Ectoparasite Community Structure of Two Bats (Myotis lucifugus and M. septentrionalis) from the Maritimes of Canada

Prevalence of bat ectoparasites on sympatric Myotis lucifugus and M. septentrionalis was quantitatively characterized in Nova Scotia and New Brunswick by making systematic collections at swarming sites. Six species of ectoparasite were recorded, including Myodopsylla insignis, Spinturnix americanus, Cimex adjunctus, Macronyssu scrosbyi, Androlaelap scasalis, and an unknown species of the genus Acanthophthirius. Male M. lucifugus and M. septentrionalis had similar prevalence of any ectoparasite (22% and 23%, resp.). Female M. lucifugus and M. septentrionalis had 2-3 times higher prevalence than did conspecific males (68% and 44%, resp.). Prevalence of infection of both genders of young of the year was not different from one another and the highest prevalence of any ectoparasite (M. lucifugus 64%, M. septentrionalis 72%) among all bat groups. Ectoparasite prevalence and intensity varied positively with roost group size and negatively with grooming efficacy and energy budgets, suggesting that these variables may be important in ectoparasite community structure

Phenotypic plasticity and local adaptation in a wild hibernator evaluated through reciprocal translocation

Phenological shifts are the most commonly reported ecological responses to climate change and can be produced rapidly by phenotypic plasticity. However, both the limits of plasticity and whether it will be sufficient to maintain local adaptation (or even lead to maladaptation) are less clear. Increased winter precipitation has been shown to lead to phenological delays and corresponding annual decreases in fitness in Columbian ground squirrels (Urocitellus columbianus). We took advantage of natural phenological variation (across elevations) in this species to better assess the extent of phenotypic plasticity in emergence dates and the relationships between emergence dates and individual annual fitness. We coupled a reciprocal translocation experiment with natural monitoring across two populations separated by ∼500 m in elevation. Individuals in both populations responded plastically to both spring temperature and winter precipitation. Translocated individuals adjusted their emergence dates to approach those of individuals in their adoptive populations but did differ significantly in their emergence dates from residents. There were no differences in annual fitness among treatment groups nor selection on emergence date within a year. Phenotypic plasticity is thus sufficient to allow individuals to respond to broad environmental gradients, but the influence of variation in emergence dates on annual fitness requires further investigation

Thermal physiology of three sympatric small mammals from southern Africa

Please read abstract in the article.ThE National Research Foundationhttp://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-79982020-01-01hj2018Mammal Research InstituteZoology and Entomolog

Thermal energetics of male courtship song in a lek-breeding bat

Abstract: The use of songs for mate-attraction is common. Intensive songs may indicate high energetic investment, reflecting an individual’s resource-holding potential and attractiveness as a prospective mate. Consequently, there can be a direct relationship between song metrics and lifetime reproductive success. While singing is held to be energetically costly, quantitative studies in mammals are lacking. Here, we present an exploratory analysis of energetic costs in a singing bat (Mystacina tuberculata). We recorded the songs of 12 male bats and quantified skin temperature (Tsk) responses using temperature telemetry to estimate energy expenditure. We hypothesised that singing would be energetically costly and predicted correlations between Tsk and song duty cycle and between duty cycle and body size. Contrary to our expectations, we found estimated energetic expenditure while singing to be comparatively low. We also found no relationship between estimated energy expenditure and duty cycle, and neither estimated energy expenditure nor duty cycle was correlated with body size. Our results suggest that energetic costs of singing in bats may be lower than previously assumed, and that song output may convey only limited fitness information. Significance statement: Song is commonly used to communicate information related to mate-attraction or territory defence. Some aspects of song production require more energy to produce, making them an honest signal of a singer’s investment. While our knowledge of bird song and its relationship to mating success is well developed, a similar understanding regarding mammalian song is severely lacking. Numerous bat species produce song, yet we know little about the energetics of song production in this large and diverse order. Using temperature telemetry, we estimate the costs of singing in a free-living lek-breeding bat. To our knowledge, this is the first study to estimate the energetic costs of song production in a mammal.</p

Thrifty Females, Frisky Males: Winter Energetics of Hibernating Bats from a Cold Climate

Mammalian hibernation consists of energy-saving torpor bouts (periods of controlled reduction in body temperature [Tb]) interspersed with brief arousals to normothermic Tb. Frequency and duration of torpor bouts and arousals can affect winter survival and are thought to be influenced by an optimization balancing the energetic benefits of prolonged torpor against the physiological and ecological costs (e.g., accumulation of metabolic wastes). Female little brown bats (Myotis lucifugus) spend their fat reserves more slowly than males during winter, presumably so they can emerge from hibernation in good condition to initiate pregnancy. We used temperature telemetry over three winters to test a prediction of the optimization hypothesis that female M. lucifugus would use longer torpor bouts and/or shorter arousals than males. Females did conserve energy relative to males by adjusting the magnitude and duration of arousals but not the duration of torpor bouts. Although torpor bout duration did not vary by sex for adults, it did vary by age. Adults initially used longer torpor bouts than young-of-the-year, but this difference declined as cave temperature warmed in spring. Males and females in better condition spent more energy during hibernation, again via increased arousal duration rather than decreased torpor bout duration. Longer arousals by males could increase reproductive fitness if males mate with torpid females throughout winter. Our results highlight demographic differences in winter behavior for small hibernators facing extreme energy limitation in cold climates and illustrate the influence that reproductive costs have on hibernation energetics

Caves, crevices and cooling capacity: Roost microclimate predicts heat tolerance in bats

The microsites that animals occupy during the rest phase of their circadian activity cycle influence their physiology and behaviour, but relatively few studies have examined correlations between interspecific variation in thermal physiology and roost microclimate. Among bats, there is some evidence that species exposed to high roost temperatures (Troost) possess greater heat tolerance and evaporative cooling capacity, but the small number of species for which both thermal physiology and roost microclimate data exist mean that the generality of this pattern remains unclear. Here, we test the hypothesis that bat heat tolerance and evaporative cooling capacity have co-evolved with roost preferences. We predicted that species occupying roosts poorly buffered from high outside environmental temperature exhibit higher heat tolerance and evaporative cooling capacity compared to species inhabiting buffered roosts in which Troost remains well below outside conditions. We used flow-through respirometry to investigate thermoregulation at air temperatures (Ta) approaching and exceeding normothermic body temperature (Tb) among six species with broadly similar body mass but differing in roost microclimate (hot vs. cool roosts). We combined these data with empirical measurements of Troost for each study population. Hot-roosting species tolerated Ta ~4°C higher than cool-roosting bats before the onset of loss of coordinated locomotion and non-regulated hyperthermia. The evaporative scope (i.e. ratio of maximum evaporative water loss [EWL] to minimum thermoneutral EWL) of hot-roosting species (16.1 ± 2.4) was substantially higher than that of cool-roosting species (5.9 ± 2.4). Maximum evaporative cooling capacities (i.e. evaporative heat loss/metabolic heat production) of hot-roosting species were >2, while the corresponding values for cool-roosting species were ≤1. The greater heat tolerance and higher evaporative cooling capacity of hot-roosting species compared with those occupying cooler roosts reveal variation in bat evaporative cooling capacity correlated with roost microclimate, supporting the hypothesis that thermal physiology has co-evolved with roost preference. A free Plain Language Summary can be found within the Supporting Information of this article

Caves, crevices and cooling capacity: Roost microclimate predicts heat tolerance in bats

The microsites that animals occupy during the rest phase of their circadian activity cycle influence their physiology and behaviour, but relatively few studies have examined correlations between interspecific variation in thermal physiology and roost microclimate. Among bats, there is some evidence that species exposed to high roost temperatures (Troost) possess greater heat tolerance and evaporative cooling capacity, but the small number of species for which both thermal physiology and roost microclimate data exist mean that the generality of this pattern remains unclear. Here, we test the hypothesis that bat heat tolerance and evaporative cooling capacity have co-evolved with roost preferences. We predicted that species occupying roosts poorly buffered from high outside environmental temperature exhibit higher heat tolerance and evaporative cooling capacity compared to species inhabiting buffered roosts in which Troost remains well below outside conditions. We used flow-through respirometry to investigate thermoregulation at air temperatures (Ta) approaching and exceeding normothermic body temperature (Tb) among six species with broadly similar body mass but differing in roost microclimate (hot vs. cool roosts). We combined these data with empirical measurements of Troost for each study population. Hot-roosting species tolerated Ta ~4°C higher than cool-roosting bats before the onset of loss of coordinated locomotion and non-regulated hyperthermia. The evaporative scope (i.e. ratio of maximum evaporative water loss [EWL] to minimum thermoneutral EWL) of hot-roosting species (16.1 ± 2.4) was substantially higher than that of cool-roosting species (5.9 ± 2.4). Maximum evaporative cooling capacities (i.e. evaporative heat loss/metabolic heat production) of hot-roosting species were >2, while the corresponding values for cool-roosting species were ≤1. The greater heat tolerance and higher evaporative cooling capacity of hot-roosting species compared with those occupying cooler roosts reveal variation in bat evaporative cooling capacity correlated with roost microclimate, supporting the hypothesis that thermal physiology has co-evolved with roost preference. A free Plain Language Summary can be found within the Supporting Information of this article

Heat tolerance in desert rodents is correlated with microclimate at inter- and intraspecific levels

Physiological diversity in thermoregulatory traits has been extensively investigated in both endo- and ectothermic vertebrates, with many studies revealing that thermal physiology has evolved in response to selection arising from climate. The majority of studies have investigated how adaptative variation in thermal physiology is correlated with broad-scale climate, but the role of fine-scale microclimate remains less clear . We hypothesised that the heat tolerance limits and evaporative cooling capacity of desert rodents are correlated with microclimates within species-specific diurnal refugia. We tested predictions arising from this hypothesis by comparing thermoregulation in the heat among arboreal black-tailed tree rats (Thallomys nigricauda), Namaqua rock rats (Micaelamys namaquensis) and hairy-footed gerbils (Gerbillurus paeba). Species and populations that occupy hotter diurnal microsites tolerated air temperatures (Ta) ~ 2–4 ℃ higher compared to those species occupying cooler, more thermally buffered microsites. Inter- and intraspecific variation in heat tolerance was attributable to ~ 30% greater evaporative water loss and ~ 44 % lower resting metabolic rates at high Ta, respectively. Our results suggest that microclimates within rodent diurnal refugia are an important correlate of intra- and interspecific physiological variation and reiterate the need to incorporate fine-scale microclimatic conditions when investigating adaptative variation in thermal physiology

Efficient evaporative cooling and pronounced heat tolerance in an eagle-owl, a thick-knee and a sandgrouse

Avian evaporative cooling and the maintenance of body temperature (Tb) below lethal limits during heat exposure has received more attention in small species compared to larger-bodied taxa. Here, we examined thermoregulation at air temperatures (Tair) approaching and exceeding normothermic Tb in three larger birds that use gular flutter, thought to provide the basis for pronounced evaporative cooling capacity and heat tolerance. We quantified Tb, evaporative water loss (EWL) and resting metabolic rate (RMR) in the ∼170-g Namaqua sandgrouse (Pterocles namaqua), ∼430-g spotted thick-knee (Burhinus capensis) and ∼670-g spotted eagle-owl (Bubo africanus), using flow-through respirometry and a stepped Tair profile with very low chamber humidities. All three species tolerated Tair of 56–60◦C before the onset of severe hyperthermia, with maximum Tb of 43.2◦C, 44.3◦C, and 44.2◦C in sandgrouse, thick-knees and eagleowls, respectively. Evaporative scope (i.e., maximum EWL/minimum thermoneutral EWL) was 7.4 in sandgrouse, 12.9 in thick-knees and 7.8 in eagle-owls. The relationship between RMR and Tair varied substantially among species: whereas thick-knees and eagle-owls showed clear upper critical limits of thermoneutrality above which RMR increased rapidly and linearly, sandgrouse did not. Maximum evaporative heat loss/metabolic heat production ranged from 2.8 (eagle-owls) to 5.5 (sandgrouse), the latter the highest avian value yet reported. Our data reveal some larger species with gular flutter possess pronounced evaporative cooling capacity and heat tolerance and, when taken together with published data, show thermoregulatory performance varies widely among species larger than 250 g. Our data for Namaqua sandgrouse reveal unexpectedly pronounced variation in the metabolic costs of evaporative cooling within the genus Pterocles.National Research Foundation of South Africahttp://frontiersin.org/Ecology_and_Evolutiondm2022Zoology and Entomolog