White-Tailed Deer II

Contributed Paper
ROOM: HCCC, Room 25A
SESSION NUMBER: 61
 

8:10AM Survival and Cause-Specific Mortality of White-Tailed Deer Fawns in Central Iowa
Patrick G. McGovern; Julie A. Blanchong; Stephen J. Dinsmore
Estimation of survival rates receives considerable attention from researchers and managers interested in population trends. Survival can vary by region, sex, age-class, and habitat. White-tailed deer (Odocoileus virginianus) fawn survival and causes of mortality are highly variable across its range. While recent studies have documented fawn survival in several Midwestern states, there have been no published estimates of fawn survival in Iowa for 30 years. We radio-collared 48 fawns from 2015-2017 in central Iowa to determine cause-specific mortality and provide updated survival estimates for use in management decisions. We recorded 21 mortalities, which were attributed to disease (n = 9), suspected predation (4), harvest (3), vehicle collision (1), starvation (1), and unknown causes (3). Estimated fawn survival was 0.78 (standard error = 0.07) through 30 days post-capture, 0.69 (0.08) through 60 days post-capture, and 0.31 (0.02) through 7 months post-capture. Our 30- and 60-day survival estimates were comparable to previously reported rates for Iowa and the Midwest; however, our 7-month estimate was much lower due to mortalities from harvest and epizootic hemorrhagic disease (EHD). The proportion of nearby woodland had a significant positive effect on fawn survival through 30 and 60 days post-capture. Woodland habitat provides permanent cover and likely increases fawn survival by reducing predation risk. Managers and landowners can maintain or restore woodland to provide fawns with sources of permanent cover in regions of limited or temporary cover like the agricultural Midwest. Sporadic disease events like EHD can be a significant cause of fawn mortality, but do not appear to reduce fawn survival in central Iowa compared to non-disease years.
8:30AM Space Use of White-Tailed Deer Neonates Using Micro-GPS Units
Tess Gingery; Duane R. Diefenbach; Chris S. Rosenberry; Bret D. Wallingford
Despite its importance for informing a range of topics including predator-prey interactions and susceptibility to mortality, movements of large herbivore neonates are poorly understood. Traditional very high frequency (VHF) radio-telemetry methods of monitoring large herbivore neonate space use and activity often collect insufficient numbers of locations needed to estimate a home range for neonates ≤ 4 weeks of age, resulting in an incomplete characterization of neonate space use. Radiocollars that use global positioning systems (GPS) obtain more locations and reduce position error but size and weight restrictions render current GPS units unavailable to study movements of neonates of even large herbivores. Our objective was to construct home ranges for white-tailed deer (Odocoileus virginianus) neonates at 1- and 4- weeks of age using GPS locations. We modified 44 commercially available GPS units designed to track domestic house cats (Felis catus) and deployed them on fawns in 2015 and 2016. We monitored 13 individuals from capture until death where the fawn lived at least one week. Fawn home range size increased with age where 1-week home ranges averaged 4.86 ha and 4-week home range size averaged 18.98 ha. Current models that use a single home range size regardless of neonate age may inaccurately portray how habitat features influence survival of large herbivore neonates. Neonatal survival partially determines population growth, and movement influences an individual’s exposure to various mortality sources, thus our results have implications for large herbivore conservation and management.
8:50AM White-Tailed Deer Neonate Survival in the Functional Absence of Predators
Jacob M. Haus; Justin R. Dion; Joseph E. Rogerson; Jacob L. Bowman
Survival and cause-specific mortality of neonate white-tailed deer has been the focus of recent research, particularly in regards to predation mortality. An understanding of the impact of predation on survival rates requires a predator-free control population. We captured 109 neonates using opportunistic capture (n = 55) and vaginal implant transmitters (VIT; n = 54) in Delaware during 2016 and 2017. Predators (i.e., black bear, bobcat, and coyotes) were functionally absent from the study area. We calculated 30-day survival using a Kaplan-Meier estimator and determined the importance of covariate on survival using Cox proportional hazard models. The overall 30-day survival estimate was 0.61 (95% CI = 0.51 – 0.72). The survival estimate for neonates captured using random searches (0.76) was greater (P < 0.01) than those for VIT neonates (0.53). Natural causes (n = 34) accounted for all of our observed mortality, including one potential predation by red fox. The top models included covariates for birth weight, doe maturity, and precipitation. Predation could be less of a limiting factor for survival than many studies have suggested. Data derived from opportunistically captured neonates may inflate estimates of survival and misrepresent cause-specific mortality. Although the influence of birth weight on survival has been reported previously, the impact of doe maturity and precipitation has not been documented. The current emphasis on predator management and the impact on deer abundance may be misplaced.
9:10AM Neonatal Predation Risk Determines Activity Patterns in Female White-Tailed Deer
Daniel A. Crawford; Michael J. Cherry; Elyse McMahon; L. Mike Conner
Anti-predator behaviors in prey arise as a function of perceived risk and the relative costs and benefits associated with competing behavioral options (e.g. vigilance, space use, or activity budgets). Behavioral tradeoffs influence individual fitness as prey attempt to maximize energetic intake while minimizing risk of predation. When behavioral responses to predation risk result in population level consequences, we observe predation risk effects. Animals face a decision-making conundrum when periods of high energetic demand coincide with periods of high predation risk. Female white-tailed deer (Odocoileus virginianus) incur their greatest energetic demand during lactation when neonates are entirely nutritionally dependent upon nursing. This period also presents the highest risk of predation to the relatively immobile neonates, as carnivores often profoundly impact neonate survival and, consequently, deer population growth rates. We investigated the extent to which the presence of offspring and predation risk influences the activity patterns of female white-tailed deer in a longleaf pine savanna. We excluded mesocarnivores from four ~40 ha plots that were each paired with ~40 ha control plots and monitored deer activity in those plots with 27 non-baited infrared motion-triggered cameras during three fawning seasons (2015-2017). We estimated detection rates and coefficients of activity overlap between females with offspring (henceforth, nursery groups) and without during the fawning season. Nursery groups overlapped less with fawnless females in control plots (0.744, 95% CI: 0.640-0.843; coefficient of overlap) than in exclusion plots (0.944, 95% CI: 0.907-0.981), a difference likely attributed to increased nocturnal activity of nursery groups in exclosures (1.98, 95% CI: 0.911-3.49; detections/1000 hours) versus controls (.388, 95% CI: 0.159-0.683). We offer the first experimental evidence that female deer with offspring recognize spatiotemporal differentials in predation risk and alter their activity patterns accordingly minimizing their offspring’s risk exposure to maximize their own reproductive fitness.
9:30AM Stressing Over Hair: Testing for the Effects of Body Condition, Demography, and Urbanization on Glucocorticoids in Urban White-Tailed Deer
Emily Potratz
White-tailed deer (deer; Odocoileus virginianus) populations, with their demographic vigor and adaptability, are growing across the Midwest, with suburbs and cities being no exception. How deer respond to the increasingly urban environment and any stressors they encounter will ultimately influence the health of the population. In order for managers to monitor those deer, we aimed to develop a technique that quantified long term stress, via hair cortisol. Our objectives were to determine the relationship between hair cortisol concentration and various biological and environmental factors. Using shaved hair from culled deer part of Illinois’ herd management program and hair from unmanaged deer, a biological validation was done by evaluating the relationship between hair cortisol concentration and individual body condition. Results showed that deer with the poorest body condition had the highest (P < 0.01) hair cortisol concentrations. Biological factors that may influence intra-population variability in stress, such as sex and age, did not (sex; P = 0.13, age; P = 0.18) influence hair cortisol concentrations. However, site location of the deer did have an effect (P < 0.01). Using a linear mixed model, deer density and habitat characteristics (vegetation, building, and road density) per site were included as variables to explain the variation. However, no models came out significant. Overall, our results confirm that Illinois’ current deer management strategy of controlling populations does maintain deer health, using body condition and stress as indicators. When populations are not managed, deer have extremely low body condition scores (1; on scale of 1 to 5) and have elevated circulating cortisol. Monitoring hair cortisol can be used as a tool to assess the health of wildlife. Knowing which populations are vulnerable due to chronic stress can be important for managers, as these individuals may be susceptible to disease.

 

Contributed Paper
Location: Huntington Convention Center of Cleveland Date: October 10, 2018 Time: 8:10 am - 9:50 am