Deer Ecology & Management

Contributed Oral Presentations

SESSION NUMBER: 32

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.

 

Surviving and Reproducing during Harsh Winters: Does Past Experience Change Future Allocation?
Tayler LaSharr; Samantha P. H. Dwinnell; Rhiannon P. Jakopak; Jill Randall; Rusty C. Kaiser; Mark Thonhoff; Brandon Scurlock; Neil Hymas; Adam Hymas; Chris Baird; Nick Roberts; Troy Fieseler; Jeff Short; Mark Zornes; Doug McWhirter; Doug Brimeyer; Gary L.
Reproduction is expensive and risky; across taxa, reproductive efforts can diminish somatic growth, reduce probability of survival, and decrease fertility. Reproductive efforts often are dependent on predictability of environments, and animals that inhabit unpredictable landscapes often adopt more conservative reproductive strategies compared with animals that inhabit landscapes with reliable resource availability. Further, winter often represents a survival bottleneck in seasonal environments, and the nutritional condition of individuals (e.g., fat reserves) entering winter influence both survival and reproduction, ultimately underpinning population dynamics. Stochastic winters are becoming more common as climate change affects ecosystems around the globe, and many populations are facing extreme conditions in winter. Individuals that experience and survive an unprecedented, harsh winter may relinquish reproductive allocation to better buffer themselves against the possibility of encountering similar conditions in the future. In line with the hypothesis of risk-sensitive reproduction allocation, we tested if individuals that experienced near-death conditions during winter would shift allocation to favor the accumulation of somatic reserves (i.e., survival) over the use of resources to recruit offspring (i.e., reproduction) following that extreme event. Following extreme winter conditions in 2016-2017 and 2018-2019, we evaluated how relative allocation of resources shifted for 166 adult, female mule deer (Odocoileus hemionus) in Wyoming, USA. During both winters, animals were subjected to high winter severity, and overwinter survival of adults dropped to 70% and 65% respectively, a stark contrast of the ~90% survival in a typical winter. Following those winters, females had higher body reserves entering winter (β= 1.68 [0.89, 2.48]) and lower recruitment of offspring (β= -2.52 [-3.03, -2.03]), indicating individuals could shift their relative allocation to favor investment in survival over reproduction. Shifts in resource allocation may help buffer adult survival against harsh environments, but may come at the cost of consistent recruitment, and have lasting implications for population persistence.
Relating Black-Tailed Deer Habitat Selection to Survival
Jessica Clark; Katie Dugger; DeWaine Jackson
Columbian black-tailed deer (Odocoileus hemionus columbianus) populations in Oregon have been declining range wide since the 1990’s, potentially due to a combination of factors including disease, increasing predator populations, changes in land management and habitat quality. The range of black-tailed deer in Oregon extends from the Pacific coast to the Cascade Mountain crest across western Oregon, thus the species is exposed to a wide variety of terrain, land cover types and mortality factors. It is assumed that individuals in these varying circumstances exhibit behavior that maximizes their survival and reproduction. However, limited data exist on Columbian black-tailed deer home range, and survival in association with habitat selection patterns. The Oregon Department of Fish and Wildlife attached GPS radio-collars to adult female black-tailed deer in 4 Wildlife Management Units (WMUs); two WMUs in the Coast Range and two WMUs in the Cascade Mountains. We estimated winter habitat selection and survival rates for the Coast Range (n=78) and the Cascade Mountains (n=67) from 2012-2017. Third order winter resource selection function (RSF) models were developed using mixed effects logistic regression with a variety of topographic, vegetative and landscape composition explanatory variables. We used results from our RSF models to explain variation in winter monthly survival rates within a known-fate framework and assess the relationship between survival rates and selected resources within deer home ranges (Coast Range home range size: x̄ = 0.55 km2; Cascade Mountains home range size: x̄ = 0.99 km2). By directly linking habitat selection with survival we can aid managers in improving habitat quality and ultimately assess the influence of resource selection on fitness at a population level.
Influence of Hunting on Survival of Adult Male Mule Deer and White-Tailed Deer in Western Kansas
Maureen Kinlan; Dr. David Haukos; Dr. Andrew Ricketts; Levi Jaster; Mitchell Kern; Talesha Karish
Abundance and occupied range of mule deer (Odocoileus hemionus) have been declining for 20 years in Kansas. The two predominant hypotheses for the loss of mule deer and concurrent expansion of white-tailed deer (O. virginianus) are changes in land use and competitive dominance of white-tailed deer. Despite the popularity and income that stem from hunting, there have been no recent studies that provide critical insight for management and conservation of sympatric populations of deer species in Kansas. We evaluated survival rates, cause-specific mortality, and influence of hunting on adult male mule and white-tailed deer in western Kansas. We aerially captured and GPS-collared 111 male mule deer and white-tailed deer at two different study sites during 2018-2020. Each deer was fitted with a high resolution GPS/VHF collar that recorded bi-hourly locations and used an activity sensor to identify mortality. Known-fate models were used to estimate seasonal and yearly survival rates between species and study sites. White-tailed deer had lower annual survival (2018: 0.600±0.08, 2019: 0.621±0.09) than mule deer both years (2018: 0.645± 0.08, 2019: 0.656 ± 0.08). Harvest was the predominant cause of mortality and greatest in the north site where 41% of mule deer, and 22% of white-tailed deer were harvested during 2018 and 2019. In the south site, 16% of mule deer and 14% of white-tailed deer were harvested. Other sources of mortality stemmed from deer-vehicle collisions, natural (includes disease, old age, and starvation), and unknown causes. Because male mortality stems primarily from harvest, this source of mortality can be adjusted by changing harvest regulations. At this time harvest is not presumed to be a main driver behind mule deer population declines in western Kansas.
Resource Selection in Multiple Spatial Scales by Female Mule Deer and White-Tailed Deer in Western Kansas
Talesha Karish; David Haukos; Andrew M. Ricketts; Levi Jaster
Abundance and occupied range of mule deer (Odocoileus hemionus) in Kansas have been declining for 20 years. Predominant hypotheses for the loss of mule deer and concurrent expansion of white-tailed deer (O. virginianus) are avoidance or adaptation to changes in land use and land cover as reflected in resource selection. The difference in resource selection possibly allows white-tailed deer to have an indirect competitive advantage over mule deer. Our objective was to evaluate and compare resource selection of adult female mule deer and white-tailed deer in western Kansas. A total of 184 females were captured and collared between two study sites that have different land use and management practices. We used logistic regression to determine resource selection by females from used points and random locations from March through January for each year. Selected resources by females were compared between a combination of reproductive stages and annual seasons. Resource selection was assessed and compared between different spatial scales of landscape, within total home range and core area. Both species had consistent selection of resources among seasons. Mule deer differed in selection between home range and core area while white-tailed deer did not. These results will be included in a larger assessment of how resource selection between these species and study sites may contribute to differing population trends.
Estimating Points of Attraction for a Mule Deer Population Following Pinyon-Juniper Removal
Jason J. Gundlach; Cody Schroeder; Joe Bennett; Kelley M. Stewart
Populations of mule deer (Odocoileus hemionus) are in decline throughout the Intermountain West, and many of those populations are declining because of changes in quality of habitat. One example of low quality habitats for mule deer in the Great Basin is expansion of Single-leaf pinyon pine (Pinus monophylla) and Utah juniper (Juniperus occidentalis) woodland, which provide minimal nutritional value to mule deer while outcompeting herbaceous vegetation in the understory. We investigated how removal of these trees on affects movement patterns of mule deer on winter range. We captured 36 adult female mule deer in the Toiyabe mountains of Nevada, from April 2018 through March 2019, and fitted individuals with GPS collars. Pinyon-juniper trees on mule deer winter range were delineated and removed within a Before-After-Control-Impact experimental design, with an impact area of roughly 2,600 acres. Data obtained from GPS collars was modeled via correlated random walk, a Markov process where the location of an individual at a time step depended on its location in a previous step. We are then able to estimate points of attraction and the strength of that attraction throughout our control and impact plots on winter range, allowing us to increase our understanding of the influence of pinyon-juniper habitat treatments on mule deer movement behaviors. Preliminary results indicate that mule deer are indeed modifying their movement behaviors following pinyon-juniper removal. Understanding which habitat covariates have the most predictive influence on movement for this population will allow wildlife managers the ability to better assess areas of ecological importance for mule deer populations throughout the Intermountain West.
Climate Drives Phenology of a Migratory Ungulate across Three Montane Environments in California
Derek B. Spitz; Bogdan Cristescu; Christopher C. Wilmers; Heiko U. Wittmer
A common assumption in spatial ecology is that a habitat’s importance depends on the time individuals spend there. Disentangling these habitat-performance relationships is more difficult for migratory species, which rely on allopatric seasonal ranges. Migratory species that are behaviorally plastic may respond to climate change by altering the time they spend in different habitats. Understanding the extent of migratory plasticity and the drivers of migratory phenology are thus key to anticipating how the behavior, distribution, and demography of migratory species will shift under a changing climate. We applied a recent expansion of model-driven movement classification methods to identify and quantify the complexity (i.e., number of annual ranges and movements) and timing of migration across three populations of mule deer and black-tailed deer (Odocoileus hemionus and O. h. columbianus; n = 188 animal-years). Each population represented a different montane environment within California (coastal, western Sierra Nevada, and eastern Sierra Nevada). We then used a time-to-event framework to test for common drivers of migratory phenology across these systems. While literature on ungulate migration has typically assumed only two seasonal ranges, 59% of the migrations we observed supported fidelity to >2 ranges. Fall movements were strongly predicted by climate metrics with colder weather accelerating the timing of migration. We found no support for population differences in the timing of these movements. Spring movements were more synchronous and showed weaker relationships to climate. Finally, we observed inter-annual changes in individual behavior in all three systems and estimated the probability that an individual maintained consistent behavior across years as 15% (95%CI 0-35%). Our results suggest that common simplifying assumptions about ungulate migration may underestimate the complexity and plasticity of these movements. As climate change continues, management of migratory populations will increasingly depend on our understanding of their behavioral plasticity.

 

Virtual
Location: Virtual Date: Time: -