Use of Artificial Roost Structures by Bats at the Indianapolis International Airport

From 1992–1996, 3204 artificial roosts of 9 types were placed in woodlots near Indianapolis International Airport in an effort to provide habitat for the federally-endangered Indiana myotis (Myotis sodalis) and to determine the feasibility of using these structures to manage bats in a rapidly developing suburban area. We surveyed these structures at least annually during 1992–1999 and found only northern myotis (Myotis septentrionalis) regularly using the structures. Four other species were occasionally found using structures including big brown bats (Eptesicus fuscus, n = 14 individuals), little brown myotis (Myotis lucifugus, n = 2), Indiana myotis (Myotis sodalis, n = 2), and one silver-haired bat (Lasionycteris noctivagans). Single, triple, and Missouri-style batboxes were almost always used, rather than the six other types of experimental roosts that had been in place. However, after 10 years in place, it appears that Indiana bats are acclimated to boxes, as 6 of them were being used rather regularly by Indiana myotis. Bat boxes can provide roosting habitat for some species under conditions where few suitable roosts exist, but assuring an abundance of natural habitats is usually more desirable for conservation of tree-roosting bats.     

Echolocation call design and limits on prey size: a case study using the aerial-hawking bat Nyctalus leisleri

The echolocation calls used by Nyctalus leisleri during search phase in open air space are between 9 and 14 ms long, with the peak energy between 24 and 28 kHz. The pulses are shallowly frequency-modulated with or without an initial steep frequency-modulated component. The diet consists primarily of small flies (Diptera), including many chironomids (wingspan 9–12 mm) and yellow dung flies (Scatophaga; wingspan 24 mm), but also of some larger insects such as dung beetles (Coleoptera; Scarabaeoidea), caddis-flies (Trichoptera) and moths (Lepidoptera). The echo target strength of some prey items was measured. Contrary to models based on standard targets such as spheres or disks, the echo strength of real insects was found to be virtually independent of the emitted frequency within the 20–100 kHz frequency range. A model was used to calculate probable detection distances of the prey by the bat. Using narrow-band calls of 13.7 ± 2.7 ms duration, a bat would detect the two smallest size classes of insect at greatest range using calls of 20 kHz. The results may therefore explain why many species of large and medium sized aerial-hawking bats use low-frequency calls and still eat mostly relatively small insects. The data and model challenges the assumption that small prey are unavailable to bats using low-frequency calls.     

有机污染物在白洋淀地区水陆交错带土壤颗粒物上的吸附

通过静态吸附实验,探讨了亲水性的苯酚和新脂性的对氯苯酚,在白洋淀地区水陆交错带－芦苇地中的天然颗粒物上的吸队规律。对于亲水性有机物,它在颗粒物上的吸附符合Ｌａｎｇｍｕｉｒ等温吸附,平衡浓度ｃｅ的对数与吸附率ｑ的对数呈直线关系;而亲脂性有机物的吸附则符合Ｌｉｎｅａｒ吸附关系,即平衡浓度ｃｅ１与吸附率ｑ１之间呈直线关系,且吸附量明显高于亲水性的有机物。     

Echolocation signals of the bat Eptesicus serotinus recorded using a vertical microphone array: effect of flight altitude on searching signals

The acoustic behaviour of Eptesicus serotinus was investigated in the field using a 13.5-m vertical, linear microphone array that allowed for simultaneous recordings at three different heights and for the calculation of flight altitude and distance from the array. Recordings were made at two locations that differed in bat species diversity. E. serotinus hunted on average at an altitude of 10.7 m (±2.7) at one location and 6.8 m (±3.6) at the other location. Search signals were 5–17 ms long depending on flight altitude, and consisted of two to three frequency-modulated harmonics. For bats flying below 8–10 m altitude, signal duration decreased with decreasing flight altitude, whereas signal interval, terminal frequency, peak frequency and frequency range of the first harmonic increased. Above 8–10 m flight altitude, the signal parameters were fairly constant. The –10 dB bandwidth and duty cycle did not change with flight altitude. Source levels were calculated to between 121 and 125 dB peSPL re 20 μPa at 10 cm. For bats flying higher than 9 m, the microphone placed 1.5 m above the ground recorded significantly reduced signal durations and frequency ranges of the first harmonic compared to the same signals recorded with the microphones at heights of 7 or 15 m. We caution the use of ground recordings to fully describe the echolocation signals of high-flying bats. We demonstrate that flight altitude significantly influences the structure of sonar signals from E. serotinus. Received: 17 May 1999 / Received in revised form: 20 September 1999 / Accepted: 25 September 1999     

Greater spear-nosed bats give group-distinctive calls

Individually distinctive vocalizations are ubiquitous; however, group distinctive calls have rarely been demonstrated. Under some conditions, selection should favor calls indicating social group membership in animals that forage in groups. Greater spear-nosed bats (Phyllostomus hastatus) give calls that appear to facilitate recognition of social group mates who are unrelated. Females give loud broadband (4–18 kHz) vocalizations termed screech calls when departing on foraging trips and at foraging sites. Screech calls help to establish foraging groups among social group members, and to maintain contact over the long distances they travel while foraging. I test two hypotheses about how screech calls may be structured to convey caller identity. Individual calls may be distinct and group members may learn to recognize each individual's calls and to associate the individual with the social group. Alternatively, groups may give distinct calls and individuals within groups may share call characteristics. To test these hypotheses I conducted multivariate acoustic analysis of multiple calls from 28 bats from three social groups. Although the ubiquity of individually distinctive calls in other taxa makes this result more likely, the results reveal that group calls are highly distinctive. Individual bats within groups are statistically indistinguishable. Calls appear to decrease slightly in frequency as bats age. Call convergence among unrelated group mates implies vocal learning in this species. Received: 28 March 1996 / Accepted after revision: 6 October 1996     

The scope and severity of white-nose syndrome on hibernating bats in North America

Assessing the scope and severity of threats is necessary for evaluating impacts on populations to inform conservation planning. Quantitative threat assessment often requires monitoring programs that provide reliable data over relevant spatial and temporal scales, yet such programs can be difficult to justify until there is an apparent stressor. Leveraging efforts of wildlife management agencies to record winter counts of hibernating bats, we collated data for 5 species from over 200 sites across 27 U.S. states and 2 Canadian provinces from 1995 to 2018 to determine the impact of white-nose syndrome (WNS), a deadly disease of hibernating bats. We estimated declines of winter counts of bat colonies at sites where the invasive fungus that causes WNS (Pseudogymnoascus destructans) had been detected to assess the threat impact of WNS. Three species undergoing species status assessment by the U.S. Fish and Wildlife Service (Myotis septentrionalis, Myotis lucifugus, and Perimyotis subflavus) declined by more than 90%, which warrants classifying the severity of the WNS threat as extreme based on criteria used by NatureServe. The scope of the WNS threat as defined by NatureServe criteria was large (36% of Myotis lucifugus range) to pervasive (79% of Myotis septentrionalis range) for these species. Declines for 2 other species (Myotis sodalis and Eptesicus fuscus) were less severe but still qualified as moderate to serious based on NatureServe criteria. Data-sharing across jurisdictions provided a comprehensive evaluation of scope and severity of the threat of WNS and indicated regional differences that can inform response efforts at international, national, and state or provincial jurisdictions. We assessed the threat impact of an emerging infectious disease by uniting monitoring efforts across jurisdictional boundaries and demonstrated the importance of coordinated monitoring programs, such as the North American Bat Monitoring Program (NABat), for data-driven conservation assessments and planning.