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Vigilance behaviour of polar bears (Ursus maritimus) in the context of wildlife-viewing activities at Churchill, Manitoba, Canada
Biological Conservation 116 (2004) 343–350 www.elsevier.com/locate/biocon
Vigilance behaviour of polar bears (Ursus maritimus) in the context of wildlife-viewing activities at Churchill, Manitoba, Canada Markus G. Dycka,*, Richard K. Baydackb a Natural Resources Institute, University of Manitoba, Winnipeg, Canada Richard K. Baydack, Faculty of Environment, Department of Geography and Environment, University of Manitoba, Winnipeg Manitoba, Canada, R3T 2N2
b
Received 27 February 2002; received in revised form 19 April 2003; accepted 10 May 2003
Abstract Viewing of polar bears (Ursus maritimus) from tundra vehicles has been offered at Churchill, Manitoba since the early 1980s. This form of wildlife viewing has provided a unique and safe way for tourists to learn about polar bears. However, these activities have largely been carried out without examining possible effects on polar bear behaviour. We studied vigilance behaviour (a scanning of the immediate vicinity and beyond) of resting polar bears to evaluate impacts from tundra vehicle activity. Focal animal sampling was used to examine whether a difference in vigilance behaviour existed when vehicles were present. We recorded the numbers of head-ups, vigilance bout length, and between-bout intervals for polar bears. In general, the frequency of head-ups increased, and the between-bout intervals decreased for male bears, when vehicles were present. Female bears behaved opposite to males. The vigilance bout lengths did not differ significantly between vehicle presence and absence. Vigilance behaviour of male bears was not magnified with increasing numbers of vehicles; therefore the threshold is one vehicle. We suggest that manipulative studies be conducted to examine how distances between vehicles and bears, tundra vehicle activity in the immediate vicinity of a bear during viewing, and noise of tourists affect increased vigilance. # 2003 Elsevier Ltd. All rights reserved. Keywords: Churchill; Polar bears; Tourism; Ursus maritimus; Wildlife viewing; Vigilance
1. Introduction Polar bears (Ursus maritimus) depend on sea ice to hunt their primary food, ringed seals (Phoca hispida), and to a lesser extent, bearded seals (Erignathus barbatus) (Stirling and Archibald, 1977; Smith, 1980). Hudson Bay is generally ice-free from July until midNovember, which forces the bears to come ashore (Stirling et al., 1977). During that time, bears feed little and they are sustained by their stored fat reserves (Lunn and Stirling, 1985; Watts and Hansen, 1987; Ramsay and Stirling, 1988). Once on land, bears segregate by sex and age class (Derocher and Stirling, 1990a, b), and spend the majority of their time resting to conserve energy while awaiting freeze-up (Knudsen, 1978; Dyck, 2001). * Corresponding author. Present address: Box 11016, Iqaluit Nunavut, Canada, X0A 0H0. E-mail address: [email protected] (M.G. Dyck). 0006-3207/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0006-3207(03)00204-0
Since the 1980s, tourism operators at Churchill have offered polar bear viewing tours during October and November where visitors are transported on tundra vehicles (large, customized bus-like vehicles) to view polar bears in the Gordon Point area (Webb, 1985; Herrero and Herrero, 1997). The Gordon Point area is a fall congregation location where polar bears await the first ice to form on Hudson Bay. During polar bear viewing excursions, bears are often approached at distances of < 40 m (Dyck, 2001), and at times are harassed (i.e. displaced) by tundra vehicles (Watts and Ratson, 1989). Wildlife viewing has become a very popular recreational activity worldwide with the number of participants steadily increasing (Walsh et al., 1989; Giannecchini, 1993). As humans seek recreation, wildlife behaviour (Boyle and Samson, 1985; Knight and Cole, 1995; Knight and Gutzwiller, 1995) and the quality of the visitor experience can be altered or negatively influenced (Vaske et al., 1995). Recent studies
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documented increased habituation, decreased feeding time, changes in hormonal milieu, decreased survivorship, increased predation, death, and increased alertness as effects of tourist activities on wildlife [e.g., Kovacs and Innes, 1990: harp seals (Phoca groenlandica); Burger and Gochfeld, 1993: boobies (Sula dactylagra and S. sula); Blane and Jaakson, 1994: Beluga whales (Delphinapterus leucas); Lott and McCoy, 1995: Asian rhinos (Rhinoceros unicornis); Giese, 1996, 1998: Ade´lie penguins (Pygoscelis adeliae); Fowler, 1999: Magellanic penguins (Spheniscus magellanicus)]. Data on how tundra vehicle activity affects polar bears at Churchill are particularly important in light of trends that indicate an increase in the length of the ice-free period (Stirling et al., 1999). If the ice-free period of Hudson Bay is increasing, tour operators could lengthen the polar bear viewing season at Churchill, consequently exposing bears to an additional stress factor. Vigilance can be defined as ‘‘a motor act, which corresponds to a head lift interrupting the ongoing activity’’ (Quenette, 1990), and involves a visual scanning of the surroundings beyond the immediate vicinity (Quenette, 1990; Treves, 2000). This behaviour has been associated with the detection of predators (see review by Elgar, 1989; Arenz and Leger, 1999a, b; Toı¨go, 1999), reduction of risk by allowing prey to perform evasive or mobbing behaviour (Curio, 1978; Lima, 1994), detection of mates and competitors (Baldellou and Heinzi, 1992; Cowlishaw, 1998), observation of conspecifics (Caine and Marra, 1988; Roberts, 1988), and avoidance of infanticide (Steenbeek et al., 1999). Several studies documented that individual vigilance decreases with increasing group size (Quenette, 1990; Kildaw, 1995; Roberts, 1996; but see Bekoff, 1995), and that differences between sex (Quenette, 1990; Burger and Gochfeld, 1994; but see Elgar, 1989), season, and habitat exist (Quenette, 1990). Vigilance behaviour conflicts with other activities, such as sleeping, feeding, grooming, or fighting (Cords, 1995; Mooring and Hart, 1995; Brick, 1998; McAdam and Kramer, 1998). As such, it is costly because it requires limited resources of time and visual attention (Altman, S., 1974; Dukas, 1998). Continued stimuli that are perceived as threats (e.g., predator presence) can elicit a hormonal chain reaction resulting in increased cardiac output, increased levels of ‘‘stress hormones’’ (i.e., glucocorticosteroids and corticosterone), and the formation of glucose at the expense of protein and fat (Chester-Jones et al., 1972; Wingfield, 1994; Wingfield et al., 1997). We examined vigilance behaviour of polar bears in the context of wildlife viewing activities at Churchill, Manitoba. The results of this study can be used as a baseline of the current situation, therefore enabling management agencies to prevent chronic stress effects from taking place. Moreover, recording vigilance may
provide a non-invasive tool, or indicator, which could be used by management agencies across various taxa when designing monitoring programmes with the goal to assess possible effects of wildlife viewing.
2. Methods 2.1. Study site We conducted this study in the Gordon Point area (approximately 58 450 N to 58 480 N, and 93 380 W to 93 500 W), which lies on the southwestern coast of Hudson Bay, approximately 30–35 km east of Churchill, Manitoba. The entire area is generally without relief with elevations less than 50 m. The coastline is characterized by gravel spits, foreshore flats, post-glacial beach ridges, and shallow lakes and ponds surrounded by willows (Salix spp.). A more detailed description of Churchill’s coastal and inland areas is given by Ritchie (1962) and Clark et al. (1997). 2.2. Vigilance behaviour of polar bears Observations of vigilance behaviour of polar bears were recorded during day-to-day activities of tour companies from 1 October through 12 November 2000, usually between 0900 and 1600 h CST. The number of tundra vehicles around a bear during viewing, and visitor behaviour on board tundra vehicles could not be controlled. We examined whether a difference in vigilance of polar bears could be detected in the presence versus absence of tundra vehicles. We observed polar bears either with spotting scopes from an 8 m high wooden observation tower at Gordon Point, usually at distances of 200–1500 m, or videotaped bears from tundra vehicles using a SONY Handycam Video Hi8 camcorder. All observation times were recorded with digital stopwatches. Bears were identified as either males or females by accompanying cubs, body sizes, scars, and head and neck shapes (Knudsen, 1978). We focused only on resting bears (e.g., lying prone in one spot, head on ground, legs sprawled out or front legs tucked under body, with flank and hindquarters on ground, or curled up; Øritsland, 1970; Caro, 1987) because the conservation of energy at this time of year may be critical in the bear’s lifecycle (Castellini and Rea, 1992; Atkinson and Ramsay, 1995; Atkinson et al., 1996). Any disturbance during resting may result in increased energy expenditure or adverse physiological responses (Watts et al., 1991). In addition, focusing on resting bears provided the same starting point for data recording, it allowed comparison of data between bears with and without tundra vehicles, and it seemed practical as most bears approached by tundra vehicles were resting. Vigilance for this purpose
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was defined as head-up movements where the head of a bear was lifted to shoulder-level or above, while the animal was lying down. We used focal animal sampling (Altman, J., 1974) to record the number of head-ups (i.e., how often the head was lifted to shoulder level or above during the observation time), vigilance bout length (i.e., time (s) that passed between a head-up and when the head was lowered back to the ground), and between-bout intervals (i.e., interval (s) between the moment when the head was on the ground from a previous vigilance bout length and a subsequent head-up). We decided to record vigilance for approximately 30 min, or until the bears stood or sat up, or walked away. The selected time interval was based on our experience while we tested for clear and distinct visibility of head movements of polar bears: during tourist viewing activities, bears were generally resting for about 20–30 consecutive minutes before changing postures. In order to allow comparison of recorded data among bears and between the treatments (i.e., with versus without vehicles), data recording and timing for all observations began with the first head-up movement after a bear was selected for observation. All observations of polar bears were conducted in accordance with the Animal Care Committee of the University of Manitoba (Protocol F 00-001). 2.3. Study design Data were recorded for a ‘‘paired’’ and ‘‘unpaired’’ experimental design. For the paired design, the same bears were observed with and without tundra vehicles. We selected the animals using a random number table from bears that were present in the Gordon Point area after a 360-degree scan with spotting scopes from an observation tower. Whenever a bear was selected, we recorded specific marks, body shape, presence of cubs, and missing appendices to allow future identification of the same animal. We then recorded vigilance behaviour either with or without tundra vehicles. Vehicles were considered to be ‘‘present’’ if within 40 m (or about four tundra vehicle lengths; Dyck 2001). If, for example, a bear’s vigilance was first recorded in the presence of a vehicle, we waited until no vehicles were in the vicinity ( 1.5–2.0 km) of that bear for at least 30 min to record vigilance without vehicles. If that was impossible to achieve because of tundra vehicle activity in the study area, we either waited until all vehicles had left the study area, or we recorded vigilance the next day before tundra vehicles arrived in the study area. All resting bears with and without tundra vehicles present in the study area, excluding bears selected for the paired design, were potential subjects for the unpaired design. First, we randomly decided whether to record vigilance with or without vehicles. If vigilance without vehicles was selected, one bear was randomly
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chosen from all bears present in the study area that had no tundra vehicles present. We used the same procedure to select bears with vehicles. 2.4. Statistical analyses Individual observation times of vigilance behaviour of bears varied and could not be recorded for 30 min maximum at all times because bears got up and walk away for no apparent reason (when without vehicles), or because of tundra vehicle commotion (i.e. vehicles passing the bear being observed while other vehicles arrived or left the vicinity of that bear). For statistical purposes, we therefore expressed each variable measured on a bear as a proportion of the total observation time of that bear. Paired t-tests were applied to the paired design to examine whether differences between sex and tundra vehicle presence existed. Two-factor analysis of variance (ANOVA) was used to determine interactions between sex and presence versus absence of tundra vehicles for the paired design. For the unpaired design, we applied one-factor ANOVA to examine whether differences existed for bears with versus without vehicles. We used simple linear regression to determine if a relationship existed between the number of vehicles around a bear and the observed variables. Mann–Whitney U tests were performed to assess differences between total vigilance time for bears with/without vehicles, and to determine whether time of day (i.e., early versus late) affected vigilance response of polar bears (Zar, 1999). All tests were two-tailed, and considered significant at =0.05. Values are expressed as mean SE.
3. Results We recorded vigilance behaviour on 43 individually identified bears, with 10 bears (six males and four females with cubs; all adults observed with and without tundra vehicles) for the paired, and 33 bears (all males; 10 with and 23 without tundra vehicles) for the unpaired design. Mean SE observation time for vigilance behaviour per bear was 20.7 1.1 min (n=53). The mean number of tundra vehicles (TV) per bear, associated with polar bear viewing activities was 2.3 0.3 TV (n=33; range: 1–7). 3.1. Behavioural results For the paired design, an interaction between sex and tundra vehicle presence or absence was detected for the numbers of head-ups (F1=16.09, P=0.001) and between-bout intervals (F1=4.67, P=0.046). Males showed a significant increase in head-up responses during vehicle presence (t5=5.9, P=0.002, n=6, effect size d=1.68, power of G-test P=0.747), whereas females’
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6.81.9 (4–12) 8.82.0 (3.8–12.6) 146.2 21.9 (111.8–210.0) 17.01.9 (11–24) 17.84.8 (7.8–40.7) 81.38.9 (52.6–104.4) 12.9 1.5 (4–33) 13.2 1.9 (4.8–50.6) 93.2 11.1 (24.6–184.1)
head-up frequency increased during vehicle absence, although not significantly. Between-bout intervals for males increased during vehicle absence, and for females during vehicle presence, but not significantly. (Fig. 1). Significant effects in the unpaired design were detected for the frequency of head-ups and the length of between-bout intervals. Tundra vehicle presence elicited a greater frequency of head-ups (F33=11.06, P=0.002, effect size d=1.10, power of G-test P=0.804), whereas vehicle absence increased the length of between-bout intervals (F33=7.76, P=0.009, effect size d=0.95, power of G-test P=0.679). As in the paired design, vigilance bout length was not affected significantly by vehicle presence or absence (Fig. 2). Descriptive statistics of the non-transformed frequencies of head-ups, vigilance bout lengths, and between-bout intervals in the presence and absence of vehicles, are given in Table 1.
4.00.9 (1–6) 8.62.6 (2.5–20.8) 606.9 150.0 (262.8–1211.0) HU (#) VBL (s) BBI (s)
6.8 1.5 (0–17) 12.5 3.4 (0–31.6) 507.1217.9 (77.7–1800)
10.52.9 (7–19) 12.52.8 (7.8–19.3) 122.940.3 (52.7–223.6)
Females (n=4) Males (n=6) Males (n=6) Males (n=10) Sex Variables
Paired Study design
Unpaired
Females (n=4)
Males (n=23)
Paired Unpaired
With Tundra Vehicle Without Tundra Vehicle
Table 1 Non-transformed descriptive statistics, presented as mean SE (range), for the numbers of head-ups (HU), vigilance bout length (VBL), and between-bout intervals (BBI) for polar bears with and without tundra vehicles of the unpaired and paired study design
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Fig. 1. Frequency of head-up, vigilance bout length, and betweenbout intervals as proportion of total observed time, for male and female polar bears in the presence and absence of tundra vehicles (TV) at Churchill [Note: Error bars represent SE; *: P=0.002 at =0.05].
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Simple linear regression indicated no significant relationship between the measured variables and the number of tundra vehicles for bears of the unpaired design. Low number of vehicles and small sample size for the paired design did not allow similar analyses. Comparisons of the variables collected between 0900 and 1115 h (first 33 percentiles) with times between 1330 and 1545 h (66–100th percentile) did not indicate a significant temporal variation in responses (head-up: U=10, Nlate=10, Nearly=5, P=0.066; vigilance bout length: U=15, Nlate=10, Nearly=5, P=0.086). There was a two-fold increase in total time spent vigilant as proportion of total time observed for bears of the unpaired design with tundra vehicles (0.175 0.03 s, range 0.034–0.614 s, n=23), as opposed to bears without vehicles (0.087 0.027 s, range 0–0.284 s, n=10), although not significant (U=65, Nwith=23, Nwithout=10, P=0.050). For the paired design, total vigilance increased significantly about seven-fold for bears with vehicles (t5=3.309, P=0.021, n=6; 0.208 0.053 s, range 0.055–0.381 s) as compared to bears without vehicles (0.027 0.012 s, range 0.004–0.087 s).
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generally conflicts with other activities (Brick, 1998, McAdam and Kramer, 1998). In our study, it conflicted with resting behaviour of bears. While on land, polar bears feed little, they live of their stored fat reserves and preserve energy by spending most of their time resting (Watts and Hansen, 1987). While polar bears live off their stored fat, body mass loss per day (BML/d) ranges between 0.25 and 1.05 kg, depending on age (Derocher and Stirling, 1995). The increase in vigilance response, in particular the head-up motion and maintenance of the head at shoulder levels for periods of time, could result in metabolic increases. Moreover, metabolism could be increased because of elevated heart rates. Tourists approaching wildlife [e.g., Ade´lie penguins (Pygoscelis adeliae), mountain sheep (Ovis canadensis)] can cause significant increases in heart rate of animals (MacArthur et al., 1982; Giese, 1998). A polar bear’s heart rate rises from 33 beats/min during sleep to 46 beats/min while lying awake (Øritsland et al., 1977), and
4. Discussion Vigilance behaviour of polar bears in the Gordon Point area at Churchill, Manitoba was significantly affected by the presence of tundra vehicles. In particular, the frequency for head-ups increased and the between-bout intervals decreased in the presence of tundra vehicles. Male bears of the paired design exhibited a similar response pattern in the absence and presence of vehicles, as did bears of the unpaired design. However, it is unclear from our study whether the vehicles or vehicle commotion alone elicited the observed responses, or if a combination of visual (i.e., vehicle, visitors on vehicles), acoustic (i.e., noise of visitors and vehicles), and olfactory stimulation (i.e., smell of vehicles, tourists, food) caused an increase in vigilance. During our study, when a single vehicle approached a bear during viewing activities and remained stationary for 120 min, habituation to the vehicle occurred, the numbers of head-ups decreased, and between-bout intervals increased after 90 min, similar to responses of vehicle absence (Dyck and Baydack unpublished data). This suggests that vehicle commotion may be the primary stimulus, however, manipulative studies would need to examine this in detail. When animals are presented with a stimulus (e.g., predator), an increased vigilance response can be the result (e.g., Quenette, 1990). In our study, the frequency of head-ups for males increased two-fold from vehicle absence to presence. In addition, the between-bout intervals were three times greater during vehicle absence as compared to presence (Fig. 2). Vigilance behaviour
Fig. 2. Frequency of head-up, vigilance bout length, and betweenbout intervals as proportion of total observed time, for male polar bears in the presence and absence of tundra vehicles (TV) at Churchill [Note: Error bars represent SE; a: P=0.002; b: P=0.009; =0.05].
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probably increases further while being approached by a tundra vehicle. In polar bears, heart rate has been shown to be an indicator of metabolism, where metabolism increases as heart rate becomes elevated (Øritsland et al., 1977; Best et al., 1981). Tourist activities at Gordon Point last approximately for 45 days (Dyck, 2001), and an additional increase in BML/d could have an effect on individual fitness if bears tend to stay in this area for a prolonged period of time, especially if individual bears are exposed repeatedly to these stimuli. This increase in BML/d could be even greater if behavioural displacement of bears by tundra vehicles occurs. The variables we measured for male bears were not magnified with an increase in numbers of tundra vehicles. Presence of a single vehicle was enough to elicit greater responses. Vigilance incurs costs (Treves, 2000), and only in case of a direct perceived threat or risk would increased vigilance (and increased costs) be advantageous to the scanning animal (Hunter and Skinner, 1998). We therefore suggest that vigilance behaviour of polar bears during wildlife viewing activities is a response similar to predator avoidance (Arenz and Leger, 1999a, b; Toı¨go, 1999). Animals perceive objects, process information, make decisions and solve problems (Griffin, 1992). Polar bears obviously are aware of their environment (e.g., being on the ice versus being on land), and components within their physical environment (e.g., conspecifics, other animals, humans and their artefacts). Moreover, polar bears should be capable of discerning different objects from one another, for example icebergs from tundra vehicles (e.g., both are white but distinctively different). Vehicles present an anthropogenic stimulus, which may be perceived by bears as ‘‘out-of-place’’, where the outcome of a possible threatening interaction is unknown, especially since vehicles are more than five times the size of bears. Female response to vehicle presence was not as expected. Frequency of head-ups was lower and lengths of between-bout intervals were greater during vehicle presence. Our sample size for females was small, and we can only speculate about the interpretation of the results. The data indicate that females appeared to be more ‘‘comfortable’’ in the presence of vehicles. Where males may perceive tundra vehicles as a threat, females may use them as a ‘‘safety buffer’’ to protect their offspring from male bears. This is supported by the increased head-up frequency and decreased lengths of between-bout intervals in the absence of vehicles, which may serve the detection of conspecifics and avoidance of infanticide (Steenbeek et al., 1999), thereby indirectly protecting offspring. During vehicle absence, resting polar bears showed vigilance behaviour. During fall, the Gordon Point area is a congregation site on shore where bears of all age and sex classes wait for the first ice to form on Hudson
Bay. Bear density in this area can reach a minimum of about 20 bears/50 km2 (Dyck, 2001) as compared to 1–7 bears/1000 km2 for other polar bear populations while distributed in their habitat (Derocher and Taylor, 1994). Polar bears have no natural predator, and the only harm is from conspecifics. Male bears engage in playfight bouts (Latour, 1981) or fight for females during the mating season (Ramsay and Stirling, 1986). Also, infanticide and cannibalism have been observed where male bears kill other bears or offspring for various reasons (Taylor et al., 1985; Derocher and Wiig, 1999; Dyck and Daley, 2002). We suggest that the primary function of vigilance without vehicles is observation of conspecifics (e.g., Caine and Marra, 1988; Roberts, 1988). However, Quenette (1990) pointed out the importance of the context in which vigilance occurs. For example, during mating season, vigilance may serve the purpose of observing conspecifics and detecting mates or competitors (e.g., Baldellou and Heinzi, 1992; Cowlishaw, 1998). Vigilance bout lengths for male bears did not differ in the presence and absence of vehicles. Bears may have been selected to scan their surrounding for a specific time to be effective in assessing the immediate vicinity, independent of the presence of a stimulus (Dimond and Lazarus, 1974). These ‘‘programmed’’ scans may prove selectively advantageous to minimize risk of injury or death when faced with opponents or mates (Maynard Smith and Parker, 1976; Clutton-Brock et al., 1979). Polar bear viewing from tundra vehicles is generally safe, and it enables thousands of tourists from all over the world to experience and learn about polar bears and their habitat. Where usually a distance between viewer and wildlife is encouraged (i.e., McNeil River, Alaska), Churchill tourists view bears from a close distance (Herrero and Herrero, 1997). The effects of tundra vehicle activities during polar bear viewing were measured using vigilance. We believe that vigilance behaviour could be a non-invasive and simple method to monitor wildlife behaviour in the context of wildlifeviewing activities. Wildlife managers can be trained to record appropriate behaviours, and to evaluate whether changes in the wildlife response occurred over time. For Churchill specifically, we suggest manipulative studies that examine how tundra vehicle distances to bears and commotion in the immediate vicinity of bears affect vigilance.
Acknowledgements This study was logistically and financially supported by Manitoba Conservation, The Great Bear Foundation Missoula, Born Free Foundation U.K., the Wyoming Chapter of The Wildlife Society, the Northern Science Training Program of the University of Manitoba, a
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Northern Research Fund by the Churchill Northern Studies Centre, J. Hare, R. Brook, W. Bernhardt, Tundra Buggy1 Tours Ltd., Great White Bear Tours Inc., Counter Assault, Coleman, countless Churchill residents, and P. Hebert. We are indebted to G. McBride, R. Pilkington, and K. Daley for their excellent assistance in the field. We are also grateful for comments on earlier drafts of the manuscript by G. Wright and an anonymous reviewer. Their constructive criticism improved the quality of the final version.
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importance of infanticide risk. Behavioural Ecology and Sociobiology 45, 137–150. Stirling, I., Archibald, W.R., 1977. Aspects of predation of seals by polar bears. Journal of the Fisheries Board of Canada 34, 1126– 1129. Stirling, I., Jonkel, C.J., Smith, P., Robertson, R., Cross, D., 1977. The ecology of the polar bear (Ursus maritimus) along the western coast of Hudson Bay. Canadian Wildlife Service Occasional Paper No. 33. Stirling, I., Lunn, N.J., Iacozza, J., 1999. Long-term trends in the population ecology of polar bears in Western Hudson Bay in relation to climatic change. Arctic 52, 294–306. Taylor, M.K., Larsen, T., Schweinsburg, R.E., 1985. Observations of intraspecific aggression and cannibalism in polar bears (Ursus maritimus). Arctic 38, 303–309. Toı¨go, C., 1999. Vigilance behaviour in lactating female Alpine ibex. Canadian Journal of Zoology 77, 1060–1063. Treves, A., 2000. Theory and method in studies of vigilance and aggregation. Animal Behaviour 60, 711–722. Walsh, R.G., John, K.H., McKean, J.R., Hof, J.G., 1989. Comparing long-run forecasts of demand for fish and wildlife recreation. Leisure Sciences 11, 337–351. Watts, P.D., Hansen, S.E., 1987. Cyclic starvation as a reproductive strategy in the polar bear. Symposium of the Zoological Society, London 57, 306–318. Watts, P.D., Ratson, P.S., 1989. Tour operator avoidance of deterrent use and harassment of polar bears. In: Bromley, M. (Ed.), Bear– People Conflicts, Proceedings of a Symposium on Management Strategies. Northwest Territories Department of Renewable Resources, Yellowknife, pp. 189–193. Watts, P.D., Ferguson, K.L., Draper, B.A., 1991. Energetic output of subadult polar bears (Ursus maritimus): resting, disturbance and locomotion. Comparative Biochemistry and Physiology A., Comparative Physiology 98, 191–193. Webb, A.J., 1985. Environmental impact of All-Terrain Vehicles in the Cape Churchill Wildlife Management Area. Master’s Practicum, University of Manitoba, Winnipeg. Wingfield, J.C., 1994. Modulation of the adrenocortical response to stress in birds. In: Davey, K.G., Peter, R.E., Tobe, S.S. (Eds.), Perspectives in Comparative Endocrinology. National Research Council Canada, Ottawa, pp. 520–528. Wingfield, J.C., Hunt, K., Breuner, C., Dunlap, K., Fowler, G.S., Freed, L., Lepson, J., 1997. Environmental stress, field endocrinology, and conservation biology. In: Clemmons, J.R., Buchholz, R. (Eds.), Behavioral Approaches to Conservation in the Wild. Cambridge University Press, London, pp. 95–131. Vaske, J.J., Decker, D.J., Manfredo, M.J., 1995. Human dimensions of wildlife management: an integrated framework for coexistence. In: Knight, R.L., Gutzwiller, K.J. (Eds.), Wildlife and Recreationists: Coexistence Through Management and Research. Island Press, Washington, DC, pp. 33–49. Zar, J.H., 1999. Biostatistical Analysis. Prentice-Hall, Inc, New Jersey.
Vigilance behaviour of polar bears (Ursus maritimus) in the context of wildlife-viewing activities at Churchill, Manitoba, Canada Markus G. Dycka,*, Richard K. Baydackb a Natural Resources Institute, University of Manitoba, Winnipeg, Canada Richard K. Baydack, Faculty of Environment, Department of Geography and Environment, University of Manitoba, Winnipeg Manitoba, Canada, R3T 2N2
b
Received 27 February 2002; received in revised form 19 April 2003; accepted 10 May 2003
Abstract Viewing of polar bears (Ursus maritimus) from tundra vehicles has been offered at Churchill, Manitoba since the early 1980s. This form of wildlife viewing has provided a unique and safe way for tourists to learn about polar bears. However, these activities have largely been carried out without examining possible effects on polar bear behaviour. We studied vigilance behaviour (a scanning of the immediate vicinity and beyond) of resting polar bears to evaluate impacts from tundra vehicle activity. Focal animal sampling was used to examine whether a difference in vigilance behaviour existed when vehicles were present. We recorded the numbers of head-ups, vigilance bout length, and between-bout intervals for polar bears. In general, the frequency of head-ups increased, and the between-bout intervals decreased for male bears, when vehicles were present. Female bears behaved opposite to males. The vigilance bout lengths did not differ significantly between vehicle presence and absence. Vigilance behaviour of male bears was not magnified with increasing numbers of vehicles; therefore the threshold is one vehicle. We suggest that manipulative studies be conducted to examine how distances between vehicles and bears, tundra vehicle activity in the immediate vicinity of a bear during viewing, and noise of tourists affect increased vigilance. # 2003 Elsevier Ltd. All rights reserved. Keywords: Churchill; Polar bears; Tourism; Ursus maritimus; Wildlife viewing; Vigilance
1. Introduction Polar bears (Ursus maritimus) depend on sea ice to hunt their primary food, ringed seals (Phoca hispida), and to a lesser extent, bearded seals (Erignathus barbatus) (Stirling and Archibald, 1977; Smith, 1980). Hudson Bay is generally ice-free from July until midNovember, which forces the bears to come ashore (Stirling et al., 1977). During that time, bears feed little and they are sustained by their stored fat reserves (Lunn and Stirling, 1985; Watts and Hansen, 1987; Ramsay and Stirling, 1988). Once on land, bears segregate by sex and age class (Derocher and Stirling, 1990a, b), and spend the majority of their time resting to conserve energy while awaiting freeze-up (Knudsen, 1978; Dyck, 2001). * Corresponding author. Present address: Box 11016, Iqaluit Nunavut, Canada, X0A 0H0. E-mail address: [email protected] (M.G. Dyck). 0006-3207/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0006-3207(03)00204-0
Since the 1980s, tourism operators at Churchill have offered polar bear viewing tours during October and November where visitors are transported on tundra vehicles (large, customized bus-like vehicles) to view polar bears in the Gordon Point area (Webb, 1985; Herrero and Herrero, 1997). The Gordon Point area is a fall congregation location where polar bears await the first ice to form on Hudson Bay. During polar bear viewing excursions, bears are often approached at distances of < 40 m (Dyck, 2001), and at times are harassed (i.e. displaced) by tundra vehicles (Watts and Ratson, 1989). Wildlife viewing has become a very popular recreational activity worldwide with the number of participants steadily increasing (Walsh et al., 1989; Giannecchini, 1993). As humans seek recreation, wildlife behaviour (Boyle and Samson, 1985; Knight and Cole, 1995; Knight and Gutzwiller, 1995) and the quality of the visitor experience can be altered or negatively influenced (Vaske et al., 1995). Recent studies
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documented increased habituation, decreased feeding time, changes in hormonal milieu, decreased survivorship, increased predation, death, and increased alertness as effects of tourist activities on wildlife [e.g., Kovacs and Innes, 1990: harp seals (Phoca groenlandica); Burger and Gochfeld, 1993: boobies (Sula dactylagra and S. sula); Blane and Jaakson, 1994: Beluga whales (Delphinapterus leucas); Lott and McCoy, 1995: Asian rhinos (Rhinoceros unicornis); Giese, 1996, 1998: Ade´lie penguins (Pygoscelis adeliae); Fowler, 1999: Magellanic penguins (Spheniscus magellanicus)]. Data on how tundra vehicle activity affects polar bears at Churchill are particularly important in light of trends that indicate an increase in the length of the ice-free period (Stirling et al., 1999). If the ice-free period of Hudson Bay is increasing, tour operators could lengthen the polar bear viewing season at Churchill, consequently exposing bears to an additional stress factor. Vigilance can be defined as ‘‘a motor act, which corresponds to a head lift interrupting the ongoing activity’’ (Quenette, 1990), and involves a visual scanning of the surroundings beyond the immediate vicinity (Quenette, 1990; Treves, 2000). This behaviour has been associated with the detection of predators (see review by Elgar, 1989; Arenz and Leger, 1999a, b; Toı¨go, 1999), reduction of risk by allowing prey to perform evasive or mobbing behaviour (Curio, 1978; Lima, 1994), detection of mates and competitors (Baldellou and Heinzi, 1992; Cowlishaw, 1998), observation of conspecifics (Caine and Marra, 1988; Roberts, 1988), and avoidance of infanticide (Steenbeek et al., 1999). Several studies documented that individual vigilance decreases with increasing group size (Quenette, 1990; Kildaw, 1995; Roberts, 1996; but see Bekoff, 1995), and that differences between sex (Quenette, 1990; Burger and Gochfeld, 1994; but see Elgar, 1989), season, and habitat exist (Quenette, 1990). Vigilance behaviour conflicts with other activities, such as sleeping, feeding, grooming, or fighting (Cords, 1995; Mooring and Hart, 1995; Brick, 1998; McAdam and Kramer, 1998). As such, it is costly because it requires limited resources of time and visual attention (Altman, S., 1974; Dukas, 1998). Continued stimuli that are perceived as threats (e.g., predator presence) can elicit a hormonal chain reaction resulting in increased cardiac output, increased levels of ‘‘stress hormones’’ (i.e., glucocorticosteroids and corticosterone), and the formation of glucose at the expense of protein and fat (Chester-Jones et al., 1972; Wingfield, 1994; Wingfield et al., 1997). We examined vigilance behaviour of polar bears in the context of wildlife viewing activities at Churchill, Manitoba. The results of this study can be used as a baseline of the current situation, therefore enabling management agencies to prevent chronic stress effects from taking place. Moreover, recording vigilance may
provide a non-invasive tool, or indicator, which could be used by management agencies across various taxa when designing monitoring programmes with the goal to assess possible effects of wildlife viewing.
2. Methods 2.1. Study site We conducted this study in the Gordon Point area (approximately 58 450 N to 58 480 N, and 93 380 W to 93 500 W), which lies on the southwestern coast of Hudson Bay, approximately 30–35 km east of Churchill, Manitoba. The entire area is generally without relief with elevations less than 50 m. The coastline is characterized by gravel spits, foreshore flats, post-glacial beach ridges, and shallow lakes and ponds surrounded by willows (Salix spp.). A more detailed description of Churchill’s coastal and inland areas is given by Ritchie (1962) and Clark et al. (1997). 2.2. Vigilance behaviour of polar bears Observations of vigilance behaviour of polar bears were recorded during day-to-day activities of tour companies from 1 October through 12 November 2000, usually between 0900 and 1600 h CST. The number of tundra vehicles around a bear during viewing, and visitor behaviour on board tundra vehicles could not be controlled. We examined whether a difference in vigilance of polar bears could be detected in the presence versus absence of tundra vehicles. We observed polar bears either with spotting scopes from an 8 m high wooden observation tower at Gordon Point, usually at distances of 200–1500 m, or videotaped bears from tundra vehicles using a SONY Handycam Video Hi8 camcorder. All observation times were recorded with digital stopwatches. Bears were identified as either males or females by accompanying cubs, body sizes, scars, and head and neck shapes (Knudsen, 1978). We focused only on resting bears (e.g., lying prone in one spot, head on ground, legs sprawled out or front legs tucked under body, with flank and hindquarters on ground, or curled up; Øritsland, 1970; Caro, 1987) because the conservation of energy at this time of year may be critical in the bear’s lifecycle (Castellini and Rea, 1992; Atkinson and Ramsay, 1995; Atkinson et al., 1996). Any disturbance during resting may result in increased energy expenditure or adverse physiological responses (Watts et al., 1991). In addition, focusing on resting bears provided the same starting point for data recording, it allowed comparison of data between bears with and without tundra vehicles, and it seemed practical as most bears approached by tundra vehicles were resting. Vigilance for this purpose
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was defined as head-up movements where the head of a bear was lifted to shoulder-level or above, while the animal was lying down. We used focal animal sampling (Altman, J., 1974) to record the number of head-ups (i.e., how often the head was lifted to shoulder level or above during the observation time), vigilance bout length (i.e., time (s) that passed between a head-up and when the head was lowered back to the ground), and between-bout intervals (i.e., interval (s) between the moment when the head was on the ground from a previous vigilance bout length and a subsequent head-up). We decided to record vigilance for approximately 30 min, or until the bears stood or sat up, or walked away. The selected time interval was based on our experience while we tested for clear and distinct visibility of head movements of polar bears: during tourist viewing activities, bears were generally resting for about 20–30 consecutive minutes before changing postures. In order to allow comparison of recorded data among bears and between the treatments (i.e., with versus without vehicles), data recording and timing for all observations began with the first head-up movement after a bear was selected for observation. All observations of polar bears were conducted in accordance with the Animal Care Committee of the University of Manitoba (Protocol F 00-001). 2.3. Study design Data were recorded for a ‘‘paired’’ and ‘‘unpaired’’ experimental design. For the paired design, the same bears were observed with and without tundra vehicles. We selected the animals using a random number table from bears that were present in the Gordon Point area after a 360-degree scan with spotting scopes from an observation tower. Whenever a bear was selected, we recorded specific marks, body shape, presence of cubs, and missing appendices to allow future identification of the same animal. We then recorded vigilance behaviour either with or without tundra vehicles. Vehicles were considered to be ‘‘present’’ if within 40 m (or about four tundra vehicle lengths; Dyck 2001). If, for example, a bear’s vigilance was first recorded in the presence of a vehicle, we waited until no vehicles were in the vicinity ( 1.5–2.0 km) of that bear for at least 30 min to record vigilance without vehicles. If that was impossible to achieve because of tundra vehicle activity in the study area, we either waited until all vehicles had left the study area, or we recorded vigilance the next day before tundra vehicles arrived in the study area. All resting bears with and without tundra vehicles present in the study area, excluding bears selected for the paired design, were potential subjects for the unpaired design. First, we randomly decided whether to record vigilance with or without vehicles. If vigilance without vehicles was selected, one bear was randomly
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chosen from all bears present in the study area that had no tundra vehicles present. We used the same procedure to select bears with vehicles. 2.4. Statistical analyses Individual observation times of vigilance behaviour of bears varied and could not be recorded for 30 min maximum at all times because bears got up and walk away for no apparent reason (when without vehicles), or because of tundra vehicle commotion (i.e. vehicles passing the bear being observed while other vehicles arrived or left the vicinity of that bear). For statistical purposes, we therefore expressed each variable measured on a bear as a proportion of the total observation time of that bear. Paired t-tests were applied to the paired design to examine whether differences between sex and tundra vehicle presence existed. Two-factor analysis of variance (ANOVA) was used to determine interactions between sex and presence versus absence of tundra vehicles for the paired design. For the unpaired design, we applied one-factor ANOVA to examine whether differences existed for bears with versus without vehicles. We used simple linear regression to determine if a relationship existed between the number of vehicles around a bear and the observed variables. Mann–Whitney U tests were performed to assess differences between total vigilance time for bears with/without vehicles, and to determine whether time of day (i.e., early versus late) affected vigilance response of polar bears (Zar, 1999). All tests were two-tailed, and considered significant at =0.05. Values are expressed as mean SE.
3. Results We recorded vigilance behaviour on 43 individually identified bears, with 10 bears (six males and four females with cubs; all adults observed with and without tundra vehicles) for the paired, and 33 bears (all males; 10 with and 23 without tundra vehicles) for the unpaired design. Mean SE observation time for vigilance behaviour per bear was 20.7 1.1 min (n=53). The mean number of tundra vehicles (TV) per bear, associated with polar bear viewing activities was 2.3 0.3 TV (n=33; range: 1–7). 3.1. Behavioural results For the paired design, an interaction between sex and tundra vehicle presence or absence was detected for the numbers of head-ups (F1=16.09, P=0.001) and between-bout intervals (F1=4.67, P=0.046). Males showed a significant increase in head-up responses during vehicle presence (t5=5.9, P=0.002, n=6, effect size d=1.68, power of G-test P=0.747), whereas females’
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6.81.9 (4–12) 8.82.0 (3.8–12.6) 146.2 21.9 (111.8–210.0) 17.01.9 (11–24) 17.84.8 (7.8–40.7) 81.38.9 (52.6–104.4) 12.9 1.5 (4–33) 13.2 1.9 (4.8–50.6) 93.2 11.1 (24.6–184.1)
head-up frequency increased during vehicle absence, although not significantly. Between-bout intervals for males increased during vehicle absence, and for females during vehicle presence, but not significantly. (Fig. 1). Significant effects in the unpaired design were detected for the frequency of head-ups and the length of between-bout intervals. Tundra vehicle presence elicited a greater frequency of head-ups (F33=11.06, P=0.002, effect size d=1.10, power of G-test P=0.804), whereas vehicle absence increased the length of between-bout intervals (F33=7.76, P=0.009, effect size d=0.95, power of G-test P=0.679). As in the paired design, vigilance bout length was not affected significantly by vehicle presence or absence (Fig. 2). Descriptive statistics of the non-transformed frequencies of head-ups, vigilance bout lengths, and between-bout intervals in the presence and absence of vehicles, are given in Table 1.
4.00.9 (1–6) 8.62.6 (2.5–20.8) 606.9 150.0 (262.8–1211.0) HU (#) VBL (s) BBI (s)
6.8 1.5 (0–17) 12.5 3.4 (0–31.6) 507.1217.9 (77.7–1800)
10.52.9 (7–19) 12.52.8 (7.8–19.3) 122.940.3 (52.7–223.6)
Females (n=4) Males (n=6) Males (n=6) Males (n=10) Sex Variables
Paired Study design
Unpaired
Females (n=4)
Males (n=23)
Paired Unpaired
With Tundra Vehicle Without Tundra Vehicle
Table 1 Non-transformed descriptive statistics, presented as mean SE (range), for the numbers of head-ups (HU), vigilance bout length (VBL), and between-bout intervals (BBI) for polar bears with and without tundra vehicles of the unpaired and paired study design
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Fig. 1. Frequency of head-up, vigilance bout length, and betweenbout intervals as proportion of total observed time, for male and female polar bears in the presence and absence of tundra vehicles (TV) at Churchill [Note: Error bars represent SE; *: P=0.002 at =0.05].
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Simple linear regression indicated no significant relationship between the measured variables and the number of tundra vehicles for bears of the unpaired design. Low number of vehicles and small sample size for the paired design did not allow similar analyses. Comparisons of the variables collected between 0900 and 1115 h (first 33 percentiles) with times between 1330 and 1545 h (66–100th percentile) did not indicate a significant temporal variation in responses (head-up: U=10, Nlate=10, Nearly=5, P=0.066; vigilance bout length: U=15, Nlate=10, Nearly=5, P=0.086). There was a two-fold increase in total time spent vigilant as proportion of total time observed for bears of the unpaired design with tundra vehicles (0.175 0.03 s, range 0.034–0.614 s, n=23), as opposed to bears without vehicles (0.087 0.027 s, range 0–0.284 s, n=10), although not significant (U=65, Nwith=23, Nwithout=10, P=0.050). For the paired design, total vigilance increased significantly about seven-fold for bears with vehicles (t5=3.309, P=0.021, n=6; 0.208 0.053 s, range 0.055–0.381 s) as compared to bears without vehicles (0.027 0.012 s, range 0.004–0.087 s).
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generally conflicts with other activities (Brick, 1998, McAdam and Kramer, 1998). In our study, it conflicted with resting behaviour of bears. While on land, polar bears feed little, they live of their stored fat reserves and preserve energy by spending most of their time resting (Watts and Hansen, 1987). While polar bears live off their stored fat, body mass loss per day (BML/d) ranges between 0.25 and 1.05 kg, depending on age (Derocher and Stirling, 1995). The increase in vigilance response, in particular the head-up motion and maintenance of the head at shoulder levels for periods of time, could result in metabolic increases. Moreover, metabolism could be increased because of elevated heart rates. Tourists approaching wildlife [e.g., Ade´lie penguins (Pygoscelis adeliae), mountain sheep (Ovis canadensis)] can cause significant increases in heart rate of animals (MacArthur et al., 1982; Giese, 1998). A polar bear’s heart rate rises from 33 beats/min during sleep to 46 beats/min while lying awake (Øritsland et al., 1977), and
4. Discussion Vigilance behaviour of polar bears in the Gordon Point area at Churchill, Manitoba was significantly affected by the presence of tundra vehicles. In particular, the frequency for head-ups increased and the between-bout intervals decreased in the presence of tundra vehicles. Male bears of the paired design exhibited a similar response pattern in the absence and presence of vehicles, as did bears of the unpaired design. However, it is unclear from our study whether the vehicles or vehicle commotion alone elicited the observed responses, or if a combination of visual (i.e., vehicle, visitors on vehicles), acoustic (i.e., noise of visitors and vehicles), and olfactory stimulation (i.e., smell of vehicles, tourists, food) caused an increase in vigilance. During our study, when a single vehicle approached a bear during viewing activities and remained stationary for 120 min, habituation to the vehicle occurred, the numbers of head-ups decreased, and between-bout intervals increased after 90 min, similar to responses of vehicle absence (Dyck and Baydack unpublished data). This suggests that vehicle commotion may be the primary stimulus, however, manipulative studies would need to examine this in detail. When animals are presented with a stimulus (e.g., predator), an increased vigilance response can be the result (e.g., Quenette, 1990). In our study, the frequency of head-ups for males increased two-fold from vehicle absence to presence. In addition, the between-bout intervals were three times greater during vehicle absence as compared to presence (Fig. 2). Vigilance behaviour
Fig. 2. Frequency of head-up, vigilance bout length, and betweenbout intervals as proportion of total observed time, for male polar bears in the presence and absence of tundra vehicles (TV) at Churchill [Note: Error bars represent SE; a: P=0.002; b: P=0.009; =0.05].
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probably increases further while being approached by a tundra vehicle. In polar bears, heart rate has been shown to be an indicator of metabolism, where metabolism increases as heart rate becomes elevated (Øritsland et al., 1977; Best et al., 1981). Tourist activities at Gordon Point last approximately for 45 days (Dyck, 2001), and an additional increase in BML/d could have an effect on individual fitness if bears tend to stay in this area for a prolonged period of time, especially if individual bears are exposed repeatedly to these stimuli. This increase in BML/d could be even greater if behavioural displacement of bears by tundra vehicles occurs. The variables we measured for male bears were not magnified with an increase in numbers of tundra vehicles. Presence of a single vehicle was enough to elicit greater responses. Vigilance incurs costs (Treves, 2000), and only in case of a direct perceived threat or risk would increased vigilance (and increased costs) be advantageous to the scanning animal (Hunter and Skinner, 1998). We therefore suggest that vigilance behaviour of polar bears during wildlife viewing activities is a response similar to predator avoidance (Arenz and Leger, 1999a, b; Toı¨go, 1999). Animals perceive objects, process information, make decisions and solve problems (Griffin, 1992). Polar bears obviously are aware of their environment (e.g., being on the ice versus being on land), and components within their physical environment (e.g., conspecifics, other animals, humans and their artefacts). Moreover, polar bears should be capable of discerning different objects from one another, for example icebergs from tundra vehicles (e.g., both are white but distinctively different). Vehicles present an anthropogenic stimulus, which may be perceived by bears as ‘‘out-of-place’’, where the outcome of a possible threatening interaction is unknown, especially since vehicles are more than five times the size of bears. Female response to vehicle presence was not as expected. Frequency of head-ups was lower and lengths of between-bout intervals were greater during vehicle presence. Our sample size for females was small, and we can only speculate about the interpretation of the results. The data indicate that females appeared to be more ‘‘comfortable’’ in the presence of vehicles. Where males may perceive tundra vehicles as a threat, females may use them as a ‘‘safety buffer’’ to protect their offspring from male bears. This is supported by the increased head-up frequency and decreased lengths of between-bout intervals in the absence of vehicles, which may serve the detection of conspecifics and avoidance of infanticide (Steenbeek et al., 1999), thereby indirectly protecting offspring. During vehicle absence, resting polar bears showed vigilance behaviour. During fall, the Gordon Point area is a congregation site on shore where bears of all age and sex classes wait for the first ice to form on Hudson
Bay. Bear density in this area can reach a minimum of about 20 bears/50 km2 (Dyck, 2001) as compared to 1–7 bears/1000 km2 for other polar bear populations while distributed in their habitat (Derocher and Taylor, 1994). Polar bears have no natural predator, and the only harm is from conspecifics. Male bears engage in playfight bouts (Latour, 1981) or fight for females during the mating season (Ramsay and Stirling, 1986). Also, infanticide and cannibalism have been observed where male bears kill other bears or offspring for various reasons (Taylor et al., 1985; Derocher and Wiig, 1999; Dyck and Daley, 2002). We suggest that the primary function of vigilance without vehicles is observation of conspecifics (e.g., Caine and Marra, 1988; Roberts, 1988). However, Quenette (1990) pointed out the importance of the context in which vigilance occurs. For example, during mating season, vigilance may serve the purpose of observing conspecifics and detecting mates or competitors (e.g., Baldellou and Heinzi, 1992; Cowlishaw, 1998). Vigilance bout lengths for male bears did not differ in the presence and absence of vehicles. Bears may have been selected to scan their surrounding for a specific time to be effective in assessing the immediate vicinity, independent of the presence of a stimulus (Dimond and Lazarus, 1974). These ‘‘programmed’’ scans may prove selectively advantageous to minimize risk of injury or death when faced with opponents or mates (Maynard Smith and Parker, 1976; Clutton-Brock et al., 1979). Polar bear viewing from tundra vehicles is generally safe, and it enables thousands of tourists from all over the world to experience and learn about polar bears and their habitat. Where usually a distance between viewer and wildlife is encouraged (i.e., McNeil River, Alaska), Churchill tourists view bears from a close distance (Herrero and Herrero, 1997). The effects of tundra vehicle activities during polar bear viewing were measured using vigilance. We believe that vigilance behaviour could be a non-invasive and simple method to monitor wildlife behaviour in the context of wildlifeviewing activities. Wildlife managers can be trained to record appropriate behaviours, and to evaluate whether changes in the wildlife response occurred over time. For Churchill specifically, we suggest manipulative studies that examine how tundra vehicle distances to bears and commotion in the immediate vicinity of bears affect vigilance.
Acknowledgements This study was logistically and financially supported by Manitoba Conservation, The Great Bear Foundation Missoula, Born Free Foundation U.K., the Wyoming Chapter of The Wildlife Society, the Northern Science Training Program of the University of Manitoba, a
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Northern Research Fund by the Churchill Northern Studies Centre, J. Hare, R. Brook, W. Bernhardt, Tundra Buggy1 Tours Ltd., Great White Bear Tours Inc., Counter Assault, Coleman, countless Churchill residents, and P. Hebert. We are indebted to G. McBride, R. Pilkington, and K. Daley for their excellent assistance in the field. We are also grateful for comments on earlier drafts of the manuscript by G. Wright and an anonymous reviewer. Their constructive criticism improved the quality of the final version.
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