Maternity Roosts Research Articles

Vocalization Development in Geoffroy's bat, Myotis emarginatus (Chiroptera: Vespertilionidae).

Postnatal development of vocalization has been studied in a small number of bats, not including the Geoffroy's bat, Myotis emarginatus. In the present study, we investigated vocalization development at a maternity roost of M. emarginatus in Kerend Cave in western Iran by sequential measurement of acoustic parameters in known-age neonates using mark-recapture sampling. Newborn pups of M. emarginatus produced both short and isolation calls. Duration of short calls of 1-day-old pups was on average 7.56 ± 0.05 ms and decreased during postnatal development to reach an adult-like duration of 2.78 ± 0.13 ms in the third week. Myotis emarginatus emitted various types of isolation calls, including classic, UP-tail-FM and CF-tail during postnatal growth. As bat pups grew, both short and isolation calls changed in their spectro-temporal structure. Discriminant function analyses showed that each bat pup has a vocal signature that facilitates mother-infant communication. The current study reveals that M. emarginatus pups are highly vocal at birth, but gradually elaborate their sounds with an increase in peak, start and end frequencies as well as with a decrease in call duration throughout the postnatal growth period.

A Noninvasive Genetic Technique Using Guano for Identification of Corynorhinus townsendii (Townsend's Big-Eared Bat) Maternity Roosts

The use of DNA from fecal samples can allow for a better understanding of the ecology of a species without capturing and handling the animals. This is particularly useful for cryptic and elusive animals, such as bats. Being able to identify critical habitat, such as maternity roosts, for bat species in areas where they depend on abandoned mines that could be slated for closure is necessary to enact appropriate protections for such roosts. In particular, Corynorhinus townsendii commonly uses abandoned mines for maternity roosts. Further, maternity roosts are difficult to identify through visual surveys when only one or a few surveys are performed before mine closures. We have developed a method for identification of C. townsendii maternity roosts that uses fecal DNA extracted from fresh guano collected from plastic sheeting placed at a mine entrance. We provide a multiplex PCR assay to amplify a control region fragment found only in C. townsendii, as well as a Y-linked protein (DBY) to detect male C. townsendii DNA. The purpose of this study was to identify a temporal shift in the presence of male C. townsendii bats, which can be useful to identify a maternity roost. This method allows for noninvasive identification of critical habitat for this species and reduces the effort and safety risk of entering mines on the part of biologists.

Moths Consumed by the Barbastelle Barbastella barbastellus Require Larval Host Plants that Occur within the Bat's Foraging Habitats

Loss of foraging habitat and reductions in insect prey are key factors responsible for declines in bat populations. Identifying important bat foraging habitats and the ecological requirements and conservation status of prey provides evidence for appropriately targeted conservation management strategies. We examined the foraging habits of the barbastelle, Barbastella barbastellus, at the northern edge of its European range using a combination of radio tracking, to determine home range use and habitat selection, and DNA metabarcoding, to identify prey items consumed. Riparian vegetation and broadleaved woodland were the habitat types most strongly selected by foraging bats. Hedgerows within pastoral habitats were also important foraging features within the landscape. We identified 120 different prey items within faecal pellets, the majority of which were moths (97.5%). The large majority (97%) of prey items consumed have larval stages dependent on host plants that are typically found within habitats selected by foraging B. barbastellus. Almost half of all moth prey species identified have undergone considerable population declines in recent decades. We present the most comprehensive list to date of prey consumed by B. barbastellus and provide evidence that conservation management policies should target the protection and enhancement of key B. barbastellus foraging habitats within a 6.5 km sustenance zone around maternity roost sites. Riparian habitat, broadleaved woodland and linear landscape features such as hedgerows should be managed to improve their value to foraging B. barbastellus as well as the developmental stages of their preferred moth prey.

Genetic variability and connectivity of the Mexican long-nosed bat between two distant roosts

AbstractGenetic variability generally is associated with adaptive potential of species and can be assessed using microsatellite markers. Mexican long-nosed bats (Leptonycteris nivalis) are endangered, migratory nectarivores thought to be experiencing population declines. Despite historical and current tracking efforts, migratory connections among roost sites remain elusive. Our objective was to assess the genetic variability and connectivity of two of the most geographically separated populations of L. nivalis currently known—a mating roost in central Mexico used from September to March, and a maternity roost in western Texas used by adult females and their young from June to August. Twelve loci developed for L. yerbabuenae and four for Glossophaga soricina amplified L. nivalis DNA; of those 16 loci, seven (all from L. yerbabuenae) were useful in genetic analyses of 113 individuals. High levels of genetic variation in L. nivalis from the two sites were not significantly different and no substructure was detected between these two roost sites separated by more than 1,200 km. Further, we recovered evidence of close relationship (parent–offspring) in nine pairs of juveniles captured at the northern roost and adults from the southern roost, confirming a connection between the two locations. For this endangered species, the level of variation detected, the lack of a recent bottleneck, and estimates of effective population size, are encouraging for future recovery. Management plans aimed at conserving Mexican long-nosed bats should recognize the need for managing these bats as a single population and conserving foraging and roosting habitat along migratory routes to reduce population fragmentation.

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.

Threat analysis of modelled potential migratory routes forMiniopterus natalensisin South Africa

AbstractMigrant cave‐dwelling insectivores that rely on specific caves for maternity and hibernation, like the Natal long‐fingered batsMiniopterus natalensisin South Africa, may be at particular risk of population decline in an urbanising world. As a step towards the conservation of caves and cave‐dwelling bats in South Africa, this study aimed to (i) broadly identify the number of caves used by bats (any species) and specificallyM. natalensis, throughout South Africa, (ii) investigate the number of maternity and hibernacula roosts currently known forM. natalensis, (iii) assess the number of caves located in formal protected areas, (iv) determine potential migration paths/corridors between hibernacula and maternity sites and (v) evaluate the potential threats (like onshore wind facilities) along potential migratory routes. A meta‐analysis of scientific literature and websites was conducted to identify caves throughout South Africa and locations of maternity and hibernacula roosts forM. natalensis. Roosts were assessed to determine whether (i) they were located in protected areas, (ii) they were used for eco‐tourism and (iii) the distance to primary roads and onshore wind energy facilities. Next, likely migratory paths were modelled between maternity and hibernacula sites using least‐cost path analysis and the threats along potential routes were investigated. A total of 92 caves were identified, 50 were reported to contain bats.M. natalensiswere recorded in 37 caves, and of those, only 9% are currently located inside protected areas. A total of 12 least‐cost paths were modelled, and various paths intersected potential threat risk elements. Our analysis provides the first description of the potential migration corridors forM. natalensisin South Africa, as well as the current conservation status of bat‐inhabited caves. For a developing country set to experience increased urbanisation pressures, this study highlights the need for conservation measures for South African caves and the dependent bats.

Temperature explains variation in seasonal temporal activity of Miniopterus natalensis more than moonlight or humidity

Animals partition their daily activities based on a variety of internal and external factors. For insectivorous bats, the availability of prey, weather conditions, moonlight and reproductive energy demands are proposed as the major influencers of temporal activity. This study investigated the temporal variation in activity of the subtropical cave-dwelling, migratory Natal long-fingered bat, Miniopterus natalensis, by temperature, humidity, lunar illumination and the time of moonrise per night. Using echolocation survey data collected 2014–2018 near a maternity roost in north-eastern South Africa, differences in activity between the summer maternity (1 September–28 February) and winter non-breeding (1 March–31 August) seasons were described. In the non-breeding season, M. natalensis exhibited peak activity during the early evening, with decreasing activity throughout the night. In the maternity season, a bimodal activity pattern was observed, probably related to peaks in insect activity and the energy requirements of lactating females. Predictably, temperature had the strongest positive influence on the magnitude of M. natalensis activity across both seasons. Humidity also positively affected activity in both seasons to a lesser extent. The time of moonrise did not affect the activity of M. natalensis during either of the seasons. Lunar illumination did not affect activity during the maternity season, but activity was diminished on nights with bright moonlight in the non-breeding season. Emergence and return times were not affected by lunar illumination in either season. The need of M. natalensis to maximise resource acquisition during the maternity season is likely a strong modulator in the temporal activity of this species and outweighs predation risk in high moonlight conditions. Subsequently, this species exhibits nightly activity behaviours that balance risk factors with intrinsic needs during different seasons.

Status of an Anomalous Population of Northern Long-Eared Bats in Coastal North Carolina

AbstractThe northern long-eared bat Myotis septentrionalis was discovered in coastal North Carolina in 2007. Work began in 2015 to document the species' distribution and behavior in eastern North Carolina, and the known range of the species has expanded from 4 coastal counties to 19. Captures occurred in all months of the year and mostly occurred in or adjacent to wetland forest. Captures occurred exclusively in the Middle Atlantic Coastal Plain ecoregion of the state, and the species has not been documented in the Southeastern Plains or Piedmont ecoregions. The lack of captures in the middle of the state suggests spatially disjunct populations in North Carolina. The bats were observed to be active throughout most of the winter and roosted in trees. During late fall–winter 2015–2018, 43 bats were tracked to 165 winter roost trees located mostly in wetland forest. The species' winter activity in coastal North Carolina represents a novel survival strategy as opposed to the hibernation behavior it is assumed to use in the rest of its range. This portion of the state is nearly devoid of caves or mines suitable for hibernacula, but has milder winters with insect activity. During spring 2019, 21 reproductive females were captured in the northern coastal plain and tracked to 64 maternity roost trees located mostly in wetland forest. Pregnant females began to be captured on April 25 and juveniles on June 16, indicating that pups are likely born in late May. Swab samples collected during late fall–winter from species susceptible to white-nose syndrome provided no evidence of Pseudogymnoascus destructans. Since northern long-eared bats in coastal North Carolina are active most of the winter and not dependent upon caves or mines for hibernation, they are likely not susceptible to white-nose syndrome. With the species in sharp decline elsewhere due to white-nose syndrome, this coastal population may serve as a refugium.

Low seasonal variation in greater mouse-eared bat (Myotis myotis) blood parameters.

The greater mouse-eared bat (Myotis myotis) is a flagship species for the protection of hibernation and summer maternity roosts in the Western Palearctic region. A range of pathogenic agents is known to put pressure on populations, including the white-nose syndrome fungus, for which the species shows the highest prevalence and infection intensity of all European bat species. Here, we perform analysis of blood parameters characteristic for the species during its natural annual life cycle in order to establish reference values. Despite sexual dimorphism and some univariate differences, the overall multivariate pattern suggests low seasonal variation with homeostatic mechanisms effectively regulating haematology and blood biochemistry ranges. Overall, the species displayed a high haematocrit and haemoglobin content and high concentration of urea, while blood glucose levels in swarming and hibernating bats ranged from hypo- to normoglycaemic. Unlike blood pH, concentrations of electrolytes were wide ranging. To conclude, baseline data for blood physiology are a useful tool for providing suitable medical care in rescue centres, for studying population health in bats adapting to environmental change, and for understanding bat responses to stressors of conservation and/or zoonotic importance.

Little Brown Bats Utilize Multiple Maternity Roosts Within Foraging Areas: Implications for Identifying Summer Habitat

Abstract Identifying habitat features that may influence the survival and fitness of threatened species is often constrained by a lack of information about the appropriate scale for habitat conservation efforts. Canada's Species at Risk Act lists little brown bats Myotis lucifugus as Endangered and there is a need to determine the scale for delineating important summer habitat features that should be protected. We used a 19-y dataset of banded little brown bats in a 15,000-km2 area of southern Yukon, Canada, to examine fidelity to roost sites and potential foraging areas. We captured and banded 4,349 bats during 208 live-trapping sessions at maternity roosts. Adult females used multiple roosts during the maternity period, separated by up to 6.1 km, within foraging areas, to which individuals exhibited fidelity. Our fidelity rates (≤ 60.5%) are the lowest, and roost-switching rates (≤ 35.5%) the greatest, reported for little brown bats. A small percentage (14.0–20.7%) of females banded as juveniles returned to their natal roosts or foraging areas as adults. We infrequently observed long-distance (25–200 km) switching to novel foraging areas (< 1% of banded bats). We established bat houses to mitigate the loss of a cabin roost; 46.3% of the bats banded at the cabin occupied these houses. The longest documented period of roost fidelity was 18 y, by a female banded as an adult. Roost fidelity by returning adult females declined annually by 3.8–5.3% due to natural mortality, roost switching, or dispersal. Having a choice of multiple maternity roosts within a foraging area may permit little brown bats to select optimal microclimatic conditions throughout the maternity season. Given that fidelity to foraging areas may be higher than to specific roost sites for little brown bats, identification of summer habitat based on foraging areas may be a more effective conservation strategy than relying solely on roost sites.

Investigating maternity roost selection by northern long-eared bats at three sites in Wisconsin

Investigating maternity roost selection by northern long-eared bats at three sites in Wisconsin

Roosting behaviour and the tree-hollow requirements of bats: insights from the lesser long-eared bat (

Access to suitable roosts is critical for the conservation of tree-hollow roosting bats worldwide. Availability of roost sites is influenced by human land-use, but also by the roosting requirements and behaviour of species. We investigated roosting behaviour of the lesser long-eared bat (Nyctophilus geoffroyi) and Gould’s wattled bat (Chalinolobus gouldii) in a rural landscape in south-eastern Australia. Forty-five N. geoffroyi and 27 C. gouldii were fitted with radio-transmitters, resulting in the location of 139 and 89 roosts, respectively. Most (88%) roosts occupied by male N. geoffroyi contained only a single individual. During the breeding season female colonies were larger, with maternity roosts containing 18.3 ± 5.7 (s.e.) individuals. Mean colony sizes for C. gouldii were 8.7 ± 1.4 individuals. Both species shifted roosts frequently: on average, individual N. geoffroyi moved every 2.2 ± 0.23 days and C. gouldii every 2.2 ± 0.14 days. Notably, lactating female N. geoffroyi shifted roosts more frequently than non-breeding females. Individuals of both species roosted within a discrete area, with roosts typically <300 m apart; and consistently returned there from foraging up to 12 km distant. This roosting behaviour highlights three important requirements: (1) a relatively large overall number of hollows to support a population; (2) discrete roost areas with a high density of suitable hollows in close proximity; and (3) a range of hollow types to provide the specialised roosts required, particularly for breeding.

Bat roosts in Tasmania’s production forest landscapes: importance of mature forest for maternity roosts

Mature forest is a key resource for hollow-using bats, but its importance in shaping where bats roost during breeding is not well understood. This lack of understanding limits the ability of forest managers to make informed decisions on the type, amount and spatial arrangement of mature forest to retain for bats in areas used for timber production. Using radio-telemetry, day roosts of three sympatric hollow-using bat species – the chocolate wattled bat (Chalinolobus morio), the Tasmanian long-eared bat (Nyctophilus sherrini) and the lesser long-eared bat (Nyctophilus geoffroyi) – were located in two forested landscapes in south-eastern Tasmania, Australia. By radio-tracking 24 bats in the maternity season, 76 roosts were located, with interspecific variation in roosting preferences evident at the roost, patch and landscape scale. Maternal colonies showed a clear selection for roosting in areas of the landscape containing the highest availability of mature forest, with smaller patches, strips and individual trees used to a greater extent for roosting in the landscape where mature forest was scarce. These findings showcase the importance of retaining mature forest at multiple spatial scales for hollow-using bats.

Roost Composition and Sexual Segregation in a Lowland Population of Daubenton's Bats (Myotis daubentonii)

Using data from 1100 day roosts containing a minimum of 9424 Myotis daubentonii bats, we compare the distribution of adult males, adult females, and juveniles, within SchweglerTM box roosts distributed across 394 ha of woodland adjacent to a river corridor in lowland England. Five social groups, containing both males and females (each comprising 55–230 adult bats per annum, using 37–127 known roosts per colony), occupy discrete roosting areas to which individuals show high inter-annual fidelity. Natal philopatry is also high, compared to between colony movements, for both sexes in our study population. Despite considerable spatial overlap and variability in roost composition over the summer (April to October), related to temporal changes in reproductive status, there is sexual segregation within day roosts. Bachelor (adult male dominated) roosts are situated significantly further from water than maternity (adult female or juvenile dominated) roosts on average. This spatial partitioning between maternity and bachelor roosts operates within rather than between colony home roost ranges, however, with adult males from some social groups found roosting closer to water than are adult females from adjacent colonies. The co-occurrence of maternity and bachelor groups roosting in close proximity, including extensive spatial overlap in roosts occupied, and temporal overlap during roost sharing between the sexes, provides novel insights into social organisation and potential drivers of sexual segregation and mating strategies for this widespread and common species within lowland habitats.

Long-Term Monitoring of the Effects of Weather and Marking Techniques on Body Condition in the Kuhl's Pipistrelle Bat, Pipistrellus Kuhlii

Bats are one of the most widespread and speciose orders of mammals. Despite their huge biodiversity, little is known about the natural behaviour and ecology of many species given the difficulty in monitoring and studying them. Pipistrellus kuhlii is one of the most common bats of the Mediterranean biome but its ecology remains ambiguous given the scarcity of longitudinal studies. Such basic information is urgently needed to predict the shift of species distribution range under climate change scenarios. Here, we analysed the effects of weather variables (namely temperature, precipitation, wind speed and air humidity) on the body conditions of P. kuhlii monitored in five maternity roosts in Southern Europe over more than a decade (17 years). Using linear mixed-effect models, we disentangled the impact of weather predictors on body condition variations in 347 individuals. Our results revealed species-specific sensitivity to variations in the monitored four main weather parameters. Through the modelling analysis, we show how weather seasonal variables recorded prior to the capture period had a substantial role in driving bat body condition. A combination of warmer spring-summers and cooler winters was found associated with optimal body condition in P. kuhlii. Our analysis also showed that P. kuhlii bats were favoured by higher spring humidity combined with intermediate precipitation and humidity levels recorded during the summers prior to the capture. The latter parameters (precipitation and humidity) were arguably linked with the proliferation of entomofauna on which bats feed. Additionally, we assessed the body condition of 45 bats that were previously captured and tagged either with bands or PIT-tags, two of the most widespread marking techniques for bats. We showed that bats carrying a ring (band) or a PIT-tag had a body condition that did not differ to that expected for untagged bats. This suggests that transponding bats has no significant effect on body condition, enabling new opportunities for passive monitoring and large-scale long-term longitudinal studies for these animals.

Social calls of Myotis nattereri during swarming: Call structure mirrors the different behavioral context.

Swarming is a characteristic behavior of bats that occurs in different social contexts. We studied the swarming behavior of Myotis nattereri at a maternity colony and at an autumn swarming site in South-West Germany by using synchronized sound and video recordings. Swarming was always associated with social vocalizations consisting of four frequently occurring call types. Call type A was a short call with a broadband steep-shallow-steep downward frequency modulation. Call type B consisted of two elements beginning with a broadband upward hooked element followed by a steep frequency modulated element. Call type C showed a characteristic rapid downward-upward-downward frequency modulation. Call type D was a long sinusoidal trill-like call with high variability in signal structure. All call types were recorded at the maternity colony, as well as at the autumn swarming site, but the incidence of each call type differed distinctly between the study sites. At the maternity roost, type A calls were most commonly produced. We found evidence for an individual signature in this call type and suggest that this social call has the function of a contact call in Natterer’s bats. At the autumn swarming site, type D calls were the most common social calls; in contrast, this call type was recorded only twice at the maternity roost. The occurrence of trills mainly at the autumn swarming site and their high variability suggests that trills function as male advertisement calls in M. nattereri.

Long term trend of an endangered bat species in north-western Italy

Thirty three maternity roosts of Rhinolophus hipposideros were monitored from 2000 to 2018 in an area of north-western Italy, between the Piedmont (13 roosts) and Liguria regions (20 roosts), and data were analysed through a TRIM statistic to calculate a robust estimation of reproductive population trends. Throughout the 19-years-long monitoring period, a total of 5135 Rhinolophus hipposideros were counted in maternity roost, with a mean of 273 (SD = 198.1) per year (mean Piedmont = 73, SD = 85.9; mean Liguria = 200, SD = 164.6). The population analysis model shows a significant overall gradient of 1.047, which corresponds to an average annual increase of 4.7 % over the period considered. The analysis suggests that in the study area, the reproductive population of Rhinolophus hipposideros monitored in the maternity roost has increased throughout the period from 2000-2018, with large increases after 2010 and different trends occurring in the two regions considered, including a significant moderate increase in Liguria and a stable trend in Piedmont. The results agreed with the recently observed trends in other European countries for this species.

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.

Multiple isotope tracers in fur keratin discriminate between mothers and offspring.

Isoscape origin models for mammals may be impaired by fractionation and routing of isotopes during lactation. Here, we tested if the stable carbon, nitrogen and hydrogen ratios of juvenile bats differ from those of their mothers and if derived isotopic dietary niches and geographical assignments vary accordingly between mothers and juveniles. During the post-lactation period, we collected fur of juvenile and female common noctule bats (Nyctalus noctula) from the same maternity roost. Using a combination of elemental analysis and stable isotope ratio mass spectrometry, we measured the hydrogen, carbon and nitrogen isotope ratios in fur keratin. The hydrogen isotope ratios were measured for the non-exchangeable portion of hydrogen in keratin. The derived isotopic niches and isoscape origin models were compared between mothers and juveniles. The fur keratin of juveniles was enriched by 1.6‰ in 15 N and depleted by 2.9‰ in 13 C compared with that of the mothers. In addition, the hydrogen isotope ratios were 13.4‰ lower in the fur keratin of juveniles than in that of mothers. The estimated isotopic niches of nursing females and juveniles were not overlapping and differed in size. Overall, the isoscape origin models projected juveniles as being from a more northern origin than the mothers; yet both models suggested the study site as a likely place of origin. Our results suggest that isotope ratio data of juvenile bats should not be used for transfer functions in isoscape origin models because of isotopic routing and discrimination during lactation. Not accounting for age effects may increase the inaccuracy of geographical assignments in mammals when based on stable hydrogen isotopes.

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.