6 research outputs found
Appendix B. Plot of Schoenfeld residuals for the effect of site 4 (relative to site 1) vs. time in the age-based semi-parametric proportional hazards model.
Plot of Schoenfeld residuals for the effect of site 4 (relative to site 1) vs. time in the age-based semi-parametric proportional hazards model
Appendix A. Table summarizing winter severities, crude mortality rates, and hunting hazards for female white-tailed deer (≥0.6 yr old), north-central Minnesota, USA, 1 January 1991–31 December 1996.
Table summarizing winter severities, crude mortality rates, and hunting hazards for female white-tailed deer (≥0.6 yr old), north-central Minnesota, USA, 1 January 1991–31 December 1996
Description of eight alternative expected space-use patterns of adult (≥1.5 years old) female white-tailed deer relative to dense conifer cover, derived from the combination of two sets of sub-hypotheses, one addressing availability of dense conifer cover on four study sites and the other their response to increasing snow depth or decreasing ambient temperature, in north-central Minnesota, 1 November–14 May 1993–1994 to 2004–2005.
<p>Description of eight alternative expected space-use patterns of adult (≥1.5 years old) female white-tailed deer relative to dense conifer cover, derived from the combination of two sets of sub-hypotheses, one addressing availability of dense conifer cover on four study sites and the other their response to increasing snow depth or decreasing ambient temperature, in north-central Minnesota, 1 November–14 May 1993–1994 to 2004–2005.</p
A Long-Term Assessment of the Variability in Winter Use of Dense Conifer Cover by Female White-Tailed Deer
<div><p>Backgound</p><p>Long-term studies allow capture of a wide breadth of environmental variability and a broader context within which to maximize our understanding of relationships to specific aspects of wildlife behavior. The goal of our study was to improve our understanding of the biological value of dense conifer cover to deer on winter range relative to snow depth and ambient temperature.</p><p>Methodology/Principal Findings</p><p>We examined variation among deer in their use of dense conifer cover during a 12-year study period as potentially influenced by winter severity and cover availability. Female deer were fitted with a mixture of very high frequency (VHF, <i>n</i> = 267) and Global Positioning System (GPS, <i>n</i> = 24) collars for monitoring use of specific cover types at the population and individual levels, respectively. We developed habitat composites for four study sites. We fit multinomial response models to VHF (daytime) data to describe population-level use patterns as a function of snow depth, ambient temperature, and cover availability. To develop alternative hypotheses regarding expected spatio-temporal patterns in the use of dense conifer cover, we considered two sets of competing sub-hypotheses. The first set addressed whether or not dense conifer cover was limiting on the four study sites. The second set considered four alternative sub-hypotheses regarding the potential influence of snow depth and ambient temperature on space use patterns. Deer use of dense conifer cover increased the most with increasing snow depth and most abruptly on the two sites where it was most available, suggestive of an energy conservation strategy. Deer use of dense cover decreased the most with decreasing temperatures on the sites where it was most available. At all four sites deer made greater daytime use (55 to >80% probability of use) of open vegetation types at the lowest daily minimum temperatures indicating the importance of thermal benefits afforded from increased exposure to solar radiation. Date-time plots of GPS data (24 hr) allowed us to explore individual diurnal and seasonal patterns of habitat use relative to changes in snow depth. There was significant among-animal variability in their propensity to be found in three density classes of conifer cover and other open types, but little difference between diurnal and nocturnal patterns of habitat use.</p><p>Conclusions/Significance</p><p>Consistent with our findings reported elsewhere that snow depth has a greater impact on deer survival than ambient temperature, herein our population-level results highlight the importance of dense conifer cover as snow shelter rather than thermal cover. Collectively, our findings suggest that maximizing availability of dense conifer cover in an energetically beneficial arrangement with quality feeding sites should be a prominent component of habitat management for deer.</p></div
Model-based predicted probabilities of adult (≥1.5 years old), female white-tailed deer using dense (≥70% canopy closure, yellow) and moderately dense (40% ≤×<70% canopy closure, red) conifer cover, and “other” (here includes conifer with <40% canopy closure, openings, and hardwoods; blue) during daytime hours (i.e., 0730–1700 hr) as a function of snow depth (panels A-D) and minimum daily temperature (panels E-H), for each of four study sites, north-central Minnesota, 1 November–14 May 1993–1994 to 2004–2005.
<p>Colored bands depict point-wise 95% bootstrap confidence intervals. To generate model-based response curves, we set availabilities of each habitat type to site-specific mean values. Similarly, we set daily snow depths (for bottom panels) and minimum temperatures (for top panels) to site-specific means.</p
Date-time plots illustrating individual variability in use of dense (≥70% canopy closure), moderately dense (40% ≤×<70% canopy closure), and open conifer cover (<40% canopy closure), and open non-conifer types (openings and hardwood types) by adult (≥1.5 years old), female white-tailed deer monitored using Global Positioning System (GPS) collars collecting locations hourly or every four hours on four study sites, north-central Minnesota, 23 January–14 April 2001, 2002, 2004, and 2005.
<p>The solid black line represents average weekly snow depths.</p