American Black Bear Thermoregulation at Natural and Artificial Water Sources Authors: Michael A

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American black bear thermoregulation at natural and artificial water sources Authors: Michael A. Sawaya, Alan B. Ramsey, and Philip W. Ramsey Source: Ursus, 27(2) : 129-135 Published By: International Association for Bear Research and Management URL: https://doi.org/10.2192/URSU-D-16-00010.1

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American black bear thermoregulation at natural and artiﬁcial water sources

Michael A. Sawaya1,3, Alan B. Ramsey2,and in 3 ways to avoid local extinction: (1) move up in ele- Philip W. Ramsey2 vation, (2) move toward the poles, and (3) alter behavior. However, these population-level responses are too 1Sinopah Wildlife Research Associates, Missoula, poorly understood to be much use to managers (Moritz MT 59802, USA and Agudo 2013). Thermoregulatory behavior may allow 2MPG Ranch, Missoula, MT 59803, USA local terrestrial wildlife populations to cope with escalat- ing thermal stress from solar radiation if conditions are Abstract: Water is essential for hydration in American favorable. However, more research is needed to under- black bears (Ursus americanus) and other species; how- stand the physiological mechanisms of complex organ- ever, its role in thermoregulation is poorly understood. isms, such as bears (Ursidae), to cope with the ecological In 2010, we established a network of remote cameras effects of climate change on species and communities to monitor wildlife in the Bitterroot Valley, Montana, (Portner and Farrell 2008). USA. One of our objectives was to document and de- American black bears (Ursus americanus; hereafter, scribe American black bear behavior at natural and arti- black bears) are particularly vulnerable to hyperthermia ﬁcial water sources. We detected male and female adult, because of their large, warm-blooded bodies with dark, subadult, and cub of year black bears immersing in wa- heat-absorbent coats, thick layers of fur and subcutaneous ter sources to thermoregulate. Bear use was concentrated fat, and lack of functioning sweat glands. The thick insu- at one livestock tank, one road puddle, and one pond lation of black bears allows them to maintain homeostasis in areas with relatively little human disturbance. Bear during hibernation but can lead to hyperthermia during use steadily increased over summer, peaking in late sum- warmer temperatures (Hellgren and Vaughan 1989) be- mer when ambient temperatures were high and fat lay- cause mammals have a relatively narrow thermal window ers were thick. Our results demonstrate that water is an to maintain their body temperatures within upper and important thermoregulatory resource for some bear pop- lower critical temperature limits (Terrien et al. 2011). ulations, though more research is needed to understand Black bear problems with heat stress are compounded how ursids use behavioral thermoregulation to dissipate in northern habitats such as Montana, USA, where bears excess body heat and avoid hyperthermia. must develop thick fat layers for long hibernation pe- riods, have an extremely condensed amount of time to Key words: anthropogenic, behavioral thermoregula- acquire annual nutrition (Jonkel and Cowan 1971), and tion, climate change, cold-water immersion, hyper- have limited opportunities for adjusting foraging strate- thermia, livestock tanks, Montana, physiology, ponds, gies. Black bears dissipate excess heat through a variety remote cameras, temperature, Ursus americanus of behaviors such as panting, balancing energy expendi- tures and caloric intake, resting in shaded day beds, lying DOI: 10.2192/URSUS-D-16-00010.1 with their belly touching cool ground, and immersing in Ursus 27(2):129–135 (2016) water. Swimming behavior has been commonly observed in black bears and grizzly bears (U. arctos) in many ge- Temperature is one of the primary factors shaping ographic areas, including Yellowstone National Park, biological systems and driving patterns of biodiversity Wyoming, USA (Gunther et al. 2015), though little (Stegen et al. 2009, Dell et al. 2011); however, behav- is known about the importance of this behavior as ioral mechanisms for maintaining core body tempera- a mechanism for thermoregulation. In 2009, we de- tures within thermoneutral zones remain poorly under- ployed a remote camera network to examine patterns stood. Climate change causes species extinction through in wildlife distribution, abundance, and behavior at MPG biotic and abiotic processes, such as exceeding physi- Ranch in the northern Bitterroot Valley, Montana. One cal heat tolerance and changing food availability (Cahill of our objectives for this broader multi-species study et al. 2012). Species can respond to a warming planet was to document and describe black bear thermoregulatory behavior observed at natural and artiﬁcial water 3email: [email protected] sources.

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Fig. 1. The 3,844-ha MPG Ranch study area where, in 2010, we established a network of remote cameras to monitor American black bears and other wildlife in the northern Bitterroot Valley, Montana, USA.

Study area primarily consists of open, west-facing, grass-covered Our 3,844-ha study area at MPG Ranch is located in the slopes with narrow deciduous woody draws that lead to northern Bitterroot Valley of western Montana (Fig. 1). bottomland riparian cover types of the Bitterroot River MPG Ranch was purchased in 2009 and transitioned to a floodplain (Noson and Rodriguez 2015). The climate is conservation property after >100 years of intensive live- temperate with relatively short, sunny summers, and long, stock use. MPG Ranch’s mission is to promote conserva- snowy winters. Average high monthly temperatures in ◦ tion through restoration, research, education, and infor- nearby Missoula, Montana, range from 29.9 CinJulyto ◦ mation sharing. One of the main objectives of the ecologi- −0.6 C in December (www.usclimatedata.com). Eleva- cal restoration efforts is to mitigate the effects of livestock tions range from the summit of Mt. Baldy (1,833 m) to the use on the land, including the removal of livestock fence. river floodplain (966 m). Tree species include Douglas However, >16 livestock tanks were kept operable to pro- fir (Pseudotsuga menziesii), subalpine fir (Abies lasio- vide drinking water and aquatic habitat for a variety of carpa), Ponderosa pine (Pinus ponderosa), and quaking mammals, birds, reptiles, and amphibians. MPG Ranch aspen (Populus tremuloides). Common large mammal

Ursus 27(2):129–135 (2016)

species include black bear, coyote (Canis latrans), elk ponds. We distributed remote cameras along game trails, (Cervus elaphus), moose (Alces alces), mountain lion water bodies, and other sites where food or other re- (Puma concolor), mule deer (Odocoileus hemionus), and sources were concentrated to maximize photographic de- white-tailed deer (O. virginianus). Seasonally available tections of bird and mammal species. The number of black bear foods include horsetail (Equisetum spp.), black operable camera-trap nights varied considerably across hawthorn (Crataegus douglasii), common chokecherry cameras and was unknown for many sites; therefore, we (Prunus virginia), and serviceberry (Amelanchier alnifo- report minimum counts, but we did not calculate de- lia); domestic apple trees (Malus domestica) also occur tection rates or perform statistical analyses (except a chi- on the ranch and provide a wildlife food source in the square test) because inoperable cameras may have missed autumn. detections. We used remote photographs from Buckeye cameras to examine general spatial and temporal patterns of black bear detection; whereas, we used remote videos Methods from Stealth Cams to document and describe thermoregu- Between 25 August 2010 and 31 December 2015, we latory behavior at natural and artificial water sources. We established and monitored a network of 60 Buckeye X80 used a chi-square test with remote video data in Program Wi-Fi–enabled remote cameras (Buckeye Cam, Athens, Excel 2016 (Microsoft Corporation, Redmond, Washing- Ohio, USA) at MPG Ranch (Fig. 1) to monitor wildlife ton, USA) to examine the hypothesis that the frequency behavior, abundance, and distribution. Buckeye cameras of bear immersion in water was related to temperature sent photographic images via email when triggered and (i.e., month) and independent of bear presence in the stored images on Secure Digital cards that we down- area (i.e., videos away from water or “other videos”). loaded every 3–6 months. We classified remote photos in Ho = bear immersion in water (no. of videos at water) a Filemaker Pro (Filemaker Inc., Santa Clara, California, and bear presence in area (no. of other videos) are not USA) database. We considered detections at the same independent. camera as unique events if images were separated by >2 hours. We recorded the camera location, date, time, temperature (◦C), and species for all camera detection events. Results For black bear images, we also recorded the following We classified >60,000 images from Buckeye cameras behaviors related to use of natural and artificial water and found 146 black bear detection events, of which 106 sources: touches water source, drinks from water source, occurred at livestock tanks. Our earliest bear detection and immerses in water source. was on 26 August 2010 and the latest bear detection was Between 5 January 2010 and 31 December 2015, we on 27 October 2015. We detected bears at 8 Buckeye established a network of 277 Bushnell Stealth Cams cameras, including 2 of the cameras at livestock tanks (Bushnell Outdoor Products, Overland Park, Kansas, (Fig. 2). Bear detection events were more frequent at USA) to document wildlife behavior, including 4 cameras North Draw Tank (N = 60) than at Sheep Camp Tank (N = that were set up at water sources deep enough for bear 46). Of the 106 detections at livestock tanks (Fig. 3), bears immersion (2 artificial livestock tanks, 1 artificial road touched the livestock tank 72 times, immersed in the puddle, 1 natural creek pond). Additionally, we video- tank 38 times, and drank 21 times (some events had >1 monitored, and collected hair samples from, 10 barbed- behavior observed so numbers do not sum to 106). The wire bear hair traps (Woods et al. 1999) and 10 bear rub latest that we observed immersion during a year was on 16 trees (Kendall et al. 2008, Sawaya et al. 2012). When trig- October 2015. Temperatures for bear detections ranged gered, Bushnell Stealth Cams recorded 1-minute video between −2.2◦C and 46.1◦C(x¯ = 18.9◦C and median clips stored on Secure Digital cards that we downloaded = 16.7◦C for all detections, x¯ = 24.4◦C and median = every 3–6 months. We used video footage to identify sex 24.4◦C for detections where immersion was observed; class (male, female) and age class (adult, subadult, cub temperatures recorded by remote cameras located in full of year) of black bears based on their morphology and sun may be higher than actual ambient temperatures). presence of dependent offspring. We confirmed bear sex Bear detections increased over the course of a summer, identities from photographic imagery with DNA collec- peaking in August and September (Fig. 3). tion and analysis following Sawaya et al. (2012) when- We classified >10,000 videos from Stealth Cams and ever possible. found black bears in 5423 of them, including 999 records Our remote cameras targeted a variety of species and at natural or artificial water sources. Our earliest bear cover types, including black bear at livestock tanks and video was captured on 20 August 2010 and the latest

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Fig. 2. Remote photographs of American black bears immersing in livestock tanks between 2010 and 2015 on the MPG Ranch study area in the northern Bitterroot Valley, Montana, USA.

video was captured on 28 October 2015. We detected was greatest during the warmest months of July and Au- bears at 215 of 277 Stealth Cam locations. We observed gust (Fig. S1). Black bear use of the most heavily used 170 events when bears immersed in water sources (n water source in our study area, Davis Creek pond, was = 61 in 2012, n = 50 in 2014, n = 59 in 2015; cam- concentrated during the hottest times of the day (Fig. S2). eras were inoperable for 2013), including 43 long swims One individual black bear exhibited some interesting be- (i.e., immersion lasting >100 sec). We identiﬁed male havior on multiple occasions by attempting to ﬂoat on and female bears of all age classes immersing in waits back while occasionally dipping its nose in water and ter sources, including mothers with dependent offspring balancing with wet paws in the air (Video S1). Multiple (Video S1). The number of black bear videos recorded at bears scent-marked at the pond site by rubbing or shaking water sources on the study area between 2010 and 2015 off on a nearby bear rub tree (Video S1). peaked in July and August (Fig. 4). Our chi-square test results (P-value < 0.001, α = 0.05) led us to reject our null hypothesis—Ho = bear immersion in water (no. of Discussion videos at water) and bear presence in area (no. of other Thermoregulatory behavior can help to offset heat videos) are not independent. The proportion of all bear stress and maintain homeostasis for some mammal videos at Davis Creek pond and proportion of long swims species (Terrien et al. 2011), yet it remains poorly

Ursus 27(2):129–135 (2016)

Fig. 3. Frequency of American black bear behaviors observed at livestock tanks between 2010 and 2015 in MPG Ranch study area located in the northern Bitterroot Valley, Montana, USA.

understood despite its potential benefits to individual fit- area and by Gunther et al. (2015), who observed griz- ness and survival. Our results suggest that natural and zly bears scent-marking on the edge of a water source in artificial water sources play an important role in allowing Yellowstone National Park. black bears at MPG Ranch to thermoregulate and coun- We observed some interesting behavioral, spatial, and teract the negative physiological effects of heat stress. temporal patterns of water source use by black bears. We detected bears of all sex and age classes on the ranch Our dense and widely distributed remote camera net- immersing in water to cool down. We conclude that nat- work allowed us to capture extensive documentation of ural and artificial water sources such as beaver (Castor thermoregulatory behavior. The repeated back-floating canadensis) ponds and livestock tanks can be valuable behavior that we captured at Davis Creek pond may help resources for ursid populations. This idea is supported to maximize evaporative cooling in areas with the great- by the scent-marking behavior that we observed by black est concentrations of blood vessels (e.g., nose, paws). bears at bear rub trees near water sources in our study Although black bear spatial use is highly concentrated at

Fig. 4. Number of 1-minute remote-video-camera clips of American black bears recorded by month at water sources on the MPG Ranch study area in the northern Bitterroot Valley, Montana, USA, between 2010 and 2015.

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1 pond, 1 road puddle, and 2 livestock tanks, high pro- temperatures of captured animals during immobilization portions of the total number of bear videos recorded on (Hellgren and Vaughan 1989, Ozeki et al. 2015). the study area during June, July, and August came from Several factors combine to make northern black bears water sources. The results of our chi-square test suggest highly susceptible to heat stress in late summer because that this relationship between immersion frequency and the rapid weight gain during hyperphagia, when bears temperature was not due simply to bear presence in the must move around and consume calories to meet extreme area. It is likely that bears selected these immersion sites, caloric demands, adds a layer of subcutaneous fat that especially the livestock tanks, for remoteness from hu- substantially thickens and inadvertently insulates during man presence, and proximity to good cover and berry some of the hottest months of the year. Black bears hiber- patches (e.g., chokecherry, hawthorn). Bears used North nating in colder temperatures expend more energy during Draw tank more than Sheep Camp tank, whereas their hibernation than in warmer conditions; therefore, bears activity at Sheep Camp tank was more nocturnal. North in more northern latitudes may need greater energy re- Draw tank is surrounded by heavy cover and is located serves (i.e., fat) to survive colder winters than do bears inside a designated wildlife security zone that receives in more southern latitudes (Toien et al. 2015). Black bear relatively little human disturbance compared with Sheep use of water sources in our study area increased steadily Camp tank. This pattern of use suggests that black bears over the summer, peaking in August and September when require a relatively high degree of security at thermoreg- late summer berry crops were ripe, subcutaneous fat lay- ulatory sites, perhaps because they are extra-sensitive to ers were thick, and ambient temperatures were relatively disturbance when immersing in water sources because of high. The physiological benefits of cold water immersion their increased vulnerability and potential to encounter may be tremendous to ursids during this critical period humans, bears, or other wildlife. of food acquisition, because they can quickly cool their Ursids use freshwater sources for a number of rea- large (and expanding) bodies and return to foraging in- sons, including grooming, dead hair removal, tool use, stead of losing valuable calories by spending potential sibling play, fishing, scent-marking, dispersal, hydration, foraging time remaining inactive in the shade. and thermoregulation. We documented many of these Black bears are distributed primarily in the cooler, behaviors and believe that bears are using natural and northern regions of North America, though they occur artificial water sources in our study area for thermoregu- as far south as Florida, USA, and Mexico (Scheick and lation because bears fully immerse in the water, and use McCown 2014). Black bears in the open, arid mountains is greatest during the hottest months and times of day. of western North America are challenged in acquiring Core body temperatures (Tb) of pre-hibernating black adequate nutrition for winter hibernation without having bears implanted with temperature sensors ranged from to spend time in day beds when food sources may be 37◦ to 38◦C(Toien et al. 2015). Rectal temperatures of abundant, but patchy and fleeting. Thermal shelters such trap-stressed, chemically immobilized black bears ranged as beaver ponds or livestock tanks could be increasingly from 35.5◦ to 43.0◦C and varied by sex and season in valuable to large-bodied mammals, such as bears, in the the Great Dismal Swamp; bears began showing signs of face of climate change by providing much-needed relief hyperthermia when rectal temperatures were ≥42.0◦C from intensifying solar radiation. Our results show that (Hellgren and Vaughan 1989). Although black bears are thermoregulatory behavior is common in our study area most active in the summer months, bears significantly and both natural and artificial water sources are impor- decreased activity patterns when ambient temperatures tant to this bear population. Consequently, we urge land were >23.0◦C in Great Smoky Mountains National Park, and wildlife managers to consider the benefits of aquatic Tennessee, USA (Garshelis and Pelton 1980) and when restoration (e.g., beaver re-introductions) and the effects ambient temperatures were >20.0◦C in the Greater Yel- of removal or alteration of water sources when setting lowstone Ecosystem (Schwartz et al. 2010). The median environmental policy or making land management deci- temperature during our observations of full-body immer- sions. Black bears are frequently observed immersing in sion in water was 24.4◦C, which is higher than the re- swimming pools and this may become a more common ported temperature thresholds for black bear inactivity occurrence with climate change, leading to increasing (Garshelis and Pelton 1980, Schwartz et al. 2010). Many potential for human–bear conflicts as upper critical tem- medical professionals consider cold-water immersion to perature limits for bears are more frequently approached. be the gold standard for treating hyperthermia in humans Although our results demonstrate that water sources are (Homo sapiens; Casa et al. 2007). In fact, bear biologists an important resource for bears beyond providing hydra- have used water for many years to bring down core body tion, more research is needed to understand how ursids

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