How to Be a Male at Different Elevations: Ecology of Intra-Sexual Segregation in the Trawling Bat Myotis daubentonii

Intra-sexual segregation is a form of social segregation widespread among vertebrates. In the bat Myotis daubentonii, males are disproportionately abundant at higher elevations, while females are restricted to lower altitude. Intra-male segregation is also known to occur yet its ecological and behavioural determinants are unclear. We studied male segregation along a river in Central Italy where we tested the following predictions: 1. Upstream ( > 1000 m a.s.l.) males will rely on scarcer prey; 2. To deal with this limitation and exploit a cooler roosting environment, they will employ more prolonged and deeper torpor than downstream (< 900 m a.s.l.) males; 3. Body condition will be better in downstream males as they forage in more productive areas; 4. To cope with less predictable foraging opportunities, upstream males will use more habitat types. Consistent with our predictions, we found that prey were less common at higher altitudes, where bats exhibited prolonged and deeper torpor. Body condition was better in downstream males than in upstream males but not in all summer months. This result reflected a decrease in downstream males’ body condition over the season, perhaps due to the energy costs of reduced opportunities to use torpor and/or intraspecific competition. Downstream males mainly foraged over selected riparian vegetation whereas upstream males used a greater variety of habitats. One controversial issue is whether upstream males are excluded from lower elevations by resident bats. We tested this by translocating 10 upstream males to a downstream roost: eight returned to the high elevation site in 1-2 nights, two persisted at low altitude but did not roost with resident bats. These results are consistent with the idea of segregation due to competition. Living at high altitude allows for more effective heterothermy and may thus be not detrimental for survival, but by staying at lower altitude males increase proximity to females and potentially benefit from summer mating opportunities.

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title: Concentration of bat activity in riparian habitats over an elevational gradient
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title: Next Generation Sequencing of Fecal DNA Reveals the Dietary Diversity of the Widespread Insectivorous Predator Daubenton’s Bat (Myotis daubentonii) in Southwestern Finland
abstract: Understanding predator-prey dynamics is a fundamental task in the evaluation of the adaptive capacities of species. However, direct observations or morphological identification of fecal remains do not offer an effective way to study the dietary ecology of elusive species, such as nocturnal insectivorous bats. However, recent advances in molecular techniques have opened a new method for identifying prey species from fecal samples. In this study, we amplified species-specific mitochondrial COI fragments from fecal DNA extractions from 34 individual Daubenton’s bats (Myotis daubentonii) collected between 2008 and 2010 from southwestern Finland. Altogether, 128 different species of prey were identified based on a comprehensive local DNA reference library. In our study area, Daubenton’s bats feed most frequently on insects of the orders Diptera (found in the diet of 94% individuals), Trichoptera (69%) and Lepidoptera (63%). The most frequent dipteran family in the diet was Chironomidae, which was found in 31 of 34 individuals. Most common prey species were chironomids Microtendipes pedellus (found in 50% of bats), Glyptotendipes cauliginellus (44%), and Procladius ferrugineus (41%). For the first time, an accurate species level list of the diet of the insectivorous Daubenton’s bat (Myotis daubentonii) in Finland is presented. We report a generally applicable method for describing the arthropod diet of vertebrate predators. We compare public databases to a national database to highlight the importance of a local reference database.

title: Mating at summer sites: indications from parentage analysis and roosting behaviour of Daubenton’s bats (Myotis daubentonii)
abstract: This study reports on evidence for successful mating of Myotis daubentonii at summer sites established by paternity analysis and behavioural observations. Parentage in individuals with high site fidelity was verified. Associations of parents in the same roosts before September and repeated fatherhood of a single resident male support the hypothesis of regular mating activities at summer sites. Based on the assumption that successful mating of many European bat species occurs at summer sites after the young are fledged, anthropogenic habitat changes should steer clear of the seasonal activity period to prevent a reduced reproduction rate of local bat populations.

title: Sex-related differences in roost-site selection by Daubenton's bats Myotis daubentonii during the nursery period
abstract: 1 
We investigated sex-related differences in roost-site selection by Daubenton's bats Myotis daubentonii in their summer habitat in central Germany. We studied whether the location of and landscape structure around nine nursery roosts and seven male-only roosts differed during the nursery period (15 May−31 July). Roosts were located by radio-tracking, and animal numbers and group composition were obtained by trapping and counting at roosts. Landscape structure was evaluated by a GIS-based habitat analysis. 
 
2 
Marked variation in animal numbers was observed both in nursery roosts (range: 6–144 individuals) and male roosts (range: 1–51 individuals). The surroundings of nursery and male roosts varied significantly in the proportion of areas belonging to different landscape elements. The areas covered by ponds, lakes and rivers, as well as the area covered by coppices were larger in the surroundings of nursery roosts. Moreover, nursery roosts lay closer to a river and at lower altitudes than male roosts. Male Daubenton's bats used more distant foraging sites than gravid or lactating females. 
 
3 
The differences in roost-site location between the two sexes are suggestive of intraspecific competition for access to productive foraging areas in the surroundings of the summer roosts, with females being dominant over males. We assume that breeding females defend climatically favourable areas with good food supply in order to increase the survival of their offspring.

title: Ecological, Physiological, and Biochemical Aspects of Torpor in Mammals and Birds
abstract: As a physiological tactic to temporarily escape the brunt of cold and shortage of food and water, many mammals and birds have evolved the ability to exhibit torpor. Torpor in these heterothermic endotherms is characterized by a periodic, facultative lowering of the “thermostat” for body temperature regulation resulting in the achievement of a hypometabolic state for energy/water conservation. Depending on the species and ecological demand, the decrease of body temperature in torpor may range from 4° to 35°C and the period of torpor from a few hours to many weeks. Unlike torpor in the ectotherms, torpid endotherms are capable of spontaneously exiting from the depressed metabolic state using exclusively endogenously produced heat to restore euthermia . This unique solution to a temporal energy/water crisis has been successfully employed by diverse groups of birds and mammals inhabiting the arctic, boreal and temperate regions where seasonal cold is predictable. Torpor has also been utilized by species inhabiting the deserts and semi-arid lands, where shortages of water and food may also manifest periodically. Somewhat surprisingly, however, torpor is also being deployed by those which inhabit the subtropical and tropical climates. In this case, daily, in addition to seasonal adversities may interfere with feeding and create a temporary energy shortage and the ability to exhibit torpor may prove to be advantageous. Extensive studies on the evolutionary, physiological and biochemical aspects have firmly established that torpor in birds and mammals is polyphyletic, and represents an advanced form of thermoregulation rather than a reversion to primitive poikilothermy (see Dawson and Hudson 1970; Hudson 1973; Lyman et al. 1982; Wang 1986, 1988; for reviews and references).

title: Natural Use of Heterothermy by a Small, Tree‐Roosting Bat during Summer
abstract: Little is known about the use of heterothermy by wild bats during summer, especially for tree‐roosting species. Because thermal conditions within tree roosts can fluctuate widely with ambient temperature, which affects thermoregulatory energy expenditure during diurnal roosting, we measured skin temperatures of free‐ranging male Nyctophilus geoffroyi (8 g) to quantify the relation between summer torpor use and roost thermal conditions. Bats roosted under bark on the northern (sunny) side of trees and entered torpor every day, usually near sunrise. Bats exhibited two bouts of torpor on most days: the first occurred in the morning, was terminated by partially passive rewarming, and was followed by a period of normothermy during the warmest part of the day; a second torpor bout occurred in the late afternoon, with arousal near sunset. On the warmest days, bats had only a single, short morning bout. On the coolest days, bats remained torpid throughout the day, and one 2‐d bout was observed. Thus, presumably owing to their poorly insulated roosts and the high energetic cost of normothermy at temperatures below 30°C, the extent and timing of heterothermy was closely related to the cycle of diurnal temperatures. Our study indicates that torpor use is important for energy maintenance during summer diurnal roosting of N. geoffroyi and likely of other small, tree‐roosting bats.

title: Patterns of daily torpor and day-roost selection by male and female big brown bats (Eptesicus fuscus)
abstract: Daily torpor can provide significant energy savings, but in bats may reduce rates of fetal and juvenile development and spermatogenesis. We examined the use of torpor during the day by male and female big brown bats (Eptesicus fuscus) in the field during the female gestation, lactation, and postlactation periods. While both sexes used torpor, males used it significantly more often and used deeper torpor than did reproductive females, indicating that the costs of torpor are higher for reproductive females. We suggest that by using shallow torpor, females may gain some of the benefits of torpor while minimizing the fitness costs. The different patterns of torpor may be responsible for observed differences in day-roost location amongst males, reproductive females, and nonreproductive females. Males should choose roosts with lower ambient temperatures than do females in order to increase the energy savings of torpor. Males and nonreproductive females roosted away from the maternity colonies more often than di...

title: Seasonal changes in daily torpor patterns of free-ranging female and male Daubenton’s bats (Myotis daubentonii)
abstract: Daily torpor can provide significant energy and water savings in bats during cold ambient temperatures and food scarcity. However, it may reduce rates of foetal and juvenile development. Therefore, reproductive females should optimize development by minimizing times in torpor. To test this hypothesis, the use of torpor by female and male free-ranging Daubenton’s bats (Myotis daubentonii) during reproduction (gestation, lactation, and post-lactation period) was investigated in 1998 and 1999. Temperature-sensitive radio transmitters were attached to the bats to measure skin temperature. Simultaneously, ambient temperature was recorded. While both sexes became torpid during daytime, male bats used daily torpor (>6°C below individual active temperature) significantly more often during reproductive period (mean: 78.4 % of day time in May and 43 % in June) than females. Female bats went into daily torpor, particularly in late summer when juveniles were weaned (mean: 66.6 % of daytime). Lowest skin temperatures occurred in a female bat with 21.0°C during post-lactation. Skin temperatures of male bats fluctuated from 16.8°C in torpor to 37.2°C during times of activity. There was a significant effect of reproductive period on skin temperature in females whereas mean ambient temperature had no significant effect. However, mean ambient temperature affected mean skin temperatures in males. Our findings indicate that female Daubenton’s bats adopt their thermoregulatory behaviour in particular to optimize the juvenile development.

title: Balancing the Energy Budget in Free-Ranging Male Myotis daubentonii Bats
abstract: Mammals use five main, mutually nonexclusive mechanisms to balance energy budgets: torpor, metabolic compensation, change in activity patterns, change in ingested energy, and/or variability in digestive efficiency. Bats, as small and actively flying mammals, have a high mass-specific energy demand; therefore, balancing mechanisms should be pronounced in this group. We found that male Myotis daubentonii exhibited marked variation in the relative importance of these different mechanisms during their period of seasonal activity in response to extrinsic (ambient temperature, insect abundance) and intrinsic (reproduction, body condition) factors. Cold ambient temperatures in spring facilitated long and frequent daily torpor bouts, whereas in early summer, increased energy intake was the dominant factor in energy balancing. Intake was further increased in late summer, when insect abundance was highest, and daily torpor bouts were shorter and less frequent than in early summer. In autumn, males used metabolic compensation to reduce their resting metabolic rate in addition to daily torpor. Metabolic compensation might be one of the mechanisms that allow males to maintain high body temperature during the day while decreasing the need for foraging time at night, thus maximizing their opportunities to mate.

title: Thermoregulation of tree-dwelling temperate bats — a behavioural adaptation to force live history strategy
abstract: Metabolic rate and body temperature (Tb) reduction during torpor can provide significant energy savings for bats during inclement weather and food scarcity. However, torpor use may slow down biochemical processes including fetal and juvenile development and sperm production. Sex-differences in the timing of reproductive activity of bats in the temperate climate zone should result in differences of the thermoregulation behaviour by males and females during summer. To test this hypothesis, we studied thermoregulation of free-ranging, tree-dwelling gleaning bats (Myotis bechsteinii) and trawling bats (M. daubentonii) during different reproductive periods. Gleaners and trawlers are able to forage on prey which is sitting on vegetation and the ground (gleaning) or which is slowly moving over water bodies (trawling). This prey is characterized by lower ambient temperature (Ta) dependent abundance than flying prey. We used temperature-sensitive radio transmitters to measure skin temperature (Tsk). Temperature telemetry over 144 census days revealed a significant effect of reproductive period and sex on Tsk. Pre-spermatogenic males exhibited a significantly greater Tsk reduction than females in early pregnancy. Males at the beginning of sperm production and in main spermatogenesis exhibited much more frequent and deeper temperature reductions than females in late pregnancy and in lactation. Lactating females maintained the highest Tsk of all bats. Post-lactating females reduced Tsk to the same extent or even more than males in advanced spermatogenesis. Our findings indicate that the thermoregulation of gleaning and trawling temperate bats is likely to be much less influenced by environmental conditions than that of aerial hawking bat species. We suggest that both sexes of Bechstein's bats and Daubenton's bats primarily adapt their thermoregulation in response to current reproductive activity.

title: Spatiotemporal pattern of local sexual segregation in a tree-dwelling temperate bat Myotis daubentonii
abstract: Sexual segregation is a common phenomenon in temperate bats, but little is known about driving forces or spatiotemporal patterns. Sexual segregation of the tree-dwelling Daubenton’s bat (Myotis daubentonii) was analyzed. Day roosts and foraging areas of radio-tracked animals were recorded during late spring, early summer, and late summer. Home ranges were calculated for each sex based on identified locations. Distance analysis between sex-specific roosts and foraging areas was conducted for each period. Mixed colonies were confirmed by trapping at roosts. Home range of males was larger (47.3 km2) than of females (9.7 km2). During late spring, distances between male and female roosts were larger (median = 715 m) than during early (median = 474 m) and late summer (median = 489 m). Distances between sex-specific foraging areas were larger during early summer (median = 2,134 m) than during both late spring (median = 1,116 m) and late summer (median = 628 m). The proportion of males in mixed groups increased from late spring (0.2 ± 0.1) to late summer (0.5 ± 0.2). These results show that sexual segregation is not static, but depends on energetic demand of individuals and mating willingness. A high energetic demand in females and low mating willingness in both sexes leads to distinct sexual segregation during late spring. When mating willingness increases, despite an increasing energy demand in males, sexes aggregate to mate.

title: Thermal energetics of female big brown bats (Eptesicus fuscus)
abstract: We investigated thermoregulation and energetics in female big brown bats, Eptesicus fuscus (Beauvois, 1796). We exposed bats to a range of ambient temperatures (Ta) and used open-flow respirometry to record their metabolic re- sponses. The bats were typically thermoconforming and almost always entered torpor at Tas below the lower critical temperature Tlc of 26.7 °C. Basal metabolic rate (BMR, 16.98 ± 2.04 mL O2·h -1 , mean body mass = 15.0 ± 1.4 g) and torpid metabolic rate (TMR, 0.460 ± 0.207 mL O2·h -1 , mean body mass = 14.7 ± 1.3 g) were similar to values re- ported for other vespertilionid bats of similar size and similar to a value for E. fuscus BMR calculated from data in a previous paper. However, we found that big brown bats had a lower Tlc and lower thermal conductance at low Ta rela- tive to those measured in the previous study. During torpor, the minimum individual body temperature (Tb) that we re- corded was 1.1 °C and the bats began defending minimum Tb at Ta of approximately 0 °C. BMR of big brown bats was 76% of that predicted for bats based on the relationship between BMR and body mass. However, the Vespert- ilionidae have been under-represented in previous analyses of the relationship between BMR and body mass in bats. Our data, combined with data for other vespertilionids, suggest that the family may be characterized by a lower BMR than that predicted based on data from other groups of bats.

title: Deep, prolonged torpor by pregnant, free-ranging bats
abstract: Many mammals save energy during food shortage or harsh weather using controlled reductions in body temperature and metabolism called torpor. However, torpor slows offspring growth, and reproductive individuals are thought to avoid using it because of reduced fitness resulting from delayed offspring development. We tested this hypothesis by investigating torpor during reproduction in hoary bats (Lasiurus cinereus, Vespertilionidae) in southern Canada. We recorded deep, prolonged torpor bouts, which meet the definition for hibernation, by pregnant females. Prolonged torpor occurred during spring storms. When conditions improved females aroused and gave birth within several days. Our observations imply a fitness advantage of torpor in addition to energy conservation because reduced foetal growth rate could delay parturition until conditions are more favourable for lactation and neonatal survival.

title: Defining torpor in free-ranging bats: experimental evaluation of external temperature-sensitive radiotransmitters and the concept of active temperature
abstract: A variety of definitions involving body temperature (Tb), metabolic rate and behavior have been used to define torpor in mammals and birds. This problem is confounded in some studies of free-ranging animals that employ only skin temperature (Tsk), a measure that approximates but may not precisely reflect Tb. We assess the accuracy of Tsk in the context of a recent definition for torpor called active temperature. We compared the active temperatures of individual big brown bats (Eptesicus fuscus), which aggregate in cavities, with solitary, foliage-roosting hoary bats (Lasiurus cinereus). In captive big brown bats, we compared Tsk and core Tb at a range of ambient temperatures for clustered and solitary roosting animals, compared Tsk and Tb during arousal from torpor, and quantified the effect of flight on warming from torpor. Hoary bats had significantly lower active temperatures than big brown bats despite having the same normothermic Tsk. Tsk was significantly lower than Tb during normothermia but often greater than Tb during torpor. Flight increased the rate of warming from torpor. This effect was more pronounced for Tsk than Tb. This suggests that bats could rely on heat generated by flight muscles to complete the final stages of arousal. Using active temperature to define torpor may underestimate torpor due to ambient cooling of external transmitters or animals leaving roosts while still torpid. Conversely, active temperature may also overestimate shallow torpor use if it is recorded during active arousal when shivering and non-shivering thermogenesis warm external transmitters. Our findings illuminate the need for laboratory studies that quantify the relationship between metabolic rate and Tsk over a range of ambient temperatures.

title: A New Comparative Metric for Estimating Heterothermy in Endotherms
abstract: A major focus in the study of endothermic thermoregulation has been the description of thermoregulatory patterns used by various species and/or populations. Compared with ectotherms, relatively few attempts have been made to study the thermoregulation of endotherms in an adaptive framework. We believe that one of the main factors limiting this area of research has been the lack of an appropriate metric to directly compare body temperature (Tb) variation across all endothermic species. Thus, we present a simple comparative metric, the heterothermy index (HI), to quantify the expression of heterothermy by endotherms during a given time frame. Key advantages of HI are that (1) it represents a new analytical technique that has different strengths than the metrics commonly used to describe variation in Tb, (2) it allows for evaluation of nonenergetic costs and benefits that affect the expression of heterothermy, and (3) it has the potential to unify research on homeotherms and heterotherms through quantitative comparative analyses that examine the entire continuum of thermoregulatory patterns. In short, we suggest that our metric provides a means to overcome one of the hurdles presently slowing the advancement of research on endothermic thermoregulation beyond the simple description of thermoregulatory patterns.

title: New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative method
abstract: Body condition is assumed to influence an animal’s health and fitness. Various non-destructive methods based on body mass and a measure of body length have been used as condition indices (CIs), but the dominant method amongst ecologists is currently the calculation of residuals from an ordinary least squares (OLS) regression of body mass against length. Recent studies of energy reserves in small mammals and starlings claimed to validate this method, although we argue that they did not include the most appropriate tests since they compared the CI with the absolute size of energy reserves. We present a novel CI (the ‘scaled mass index’) based on the central principle of scaling, with important methodological, biological and conceptual advantages. Through a reanalysis of data from small mammals, starlings and snakes, we show that the scaled mass index is a better indicator of the relative size of energy reserves and other body components than OLS residuals, performing better in all seven species and in 19 out of 20 analyses. We also present an empirical and theoretical comparison of the scaled mass index and OLS residuals as CIs. We argue that the scaled mass index is a useful new tool for ecologists.

title: Female Mate Choice Can Drive the Evolution of High Frequency Echolocation in Bats: A Case Study with Rhinolophus mehelyi
abstract: Animals employ an array of signals (i.e. visual, acoustic, olfactory) for communication. Natural selection favours signals, receptors, and signalling behaviour that optimise the received signal relative to background noise. When the signal is used for more than one function, antagonisms amongst the different signalling functions may constrain the optimisation of the signal for any one function. Sexual selection through mate choice can strongly modify the effects of natural selection on signalling systems ultimately causing maladaptive signals to evolve. Echolocating bats represent a fascinating group in which to study the evolution of signalling systems as unlike bird songs or frog calls, echolocation has a dual role in foraging and communication. The function of bat echolocation is to generate echoes that the calling bat uses for orientation and food detection with call characteristics being directly related to the exploitation of particular ecological niches. Therefore, it is commonly assumed that echolocation has been shaped by ecology via natural selection. Here we demonstrate for the first time using a novel combined behavioural, ecological and genetic approach that in a bat species, Rhinolophus mehelyi: (1) echolocation peak frequency is an honest signal of body size; (2) females preferentially select males with high frequency calls during the mating season; (3) high frequency males sire more off-spring, providing evidence that echolocation calls may play a role in female mate choice. Our data refute the sole role of ecology in the evolution of echolocation and highlight the antagonistic interplay between natural and sexual selection in shaping acoustic signals.

title: The paradigm of body condition: a critical reappraisal of current methods based on mass and length
abstract: 1. Body condition is a major concept in ecology addressed in countless studies, and a variety of non-destructive methods are used to estimate the condition of individuals based on the relationship between body mass M and measures of length L. There is currently no consensus about the most appropriate condition index (CI) method, and various traditions have been established within subdisciplines in which ecologists tend to apply that method used previously by their peers. 
 
 
 
2. Here, we present a reappraisal of six conventional CI methods: Fulton’s index (K = M/L3), Quetelet’s index (BMI = M/L2), Relative condition (Kn, computed as the observed individual mass divided by the predicted mass Mi* = a Lib where a and b are determined by ordinary least squares (OLS) regression of M against L), Relative mass (Wr, where a and b above are determined from a reference population), the Residual index (Ri, the residuals from an OLS regression of M against L) and ancova. We compare the performance of these methods with that of the Scaled mass index, a novel method which was previously shown to perform better than Ri as a predictor of fat and other body components [ (2009) Oikos, 118, 1883]. 
 
 
 
3. To be reliable, a CI method must successfully account for the changing relationship between M and L as body size changes and growth occurs (i.e. for the scaling relationship between M and L). Using data from three species of small mammals we show that, unlike the Scaled mass index, all six conventional methods fail to do this, and as a result they consistently lead to significant differences in CIs between age classes and sex that are a mere consequence of changes in body size. The Scaled mass index was also particularly successful at detecting changes in CI resulting from high levels of contaminants.

title: Analysis of Wildlife Radio-Tracking Data
abstract: Preliminaries. Design of Radio-Tracking Studies. Effects of Tagging on the Animal. Estimating Animal Locations. Designing and Testing Triangulation Systems. Simple Movements. Home Range Estimation. Habitat Analysis. Survival Rate Estimation.  Data Analysis System. Appendices. Each chapter includes references. Index.

title: Compositional Analysis of Habitat Use From Animal Radio-Tracking Data
abstract: Analysis of habitat use based on radio-tagged animals presents difficulties inadequately addressed by current methods. Areas of concern are sampling level, data pooling across individuals, non-independence of habitat proportions, differential habitat use by groups of animals, and arbitrary definition of habitat availability. We advocate proportional habitat use by individual animals as a basis for analysis. Hypothesis testing of such nonstandard multivariate data is done by compositional analysis, which encom- passes all MANOVA/MANCOVA-type linear models. The applications to habitat use range from testing for age class effects or seasonal differences, to examining relationships with food abundance or home range size. We take as an example the comparison of habitat use and availability. The concepts are explained and demonstrated on two data sets, illustrating different methods of treating missing values. We compare utilized with available habitats in two stages, examining home range selection within the overall study area first, then habitat use within the home range. At each stage, assuming that use differs from random, habitats can be ranked according to relative use, and significant between-rank differences located. Compositional analysis is also suited to the analysis of time budgets or diets.

title: K-select analysis: a new method to analyse habitat selection in radio-tracking studies
abstract: Two kinds of wildlife habitat studies can be distinguished in the literature: hindcasting and forecasting studies. Hindcasting studies aim to emphasize among a large set of habitat variables those that are of interest for the focus species, whereas forecasting studies are intended to predict habitat selection according to a small number of habitat variables for a given area. We provide here a new analytical tool which relies on the concept of ecological niche, the K-select analysis, for hindcasting studies of habitat selection by animals using radio-tracking data. Each habitat variable defines one dimension in the ecological space. For each animal, the difference between the vector of average available habitat conditions and the vector of average used conditions defines the marginality vector. Its size is proportional to the importance of habitat selection, and its direction indicates which variables are selected. By performing a non-centered principal component analysis of the table containing the coordinates of the marginality vectors of each animal (row) on the habitat variables (column), the K-select analysis returns a linear combination of habitat variables for which the average marginality is greatest. It is a synthesis of variables which contributes the most to the habitat selection. As with principal component analysis, the biological significance of the factorial axes is deduced from the loading of variables. An example is provided: habitat selection by wild boar is studied in a Mediterranean habitat using the K-select analysis. The numerous advantages of the analysis (a large number of variables that can be included, individual variability in habitat selection taken into account, a lack of too strict underlying hypotheses) make it a powerful approach in radio-tracking studies designed to identify habitat variables that are selected by animals.

title: Chironomid Midges as Indicators of Organic Pollution in the Scioto River Basin, Ohio
abstract: Faunal and water chemistry data were derived from an extensive survey of streams in the Scioto River basin, Ohio and analyzed to determine biotic indicators of water quality. The data for 11 water chemistry characteristics were simplified by means of factor analysis, which generated three new axes (alkalinity-hardness, enrichment (sewage), agricultural runoff) that explained 71.5% of the total variance. The distributions of 14 common larval chironomid genera were then placed upon these new axes, based on coordinates generated for each sample site. These genera were found to occupy significantly different environments. Heuristic analysis of the data identified five groups of genera, each indicating particular water quality conditions: 1) Stictocbironomus—hard, alkaline unpolluted water; 2) Pentaneura, Cricotopus, and Tanytarsus—sewage enriched water; 3) Procladius and Dicrotendipes—high agricultural runoff; 4) Ablabesmyia and Tribelos —general organic pollution, soft acid water; and 5) Micropsectra, Microtendipes, Glyptotendipes, Chironomus, Polypedilum, and Cryptochironomus — facultative genera.

title: Midges and palaeotemperature reconstruction—the North American experience
abstract: The development of midge-based palaeoclimatology in North America is reviewed, with a focus on Lateglacial and Holocene climatic change. Although relatively few sites have been studied, midge-inferred palaeotemperatures reveal detailed records of Lateglacial climate oscillations and more subtle Holocene temperature changes. Holocene climate changes are often at, or near, the detection limit using current palaeotemperature inference models. Interference from other environmental variables, including water depth and oxygen concentration changes are discussed, as well as the challenges inherent to developing better models. The isotopic signature of chitin preserved in midge head capsules has opened new avenues for midge–palaeotemperature inference. Through coordinated research efforts, national and international collaborations will provide opportunities to reconstruct Holocene palaeoclimate at continental and hemispheric scales.

title: Bat conservation and large dams: spatial changes in habitat use caused by Europe's largest reservoir
abstract: Large dams have had a major impact on a number of botanical and faunal groups. Nevertheless, little is known about their effect on bat populations. As part of a multipurpose project, the Alqueva dam was constructed during 2001 in Alentejo (Southern Portugal) and has created the largest reservoir in Europe. Its construction caused major changes in the region, mainly due to the deforestation and submersion of an area of 250 km 2 . A 2-stage survey was implemented in order to evaluate the impact of these landscape changes on bat populations present in the region, as well as to define minimization and compensation measures. Bat activity was surveyed prior to and after the deforestation and flooding of the area, mainly through the use of ultra-sound detectors. The results show a clear decline in bat activity over the area now submerged; islands within the reservoir seem to be the only remaining foraging areas. Furthermore, bat activity increased in the area surrounding the reservoir. In this area, bats used similar foraging habitat types during both stages of the survey, confirming the importance of riparian habitats as foraging areas. Bat populations of this region were thus affected simultaneously by the disappearance of around 200 km of riparian habitat, extensive loss of roosts and the creation of a vast homogeneous habitat that is rarely used for foraging. In pro- jects of this dimension, the future of bat communities is clearly dependent on the preservation of roosts and the most important habitats surrounding the reservoir.

title: Thermoregulation in male temperate bats depends on habitat characteristics
abstract: Several energy-saving strategies have evolved in animals, one example being the short-term reduction of metabolism and body temperature (torpor) in endotherms. For bats, pronounced torpor behaviour has been described. The aim of this study was to assess individual variation in torpor expression of male Myotis daubentonii, and to analyse whether this variation is related to habitat characteristics. For that we measured skin temperatures of bats from different habitats using radio transmitters and also recorded ambient temperature. Skin temperature was corrected for ambient temperature and individual body mass. Cluster analysis of residuals revealed two different thermoregulatory strategies. Males in cluster 1 were more often encountered torpid and reached lower minimum skin temperatures than males in cluster 2. The differences in behaviour were related to environmental variables (water surface area near the roost, roost altitude, precipitation, ambient temperature in the warmest quarter of the year). Males from cluster 1 occupied less favourable habitats (less water surface, higher altitudes, wetter and colder climate) than males from cluster 2. Our data suggest a linkage between torpor behaviour and habitat characteristics. These characteristics could be used to identify favourable and marginal habitats for M. daubentonii.

title: Thermal physiology of pregnant and lactating female and male long-eared bats, Nyctophilus geoffroyi and N. gouldi
abstract: During roosting in summer, reproductive female bats appear to use torpor less frequently and at higher body temperatures (Tb) than male bats, ostensibly to maximise offspring growth. To test whether field observations result from differences in thermal physiology or behavioural thermoregulation during roosting, we measured the thermoregulatory response and energetics of captive pregnant and lactating female and male long-eared bats (Nyctophilus geoffroyi 8.9 g and N. gouldi 11.5 g) during overnight exposure to a constant ambient temperature (Ta) of 15°C. Bats were captured 1–1.5 h after sunset and measurements began at 21:22±0:36 h. All N. geoffroyi entered torpor commencing at 23:47±01:01 h. For N. gouldi, 10/10 males, 9/10 pregnant females and 7/8 lactating females entered torpor commencing at 01:10±01:40 h. The minimum Tb of torpid bats was 15.6±1.1°C and torpid metabolic rate (TMR) was reduced to 0.05±0.02 ml O2 g−1 h−1. Sex or reproductive condition of either species did not affect the timing of entry into torpor (F=1.5, df=2, 19, P=0.24), minimum TMR (F=0.21, df=4, 40, P=0.93) or minimum Tb (F=0.76, df=5, 41, P=0.58). Moreover, sex or reproductive condition did not affect the allometric relationship between minimum resting metabolic rate and body mass (F=1.1, df=4, 37, P=0.37). Our study shows that under identical thermal conditions, thermal physiology of pregnant and lactating female and male bats are indistinguishable. This suggests that the observed reluctance by reproductive females to enter torpor in the field is predominantly because of ecological rather than physiological differences, which reflect the fact that females roost gregariously whereas male bats typically roost solitarily.

title: Winter activity of a population of greater horseshoe bats, Rhinolophus ferrumequinum
abstract: Activity patterns of greater horseshoe bats Rhinolophus ferrumequinum were investigated at caves in Cheddar (south-west England) during the hibernation season. An ultrasound detector and datalogger were used to monitor and record the number of echolocation calls in a single cave. Activity of R. ferrumequinum remained largely nocturnal throughout winter, and the mean time of activity over 24 h was 88 to 369 min after sunset. There was an increase in diurnal activity from late May to early June, probably because bats remained active after foraging at dawn towards the end of the hibernation season. Visits to the cave did not increase bat activity. Cave air temperature reflected external climatic temperature, although there was variation in cave temperature and its range within and among caves. Individual R. ferrumequinum are usually dispersed in caves in regions where temperature fluctuations correlate with climatic variations in temperature. There was a positive correlation between the number of daily bat passes monitored by the bat detector and datalogger (= daily activity) and cave temperature. Nocturnal activity may be sometimes associated with winter feeding. Neither date nor barometric pressure had a significant effect on daily activity. Activity patterns largely reflected the findings from individual R. ferrumequinum studied by telemetry (Park, 1998), in that bat activity increased with cave and climatic temperatures, and the temporal pattern of activity remained consistently nocturnal throughout winter, starting at dusk.

title: Torpor, arousal and activity of hibernating Greater Horseshoe Bats (Rhinolophus ferrumequinum)
abstract: 1. Patterns of torpor, arousal and activity in free-living Greater Horseshoe Bats, Rhinolophus ferrumequinum (Schreber), were investigated during the hibernation period by using temperature-sensitive radio-transmitters. 
 
2. Torpor bouts varied between 0·1 and 11·8 days, with individual means ranging from 1·3 to 7·4 days. Torpor bout duration decreased with increasing ambient temperature. 
 
3. Activity duration varied from 37 min to 54 h 24 min, with individual means ranging from 2 : 29 to 8 : 58 h. Activity duration increased with ambient temperatures above approximately 10 °C. 
 
4. Ten of 11 bats synchronized their arousals with dusk. The circadian rhythm of one bat showed a free-running pattern over a period of about 5 weeks. Arousals were more highly synchronized, and closer to dusk, in individuals with lower body condition. 
 
5. That bats forage in mild weather is supported by the strong synchronization of arousals with dusk, especially in bats with low body condition. 
 
6. Patterns of torpor and subsequent activity are consistent with predictions that torpor lasts until a critical metabolic or water imbalance is achieved. Because metabolism and water loss are temperature-dependent, torpor bout duration decreases with increasing temperature. The imbalance is corrected during subsequent activity, which is relatively constant in duration until a temperature threshold of 10 °C, above which increasing levels of foraging lead to longer activity bouts.

title: Winter foraging activity of Central European Vespertilionid bats
abstract: The winter activity of bats was studied in an area of Bavaria, Southern Germany, for seven consecutive years (2007–2013). Echolocation calls were recorded in known foraging areas between October and March of each winter, and bats were regularly seen on evenings with temperatures above +6 °C, except for the period between mid-December and mid-February, when even bouts of warm weather did not appear to trigger foraging activity. Below +3 °C no bats appeared in the foraging areas. The most frequently recorded species were Nyctalus noctula, Pipistrellus pipistrellus, Pipistrellus nathusii and Vespertilio murinus. Final buzzes indicating attempts to catch prey were recorded for these species even in December and February, which supports the idea that the bats were not only in search of water or just moving between roosts. Myotis species, on the other hand, which hibernate in roosts offering more constant temperature conditions, were not observed at all between mid-November and March. Further investigations have to show whether warmer winter evenings offer bats an opportunity for casual hunting or whether winter foraging expresses an urgent need for weak individuals.

title: Echolocation constraints of Daubenton’s Bat foraging over water
abstract: Daubenton’s Bats ( Myotis daubentonii) foraging over a stream concentrated their activity over calm surfaces, avoiding an adjacent area with small ripples (< 3 cm high). Aerial insects were most abundant over the ripples, so insect distribution could not explain why the bats avoided this area. 2. The bats flew low over water and always ( N = 22) directed the head forwards, presumably emitting the echolocation beam parallel to the surface, thus minimizing clutter. At an angle of incidence of 30° there was significantly more clutter from the rippled water. 3. The ripples produced ultrasonic noises in the form of transient pulses at an average rate of 6·2 per second. In the present case, such pulses were common enough potentially to interfere with target detection by the bats. Transient noises and echo clutter from moving ripples may be the principal reason why bats generally avoid foraging low over turbulent water. 4. The target strength of a potential insect prey at the water surface and the source levels of the bats’ searching signals were measured to use in estimating the echo level at the bat when it detects the prey. The echo level at detection (+ 38 dB sound pressure level) was about the same as the clutter level extrapolated to the detection distance. This suggests that Daubenton’s Bat operates at very low signal-to-noise ratios when foraging for insects near the water surface.

title: Use of foraging habitats by bats in a Mediterranean area determined by acoustic surveys: conservation implications
abstract: We determined habitat use by foraging bats by broad-band acoustic surveys in 10 habitat types from a Mediterranean area (southern Italy). We applied discriminant functions to identify time-expanded echolocation calls from free-flying bats. 
 
Moon phase and cloud cover had no effect on bat activity. Only Hypsugo savii was influenced by temperature, and activity of Myotis daubentonii and Myotis capaccinii was reduced at higher wind speeds. Both total numbers of bat passes and feeding buzzes were highest over rivers and lakes. Pipistrellus kuhlii and H. savii were most frequently recorded. Pipistrellus kuhlii, Pipistrellus pipistrellus and Tadarida teniotis proved generalists in using foraging habitats. 
 
Water sites and conifer plantations were respectively the most and the least used habitats by H. savii. Rivers were especially important to Myotis bats, Miniopterus schreibersii and Pipistrellus pygmaeus. Unlike P. kuhlii, P. pipistrellus was frequent in beech woodlands; P. pygmaeus made a considerable use of chestnut woodlands and Myotis spp. were moderately active in both these woodland types. 
 
A large number of endangered or vulnerable species featured in riparian habitats, broadleaved woodlands and olive groves. Riparian and woodland habitats constitute an important target for conservation. Typical land use forms such as woodlands used for chestnut production and traditionally managed olive groves should be encouraged in conservation plans. The negative impact of urbanisation on bats might be counteracted by fostering trees, gardens and small cultivated patches. Farmland practices should encourage landscape complexity and limit the use of pesticides.

title: The effect of familiarity on echolocation in the megachiropteran bat Rousettus aegyptiacus
abstract: Much is known about the way bats adjust their echolocation behaviour in response to environmental structure or to locate insect prey. By contrast, little is known about how echolocation calls are modulated in response to familiarity of the environment and objects within it. Here we show that the echolocating Megachiropteran bat Rousettus aegyptiacus produces echolocation signals at the same rate whether an obstacle is predictable or unpredictable in location, but that it has a reduced rate of echolocation signal production in a familiar environment with no obstacle present. This suggests that signal production is reduced in a familiar environment absent of 'clutter' but that probing the environment for maximum information is more important for this species than minimizing any cost of probing the environment in a cluttered space.

title: Sensory Ecology of Water Detection by Bats: A Field Experiment
abstract: Bats face a great risk of dehydration, so sensory mechanisms for water recognition are crucial for their survival. In the laboratory, bats recognized any smooth horizontal surface as water because these provide analogous reflections of echolocation calls. We tested whether bats also approach smooth horizontal surfaces other than water to drink in nature by partly covering watering troughs used by hundreds of bats with a Perspex layer mimicking water. We aimed 1) to confirm that under natural conditions too bats mistake any horizontal smooth surface for water by testing this on large numbers of individuals from a range of species and 2) to assess the occurrence of learning effects. Eleven bat species mistook Perspex for water relying chiefly on echoacoustic information. Using black instead of transparent Perspex did not deter bats from attempting to drink. In Barbastella barbastellus no echolocation differences occurred between bats approaching the water and the Perspex surfaces respectively, confirming that bats perceive water and Perspex to be acoustically similar. The drinking attempt rates at the fake surface were often lower than those recorded in the laboratory: bats then either left the site or moved to the control water surface. This suggests that bats modified their behaviour as soon as the lack of drinking reward had overridden the influence of echoacoustic information. Regardless of which of two adjoining surfaces was covered, bats preferentially approached and attempted to drink from the first surface encountered, probably because they followed a common route, involving spatial memory and perhaps social coordination. Overall, although acoustic recognition itself is stereotyped and its importance in the drinking process overwhelming, our findings point at the role of experience in increasing behavioural flexibility under natural conditions.

title: Dispersal of adult aquatic Chironomidae (Diptera) in agricultural landscapes
abstract: This study investigates the possible influence of terrestrial landscape structure on the spatial distribution of adult Chironomidae emerging from water bodies in three agricultural areas, each with hedgerow networks, in Brittany (France). 
 
2 
Using spatially explicit data from 128 yellow pan traps set in pairs at the bottom of hedges throughout the three study areas, we show that landscape structure and heterogeneity must be considered at two different spatial scales. 
 
3 
At a global scale, distance to water bodies was the main factor explaining the spatial distribution of adult chironomids: both species richness and abundance changed beyond a critical distance to the stream, resulting in different species assemblages of flying insects. 
 
4 
At a local scale, the abundance of species and individuals at rest in hedges changed with the quality of the hedge (mainly determined by canopy width and cover of the different vegetation layers). 
 
5 
The density of the hedgerow network, and landscape openness, both influenced the dispersal of chironomid species from water bodies. 
 
6 
This study, which provides the first estimate of the dispersal capabilities of chironomids in particular landscapes, suggests that the terrestrial environment is an essential component of population dynamics and community structure in aquatic Chironomidae.

title: Habitat selection and spatial use by the trawling bat Myotis capaccinii (Bonaparte, 1837)
abstract: Habitat selection and spatial use was studied in a population of Myotis capaccinii (Bonaparte, 1837) in the eastern Iberian Peninsula during the spring of 2004. The radio-tracked bats used only aquatic habitats as foraging sites, and most foraging activity concentrated on rivers. Rivers were positively selected and showed the highest preference rank. Pools were also positively selected but only a single pool was used through the tracking period. Foraging was not evenly distributed along rivers. The features of the water surface further determined habitat selection. Open waters with smooth surfaces were selected over cluttered surfaces or waters completely covered by vegetation. This microhabitat preference is thought to be due to a greater efficiency in prey detection and capture over open calm waters. Nonetheless, the extremely high aggregation of foraging individuals observed suggests that the distribution of prey might also affect the location of foraging sites along rivers. Thus, conservation management of M. capaccinii should ensure protection of low-flowing or stagnant waters in rivers around the bats' main caves.

title: Foraging behaviour of the long-fingered bat Myotis capaccinii: implications for conservation and management
abstract: The main factors threatening Myotis capaccinii (Bonaparte, 1837) are considered to be foraging habitat degradation and roost loss. Conservation strategies that focus on the protection of roosts are feasible as long as direct threats by human activities are correctly identified. However, before protection of foraging habitat can be implemented more accurate information is required. We review the available information of relevance to foraging habitat management for the species. Three main topics are considered based on the results of a radiotelemetry study on 45 ind.  habitat dependence, features of foraging habitat, and spatial range. M. capaccinii foraged almost completely over aquatic habitats as in other telemetry studies. We discuss the importance of terres- trial habitats and the dependence of the species on aquatic habitats. It has been proposed that sev- eral factors affect habitat selection in this species. The presence of smooth, clutter-free water surfaces seems to be the most important structural factor, but we found that prey richness also affected habi- tat selection. Effects of features related to riparian vegetation and water quality are thought to vary according to local conditions. Preference for wide water bodies is probably linked to preference for smooth surfaces, where detection and trawling of prey is favoured. As highlighted by recent teleme- try studies, we observed M. capaccinii foraging at long distances from the roost. Therefore, the area of application for conservation measures should be large: we suggest a protection radius of 20 km around roosts.

title: Sympatric Woodland Myotis Bats Form Tight-Knit Social Groups with Exclusive Roost Home Ranges
abstract: The structuring of wild animal populations can influence population dynamics, disease spread, and information transfer. Social network analysis potentially offers insights into these processes but is rarely, if ever, used to investigate more than one species in a community. We therefore compared the social, temporal and spatial networks of sympatric Myotis bats (M. nattereri (Natterer's bats) and M. daubentonii (Daubenton's bats)), and asked: (1) are there long-lasting social associations within species? (2) do the ranges occupied by roosting social groups overlap within or between species? (3) are M. daubentonii bachelor colonies excluded from roosting in areas used by maternity groups?  Using data on 490 ringed M. nattereri and 978 M. daubentonii from 379 colonies, we found that both species formed stable social groups encompassing multiple colonies. M. nattereri formed 11 mixed-sex social groups with few (4.3%) inter-group associations. Approximately half of all M. nattereri were associated with the same individuals when recaptured, with many associations being long-term (>100 days). In contrast, M. daubentonii were sexually segregated; only a quarter of pairs were associated at recapture after a few days, and inter-sex associations were not long-lasting. Social groups of M. nattereri and female M. daubentonii had small roost home ranges (mean 0.2 km2 in each case). Intra-specific overlap was low, but inter-specific overlap was high, suggesting territoriality within but not between species. M. daubentonii bachelor colonies did not appear to be excluded from roosting areas used by females.  Our data suggest marked species- and sex-specific patterns of disease and information transmission are likely between bats of the same genus despite sharing a common habitat. The clear partitioning of the woodland amongst social groups, and their apparent reliance on small patches of habitat for roosting, means that localised woodland management may be more important to bat conservation than previously recognised.

title: Dispersion and habitat use by Myotis daubentonii and Myotis nattereri during the swarming season: implications for conservation
abstract: We radio-tracked 24 Myotis daubentonii and 35 Myotis nattereri during the swarming season to determine the catchment area of a swarming site and to study habitat preferences of the bats so that important foraging habitats within the catchment area could be identified. Sixty-one percent of individuals were relocated and 39 day roosts were found for 31 bats. Maximum range from the swarming site was 26.7 km for M. daubentonii and 24.8 km for M. nattereri . Minimum convex polygons depicting the minimum catchment area of the swarming site measured 254 km 2 for M. daubentonii and 497 km 2 for M. nattereri . Including recoveries of ringed bats increases the area enclosed by the maximum range to at least 4118 km 2 . Compositional analysis of habitat used in relation to that available suggested selection of mixed agricultural areas by M. nattereri . Broad-leaved woodland was preferred for foraging. Parkland, woodland and open-water habitats were common around roosts of M. daubentonii . Such habitats should be conserved and enhanced to protect these species. Some individuals of both sexes returned to the swarming site of capture, but none visited another swarming site. Bats may be faithful to only one site and may be inflexible should that site be destroyed. Because the catchment area of swarming sites is large, such sites are probably important centres of outbreeding. Protection of these mating sites should be a conservation priority, and key habitats should be protected over a large area around swarming sites.

title: Body weight provides insights into the feeding strategy of swarming bats.
abstract: Temperate bat species that hibernate in underground sites are known to visit hibernacula in late summer where they perform an activity known as "swarming". We analysed trends in body mass-to-forearm ratio - the body condition index (BCI) - to investigate whether bats arrive at swarming sites following intensive nocturnal feeding. In a two-year study, Myotis daubentonii , M. brandtii and M. dasycneme were captured by mist-net at one swarming site from late July until early October. In late summer, the BCIs of captured males, females and subadult bats were positively correlated to the time of their capture during the night. In September, adult bats had higher BCIs than in late summer and the BCI did not increase during the night. For subadult M. daubentonii , the BCI was positively correlated to the time of capture in early autumn. Our results indicate that in late summer bats feed intensively during the first hours of the night before visiting swarming sites. In early autumn, subadult bats may go on feeding to complete fat accumulation.