• FACTORS AFFECTING THE PROBABILITY OF ACOUSTIC DETECTION AND SITE OCCUPANCY OF BATS IN CENTRAL INDIANA

      Kaiser, Zachary David Epping (Indiana State University, 2014-05)
      Documenting the presence of rare bat species can be difficult. The current summer survey protocol for the federally endangered Indiana bat (Myotis sodalis) requires passive acoustic sampling with directional microphones (e.g., Anabats), but there are still questions about best practices for choosing survey sites and appropriate detector models. Indiana bats are capable of foraging in an array of cover types, including structurally-complex, interior forests. Further, data acquisition among different commercially available bat detectors is likely highly variable, due to the use of proprietary microphones with different frequency responses, sensitivities, and directionality. We paired omnidirectional Wildlife Acoustic SM2BAT+ (SM2) and directional Titley Scientific Anabat SD2 (Anabat) detectors at 71 random points near Indianapolis, Indiana from May-August 2012-2013 to compare data acquisition by phonic group (low, mid, Myotis) and to determine what factors affect probability of detection and site occupancy for Indiana bats when sampling with acoustics near an active maternity colony (0.20-8.39 km away). Weatherproofing for Anabat microphones was 45° angle PVC tubes and for SM2 microphones was their foam shielding; microphones were paired at 2 m and 5 m heights. Habitat and landscape covariates were measured in the field or via ArcGIS. We adjusted file parameters to make SM2 and Anabat data comparable. Files were identified using Bat Call ID software, with visual inspection of Indiana bat calls. The effects of detector type, phonic group, height, and their interactions on mean files recorded per site were assessed using generalized estimating equations and LSD pairwise comparisons. We reduced probability of detection (p) and site occupancy (ψ) model covariates with Pearson’s correlation and PCA. We used Presence 6.1 software and Akaike’s Information Criteria to assess models for p and ψ. Anabats and SM2s did not perform equally. Anabats recorded more low and midrange files, but fewer Myotis files per site than SM2s. When comparing the same model of detectors, deployment height did not impact data acquisition. Weatherproofing may limit the ability of Anabats to record Myotis, but Anabat microphones may have greater detection ranges for low and midrange bats. Indiana bat detections were low for both detector types, representing only 4.4% of identifiable bat files recorded by SM2s. We detected Indiana bats at 43.7% of sampled sites and on 31.4% of detector-nights; detectability increased as “forest closure” and mean nightly temperature increased, likely due to reduced clutter and increased bat activity, respectively. Proximity to colony trees and specific cover types generally did not affect occupancy, suggesting that Indiana bats use a variety of cover types in this landscape. Omnidirectional SMX-US microphones may be more appropriate for Indiana bat surveys than directional Anabat microphones. However, we conclude that 2 nights of passive acoustic sampling per site may be insufficient for reliably detecting this species when it is present. In turn, the use of acoustic monitoring as a means to document presence or probable absence should be reassessed.
    • Insect Abundance and Variability in an Urban-Rural Landscape and Comparison to Foraging Habitat Selection of Bats

      Oehler, Nicole M. (2012-01-19)
      I conducted a study of the relationship between prey availability and foraging habitat selection of Indiana bats (Myotis sodalis), big brown bats (Eptesicus fuscus), eastern red bats (Lasiurus borealis) and evening bats (Nycticeius humeralis) in an urban-rural landscape matrix of southwestern Indianapolis. Insects were collected from nine different habitat types found within the range of these species. Insect data were collected from 2006 to 2008 using sticky traps placed in each habitat type. Habitat types were ranked by importance to each bat species (based on previous studies) and then compared to the average number of prey insects captured per habitat sticky trap. Only the average number of insects captured per habitat sticky trap that were big brown bat and eastern red bat prey varied significantly between all nine habitat types. The average number of prey insects captured per habitat sticky trap that were Indiana bat, big brown bat, eastern red bat and evening bat prey were strongly significantly different between sampling dates within seasons. The average number of prey insects captured per habitat sticky trap that were big brown bat and evening bat prey varied significantly between sampling dates between seasons. The average number of prey insects per habitat type did not correlate significantly with habitat selection by any of the four bat species.