Agricultural intensification alters bat assemblage composition and abundance in a dynamic Neotropical landscape

The recent trend of agricultural intensification in tropical landscapes poses a new threat to biodiversity conservation. Conversion of previously heterogeneous agricultural landscapes to intensive plantation agriculture simplifies and homogenizes the landscape, reducing availability, and connectivity of natural habitat for native species. To assess the impact of agricultural intensification on bats, we characterized the bat assemblage in the Sarapiquí region of Costa Rica, where heterogeneous land uses are being converted to intensive, large‐scale pineapple plantations. In 2012 and 2013, we sampled bats in 20 remnant forest patches surrounded by varying proportions of pasture, mature forest, and pineapple and captured 1821 individual bats representing 39 species. We used ordination analyses to evaluate changes in species composition, where pineapple is the main component of the agricultural matrix. We identified landscape metrics specifically correlated with pineapple and used multiple linear regression to test their effects on bat species richness, diversity, and guild‐specific relative abundance. Results suggest pineapple expansion is driving changes in assemblage composition in remnant forest patches, resulting in new assemblages with higher proportions of frugivorous bats and lower proportions of insectivorous bats than in continuous mature forests. In addition, while pineapple does not diminish total bat species richness and diversity, the reduced forest cover and increased distance between forest patches in pineapple plantations has a significant negative impact on the relative abundance of insectivores. We also identify a potential threshold effect whereby patches surrounded by more than 50 percent forest can retain assemblage composition similar to that found in continuous mature forest.     

Bats relocate maternity colony after the natural loss of roost trees

Understanding the ephemerality of trees used as roosts by wildlife, and the number of roost trees needed to sustain their populations, is important for forest management and wildlife conservation. Several studies indicate that roosts are limiting to bats, but few studies have monitored longevity of roost trees used by bats over several years. From 2004–2007 in Cypress Hills Interprovincial Park, Saskatchewan, Canada, several big brown bats (Eptesicus fuscus) from a maternity group roosted in cavities in trembling aspen (Populus tremuloides) trees approximately 7 km southeast away from their original known roosting area (RA1). Using a long-term data set of the roost trees used by bats in this area from 2000–2007, we evaluated whether the movement of bats to the new roosting area (RA4) corresponded with annual and cumulative losses of roost trees. We also determined whether longevity of the roosts from the time we discovered bats first using them differed between the 2 roosting areas based on Kaplan-Meier estimates. Bats began using RA4 in addition to RA1 in 2004, when the cumulative loss of roost trees in RA1 over 3 consecutive years reached 18%. Most bats exclusively roosted in RA4 in 2007, when the cumulative loss of roost trees over 6 consecutive years had reached 46% in RA1. Annual survival for roost trees, from when we first discovered bats using them, was generally lower in RA1 than in RA4. Our results suggest that the movement of bats to the new roosting area corresponded with high losses of roost trees in RA1. This provides additional evidence that to maintain high densities of suitable roost trees for bats in northern temperature forests over several decades, management plans need to recruit live and dead trees in multiple age classes and stages of decay that will be suitable for the formation of new cavities. © 2019 The Wildlife Society.     

Trophic niche changes associated with habitat fragmentation in a Neotropical bat species

Habitat fragmentation could alter ecological traits including species trophic habits. Here, we used carbon and nitrogen stable isotope ratios to establish differences in isotopic niche width and food resource use between forest fragments and the continuous forest for the phyllostomid frugivorous bat Artibeus lituratus. Using mist nests, we captured bats from two forest fragments and two sites in continuous forest, and sampled from each individual captured three body tissues with contrasting turnover rates (skin, muscle, and liver). Samples were collected between February and March (austral summer) and between August and September (austral winter). In addition, in each sampling site and season we collected potential food resources (fruits and insects) consumed by our A. lituratus. Our findings indicate that A. lituratus had a predominantly omnivorous diet, with high consumption of insects during summer in forest fragments. The increasing consumption of insects in these fragments seems to have led to a wider isotopic niche, in relation to the continuous forest. Because A. lituratus is typically a seed disperser, changes in trophic habits in the forest fragments from frugivory to insectivory may diminish their role in forest regeneration. Abstract in Portuguese is available with online material.     

Postnatal growth,age estimation and development of foraging behaviour in the fulvous fruit bat<Emphasis Type="Italic">Rousettus leschenaulti</Emphasis>

This study documents the postnatal growth, age estimation and development of the foraging behaviour of the fulvous fruit batRousettus leschenaulti under captive conditions. At birth, the young were naked and pink with closed eyes and folded pinnae. By day four of age, their eyes had opened and the pups began to move. The mean length of forearm in 5-day-old pups was 24.9 mm and body mass was 10.8 g, equivalent to 32.3% and 14.2% of the values from postpartum females. The length of forearm and body mass increased linearly until 45 and 50 days, respectively, and thereafter maintained an apparent stability. The epiphyseal gap of the fourth metacarpal-phalangeal joint increased until 15 days, then decreased linearly until 75 days and thereafter closed. Age was estimated quantitatively, based on linear changes observed in the length of the forearm and epiphyseal gap. Pups began to roost separately, but adjacent to their mothers when 30 days old and flew clumsily when they were about 40 days old. After attaining clumsy flight, the young bats made independent foraging attempts feebly by biting and licking small fruit pieces. Young bats were engaged in suckling as well as ingesting fruits when they were about 50 days old. Between 55 and 65 days, they flew well and fed on fruits. At the age of 75 days, the young bats were completely weaned and at two months, their foraging behaviour was similar to that of their mothers. There was no significant difference in the growth pattern of the young maintained in captivity compared with those under natural conditions.     

恒频-调频蝙蝠下丘神经元的恢复周期决定声脉冲跟随率

为探究恒频-调频蝙蝠下丘神经元恢复周期特点及其对声脉冲跟随率的影响,实验采用模拟的大蹄蝠(Hipposideros armiger)自然状态下的恒频-调频发声信号为声刺激,在5只听力正常的大蹄蝠上记录了下丘神经元的声反应和恢复周期(n = 93)．结果发现,根据神经元恢复率达50%时的双声刺激间隔(inter pulse interval,IPI),可将其分为长时恢复型(long recovery,LR;47.4%)、中等时间恢复型(moderate recovery,MR;35.1%)和短时恢复型(short recovery,SR;17.5%)．每种类型依据其恢复率随IPI增加而呈现的不同变化又可进一步分为单IPI反应区神经元,多IPI反应区神经元,以及单调IPI反应神经元．LR,MR和SR型神经元恢复率达50%时的平均IPI分别为(64.0 ± 24.8),(19.6 ± 5.8)和(7.1 ± 2.4) ms (P < 0.001),相对应的平均理论每秒声脉冲数分别为(18.2 ± 7.0),(55.4 ± 15.7)和(171.3 ± 102.9) Hz (P < 0.001)．结果提示,单IPI和多IPI反应区神经元具有特殊IPI反应特性,能对蝙蝠捕食和巡航期间所处的时相做出准确判断,而单调IPI反应神经元对IPI变化的敏感性较强,但时相判断性较差．另外LR,MR和SR型神经元恢复周期和理论脉冲跟随率的平均结果均能与这种蝙蝠回声定位期间3个时相的发声行为相匹配,且神经元恢复周期参与决定声脉冲跟随率,满足了蝙蝠巡航、捕食的行为学需要．     

Urban Maternity-Roost Selection by Big Brown Bats in Colorado

Abstract: Despite prevalent use of anthropogenic structures by bats and the associated implications for public health, management, and bat conservation, very little quantitative information exists about urban roost characteristics and their selection by bats. During the summers of 2001 to 2004 we conducted fieldwork in Fort Collins, Colorado, USA, situated on the northern end of Colorado's Front Range, to address questions of roost selection by the big brown bat (Eptesicus fuscus). The city has experienced its greatest growth in the past half century, with its population increasing by 30% in the last decade. Similar growth in new buildings has occurred, with the number of new housing permits issued annually doubling in the past decade. We located 142 roosts using radiotelemetry or by citizen calls in response to a newspaper article and flyers. To determine characteristics of roost selectivity by bats, we compared variables for known maternity roosts and randomly selected buildings at microhabitat and landscape scales using logistic regression; we used an information theoretic approach to determine which variables were most important. We considered 44 and 100 buildings in the microhabitat and landscape scale analyses, respectively. At the microhabitat scale maternity roosts had exit points with larger areas that were higher from the ground and had warmer average temperatures than randomly selected buildings. At the landscape scale distances to similarly categorized roosts were smaller, and urbanization variables such as lower building density, higher street density, and lower traffic count density were most important. Results for variables important to urban-roosting big brown bats were often analogous to studies that characterized maternity roosts found in tree snags and rock crevices. In addition, changes in the landscape, not only in the form of anthropogenic structures but also in water availability and vegetation structure such as riparian forests, may have led to population increases and range expansions of the big brown bat. Because big brown bats appear to selectively choose specific combinations of characteristics found at maternity roosts, not all available structures can be considered suitable and exclusion from established maternity roosts may negatively impact bat populations.     

Rangewide phylogeography in the greater horseshoe bat inferred from microsatellites: implications for population history, taxonomy and conservation

The distribution of genetic variability across a species' range can provide valuable insights into colonization history. To assess the relative importance of European and Asian refugia in shaping current levels of genetic variation in the greater horseshoe bats, we applied a microsatellite-based approach to data collected from 56 localities ranging from the UK to Japan. A decline in allelic richness from west Asia to the UK and analyses of F(ST) both imply a northwestward colonization across Europe. However, sharp discontinuities in gene frequencies within Europe and between the Balkans and west Asia (Syria/Russia) are consistent with suture zones following expansion from multiple refugia, and a lack of recent gene flow from Asia Minor. Together, these results suggest European populations originated from west Asia in the ancient past, and experienced a more recent range expansion since the Last Glacial Maximum. Current populations in central Europe appear to originate from the Balkans and those from west Europe from either Iberia and/or Italy. Comparisons of R(ST )and F(ST) suggest that stepwise mutation has contributed to differentiation between island and continental populations (France/UK and China/Japan) and also among distant samples. However, pairwise R(ST) values between distant populations appear to be unreliable, probably due to size homoplasy. Our findings also highlight two priorities for conservation. First, stronger genetic subdivision within the UK than across 4000 km of continental Eurasia is most likely the result of population fragmentation and highlights the need to maintain gene flow in this species. Second, deep splits within China and between Europe and China are indicative of cryptic taxonomic divisions which need further investigation.     

Curtailment and acoustic deterrents reduce bat mortality at wind farms

The impacts of wind energy on bat populations is a growing concern because wind turbine blades can strike and kill bats, and wind turbine development is increasing. We tested the effectiveness of 2 management actions at 2 wind-energy facilities for reducing bat fatalities: curtailing turbine operation when wind speeds were <5.0 m/second and combining curtailment with an acoustic bat deterrent developed by NRG Systems. We measured the effectiveness of the management actions using differences in counts of bat carcasses quantified by daily and twice-per-week standardized carcass searches of cleared plots below turbines, and field trials that estimated searcher efficiency and carcass persistence. We studied turbines located at 2 adjacent wind-energy facilities in northeast Illinois, USA, during fall migration (1 Aug–15 Oct) in 2018. We estimated the effectiveness of each management action using a generalized linear mixed-effects model with several covariates. Curtailment alone reduced overall bat mortality by 42.5% but did not reduce silver-haired bat (Lasionycteris noctivagans) mortality. Overall bat fatality rates were 66.9% lower at curtailed turbines with acoustic deterrents compared to turbines that operated at manufacturer cut-in speed. Curtailment and the deterrent reduced bat mortality to varying degrees between species, ranging from 58.1% for eastern red bats (Lasiurus borealis) to 94.4 for big brown bats (Eptesicus fuscus). Hoary (Lasiurus cinereus) and silver-haired bat mortality was reduced by 71.4% and 71.6%, respectively. Our study lacked a deterrent-only treatment group because of the expense of acoustic deterrents. We estimated the additional reduction in mortality with concurrent deployment of the acoustic deterrent and curtailment under the assumption that curtailment and the acoustic deterrent would have reduced mortality by the same percentage at adjacent wind-energy facilities. Acoustic deterrents resulted in 31.6%, 17.4%, and 66.7% additional reductions of bat mortality compared to curtailment alone for eastern red bat, hoary bat, and silver-haired bat, respectively. The effectiveness of acoustic deterrents for reducing bat mortality at turbines with rotor-swept area diameters >110 m is unknown because high frequency sound attenuates quickly, which reduces coverage of rotor-swept areas. Management actions should consider species differences in the ability of curtailment and deterrents to reduce bat mortality and increase energy production.