Appendix 4-1 Seasonal Acoustic Monitoring Study on Oahu Army Installations C. Pinzari USGS 2014

Transcription

1 Hawaiian Hoary Bat Seasonal Acoustic Monitoring Study on Oahu Army Installations Data prepared by C. Pinzari, for CSU, March 2014 Survey Goals Establish bat presence or absence on U.S. Army managed lands. If bats present, survey throughout the year (at least 3 times) to document potential seasonal use of habitats by bats. Record bat events at station locations and determine temporal patterns of bat use. Survey Methods Acoustic surveys for bats were conducted on a seasonal basis at each installation for a total of 301 nights from 2010 to Three to four SM2Bat+ ultrasonic bat detectors (Wildlife Acoustics) were placed at least 800 meters apart in six regional installations of interest; Kahuku Training Area, Kawailoa Training Area, Schofield Barracks East and West Ranges (SBE, SBW), Dillingham Air Field, and Makua Military Reservation. Surveys were conducted on bi-monthly basis if possible, and recorded at least 3 and up to 19 nights consecutively during each deployment. The three installations in the Koolau Group (Kahuku, Kawailoa, and East Range) received at least 6 surveys, while the three installations in the Waianae Group (West Range, Dillingham, and Makua) only received 3 surveys each. Bat detectors were set to record bat echolocation calls or pulses from dusk until dawn, and a bat event was triggered, recorded as a sound file, and logged for each pass a flying bat made by the microphone of a detector during the night. The number of bat events and number of echolocation pulses within an event can be used to confirm bat presence and describe bat activity levels. Bat events can also contain information on foraging activity, by the presence of characteristic echolocation pulses that form a feeding buzz. Files collected during the recordings were scanned and filtered for bat presence using the program Kaleidoscope (version , Wildlife Acoustics) and visually inspected by sound and sight to confirm and count bat echolocation pulses. Foraging activity was also noted in call events containing feeding buzzes. Bat detectability (p), signifying presence or absence of the species for each survey was calculated using the program Presence (version 6.2, J.E. Hines, USGS) 1

2 Survey Map Figure 1. Map of the six installation areas which received bat acoustic surveys and locations of bat detector stations. Yellow dots represent bat stations which with no bat detections. Red dots indicate positively confirmed bat detections, with the size of dot corresponding to the total number of events (1-11) recorded during all surveys at that point station. The purple dot represents the only station to record over 11 events (723), and show significant foraging activity. 2

3 Results and Discussion Survey results show low measures of bat detectability at most locations, yet bats were present at all areas surveyed at least during half of the bat detector stations (Figure 1). Bats were present during a minimum of 3% and a maximum of 28% of the nights during a survey period. Bats were present 61 nights out of 301 total nights surveyed, around 20% of the nights based on these overall seasonal measures. This study recorded 790 bat call events, and 10,958 echolocation pulses. However, there were individual differences in bat activity and detectability at each installation, and the variation in these measures can be seen in the following subsections. Koolau and Waianae Regions Survey areas around the Waianae Mountains group (Makua, Dillingham, and SBW) returned higher detectability values than the Koolau Mountains group (East Range, Kawailoa, and Kahuku); however the Waianae group surveys had a smaller sample size, and were only conducted in the second half of the year when bats are usually more active and location means do not accurately reflect the true seasonal nature of the area (Figure 2). The Koolau group which received a larger number of surveys covering the entire seasonal period is a more accurate reflection of bat activity Mean Detectability (p) Makua (2) Dillingham (2) SBW (3) East Range (6) Kawailoa (6) Kahuku (7) Survey Area Name (#surveys) Figure 2. Mean bat detectability (p) with standard error for each survey area. Number of surveys conducted at each location appears in parenthesis. Seasonal Activity and Foraging Behavior Bat activity was seasonal in nature, with bat presence being detected and greater numbers of call events and pulses usually being recorded during the fall months (August through November) while little to no activity is typical during the winter months (December through March). However, some installations showed notable activity during the pupping 3

4 season (June at Kawailoa) and over the winter period (December at SBW and Makua). The majority of bat events recorded at all stations were indicative of a single pass by the microphone with search-like echolocation pulses. Foraging behavior was documented in several recordings from Kahuku in May, Dillingham in November, and overwhelmingly from SBW during the December 2013 survey period. Bat Presence Comparisons Compared to other locations on Oahu Bat detectability values are similar to nearby locations sampled by USGS around Kawailoa, Kahuku, and SB East Range (C. Pinzari, personal communication). Compared to outer Hawaiian Islands Bat detectability values on Oahu in general are much lower than those from surveys on Hawaii, Maui, and Kauai Islands, where bats are usually detected above 20% of the time throughout the seasonal cycle when comparing values from week-long bi-monthly surveys (C. Pinzari, personal communication). Without accurate methods to directly count individuals from recorded events, and without available population estimates, the low bat detectability (low bat presence) on Oahu may be due to lower density of bats or may be due to lower availability of desired habitat for roosting and foraging, or a combination of both. Bats may be more dispersed, and need to travel greater distances to find suitable roosts, to track prey resources, and find mates. 4

5 Kahuku Training Area Bats were present at the Kahuku Training Area surveys during May, August, October, and September (Figure 3). Foraging activity was documented in May, and the highest activity occurred during September and August (Table 1). When present, bats were recorded throughout the night, with greater activity during 20:00 and 1:00 (Figure 4). Survey Month - Year Start Date End Date Recording Stations Nights Sampled Active Nights Events Pulses Detectability (p) Foraging 1 September-10 9/23/2010 9/29/ No 2 December-10 12/29/2010 1/5/ No 3 March-11 2/28/2011 3/2/ No 4 April-11 4/11/2011 4/18/ No 5 May-11 5/19/2011 5/27/ Yes 6 August-11 8/8/2011 8/15/ No 7 October-11 10/26/ /1/ No Totals Table 1. Results from Kahuku Training Area bat surveys. For each survey; start date, end date, numbers of recording stations, nights sampled, nights with bat activity, number of events and echolocation pulses recorded. Presence reported as detectability (p), the probability of detecting a bat given the sampling effort. The presence of foraging activity is also listed for each survey Detectability (p) September-10 December-10 March-11 April-11 May-11 August-11 October-11 Survey Month - Year Figure 3. Bat detectability values for seven surveys conducted at Kahuku Training Area from September 2010 to October Numbers above bars represent the detection frequency (1.0 is equivalent to 100%) of pooled units for each survey. For example, 0.17 would represent bats being present 17% of the time during the recording period for all units recording during the survey. A zero represents a survey which recorded no bat detections, meaning bats were absent during the recording period. 5

6 Sep-10 May-11 Aug-11 Oct-11 Bat Activity (Pulses) Time of Night (Hour) Figure 4. Temporal distribution of bat activity at Kahuku Training Area. Number of bat echolocation pulses recorded during each one hour period of the night (16:00 to 07:00) for all surveys in which bats were present. 6

7 Schofield Barracks East Range Bats were present at the East Range surveys during March, August, and November (Figure 5). No foraging activity was documented, and the highest activity occurred during August (Table 2). When present, bats were recorded throughout the night, with greater activity during 19:00 and 2:00 (Figure 6). Survey Month-Year Start Date End Date Recording Stations Nights Sampled Active Nights Events Pulses Detectability (p) Foraging 1 November-10 11/1/ /9/ No 2 January-11 1/6/2011 1/13/ No 3 March-11 3/22/2011 3/28/ No 4 May-11 5/5/2011 5/13/ No 5 August-11 8/17/2011 8/25/ No 6 November-11 11/7/ /14/ No Total Table 2. Results from the Schofield Barracks East Range bat surveys. For each survey; start date, end date, numbers of recording stations, nights sampled, nights with bat activity, number of events and echolocation pulses recorded. Presence reported as detectability (p), the probability of detecting a bat given the sampling effort. The presence of foraging activity is also listed for each survey Detectability (p) November-10 January-11 March-11 May-11 August-11 November-11 Survey Month-Year Figure 5. Bat detectability values for six surveys conducted at Schofield Barracks East Range from November 2010 to November Numbers above bars represent the detection frequency (1.0 is equivalent to 100%) of pooled units for each survey. For example, 0.06 would represent bats being present 6% of the time during the recording period for all units recording during the survey. A zero represents a survey which recorded no bat detections, meaning bats were absent during the recording period. 7

8 Bat Activity (Pulses) Nov-10 Mar-11 Aug-11 Nov-11 Time of Night (Hour) Figure 6. Temporal distribution of bat activity at Schofield Barracks East Range. Number of bat echolocation pulses recorded during each one hour period of the night (16:00 to 07:00) for all surveys in which bats were present. 8

9 Kawailoa Training Area Bats were present at the Kawailoa surveys during June, September, and October (Figure 7). No foraging activity was documented, and the highest activity occurred during June (Table 3). When present, bats were recorded throughout the night, with greater activity during 18:00 and 2:00 (Figure 8). Survey Month - Year Year Start Date End Date Recording Stations Nights Sampled Active Nights Events Pulses Detectability (p) Foraging 1 September /14/2011 9/22/ No 2 December /5/ /11/ No 3 February /13/2012 2/20/ No 4 June /26/2012 7/2/ No 5 October /16/ /29/ No 6 January /8/2013 1/21/ No Totals Table 3. Results from the Kawailoa Training Area bat surveys. For each survey; start date, end date, numbers of recording stations, nights sampled, nights with bat activity, number of events and echolocation pulses recorded. Presence reported as detectability (p), the probability of detecting a bat given the sampling effort. The presence of foraging activity is also listed for each survey Detectability (p) September-11 December-11 February-12 June-12 October-12 January-13 Survey Month - Year Figure 7. Bat detectability values for six surveys conducted at Kawailoa Training Area from September 2011 to January Numbers above bars represent the detection frequency (1.0 is equivalent to 100%) of pooled units for each survey. For example, 0.04 would represent bats being present 4% of the time during the recording period for all units recording during the survey. A zero represents a survey which recorded no bat detections, meaning bats were absent during the recording period. 9

10 Bat Activity (Pulses) Sep-11 Jun-12 Oct-12 Time of Night (Hour) Figure 8. Temporal distribution of bat activity at Kawailoa Training Area. Number of bat echolocation pulses recorded during each one hour period of the night (16:00 to 07:00) for all surveys in which bats were present. 10

11 Mauka Military Reservation Bats were present at the Makua surveys during October and December (Figure 9). No foraging activity was documented, and the highest activity occurred during October (Table 4). When present, bats were recorded throughout the night, with greater activity during 22:00 and 2:00-3:00 (Figure 10). Survey Month -Year Year Start Date End Date Recording Stations Nights Sampled Active Nights Events Pulses Detectability (p) Foraging 1 December /17/2012 1/1/ No 2 April /3/2013 4/22/ x x x x No data 3 October /30/ /18/ No Total Table 4. Results from the Makua Military Reservation bat surveys. For each survey; start date, end date, numbers of recording stations, nights sampled, nights with bat activity, number of events and echolocation pulses recorded. Presence reported as detectability (p), the probability of detecting a bat given the sampling effort. The presence of foraging activity is also listed for each survey. 1 Detectability (p) x December-12 April-13 October-13 Survey Month - Year Figure 9. Bat detectability values for two surveys conducted at Makua Military Reservation from December 2012 and October Survey during April 2013 (x) retrieved no data due to equipment malfunction. Numbers above bars represent the detection frequency (1.0 is equivalent to 100%) of pooled units for each survey. For example, 0.12 would represent bats being present 12% of the time during the recording period for all units recording during the survey. A zero represents a survey which recorded no bat detections, meaning bats were absent during the recording period. 11

12 Dec-12 Oct-13 Bat Activity (Pulses) Time of Night (Hour) Figure 10. Temporal distribution of bat activity at Makua Military Reservation. Number of bat echolocation pulses recorded during each one hour period of the night (16:00 to 07:00) for all surveys in which bats were present. 12

13 Dillingham Air Field Bats were present at the Dillingham surveys during September and November (Figure 11). Foraging activity was documented during November, and the highest activity occurred during September (Table 5). When present, bats were recorded throughout the night, with greater activity during 22:00 and 0:00-1:00 (Figure 12). Survey Month- Year Year Start Date End Date Recording Stations Nights Sampled Active Nights Events Pulses Detectability (p) Foraging 1 November /30/ /14/ Yes 2 March /1/2013 3/19/ x x x x No 3 September /9/2013 9/22/ No Total Table 5. Results from the Dillingham Air Field bat surveys. For each survey; start date, end date, numbers of recording stations, nights sampled, nights with bat activity, number of events and echolocation pulses recorded. Presence reported as detectability (p), the probability of detecting a bat given the sampling effort. The presence of foraging activity is also listed for each survey Detectability (p) x November-12 March-13 September-13 Survey Month - Year Figure 11. Bat detectability values for two surveys conducted at Dillingham Air Field from November 2012 and September Survey during March 2013 (x) retrieved no data due to equipment malfunction. Numbers above bars represent the detection frequency (1.0 is equivalent to 100%) of pooled units for each survey. For example, 0.20 would represent bats being present 20% of the time during the recording period for all units recording during the survey. A zero represents a survey which recorded no bat detections, meaning bats were absent during the recording period. 13

14 Nov-12 Sep-13 Bat Activity (Pulses) Time of Night (Hour) Figure 12. Temporal distribution of bat activity at Dillingham Air Field. Number of bat echolocation pulses recorded during each one hour period of the night (16:00 to 07:00) for all surveys in which bats were present. 14

15 Schofield Barracks West Range (SBW) Bats were present during each of the West Range surveys during July, November, and December (Figure 13). Foraging activity coincided with the highest activity, which was documented during December (Table 6). Bats were recorded throughout the night, with greater activity during 1:00-2:00 and 5:00 (Figure 14). Survey Month - Year Year Start Date End Date Recording Stations Nights Sampled Active Nights Events Pulses Detectability (p) Foraging 1 November /21/ /5/ No 2 July /6/2013 7/21/ No 3 December /22/2013 1/2/ , Yes Totals Table 6. Results from the SBW bat surveys. For each survey; start date, end date, numbers of recording stations, nights sampled, nights with bat activity, number of events and echolocation pulses recorded. Presence reported as detectability (p), the probability of detecting a bat given the sampling effort. The presence of foraging activity is also listed for each survey Detectability (p) November-12 July-13 December-13 Survey Month - Year Figure 13. Bat detectability values for three surveys conducted at SBW from November 2012, July 2023, and December Numbers above bars represent the detection frequency (1.0 is equivalent to 100%) of pooled units for each survey. For example, 0.28 would represent bats being present 28% of the time during the recording period for all units recording during the survey. A zero represents a survey which recorded no bat detections, meaning bats were absent during the recording period. 15

16 Nov-12 Jul-13 Bat Activity (Pulses) A Time of Night (Hour) 2500 Dec-13 Bat Activity (Pulses) B Time of Night (Hour) Figure 14. Temporal distribution of bat activity at Schofield Barracks West Range. Number of bat echolocation pulses recorded during each one hour period of the night (16:00 to 07:00) for all surveys in which bats were present. Panel A displays the activity from the November 2012 and July 2013 surveys. Panel B displays the activity from the December 2013 survey, which recorded the heaviest activity levels with 89 foraging events throughout the night, with maximum activity reaching 2,000 echolocation pulses recorded during the hour. 16

17 Recommendations Now that bat presence has been established, extend survey periods to longer than one week. The number of stations has been sufficient for each area considered, and future surveys should maintain monitoring at these sites. Waianae group locations need more surveys to balance out survey effort, collect data over one entire season, especially due to notable foraging activity and use during the winter months. Design of recording station set up should change to increase potential detection opportunity for bats, decrease the collection of noisy recordings, and ensure that data collected may be comparable to outside studies on Oahu and the outer islands. The microphone should not be installed on the side of SM2bat device; the microphone should be mounted on top of a 10 foot pole with a cord to connect it to the unit, thus is becomes elevated into the airspace used by flying bats. This pole should then be placed in an area with open air space around it, preferably on the edge of vegetation or a structure, so that it blends into the surroundings. It s possible that microphone placement could have limited the number of bat call detections recorded, and in turn resulted in low detectability estimates for this study. 17