Influence of the thermal environment on forest cover selection and activity of moose in summer
Creators: name: Demarchi, Michael W.
Publisher: name: University of British Columbia
Year: 2008

description: I investigated summer thermal cover and the influence of the thermal environment on habitat selection and activity of moose (Alces alces). Hemispherical photography was used to estimate the sky view factor (SVF) and effective leaf area index (Le) of coniferous stands as a function of crown closure class (CCC) values from forest cover maps. Moosehorn readings taken at hemispherical photo sites indicated that the CCC scheme correctly ranked stands by canopy closure. The stand attributes of SVF and Le, together with weather data collected in the study area, were entered into a model that simulated the operative temperature (Te) experienced by a moose. 'Hot' conditions existed when Te in the open (Teopen) exceeded the upper limit of the upper critical temperature (UCT) range of moose (Te &gt;29.5 °C). 'Cool' conditions existed when Teopen was below the lower limit of the UCT range (Te &lt;13 °C). Other research has shown that moose are very prone to thermal stress. During the study, weather conditions were encountered that had the potential to thermally stress moose. Simultaneous Te values declined exponentially with increasing CCC, indicating that a gradient of thermal cover existed across CCCs. At CCCs greater than 4, little additional thermal cover value was realized. Two hundred and fifty two radio locations were made on four adult cow moose. Because 'hot' and 'cool' weather conditions corresponded to 'light' and ‘dark' conditions respectively, the effects of heat and light on habitat selection were indirectly assessed. Moose selected increased cover during 'hot' (thus ‘light') conditions (p &lt; 0.05). The patterns of habitat selection during 'light’ conditions indicated that relative use of CCC = 0 sites increased significantly (p &lt;0.05) as Te open decreased. Shade from willow canopies and convection by water may have allowed or caused moose to use some CCC = 0 sites when ambient conditions exceeded the UCT. When Teopen was 'hot' (thus 'light’ conditions), moose located under coniferous cover tended to remain under such cover during subsequent locations. These observations support the conclusion that the thermal environment influenced habitat selection. No correlations between the moose location attributes of distance to an edge/water/road and time of day or Te open were found. Moose activity/inactivity was inferred from modulating/non-modulating radio signals 326 times. Moose were more active during 'cool' (thus 'dark') conditions (p &lt; 0.05). A negative correlation (r = -0.47) between the percent of active locations and mean Teopen for the hours of 11:00 until 24:00 PDT indicated that moose activity was likely thermally constrained. The mean straight line velocity (MSLV) between successive moose locations did not differ across hours from 11:00 until 24:00 (p &gt; 0.05). MSLV was not correlated with Teopen; however, a decrease in average MSLV values from 12:00 until 17:00 did correspond to sustained conditions of Teopen values above the UCT. The susceptibility of moose to heat stress, the effectiveness of conifer stands in providing thermal cover, and the relations between habitat selection and the thermal environment suggest that thermal cover is a required, manageable component of cow moose summer range in the study area.