White-Tailed Deer Ecology & Management II

Contributed Oral Presentations

SESSION NUMBER: 72

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

 

Effects of Water Salinity on Dry Matter Intake by White-Tailed Deer
Austin K. Killam; Clayton D. Hilton; David G. Hewitt; Aaron M. Foley; Natasha L. Bell; David B. Wester
Surface water in the southwestern United States is often limited due to frequent droughts. Large mammals in this environment are forced to rely on pumped ground water or rapidly evaporating pools of poor-quality water that may contain high (≥7,000ppm) levels of salt and dissolved solids. Our objective was to identify 1) the upper threshold of salinity that white-tailed deer (Odocoileus virginianus) will drink, 2) if water salinity affects daily water intake across seasons, and 3) if water and dry matter intake decline with increasing salinity in white-tailed deer. Salinity is the focus of this study because it is the primary cause of poor-quality water in South Texas. To evaluate the impact of water salinity on dry matter and water intake of white-tailed deer, we offered deer water ad libitum at varying (1,000, 2,500, 4,000, 6,000, and 7,500ppm) salinity in autumn 2019, spring 2020, and summer 2020. Water treatments were given in a Latin square design with a 5-day transition period followed by a 5-day treatment period. During autumn, the effect of salinity treatment on daily water consumption varied by max temperature (P=0.005). At low temperature (24C), water intake was highest for the high salinity treatment. As temperature increased, water consumption increased for low and moderate salinity treatments (P≤0.008) so that at the highest temperature (34C), water intake was similar to the high salinity treatment. Daily water consumption of the control treatment was less than other treatments at 34C. Little is known about the relationship between water quality and dry matter intake. This will allow property managers to asses when the quality of supplemental water needs to be managed in periods of drought.
Convenience Or Selection? a Look at the Resource Selection of Michigan White-Tailed Deer
Jonathan K. Trudeau; David Williams; Sonja Christensen; Dwayne Etter; William Porter
At the stem of all wildlife ecology is the concept that animals exist in an environment for one reason: suitable resources are available. White-tailed deer (Odocoileus virginianus), like other generalist species, have perfected the ability to adapt to a wide variety of environments. However, despite there being a plethora of information on the resource selection of white-tailed deer across North America, there is little information on how resource selection changes as the environments they encounter change. Traditional resource selection analyses often fail to account for how selection changes with landscape context, but modern step-selection analyses account for the changes in available versus used land cover, allowing researchers to assess resource selection in a novel way. We sought to understand the resource selection of white-tailed deer across a developmental gradient and determine how the increasing availability of human development impacted the use of habitats considered to be ideal, such as forests and agricultural lands. We fit >130 deer with global positioning collars between January and April of 2018-2020 in the mixed agriculture-forest and suburban landscape of south-central Michigan. We used a step-selection approach to identify areas available to each deer based on a random sample of movements generated from known movement characteristics of each deer and compared those to the land cover used. Deer used forested land cover at a higher rate than other land cover types, regardless of human development. However, as the percentage of human development increased in the surrounding landscape, deer selected more heavily for forest and agricultural lands. Our study demonstrates how traditional methods for identifying important land covers across a heterogeneous landscape fail to account for behavior changes in deer in response to the change in available land cover types, and how these differences may impact management decisions.
Development of a Sightability Model for Helicopter Surveys Using Surrogates of White-Tailed Deer
Jordan Ryan Dyal; Karl V. Miller; Michael J. Cherry; Gino J. D’Angelo
On large management units where terrain allows observation of white-tailed deer (Odocoileus virginianus) from the air, helicopter surveys can provide managers with cost-effective and accurate estimates of population abundance. However, imperfect detection of deer biases abundance estimates resulting in potentially inappropriate management recommendations (e.g., harvest prescriptions). Sightability estimators are designed to model detection heterogeneity based on factors that affect observer detection of target animals. Sightability models have been developed for numerous ungulate species; however, detection probability of white-tailed deer during helicopter surveys in Florida has not yet been established. Our objective was to model detection probability of white-tailed deer as a function of covariates including distance from transect, vegetation obstruction, and light conditions to improve population estimates derived from helicopter surveys. We conducted our study on a 2,620-ha study area within a 120,968-ha cattle ranch in central Florida. We placed 3-D archery targets as surrogates for white-tailed deer at randomly selected locations unknown to observers across a combination of distances and vegetation types. We conducted 12 flights during July 2019 for a total of 336 potential observations of surrogates. Detection probability on the flight path ranged from 0.95 (95% CI = 0.89-0.98) to 0.05 (95% CI = 0.01-0.18). Our results indicated that distance from the transect and vegetative obstruction negatively affect detection of deer, especially when vegetative obstruction is greater than 50% and distances greater than 50 m; however, while light had no effect. Observers simultaneously recorded live deer during flights, of which only 41% of groups were observed while movement was occurring. Our results demonstrate support for using stationary 3-D archery targets as surrogates of deer during model development. We recommend adopting our methods in other landscapes and management units to develop sightability models to account for imperfect detection of white-tailed deer.
Survival and Cause-Specific Mortality of Localized Populations of Urban and Rural White-Tailed Deer in Southern Indiana
Garrett B. Clevinger; Jonathan K. Trudeau; Michael J. Cherry; Timothy C. Carter
Human development is rapidly increasing globally and can have strong effects on wildlife population dynamics. Understanding the effects of human development on population vital rates such as survival and cause-specific mortality is key to sound wildlife management. However, management decisions impacting both urban and rural wildlife populations may often be undermined due to potential variations in the scale and duration of studies from which the management plans are influenced. Therefore, study samples which contain both urban and rural individuals, monitored at the same place and time, may be warranted in order to best predict management implications. White-tailed deer (Odocoileus virginianus) are a dynamic species which are often revered as a popular subject of outdoor activities (e.g. hunting, wildlife viewing), as well as despised as culprits of negative, human-wildlife conflicts (e.g. vehicle collisions, property damage). We analyzed survival and cause-specific mortality rates of deer located within the city of Bloomington, Indiana as well as deer located in adjacent rural landscapes simultaneously from 2015-2017. We used Cox proportional hazards models to predict the influence of urbanization on adult deer survival. We found no effect of urbanization on survival rates, and while the leading causes of mortality in our study were attributed to vehicle collisions (n=11) in urban areas and hunter related events (n=8) in rural areas, survival rates were remarkably similar between sites. Combined annual survival rate was 0.70 (95%CI: 0.61-0.80), with deer in rural areas averaging 0.69 (95%CI: 0.55-0.87) and deer in urban areas averaging 0.70 (95%CI: 0.59-0.83). While survival rates fluctuated between sexes, with females (0.76; 95%CI: 0.66-0.89) having higher survival than males (0.62; 95%CI: 0.47-0.79) across both landscapes, our analyses found that as mortality type changed, survival rates were not impacted by urbanization.
Evaluating Unmanned Aerial Vehicles (UAVS) for Estimating White-Tailed Deer Population Sizes
Jesse Exum; Aaron M. Foley; Randy W. DeYoung; David G. Hewitt; Jeremy Baumgardt; Mickey W. Hellickson
Helicopters are commonly used to conduct surveys of white-tailed deer; however, they can be expensive, risky, and not always practical. Unmanned aerial vehicles (UAVs) are an emerging technology that has yet to be fully evaluated for wildlife surveys in South Texas. We conducted repeated UAV surveys on 5 study sites with varying numbers of white-tailed deer (Odocoileus virginianus). UAVs were equipped with a dual thermal and optical video camera. Heat signatures were detected in the thermal imagery, then animals were identified via optical imagery. Year 1 surveys were conducted by contractors during November 2018 and February 2019 at 40-50 m above ground level (AGL) and 36-50 km/hr. Year 2 surveys were conducted in-house from February through April 2020 with a reduced AGL (37 m) and slower speed (24 km/hr). During Year 1, 60.3% (range = 33.3 – 86.5) of thermal signatures were identified with optical imagery and raw drone counts were 44.2% (range = 9.7 – 84.0) of September helicopter counts. Inconsistency in survey protocol by contractors made it difficult to determine if variation in drone counts was true variation in animal counts. Data from 3 surveys on 1 site in Year 2 indicated 85.7% (range = 73.8 – 92.9) of thermal signatures were identified in optical imagery and raw deer counts were consistent (range = 56 – 65) suggesting that flying lower and slower improved estimates. Year 2 analysis is in progress and additional results will be discussed.

 

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