR assays for 18 British and Irish bat species to enable non‐invasive, large‐scale distribution monitoring, which were then applied to a field survey in Ireland. One hundred and sixty-four DNA samples were collected from 95 bat roosts, of which 73% of samples were identified to species, and the resident bat species were identified at 89% of roosts. However, identification success varied between roost types, ranging from 22% for underground sites to 92% for bat boxes. This panel of DNA tests will be especially useful in cases where roosts contain multiple species, where the number of bats present is small, or bats are otherwise difficult to directly observe. The methodology could be applied to the surveillance of proposed development sites, post development mitigation measures, distribution surveys, bat box schemes and the evaluation of agri-environmental bat box schemes.

Testing multichambered bat box designs in a habitat-offset area in eastern Australia: influence of material, colour, size and box host

Bat boxes are frequently used as conservation and habitat-offset measures, yet their effectiveness is equivocal, particularly in Australia. Boxes used in Australia are largely voluminous-type boxes with Chalinolobus gouldii (Gould’s wattled bat) frequently dominating their use. We tested multichambered boxes comprising fissure-type cavities made from either plywood (~20000cm3) or woodcement (~7400cm3). We investigated whether occupancy was influenced by box colour (white boxes facing morning sun versus black boxes facing afternoon sun), box material/size, chamber width (15mm versus 20mm) and box host (tree versus pole). Boxes were monitored over 1.8 years. Overall, 245 bat observations were recorded. Boxes were frequently used (15% of 1088 box checks) by Nyctophilus geoffroyi (lesser long-eared bat), a species uncommonly reported to use boxes, which used 50 of the 64 boxes (78%), including for maternity roosting (n=6). In comparison, C. gouldii was rarely detected (1% of box checks). Two other species were also found in boxes at low frequencies. Modelling showed a preference by N. geoffroyi for black boxes, the larger plywood box and boxes installed on poles. Fissure-type boxes appear to meet the roost requirements of N. geoffroyi but not that of C. gouldii, the species principally detected in voluminous-type boxes and postulated to gain a competitive advantage. The black woodcement box was the second most frequently used design, demonstrating that this long-lasting box material can be a suitable alternative to the less durable plywood material. Given that just one species commonly used boxes, there is a need for further research on box designs.

First Utilization Record of Bat Box for Bat Conservation in Korea

First Utilization Record of Bat Box for Bat Conservation in Korea

Limited use of bat boxes in a rural landscape: implications for offsetting the clearing of hollow‐bearing trees

Bat boxes frequently form part of hollow‐bearing tree offsets; however, their effectiveness is poorly documented. We investigated the effectiveness of a bat box program designed to partially offset tree hollow loss from clearing for a coal mine. During the first year of monitoring, we detected bats in 5% of 1,308 box checks. Only 3 of 13 local tree cavity‐roosting bat species/species groups used boxes and occupancy was not strongly associated with modeled box and site attributes. In the second year, we tested two hypotheses that may explain the relatively low box use: (1) solar exposure of boxes was inadequate for heterothermic bats and (2) available box designs were of low suitability. Relocating boxes to increase solar exposure did not increase use, or enhance the temperature profiles of relocated boxes. Introduction of a new box design led to 11 times higher use compared with existing designs forNyctophilusspp. (long‐eared bat). Overall, our data suggest that the bat box program was ineffective due to few bat species using boxes, infrequent box use by three species, and rarity of maternity roosting. The knowledge gap of species‐specific box designs and roosting ecology limits the effectiveness of boxes to offset cleared hollow‐bearing trees. Lack of knowledge and the widespread use of bat boxes to offset lost tree hollows highlights the need to (1) rigorously protect hollow‐bearing trees and (2) advance our understanding of species‐specific roost ecology, box design preferences and mechanical hollow creation into trees, before artificial hollows can be considered a meaningful offset measure.

Flexible roost selection by Gould’s wattled bats (Chalinolobus gouldii) using bat boxes in an urban landscape

Bat boxes are often used as a conservation tool in human-disturbed landscapes across Australia; however, to assess their effectiveness we need to understand the factors influencing their occupancy by insectivorous bats. We investigated roost selection by Gould’s wattled bat (Chalinolobus gouldii) using 76 bat boxes, comprising six designs, across three sites in suburban Melbourne, Australia. We conducted monthly surveys for a year and recorded the physical characteristics of each box. Five species of bats were recorded but Gould’s wattled bats dominated box occupancy year-round at all three sites. Group sizes ranged from 1 to 58 individuals, with maternity colonies forming over summer. There was little consistency in the use of selection criteria by Gould’s wattled bats when choosing a bat box as a day roost, with considerable variability across sites and seasons, highlighting the flexibility in roost site selection by this widespread, adaptable species. Our findings show that bat boxes can be an effective tool for providing supplementary roosts for Gould’s wattled bats in urbanised landscapes. However, little is known about the impact on the whole bat community, especially disturbance-sensitive taxa, of artificially increasing roosting resources for common species.

In artificial roost comparison, bats show preference for rocket box style.

Understanding microhabitat preferences of animals is critical for effective conservation, especially for temperate-zone bats, which receive fitness benefits from selecting optimal roost microhabitats. Artificial roost structures are increasingly being used in conservation efforts for at-risk bat species. To evaluate microhabitat differences in common artificial roost structures and determine if roost selection occurs based on structure type, we installed artificial roosts of three different styles (bat box, rocket box, and bark mimic) in six clusters. We compared size and measured temperature parameters (12 points/roost) while bats were excluded from one cluster. We simultaneously conducted census counts during the active season at five more clusters open to bats for 1–2 years. The rocket box style provided larger entrance area, surface area, and volume versus other roost types. Microclimate varied with roost design. More positions inside the bat box and rocket box stayed within critical temperature limits for bats (0–45°C)—i.e., were usable. The bark-mimic provided less usable space than the rocket box and, often, large proportions of the roost were > 45°C. The rocket box provided the widest temperature availability in a given hour (max range available 7°C) and was more stable than the bark mimic. A maternity colony of Indiana bats (Myotis sodalis) selected the rocket box style; four of five available rocket boxes became primary maternity roosts, with 2–210 bats emerging per night. Future work should aim to manipulate roost size, temperature availability, and temperature stability in isolation to identify which features drive roost microhabitat selection by bats. Comparative studies of artificial roosts account for some inherent irregularity in natural systems, allowing us to study the dynamics of roost microhabitats. We recommend season-long monitoring of microhabitat in novel artificial refuges and comparative studies of artificial and natural roosts, and urge managers to consider potential positive and negative effects when substituting artificial roosts for natural habitat.

Long-term monitoring suggests bat boxes may alter local bat community structure

Bat boxes are often used to provide supplementary roosting habitats; however, little is known of their impacts on community composition. Data collected from a 25-year box-monitoring and 31-year harp trapping case study provides preliminary evidence that the installation of boxes may have contributed to one species, Gould’s wattled bat (Chalinolobus gouldii), dominating the bat community of a periurban park in Melbourne. This highlights the need for systematic monitoring and empirical assessment of conservation-focused bat box programs.