DOI: 10.5061/dryad.5tb2rbp7s
title: Behavioral responses of a large, heat-sensitive mammal to climatic variation at multiple spatial scales

description: 1. Climate warming creates energetic challenges for endothermic species by
 increasing metabolic and hydric costs of thermoregulation. Although
 endotherms can invoke an array of behavioral and physiological strategies
 for maintaining homeostasis, the relative effectiveness of those
 strategies in a climate that is becoming both warmer and drier is not well
 understood. 2. In accordance with the heat dissipation limit theory, which
 suggests that allocation of energy to growth and reproduction by
 endotherms is constrained by the ability to dissipate heat, we expected
 that patterns of habitat use by large, heat-sensitive mammals across
 multiple scales are critical for behavioral thermoregulation during
 periods of potential heat stress and that they must invest a large portion
 of time to maintain heat balance. 3. To test our predictions, we evaluated
 mechanisms underpinning the effectiveness of bed sites for ameliorating
 daytime heat loads and potential heat stress across the landscape while
 accounting for other factors known to affect behavior. We integrated
 detailed data on microclimate and animal attributes of moose Alces alces,
 into a biophysical model to quantify costs of thermoregulation at fine and
 coarse spatial scales. 4. During summer, moose spent an average of 67.8%
 of daylight hours bedded, and selected bed sites and home ranges that
 reduced risk of experiencing heat stress. For most of the day, shade could
 effectively mitigate the risk of experiencing heat stress up to 10°C, but
 at warmer temperatures (up to 20℃) wet soil was necessary to maintain
 homeostasis via conductive heat loss. Consistent selection across spatial
 scales for locations that reduced heat load underscores the importance of
 the thermal environment as a driver of behavior in this heat-sensitive
 mammal. 5. Moose in North America have long been characterized as
 riparian-obligate species because of their dependence on woody plant
 species for food. Nevertheless, the importance of dissipating endogenous
 heat loads conductively through wet soil suggests riparian habitats also
 are critical thermal refuges for moose. Such refuges may be especially
 important in the face of a warming climate in which both high
 environmental temperatures and drier conditions will likely exacerbate
 limits to heat dissipation, especially for large, heat-sensitive animals.
description: Bed site data: We placed mini weather stations (Kestrel
 Instruments 5500 Weather Meter, Boothwyn, PA) at four bed sites at a time,
 which we randomly selected from bed sites used by an individual moose
 during the previous two weeks. We collected data on three available sites
 for each used site (4 used sites with 3 random sites each; 16 total
 weather stations per day). We defined available bed sites as those at a
 random distance (values between 15m and 330m sampled uniformly via random
 number generator) at a random angle (values between 1 and 359 degrees
 sampled uniformly via random number generator). We set the distance
 boundary by averaging the daily mean displacement of adult female moose in
 the Snowy Mountain Range during the summer (June–September) of 2017. Sites
 were selected based on the physical location determined by distance and
 angle away from the bed site and in a space large enough to accommodate a
 bedded moose. We placed a mini weather station in the
 approximate center of each used bed site. Available sites did not have
 matted vegetation; thus, we determined the center of the available bed
 site by choosing an area in which a moose could bed down. The weather
 stations collected data on temperature, wind speed, and relative humidity
 every five minutes and were left in place for at least 24 hours to capture
 one entire day from sunrise to sunset.  We installed the mini weather
 stations on small tripods ~30 cm off the ground (approximate center of the
 core of a bedded moose) on a rotating mount with a wind vane to enable the
 meter to accurately track wind speed.  We collected
 additional data on landcover type, canopy cover, and a qualitative measure
 of soil moisture at visited bed sites. We measured canopy cover at the
 four corners of the bed site using a GRS densitometer (Graphic Resource
 Solutions, Arcata, CA; Paletto & Tosi 2009), resulting in a
 percentage canopy cover reported in 25% increments.  We measured canopy
 cover from 0.75-m above the ground to approximate the height of the head
 of a bedded moose. Landcover type at the bed site and the immediate area
 was classified as either pine, aspen, wet meadow complex, sagebrush
 (<em>Artemisia</em> spp.), high-alpine tundra, meadow, or
 burned area. Roughly 78% of the study area was forested, the majority of
 which (~65%) was dominated by lodgepole pine (Pinus contorta). Other pine
 species included Engelmann spruce
 (<em>Picea</em> <em>engelmanii</em>) and subalpine
 fir (<em>Abies</em> <em>lasiocarpa</em>). Forests
 in the study area were heavily affected by a mountain pine beetle
 (<em>Dendroctonus</em> <em>ponderosae</em>) epidemic in 1996, and many standing dead trees remained (Dillon et al. 2005).  In addition to the dominant conifer species, stands of quaking aspen (<em>Populus</em> <em>tremuloides</em>) accounted for ~3.8% of the land area. Wet meadow complexes (riparian areas) comprised of several willow species (<em>Salix</em> spp.), mountain big sagebrush (<em>Artemisia</em> <em>tridentata</em> ssp. <em>Vaseyana</em>), alpine meadows, and small areas of high-alpine tundra accounted for the remaining 18.2% (Dillon et al. 2005). In July 2018, the northeast corner of the study area burned. Several moose used this area both before and after the fire, and thus we did not censor any data from the fire-affected area. There were many wet landcover types in the Snowy Mountains ranging from riparian to wet meadows, ponds, fens, or some combination thereof; for our purposes, we refer to them as riparian. Given the limited number of bed sites occurring in some vegetation classes, we combined fire-affected areas, sagebrush, and dry meadows into a category we refer to as other. If the site was in an area of mixed vegetation, we recorded the predominant type. Roughly 78% of the study area was forested, the majority of which (~65%) was dominated by lodgepole pine (Pinus contorta). For the bed-site analysis, we used microclimate data from the Kestrel weather stations in used and available bed sites in each vegetation class to parameterize the microclimate model. We averaged daily minima and maxima for each variable (i.e., temperature, wind speed, and humidity) over each week of the summer which was then used by the Niche Mapper microclimate submodel to calculate profiles for the “average” day each week.  We used two scenarios for canopy cover to capture the full range of variation: maximum percent canopy cover for the vegetation class in question or the minimum percent canopy cover (averaged from recorded bed site data). Large weather station data: We installed 5 large weather stations in different landcover types throughout the study area (Snowy Mountain Range, WY, USA) in May of 2018, and stations were left in place through December 2019. We used HOBO micro-station data loggers programmed to record weather data every five minutes continuously throughout the day. We mounted HOBO 12-bit temperature and relative humidity sensors in radiation shields and fit them on a 2-m tripod with a HOBO wind sensor set (measures wind speed and direction) attached to a cross arm at the top of each station. We installed each station in a different landcover type; aspen, intact pine, beetle-killed pine, sagebrush, and wet meadow complex. Data were then averaged over each hour for each climate variable. Minimum and maximum values were also recorded for each hour.
description: For these purposes, the bed site and large weather station data
 are uploaded as CSV files that can be opened using Excel.