**3. Results**

The concern that the more sensitive bat detector (miniMIC) would be more adversely impacted by road noise or airflow was fully realized. The detector was sensitive to wind resistance at speeds over 10 km/h, recording tens of thousands of audio files, all obscured with background noise. This made analysis of these data impossible. Therefore, comparisons of continuous and point count sampling results could only be performed with data obtained from the EM3 detector.

Average passes per minute recorded along the 26 transects was not significantly different between continuous sampling versus point count sampling (0.076 vs. 0.067 passes/min, respectively, P = 0.097, **Table 1**). Comparisons of the proportion of bat passes identified to species and total number of species documented using the two approaches revealed largely similar results as well. Of all the passes recorded for the entire sample during continuous sampling, 20% were able to be identified to species, yielding an overall rate of 0.015 passes per minute identified to species (**Table 1**). At point count sites, 24.5% of passes were able to be identified to species, yielding a rate of 0.016 passes per minute identified to species (**Table 1**). Both approaches also documented the same four species: big brown bat (*Eptesicus fuscus*), red bat (*Lasiurus borealis*), evening bat (*Nycticeius humeralis*), and silver-haired bat (*Lasionycteris noctivagans*).

obtained vastly more calls identified to species throughout the study compared to the EM3 (2276 vs. 52, respectively, **Table 2**). Lastly, the miniMIC not only documented the four species found with the EM3 (see above), but it also uncovered three additional species: hoary bat (*Lasiurus cinereus*), tricolored bat (*Perimyotis subflavus*), and one or more species in the genus

**Table 2.** Comparison of bat detection rates between the two different bat detectors at 260 point count sampling sites.

Mean (SD) passes at each site 0.812 (5.15) 13.17 (24.24)

The miniMIC documented significantly more calls than the EM3 (Wilcoxon test, N = 260, P < 0.001).

Mean passes/minute 0.067 1.098 Total passes recorded 211 3550 Percent passes identified to species 24.5% 64.1% Passes/minute identified to species 0.016 0.724 Total passes identified to species 52 2276 Total number of species identified 4 7

**EM3 detector miniMIC detector**

http://dx.doi.org/10.5772/intechopen.75834

13

Comparison of Driving Transect Methods for Acoustic Monitoring of Bats

Bats face a growing array of threats. Many of these threats have complex and overlapping geographic distributions. Given the uncertainty of how these threats interact and impact bats across the landscape, it is becoming increasingly important to monitor populations across large geographic areas. Driving transects offer one the most cost effective and least laborintensive tools for doing this. However, driving transects can be implemented in different ways and it is important to determine which approach is superior in terms of the amount and

When comparing results from a single detector capable of yielding analyzable audio files from both continuous and point count sampling, these two methods appear comparable. Specifically, mean number of passes per minute, percent of passes identified to species, passes per minute identified to species, and number of species identified were similar between the two approaches (**Table 1**). They also documented the same four species. If this holds with other detectors that are similarly unaffected by airflow or driving noises, we conclude that either driving transect technique can be a viable option. With such detectors, the needs of the particular project should dictate which option is selected. For example, if one seeks to test hypotheses about habitat use or other factors, the ability to use a variety of standard statistical techniques such as ANOVA (or nonparametric equivalents) for data from discrete sampling points may indicate the point count method is preferable. If, on the other hand, one simply seeks to document the bat fauna of an area, particularly in places it may not be safe to stop and

*Myotis* (we were unable to confidently identify the specific species).

record for extended periods, continuous sampling might be preferable.

**4. Discussion**

quality of data obtained.

Since data obtained with the more sensitive miniMIC detector during continuous sampling could not be analyzed, comparisons of the two detectors were restricted to point count sampling. Here, considerable differences were uncovered. The average number of bat passes recorded at each site were significantly higher using the miniMIC detector compared to the less sensitive EM3 detector (mean = 13.17 vs. 0.812 bat passes per site, respectively, N = 260, P < 0.001, **Table 2**). This translates to an average of 1.098 passes per minute for the miniMIC versus 0.067 for the EM3 (**Table 2**). Magnified over 52 hours of recording at the 260 sites, this resulted in a considerably higher number of total bat passes recorded with the miniMIC (3550) compared to the EM3 (211) (**Table 2**). Furthermore, due to the superior resolution of the audio files obtained with the miniMIC, a considerably higher proportion of bat passes were able to be identified to species (64.1% vs. 24.5%, **Table 2**). The combination of a higher number of calls recorded with a higher proportion identified to species meant that the miniMIC


Passes per minute were not statistically different between the two approaches (Wilcoxon test, N = 26, P = 0.097).

**Table 1.** Comparison of bat detection rates between continuous versus point count sampling along 26 transects using the EM3 bat detector.


**Table 2.** Comparison of bat detection rates between the two different bat detectors at 260 point count sampling sites.

obtained vastly more calls identified to species throughout the study compared to the EM3 (2276 vs. 52, respectively, **Table 2**). Lastly, the miniMIC not only documented the four species found with the EM3 (see above), but it also uncovered three additional species: hoary bat (*Lasiurus cinereus*), tricolored bat (*Perimyotis subflavus*), and one or more species in the genus *Myotis* (we were unable to confidently identify the specific species).
