Bat Trapping in Stanley Park. August 7 th, Report for Permit SU

Transcription

1 Bat Trapping in Stanley Park August 7 th, 2011 Report for Permit SU Trapping Efforts: August 7 th, 2011 Report Date: January 20 th, 2012 Work conducted by: Dr. R Millikin, PhD and D. Dagenais, BSc Page 1 of 7

2 Abstract On August 7 th, 2011, two mist nets were used to trap bats in Stanley Park. Two Yuma myotis were captured over a three hour period. Trapping was independent of any Stanley Park Ecology Society Study. The trapping was conducted to train Ms. Dagenais, a Graduate candidate at Simon Fraser University, on the use of mist nets and the identification of bats. Table of Contents Introduction...3 Methods...4 Results...5 Discussion...6 Recommendations...6 Literature Cited...7 Lists of Figures and Tables Figure 1. The location of Lost Lagoon within Stanley Park, Vancouver, BC and the location of the trapping site at the northwest end of the lake ( )... 3 Figure 2. Configuration of the mist nets along the shore of Lost Lagoon Table 1. Potential bat species inhabiting Vancouver and the Stanley Park area within the ICHdm, and their provincial listing. Highlighted rows indicate the species that have been positively identified to inhabit the park Table 2. Parameters collected during bat trapping in Stanley Park, Vancouver, BC Page 2 of 7

3 Introduction Stanley Park is located in the heart of Vancouver, British Columbia. It lies between the downtown core and North Vancouver. The park is managed by the City of Vancouver. It encompasses 400 hectares of coastal forest within the Coastal Western Hemlock biogeoclimatic zone and the dry maritime subzone (CWHdm) (Green and Klinka 1994). It is located in the Georgia Depression Ecoprovince, the Lower Mainland Ecoregion, and the Fraser Lowland Ecosection. Stanley Park is an oasis for multiple urban wildlife species that are studied and assessed by the Stanley Park Ecology Society (SPES). Bats studies using acoustic surveys and mist net trapping show four species of bats inhabit Stanley Park. These bats typically begin foraging 15 minutes past sunset and forage predominantly over freshwater. Beaver Lake and Lost Lagoon are the two main foraging habitats. Bats are present year round in the park with most activity in spring and summer (Rutherford and Sinclair 2010). Following the bat study, monthly bat surveys are conducted at Beaver Lake by the SPES and BCIT students. To avoid conflict with these surveys, Lost Lagoon was chosen for this project. Lost Lagoon is a small lake located in the south end of the park and is accessible by several trails along its perimeter (Figure 1). As Lost Lagoon provides ideal foraging habitat for bats, it would provide ample opportunity to observed, trap, and identify bats. Lost Lagoon Figure 1. The location of Lost Lagoon within Stanley Park, Vancouver, BC and the location of the trapping site at the northwest end of the lake ( ). Page 3 of 7

4 Acknowledgements We would like to thank Erin Rutherford, BCIT student and Robyn Worcester, Conservation Program Manager for SPES for sharing their knowledge of bats at Stanley park, and for providing the Bats of Stanley Park report. Methods Two mist nets (2.5m high, 12m long, with a 30mm mesh) were placed along the shore of a drainage originating from the northwest corner of Lost Lagoon (Figure 2). The mist nets were set up at sunset to capture the first peak in foraging activity. These nets were placed along paths accessing the water and were inspected with flashlights every minutes. 2 1 Pedestrian Bridge Lost Lagoon Figure 2. Configuration of the mist nets along the shore of Lost Lagoon. Any bat captured was immediately removed, measured, and identified. Gloves were worn while handling the bats and both handlers had current rabies shots. Measurements were taken with calipers to 1/100 th of a millimetre and included: ear length, tragus length, and forearm length. These metrics, as well as, the tail and calcar characteristics were noted for species identification (van Zyll de Jong 1985). Bats were assessed for age and sex. Following identification, bats were released away from the nets to avoid recapture. The mist nets were closed and removed three hours after opening; very little bat activity was detected at 23:00hrs. Photographs of the captured bats were taken, however due to poor lighting, the photos were of poor quality. Page 4 of 7

5 Results Ten bat species are found throughout Vancouver, BC and the Lower Mainland and are thought to use the habitat found in Stanley Park; however only four have been identified in the park (Rutherford and Sinclair 2010). Of the ten species found in the general area, two are provincially listed blue and red, and the four known to use the habitat found within the park are yellow listed species (Table 1). Table 1. Provincial listing of the bat species potentially inhabiting Vancouver and the Stanley Park area within the ICHdm. The highlighted rows are the species positively identified in the park. Bat Species Common Name Provincial Listing Corynorhinus townsendii Townsend s Big-eared Bat Blue Eptesicus fuscus Big Brown Bat Yellow Lasionycteris noctivagans Silver-haired bat Yellow Lasiurus cinereus Hoary Bat Yellow Myotis californicus California Myotis Yellow Myotis evotis Western Long-eared Myotis Yellow Myotis keenii Keen s Long-eared Myotis Red Myotis lucifugus Little Brown Bat/Myotis Yellow Myotis volans Long-legged Myotis Yellow Myotis yumanensis Yuma Myotis Yellow Red-listed: a species that is extirpated, endangered, or threatened in British Columbia. Blue-listed: a species that is considered vulnerable and/or of special concern in British Columbia. Yellow-listed: all species not included on the Red or Blue lists; a species that is either uncommon, common, has declining or increasing populations. Numerous bats, greater than 100, were observed on August 7 th, 2011 foraging over Lost Lagoon, in Stanley Park, Vancouver, BC and flying north over the trap site to another foraging area. Bats emerged from a southern area of Stanley Park in the direction of the golf course. Bat emergence occurred approximately 15 minutes after sunset and bat activity peaked within the first hour after sunset. This concentration of activity at dusk, suggests that a roost is located in the southern area of the park in addition to the roost identified near Beaver Lake. The variety in size and flight behaviour of individuals during the hour of emergence, suggests multiple species use Lost Lagoon to forage. Two bats were captured along the shore of Lost Lagoon in three hours. Both bats were identified as adult Yuma myotis (Myotis yumanesis), which are yellow-listed in BC. The parameters collected to identify the species captured are shown below (Table 2). Half of the bats captured in the study were this species (Rutherford and Sinclair 2010). Page 5 of 7

6 Table 2. Parameters collected during bat trapping in Stanley Park, Vancouver, BC. Bat Spp Time Captured et Age Sex Ear Length (mm) Tragus Length (mm) Forearm Length (mm) Tail Calcar Yuma Myotis Yuma Myotis 21:24hr 2 Ad M Protruding, Fringed 21:48hr 1 Ad F Protruding, Fringed Unkeeled Unkeeled Discussion The capture rate was 0.67 bats per net hour. This is comparable to the per net-hour recorded by Rutherford and Sinclair (2010), Mist nets may not be ideal to gain research experience, as only a few bats can be captured in one evening. During trapping efforts, bats flew over the nets at the last minute, thus reducing their chances of being captured. Mist netting may have been more successful if the nets were placed in a series rather than in a line. In theory, bats avoiding the first net may not be able to avoid the second or third net as easily. Trapping success may also have been increased if the nets were placed across the drainage rather than along the shoreline. On site observations noted a greater number of bats foraging over the water adjacent to the mist net locations rather than along the shore. The bats would fly low over the water to forage and drink, and would then fly at a much higher height over the shore north into the forest to another foraging ground. Due to the height of the nets any bat flying greater than 2.5m was not captured. Remote sensing using radar and acoustic technology could provide flight path trajectories over a larger area, help identify bats using an area, and determine sources of emergence. Technology, such as EchoTrack s radar-acoustic system has tracked 200 individuals (birds ad bats) simultaneously in a 2000m radius circle and could be used in further Stanley Park bat studies. Recommendations To increase training on bat identifying and handling, multiple training sessions should be considered and mist nets should be placed in a row across the water to increase the chances of capturing bats. Acoustic analysis should be conducted simultaneously to the netting to identify the source of species the species flying through the area. Radar could help identify the source of emergence. Page 6 of 7

7 Literature Cited Green, R., and K. Klinka A field guide for site identification and interpretation for the Vancouver Forest region. Ministry of Forests. Victoria, BC. Pp 293. Nagorsen, D.W., and R.M. Brigham. Bats of British Columbia (Volume 1) UBC Press and Royal British Columbia Museum. Victoria, BC. Pp 164. Rutherford, E., and D. Sinclair Bats of Stanley Park. British Columbia Institute of Technology, Diploma of Technology: Fish, Wildlife, and Recreation Program. Vancouver, BC. Pp 57. van Zyll de Jong, C.G Handbook of Canadian mammals Volume 2: Bats. National Museums of Canada Publication. Ottawa, ON. Pp 212. Page 7 of 7