Pallid Bat (Antrozous Pallidus) Foraging Over Native and Vineyard Habitats in British Columbia, Canada

816 Pallid bat (Antrozous pallidus) foraging over native and vineyard habitats in British Columbia, Canada

D.A. Rambaldini and R.M. Brigham

Abstract: Optimal foraging theory predicts organisms will forage in habitats providing the most profitable prey. Human alterations to ecosystems may affect predators’ foraging activity by changing landscape features, prey types, and prey availability. Assessing the selection of foraging habitats in a heterogeneous landscape can provide data to improve land management and conservation policies. In Canada, the pallid bat (Antrozous pallidus (LeConte, 1856); Vespertilionidae) is listed as threatened partly because of loss or modification of shrub–steppe habitat. Our purpose was to determine if vineyards provide a suitable surrogate for foraging habitat relative to native habitat. We used pitfall traps to compare prey abundance in each habitat and analyzed faeces to assess diet composition. Over 24 nights, we surveyed both habitats for foraging bats. Bats foraged over vineyards, but we recorded significantly more foraging activity over native habitat. We collected over 2000 arthropods in pitfall traps and found significantly more in native habitat compared with vineyards. Species eaten by pallid bats were present in both habitats. Scarab beetles (Coleoptera: Scarabidae) and Jerusalem crickets (Orthopthera: Stenopelmatidae) represented the principal prey. The use of vineyards by pallid bats for foraging suggests that while they are adapting to a changing landscape, reduced prey abundance in vineyards may negatively affect them over the long term. Résumé : La théorie de la quête optimale prédit que les organismes vont rechercher leur nourriture dans les habitats qui fournissent les proies les plus profitables. Les modifications anthropiques des écosystèmes peuvent affecter les activités de recherche de nourriture des prédateurs en changeant les caractéristiques du paysage, les types de proies et la disponibilité de ces proies. L’évaluation de la sélection des habitats de recherche de nourriture dans un paysage hétérogène peut fournir des données pour améliorer les politiques de gestion des terres et de conservation. Au Canada, la chauve-souris blonde (Antro- zous pallidus (LeConte, 1856); Vespertilionidae) est sur la liste des espèces à risque en partie à cause de la perte ou de la modification de l’habitat de steppe buissonneuse. Notre objectif est de déterminer si les vignobles représentent pour lui un substitut adéquat pour la recherche de nourriture par rapport à son habitat naturel. Des pièges à fosse nous ont servi à com- parer l’abondance des proies dans chaque habitat et l’analyse de fèces à déterminer la composition du régime alimentaire. Nous avons surveillé les chauves-souris en quête de nourriture dans les deux habitats au cours de 24 nuits. Les chauves-souris recherchent leur nourriture au-dessus des vignobles, mais il y a significativement plus d’activités de quête de

For personal use only. nourriture au-dessus de l’habitat naturel. Nous avons récolté plus de 2000 arthropodes dans les pièges à fosse et en avons trouvé significativement plus dans l’habitat naturel que dans les vignobles. Les espèces consommées par les murins pâles sont présentes dans les deux habitats. Les coléoptères scarabées (Coleoptera : Scarabidae) et les grillons sténopelmatidés (Orthoptera : Stenopelmatidae) constituent les proies principales. L’utilisation des vignobles par les murins pâles pour la recherche de leur nourriture laisse croire que, bien qu’ils soient en train de s’adapter à un paysage changeant, l’abondance ré- duite des proies peut les affecter négativement à long terme. [Traduit par la Rédaction]

Introduction al. 2009; Menz et al. 2009). Ecosystems modified by humans typically may be less suitable as foraging habitat because of Predators are expected to select the most profitable forag- alterations in landscape structures and in prey availability and ing habitat and prey available (Pulliam 1974; Smith 1978), abundance. Data on foraging behaviour and habitat use because the latter provides a greater net benefit. Similarly, within a heterogeneous landscape can help elucidate the eco- Can. J. Zool. Downloaded from www.nrcresearchpress.com by University of Toronto on 08/26/11 predators should forage in habitats that have abundant profit- logical needs of predators and can be used to improve land able prey to minimize the energy and time spent searching. management and conservation policies. Other factors, such as proximity to shelter and water, preda- The pallid bat (Antrozous pallidus (LeConte, 1856)) is a tion risk, prey accessibility, competition, season, and need to medium-sized vespertilionid (13–29 g body mass and 45– feed young, may also affect where animals forage (Fleming 60 mm forearm length) that inhabits low-elevation and Heithaus 1986; Jones et al. 2001; Weimerskirch et al. (<1830 m) arid and semiarid regions across western North 2004; Creel et al. 2005; Heithaus and Dill 2006; Flaquer et America (Hermanson and O’Shea 1983). The northernmost

Received 29 November 2010. Accepted 30 May 2011. Published at www.nrcresearchpress.com/cjz on 26 August 2011. D.A. Rambaldini.* Nk’Mip (Osoyoos) Indian Band, Oliver, BC V0H 1T0, Canada. R.M. Brigham. Department of Biology, University of Regina, Regina, SK S4S 0A2, Canada. Corresponding author: D.A. Rambaldini (e-mail: [email protected]). *Present address: 106 Camborne Avenue, Toronto, ON M3M 2R4, Canada.

Can. J. Zool. 89: 816–822 (2011) doi:10.1139/Z11-053 Published by NRC Research Press Rambaldini and Brigham 817

extent of its range is the Okanagan Valley (49°N, 119°W), tridentata Nutt.), gray rabbitbrush (Ericameria nauseosa var. British Columbia, Canada. It roosts most commonly in rocky nauseosa (Pall. ex Pursh) G.L. Nesom & Baird), Ponderosa outcrops, caves, and buildings (Hermanson and O’Shea pine, and a variety of bunchgrasses. Most land of low eleva- 1983). Pallid bats are opportunistic foragers that glean a vari- tion has been modified for agricultural, residential, commer- ety of relatively large (up to 6 cm body length) arthropods cial, or recreational use. Agricultural uses include vineyards, from surfaces, but they also capture insects on the wing fruit orchards, vegetable farms, and pastures. (Bell 1982; Fuzessery et al. 1993; Johnston and Fenton We conducted surveys for foraging bats within ~600 m of 2001). They occasionally eat reptiles and small mammals the base of a mountain that is the site of the largest known (Hermanson and O’Shea 1983). Pallid bats generally forage roost of pallid bats in the valley (supplementary Fig. S1).1 over open habitats with minimal ground cover such as Up to 130 individuals occupy a rock slab from late May to shrub–steppe grasslands, oak–savannah woodlands, forests of late July (D.A. Rambaldini, unpublished data). We chose this Ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & location, and not random ones, because our purpose was to C. Lawson), talus slopes, gravel roads, and modified habitats quantify habitat use where both native and vineyard habitats including fields of alfalfa (Medicago sativa L.) and fruit or- were equally available and where a large number of foraging chards (Hermanson and O’Shea 1983; Ball 2002). Although bats would be present each night. This location satisfied both they echolocate while flying, they locate most prey using criteria; however, caveats of our design were the lack of rep- passive acoustic cues (Bell 1982; Fuzessery et al. 1993). lication across locations and that all surveys measured forag- In Canada, the pallid bat is listed as threatened (COSEWIC ing activity solely in the first half of the night. We only 2010) because of its limited range within the Okanagan Valley sampled during the first half of the night because few bats and because of loss or modification of roosting and foraging were observed foraging later. It is common for insectivorous habitat to urban development, agricultural expansion, and pes- bats in temperate regions to forage primarily in the first half ticide use. Nearly 70% of habitat consisting of native antelope of the night (Hayes 1997; Rambaldini and Brigham 2008; bitterbrush (Purshia tridentata (Pursh) DC.) in the Okanagan Wang et al. 2010) and therefore we are confident that our ob- Valley has been transformed (Lea 2008). The diminished avail- servations provide a reliable representation of the foraging ability of shrub–steppe grasslands may negatively have an im- activity of pallid bats. pact on pallid bats by forcing individuals to either fly longer We surveyed using a Unitec GS-15 Generation III Night distances to high-quality foraging habitat or spend more time Vision monocular and (or) a Unitec GS-SuperGeneration foraging in lower quality habitat. For a population that likely Night Vision monocular (GSIC, Richmond Hill, Ontario, faces physiological challenges given the environmental condi- Canada) and a one million candlelight power Garrity spot- tions at the northernmost extent of its’ range, this may have light fitted with an IR filter (US Night Vision, Costa Mesa, conservation ramifications (Rambaldini and Brigham 2008). California, USA). Visibility was influenced by topography The viticulture industry in British Columbia increased in and lunar illumination, so we calibrated observers using a area by 20% between 2004 and 2006 (Lea 2008). Vineyards sock that was similar in size and color to a pallid bat. The

For personal use only. are expected to expand by another 35% to eventually cover sock, when hung from a short pole over unobstructed level >4000 ha, mostly in the Okanagan (Lea 2008). Pallid bats ground, could be clearly distinguished at a distance of occupy an estimated 10 000 – 50 000 ha in the southern Oka- ~20 m. nagan Valley Basin (British Columbia Conservation Data We were able to visually discriminate foraging pallid bats Centre 2010), and vineyards could potentially cover 10%– from other local species that have been captured at our study 40% of this range. However, unlike habitat converted for ur- site (e.g., mule-eared bat (Plecotus townsendii Cooper, 1837), ban infrastructure, agricultural lands such as vineyards poten- spotted bat (Euderma maculatum (J.A. Allen, 1891)), big tially provide foraging habitat for these bats. Thus, our brown bat (Eptesicus fuscus (Beauvois, 1796)), silver-haired purpose was to determine if pallid bats forage in vineyards, bat (Lasionycteris noctivagans (LeConte, 1831)), California to compare prey availability in vineyards and native habitat, myotis (Myotis californicus (Audubon and Bachman, 1842)), and to assess the diet of bats. We expected bats would forage small-footed bat (Myotis leibii (Audubon and Bachman, over vineyards and opportunistically take available prey. 1842)), long-eared myotis (Myotis evotis (H. Allen, 1864)), However, we hypothesized that they would forage more often Keen s myotis (Myotis keenii (Merriam, 1895)), little brown over native habitat because we expected unmodified habitat ’ bat (Myotis lucifugus (LeConte, 1831)), fringed myotis (Myo- Can. J. Zool. Downloaded from www.nrcresearchpress.com by University of Toronto on 08/26/11 would have a greater abundance and diversity of potential tis thysanodes Miller, 1897), long-legged myotis (Myotis vol- prey. ans (H. Allen, 1866)), and Yuma myotis (Myotis yumanensis (H. Allen, 1864)); D.A. Rambaldini, unpublished data) by the Materials and methods relatively pale fur, larger body size, and gleaning foraging All protocols were approved by the University of Regina style characteristic of pallid bats (Bell 1982; Hermanson and Animal Care Committee Animal Utilization Protocol No. 02- O’Shea 1983). We also observed pallid bats flying directly to 01 and by the Nk’Mip (Osoyoos) Indian Band Council. We the survey area when they emerged from the roost, which collected data from 24 May to 17 July 2005 on the Nk’Mip confirmed that this species foraged in the survey sites. We (Osoyoos) Indian Band Reserve, ~25 km north of the did not concurrently use radio telemetry or acoustic monitor- Canada–USA border. The Okanagan Valley is a semiarid ing to corroborate our visual observations. However, pallid ecosystem classified as shrub–steppe with native vegetation bats usually do not echolocate while gleaning prey (Barber dominated by antelope bitterbrush, big sagebrush (Artemisia et al. 2003) and therefore using bat detectors likely would

1Supplementary data are available with the article through the journal Web site (http://nrcresearchpress.com/doi/suppl/10.1139/z11-053).

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not have improved the confidence in our identification of for- face, and contained 2 cm of 10% propylene glycol. We cov- aging pallid bats. ered each trap with a lid held by supports. We did not use We began surveys 35–45 min after sunset (2044–2106), data from disturbed traps (n = 3 in vineyards), and therefore corresponding to the time when the bats emerged. An eve- we only analyzed data from 15 vineyard traps. ning survey consisted of three pairs of equal length sessions, We identified arthropods to genus whenever possible but and each pair included one session in native habitat and one not beyond class for arachnids. We classified specimens by in vineyard habitat. During each session, we randomly deter- body length, with each size class differing by increments of mined the direction of observation by spinning a compass 0.5 cm from class 1 (<0.5 cm) to class 9 (>4.0 cm). We dial. Session pairs lasted 20–40 min followed by a 5–10 min used a two-sample paired t test to compare total number col- break. Each survey was conducted by two crew members— lected in each habitat and ANOVA to compare the number of one who made the observations and one who recorded the specimens in each size class. We used the Shannon–Weaver data. Crew members alternated duties during each subsequent diversity index (H′) to compare diversity between habitats, session, so that each member acted as an observer and a re- where Hmax (calculated as the natural logarithm of the total corder at least twice during a survey. number of species collected) is the maximum possible diver- The field of vision through the monocular was ~60°. We sity in each sample that occurs when all species are collected counted each bat as a single observation, no matter how in equal numbers. long it remained in our field of view. Most bats flew in one To compare the number of each taxa group we collected in direction away from the roost until out of view, thus double- the two habitats, we used paired t tests for the following counting was unlikely. groups of data: total class Arachnida; total order Coleoptera, We recorded the number of bats observed, direction of total order Lepidoptera, total order Orthoptera; total other flight, and behaviour. We defined bats as “commuting” or class Insecta (including orders Dermaptera, Diptera, Hemi- “foraging” using characteristics of flight style, speed, and ptera, Hymenoptera, and Odonata); and total other (including height from the literature (Hayward and Davis 1964; O’Shea classes Mammalia and Reptilia, as well as unknown arthro- and Vaughan 1977; Bell 1982). “Commuting” bats were pods). We did not statistically compare the prey consumed those flying >3 m aboveground at any speed or flying 1– by bats with the samples collected in pitfall trap because 3 m aboveground at >3 m·s–1. “Foraging” bats flew ≤1m 83% of the diet of pallid bats comprised three genera that ac- aboveground at any speed or at ≤3 m·s–1 and <3 m. Bats counted for <3% of the arthropods that we collected in either were also deemed to be foraging if, regardless of speed or habitat. height aboveground, they were observed circling, swooping, To compare prey availability between habitats, we classi- hovering, landing, or taking off. We calibrated our visual es- fied arthropods from each trap into “probable” versus “un- timates of height and speed relative to landscape features, likely” prey to be captured by pallid bats based on data from such as antelope bitterbrush and sage bushes in native habitat the literature (Orr 1954; Ross 1967; O’Shea and Vaughan and rows of grapes in vineyards. To calibrate our estimates of 1977; Johnston and Fenton 2001). We analyzed these data

For personal use only. 1 flight speed, we observed a tennis ball thrown at ~3 m·s– with a paired t test. “Probable” prey consisted of various (calculated using a tape measure and stop watch). members of class Insecta: Coleoptera (Carabidae, Scarabaei- We used a paired t test to compare the overall number of dae, Tenebrionidae), Hymenoptera (Formicidae), Lepidop- bats per night, number of bats per minute, and type of activ- tera, and Orthoptera (Acrididae, Gryllacrididae, Gryllidae, ity (number of commuting bats per night and number of for- Stenopelmatidae, and Tettigoniidae); class Arachnida: Solifu- aging bats per night) recorded in each habitat. We compared gae and Araneae (Araneidae, Lycosidae, and Salticidae); and time-standardized data (number of commuting bats per mi- class Mammalia: Rodentia (Muridae). “Unlikely” prey were nute and number of foraging bats per minute) within, as well specimens <1.5 cm long and also included select families of as between, habitats using a two-way ANOVA. the class Insecta: Dermaptera, Diptera, Hymenoptera (Vespi- To assess diet, we collected faeces from below the roost dae), and Odonata; class Arachnida: Aranaea (Theriidae) and (n = 71) and from captured bats. We caught bats in mist Opiliones; and class Malacostraca: Isopoda (Oniscidea). nets (10 m high, 6–12 m long) set in foraging areas. We col- For all statistical tests, we employed an a value of 0.05 lected faecal samples (n = 22) from one adult female and and report means ± 1 SE for n observations. We used SPSS five adult males, captured between 28 June and 10 August. version 12.0 Base (SPSS Inc., Chicago, Illinois, USA) for all Can. J. Zool. Downloaded from www.nrcresearchpress.com by University of Toronto on 08/26/11 The small sample size precluded assessing variation owing analyses. To normalize the distributions, we log10-trans- to sex or season. formed the data for the number of commuting bats per mi- We identified arthropods in each pellet under a dissecting nute, square-root-transformed the number of foraging bats microscope by comparing remains with reference specimens. per minute over vineyards, and reflected (by applying a re- We tabulated pellet contents as frequency of occurrence of flection, calculating the log10 of that value, and applying an- each taxon (Safi and Kerth 2004) and assessed diet diversity other reflection to eliminate the negative skew and high using Emlen’s index, D, following the method of Johnston kurtosis) the number of Lepidoptera collected by pitfall traps and Fenton (2001). in native habitat. We used two grids of pitfall traps in native vegetation (n = 16 traps; total area covered = 160 m2) and two in vineyards (n = 18 traps; total area = 180 m2) where we surveyed bats. Results Traps were set ~10 m apart and left open for the entire study We recorded significantly more foraging activity over na- period. Each trap consisted of a plastic cup (~10 cm deep, tive habitat than over vineyards (Table 1). In total, we re- 8.5 cm in diameter) dug into the ground, flush with the sur- corded 315 bats in 1315 min of surveys in native habitat and

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Table 1. Data on foraging by pallid bats (Antrozous pallidus) between habitats (n = 24 nights of surveys in both habitats) with letters show- ing statistically significant differences between habitats.

Native Vineyard Paired Variable Mean ± SE Range Mean ± SE Range t test F df p No. of bats·night–1 16.6±1.60 2–33 8.5±0.77 2–14 4.55 — 36 <0.001 No. of bats·min–1 0.26±0.31 0.21–0.56 0.14±0.02 0.05–0.30 3.62 — 36 0.001 No. of bats commuting·night–1 5.5±0.53 0–9 5.7±0.48 2–10 –0.22 — 36 0.826 No. of bats foraging·night–1 11.1±1.27 1–25 2.8±0.38 0–7 6.20 — 21.3 <0.001 No. of bats commuting·min–1 0.005±0.001a 0–0.119 0.011±0.001b 0.01–0.023 — 64.3 2, 27 <0.001 No. of bats foraging·min–1 0.010±0.001c 0.004–0.021 0.005±0.001a 0–0.011 ————

Table 2. The diet of adult pallid bats (Antrozous pallidus) based on the dissection of n = 22 faecal pellets collected from captured individuals and of faecal samples collected from below a colony day roost (n = 71 faecal pellets) with the frequency of occurrence per sample of each prey taxa eaten shown in parentheses.

Reproductive Date Sex status* Site† n‡ Contents of faecal pellets Faecal samples from captured bats 28 June Male NS V 4 Coleoptera: Polyphylla decemlineata (4), miscellaneous (1) 13 July Male NS V 5 Coleoptera: Phyllophaga spp. (5) 1 August Male S R 4 Coleoptera: Polyphylla decemlineata (3); Lepidoptera (3); Orthoptera: Stenopelmatus spp. (2), Tettigonidae (2) 10 August Female L R 2 Coleoptera: Polyphylla decemlineata (1); Orthoptera: Acrididae (1), Stenopelmatus spp. (1) Male S R 2 Coleoptera: Polyphylla decemlineata (2) Male S R 5 Orthoptera: Stenopelmatus spp. (5)

Faecal samples collected from beneath a colony day roost 1 June —— —24 Coleoptera: Polyphylla decemlineata (24); Lepidoptera (1); Orthoptera: Acrididae (1), Tettigonidae (1); unknown (1) 25 June —— —23 Coleoptera: Phyllophaga spp. (14), Polyphylla decemlineata (3), Prionus californicus (1); Lepidoptera (2); Orthoptera: Ceuthophilus spp. (1),

For personal use only. Stenopelmatus spp. (6), Tettigonidae (3) 14 July —— —24 Coleoptera: Phyllophaga spp. (12), Polyphylla decemlineata (23), miscellaneous (1); Lepidoptera (1); Orthoptera: Stenopelmatus spp. (1); leaf or plant (1) Note: Common names, authorities, and years of items in faecal pellets: ten-lined June beetle (Polyphylla decemlineata (Say, 1823)); species of the genus Phyllophaga Harris, 1827; species of the genus Stenopelmatus Burmeister, 1838; California prionus (Prionus californicus Motschulsky, 1845); species of the genus Ceuthophilus Scudder, 1863. *Reproductive status is as follows: NS, nonscrotal; S, scrotal; L, lactating. †Site of capture is as follows: V, vineyards; R, upon emergence from the (night) roost. ‡n is the number of faecal pellets dissected.

162 bats in 1303 min in vineyards (n = 24 nights surveying 17.49 specimens per trap; trap grid D, 33.3 ± 16.27 speci- both habitats). mens per trap). There was greater biodiversity of arthropod Based on an analysis of 93 faecal pellets (Tables 2 and 3), families in native habitat (n = 31 families) compared with Can. J. Zool. Downloaded from www.nrcresearchpress.com by University of Toronto on 08/26/11 we found that pallid bats ate mostly scarab beetles (Scara- vineyards (n = 26). At the genus and species level, biodiver- baeidae: Coleoptera; 71.1% of prey taken) followed by Jeru- sity was high in both habitats (native, H′ = 2.86; vineyard, salem crickets (Stenopelmatidae: Orthoptera; 11.7%), and had H′ = 2.96; Hmax = 3.22). The mean body length of speci- low diet diversity (D = 0.59). Faeces also contained ectopar- mens from native habitat (median = size class 6; mode = asites (Arachnida: Acari; n = 22 pellets), which the bats class 2) was significantly longer than from vineyards (me- likely ingested while grooming, but we excluded these from dian = class 4; mode = class 1; F[1,8] = 7.05, p = 0.03; ob- the analysis. served power = 0.64). We collected >2000 specimens in pitfall traps (Table 3), We caught significantly more arachnids, colopterans, or- with more caught in native habitat (n = 764, excluding silver- thopterans, and oniscids in pitfall traps in native compared fish (Lepisma saccharina L., 1758; order Thysanura) that with vineyard habitat, whereas we collected significantly were captured in disproportionately large numbers and were more lepidopterans and miscellaneous insect taxa in vine- excluded from our analysis; trap grid A, 16.0 ± 4.97 speci- yards (Table 3). There was no significant difference in the mens per trap; trap grid B, 68.2 ± 25.88 specimens per trap) number of rodents or anurans trapped between the two habi- versus vineyards (n = 590 specimens; trap grid C, 32.2 ± tats.

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Table 3. Percent frequency (n = 93 faecal pellets) of taxa in the diet of pallid bats (Antrozous pallidus) from British Columbia compared with potential prey collected in pitfall traps in native and vineyard habitats, and paired t statistics from comparisons of contents of pitfall traps between the two habitats (*, p < 0.05).

Percent frequency

Prey taxa Genus or species Diet Native Vineyard t [29] Arachnida Aranaea Araneidae 0.8 8.8 3.9 Lycosidae — 9.4 5.0 Salticidae — 0.1 — Theriidae Latrodectus spp. — 0.8 0.3 Miscellaneous — 3.7 4.1 Opiliones: Miscellaneous —— 0.5 Solifugae: Eremobatidae Eremobates gladiolus — 0.3 0.2 Total Arachnida 0.8 23.1 14.0 3.14* Insecta Coleoptera Carabidae — 13.6 4.7 Cerambycidae Prionus californicus 0.8 —— Curculionidae —— — Histeridae — 0.7 4.3 Scarabaeidae Phyllophaga spp. 24.2 — 2.4 Polyphylla decemlineata 46.9 — 0.2 Tenebrionidae Tenebrio spp. — 13.9 2.6 Miscellaneous 1.6 2.5 — Total Coleoptera 73.5 30.7 14.2 2.67* Lepidoptera: Miscellaneous 5.5 0.1 1.0 Total Lepidoptera 5.5 0.1 1.0 3.89* Orthoptera Acrididae 1.6 11.8 — Gryllidae Gryllus spp. — 2.6 0.7 Rhaphidophoridae Ceuthophilus spp. 0.8 0.9 0.2

For personal use only. Stenopelmatidae Stenopelmatus spp. 11.7 0.8 — Tettigoniidae 4.7 5.5 — Total Orthoptera 18.8 21.6 0.9 5.56* Dermaptera: Forficulina —— 0.3 Diptera Muscoidae — 3.0 26.3 Miscellaneous — 0.3 13.6 Hemiptera: Lygaeidae Geocoris spp. — 0.1 0.5 Hymenoptera Formicidae — 10.2 16.9 Vespidae — 6.5 8.3 Miscellaneous — 1.3 0.5 Odonata: Miscellaneous — 0.1 0.9 Total Other Insecta — 21.5 67.0 –2.67*

Can. J. Zool. Downloaded from www.nrcresearchpress.com by University of Toronto on 08/26/11 Total Insecta 97.8 73.9 83.1 Malacostraca Isopoda: Oniscidea — 1.4 0.3 Total Malacostraca — 1.4 0.3 3.10* Other Mammalia: Muridae, Rodentia — 0.3 0.3 Reptilia: Anura, Ranidae —— 0.2 Unknown 0.8 1.0 1.0 Leaf or plant 0.8 —— Total Other 1.6 1.3 1.5 0.06 Note: Common names, authorities, and years of items in faecal pellets: species of the genus Latrodectus Walckenaer, 1805; sun scorpion (Eremobates gladiolus Muma, 1951 = Eremobates scaber (Kraepelin, 1901)); species of the genus Tenebrio L., 1758; species of the genus Gryllus L., 1758; species of the genus Geocoris Fallén, 1814.

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More “probable” prey (as per our classifications) were col- the northern limits of their range where physiological chal- lected in pitfall traps from native habitat (native habitat, lenges are presumably more significant than in more southern 17.3 ± 5.8; vineyard habitat, 2.8 ± 1.0; t[34] = 2.46, p = habitats, pallid bats have reduced access to highly profitable 0.02; r = 0.39). The dominant probable prey present in na- prey such as Jerusalem crickets. tive habitat was represented by Orthopterans (specifically The arthropods that we caught in vineyard pitfall traps families Acrididae, Gryllidae, and Tettigoniidae), whereas in were significantly smaller, less diverse (at the family level), vineyards the probable prey that we collected was represented and of taxa that were either not part of the diet or less likely by Coleopterans (specifically families Carabidae, Scarabaei- to be consumed by pallid bats (based on our classifications; dae, and Tenebrionidae). see Materials and methods) than the specimens that we collected in native habitats. The high frequency of occurrence Discussion of scarab beetles in the faecal samples and their low abundance in pitfall traps suggest that pallid bats in British Co- Activity of pallid bats over native habitat was significantly lumbia may be catching these on the wing or gleaning them greater than over vineyards. We observed a greater absolute from plant surfaces, not from the ground. number of pallid bats flying over native habitat each night. Taken together our data from surveys, diet analysis, and However, we also recorded significantly more foraging activ- pitfall trapping suggest that although vineyards provide lower ity in native habitat compared with vineyards. Considering quality foraging areas relative to native habitat, pallid bats that our observation efforts and the availability of the two still use them. This outcome should provide strong incentive habitats were approximately equal, these data suggest that to conserve the remaining native habitat in the Okanagan pallid bats from the largest known roost in the Okanagan for- Valley, as well as to also focus attention on the management age more frequently over native habitat, at least in the first of vineyards as foraging areas for bats (for example by leav- half of the night. However, in spite of the significant differing patches of native habitat interspersed between blocks of ences, it is clear that this species does forage over vineyards. vine rows, which may increase prey quality and availability). Several factors may account for the difference in habitat use. Bats emerging from roosts and travelling to foraging Acknowledgements areas, water, or night roosts fly over vineyards for at least a Financial support was provided by a Natural Sciences and portion of their journey. For any predator, it is likely efficient Engineering Research Council of Canada (NSERC) Postgrad- to search for prey en route to the ultimate destination, espe- uate Scholarship A to D.A.R.; NSERC Discovery Grant to cially if profitable prey occur in all habitats traversed. We R.M.B.; University of Regina Interdepartmental Recovery posit that for pallid bats native habitat is more profitable Fund and the Science Horizons Youth Internship Program than vineyards, but because both were near (<1 km from) (Environment Canada); Endangered Species Recovery Fund the day roost and because beetles were abundant in vine- (Environment Canada and World Wildlife Fund of Canada); yards, bats foraged in both, as we expected. Vancouver Foundation; Toronto Dominion Friends of the En- For personal use only. For a gleaning bat, prey accessibility (i.e., absence of vironment Foundation; Brink/McLean Grasslands Conserva- ground cover) may influence habitat use (Bell 1982) and tion Fund (The Nature Trust of B.C.); Bat Conservation vineyards have large areas of open ground where pallid bats International; Nk’Mip (Osoyoos) Indian Band; Nk’Mip Des- could land to catch prey. This benefit may outweigh the fact ert and Heritage Centre; and Osoyoos Desert Centre. The that our pit trapping data suggest that vineyards provide sig- funders had no role in study design; data collection and anal- nificantly lower prey quality (up to six times fewer of the ysis; decision to publish; or preparation of the manuscript. prey taxa pallid bats are likely to capture) and abundance. Logistic support and field assistance from R. Hall, S. Bryson, Prey quality is an important factor for predator energy budg- C. Louie, J. Barrett, J. Hall, K. Hall, Kx Hall, M. Hall, D. ets. Ball (1998) calculated that the energy provided by a sin- Makortoff, G. McKeown, S. Cipes, O. Dyer, M.B. Fenton, gle Jerusalem cricket was equivalent to about 29–30 L. Friis, K. Gano, C. Harbison, M. Holm, S. Hureau, J. Phyllophaga spp., and that a single Jerusalem cricket would Muirhead, P. Ord, L. Pica, M. Sarell, G. Scudder, D. Sharpe, provide nearly all of the daily energy requirement of an adult B. White, K. Woodruff, M. Sheridan, and T. Osborne were pallid bat. Our data suggest that beetles are most likely the greatly appreciated. R. Barclay, A. Drake, D. Drake, and two predominant prey that bats capture when foraging over vine- anonymous reviewers provided useful comments on earlier Can. J. Zool. Downloaded from www.nrcresearchpress.com by University of Toronto on 08/26/11 yards (Table 3), whereas they may capture other prey, such as drafts of the manuscript. This study is dedicated to the loving Jerusalem crickets and katydids, in addition to beetles when memory of Makwala Marshall Derrickson-Hall. foraging in native habitat. In the Okanagan Valley, Jerusalem crickets have been collected only in native habitat (Scudder References 1997; Griesdale 2005; this study). Ball, L.C. 1998. Roosting behavior of pallid bats (Antrozous Pallid bats in British Columbia likely eat primarily beetles pallidus): energetic and ecological mechanisms. Ph.D. thesis, because they are the most frequently encountered energy-rich College of Science, University of Nevada, Reno. prey. In 2005, male and female pallid bats in neighbouring Ball, L.C. 2002. A strategy for describing and monitoring bat habitat. Washington State (Winthrop Township and Washington Clo- J. Wildl. Manage. 66(4): 1148–1153. doi:10.2307/3802947. sure Hanford Nuclear Reservation in Richland, areas which Barber, J.R., Razak, K.A., and Fuzessary, Z.M. 2003. Can two are dominated by native habitat; Wooten 2003) ate primarily streams of auditory information be processed simultaneously? Jerusalem crickets (35.5% of prey eaten, n = 39 faecal pel- Evidence from the gleaning bat Antrozous pallidus. J. Comp. lets) and had greater diet diversity compared with the Okana- Physiol. A Neuroethol. Sens. Neural Behav. Physiol. 189(11): gan bats (D = 0.82; D.A. Rambaldini, unpublished data). At 843–855. doi:10.1007/s00359-003-0463-6. PMID:14564468.

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