The use of sewage treatment works as foraging sites by insectivorous bats

Sewage treatment works with percolating filter beds are known to provide profitable foraging areas for insectivorous birds due to their association with high macroinvertebrate densities. Fly larvae developing on filter beds at sewage treatment works may similarly provide a valuable resource for foraging bats. Over the last two decades, however, there has been a decline in filter beds towards a system of “activated sludge”. Insects and bat activity were surveyed at 30 sites in Scotland employing these two different types of sewage treatment in order to assess the possible implications of these changes for foraging bats. Bat activity (number of passes) recorded from broad-band bat detectors was quantified at three points within each site. The biomass of aerial insects, sampled over the same period as the detector surveys, was measured using a suction trap. The biomass of insects and activity of Pipistrellus spp. was significantly higher at filter beds than at activated sludge sites. In addition, whilst foraging activity of Pipistrellus spp. at filter beds was comparable to that of adjacent “good” foraging habitat, foraging at activated sludge sites was considerably lower. This study indicates the high potential value of an anthropogenic process to foraging bats, particularly in a landscape where their insect prey has undergone a marked decline, and suggests that the current preference for activated sludge systems is likely to reduce the value of treatment works as foraging sites for bats

Secondary use of aspen cavities by tree-roosting big brown bats

To further explore natural roost-site selection by temperate bats, we examined the use of tree roost sites by big brown bats (Eptesicus fuscus) in the West Block of Cypress Hills Provincial Park, Saskatchewan, an area where the number of human structures is limited. In this area, we found big brown bats roosted exclusively in cavities of trembling aspen trees (Populus tremuloides), despite the availability of cavities in snags of conifer trees. Most cavities had been excavated and previously used by yellow-bellied sapsuckers (Sphyrapicus varius). The use of aspens by sapsuckers relates to the relatively soft wood and susceptibility to heart rot of these trees, which provide ideal conditions for nesting: decayed heartwood with a firm sapwood shell. Orientation of cavity entrances was close to due south. The width of bats and the width of cavity entrances differed, suggesting that bats are not using roosts for protection from predators or exclusion of competitors. Bats showed fidelity to a particular group of roost trees because, despite roost switching, bats reunited in subsequent roost sites. During the day, temperatures in aspen cavities were approximately 50C cooler than in cavities of conifer snags. Microclimate differences, including temperature, may be why aspen cavities are selected over available cavities in conifer snags. All of the randomly selected cavities in aspen that we searched showed evidence of use by bats, which suggests roost sites for big brown bats in southwestern Saskatchewan may be a limiting resource

Interspecific variation in heat tolerance and evaporative cooling capacity among sympatric temperate-latitude bats

We tested the hypothesis that interspecific variation in chiropteran heat tolerance and evaporative cooling capacity is correlated with day-roost microclimates, using three vespertilionid bats that occur sympatrically during summer in Saskatchewan, Canada. We predicted that hoary bats (Lasiurus cinereus (Palisot de Beauvois, 1796); 22 g) would have higher heat tolerance than little brown bats (Myotis lucifugus (Le Conte, 1831); 7 g) and silver-haired bats (Lasionycteris noctivagans (Le Conte, 1831); 13 g), as the latter two species roost in tree crevices or cavities that are more thermally buffered than the foliage roosts of hoary bats. We measured core body temperature (Tb; passive integrated transponder tags), evaporative water loss, and resting metabolic rate (flow-through respirometry) while exposing individuals to a stepped profile of increasing air temperature (Ta) from 30 °C in 2 °C increments. Experiments were terminated when individuals became hyperthermic (Tb 42.5 °C), with maximum Ta (Ta,max) ranging from 42.0 to 49.7 °C. As predicted, hoary bats had the highest heat tolerance and evaporative cooling capacity, reaching Ta,max 2.4 and 1.2 °C higher than little brown and silver-haired bats, respectively. Our results are consistent with the hypothesis that heat tolerance of bats is correlated with roost microclimates, although interspecific variation in body mass and phylogeny may confound these conclusions.Nous avons vérifié l’hypothèse voulant que les variations interspécifiques de la tolérance à la chaleur et de la capacité de refroidissement par évaporation chez les chiroptères soient corrélées aux microclimats des gîtes diurnes, en utilisant trois chauves-souris de la famille des vespertilionidés présentes en sympatrie en été en Saskatchewan (Canada). Nous avions prédit que la tolérance à la chaleur des chauves-souris cendrées (Lasiurus cinereus (Palisot de Beauvois, 1796); 22 g) serait plus grande que celles des vespertilions bruns (Myotis lucifugus (Le Conte, 1831); 7 g) et des chauves-souris argentées (Lasionycteris noctivagans (Le Conte, 1831); 13 g), puisque les gîtes diurnes de ces deux dernières espèces sont des fentes ou cavités dans les arbres caractérisées par des températures moins variables que les gîtes dans le feuillage des chauves-souris cendrées. Nous avons mesuré la température corporelle centrale (Tb; radioétiquettes passives intégrées), la perte d’eau par évaporation et le métabolisme au repos (respirométrie dynamique), alors que les spécimens étaient exposés à des températures de l’air (Ta) commençant à 30 °C et augmentant par incréments de 2 °C. Les manipulations cessaient que les spécimens devenaient hyperthermiques (Tb 42,5 °C), les Ta maximums (Ta,max) allant de 42,0 à 49,7 °C. Comme prévu, les chauves-souris cendrées présentent la plus forte tolérance à la chaleur et la plus grande capacité de refroidissement par évaporation, atteignant des Ta,max de 2,4 et 1,2 °C supérieures à celles des vespertilions bruns et des chauves-souris argentées, respectivement. Nos résultats concordent avec l’hypothèse selon laquelle la tolérance à la chaleur des chauves-souris est corrélée aux microclimats des gîtes, bien que des variations interspécifiques de la masse corporelle et la phylogénie puissent nécessiter de nuancer ces conclusions. [Traduit par la Rédaction]Canadian Queen Elizabeth II Diamond Jubilee Scholarship program and Natural Science and Engineering Research Council of Canada.http://www.nrcresearchpress.com/journal/cjzpm2021Mammal Research InstituteZoology and Entomolog

Environmental correlates and energetics of winter flight by bats in Southern Alberta, Canada

Winter activity of bats is common, yet poorly understood. Other studies suggest a relationship between winter activity and ambient temperature, particularly temperature at sunset. We recorded echolocation calls to determine correlates of hourly bat-activity in Dinosaur Provincial Park, Alberta, Canada. We documented bat activity in temperatures as low as -10.4째C. We observed big brown bats (Eptesicus fuscus (Palisot de Beauvois, 1796)) flying at colder temperatures than species of Myotis bats (genus Myotis (Kaup 1829). We show that temperature and wind are important predictors of winter activity by E. fuscus and Myotis, and that Myotis may also use changes in barometric pressure to cue activity. In the absence of foraging opportunity, we suggest these environmental factors relate to heat loss and thus the energetic cost of flight. To understand the energetic consequences of bat flight in cold temperatures, we estimated energy expenditure during winter flights of E. fuscus and Myotis lucifugus using species-specific parameters. We estimated that winter flight uses considerable fat stores and that flight thermogenesis could mitigate energetic costs by 20% or more. We also show that temperature-dependent interspecific differences in winter activity likely stem from differences between species in heat loss and potential for activity-thermoregulatory heat substitution.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Added precision in 57Fe Mossbauer spectroscopy

This paper contains (1) the necessary mathematics for a precise interpretation of Mossbauer data, and (2) a characterization of a spectrometer designed specifically to maximize the information avalable from these data. The innovative aspects of this spectrometer are that it provides a known absorber lineshape, that it is quantitative, and that is provides information of the vibrational states of the absorber via the second order Doppler shift vs temperature and the total absorption vs temperature. The spectrometer allows sample temperature and applied magnetic field to be varied in any combination of 2-350 K or 0-6 T, respectively. Simultaneous collection of four data streams allows an accurate representation of the transmission spectrum. Sophisticated computer treatment with extensive use of least squares fitting procedures and fast Fourier transform techniques provides the final output display of sample cross-section vs standardized source velocity. The cross-section display is shown to be independent of the thickness of samples with Mossbauer optical densities up to 3. In addition, we report the method and results of measurements which must precede the operation of the spectrometer: (1) the absorption coefficient of iron at 14 keV: (498+/-7)cm-1, (2) the Debye temperature of our source (57Co in rhodium matrix): (361+/-20)K, (3) the source lineshape: three Lorentzians with Heisenberg linewidth, a center line with twice the intensity of the symmetrically placed outer lines which are spaced 0.055 mm/s apart, (4) the Mossbauer effect cross-section for 57Fe: (2.4+/-0.2) x 10-18 cm2, (5) the Debye temperature of iron (NBS # 1541): (430+/-30) K, and (6) the values for the Hamiltonian parameters of iron metal (NBS # 1541) at 290, 101 and 4.2 K. The precision of the determined Hamiltonian parameters is defined in terms of a statistic with a weighted [chi]2 distribution.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22843/1/0000403.pd