SPATIAL AND TEMPORAL PATTERNS IN WHITE-TAILED DEER FAWN SURVIVAL AND CAUSE-SPECIFIC MORTALITY
- Author:
- Gingery, Tess
- Published:
- [University Park, Pennsylvania] : Pennsylvania State University, 2018.
- Physical Description:
- 1 electronic document
- Additional Creators:
- Diefenbach, Duane
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- Restrictions on Access:
- Open Access.
- Summary:
- Juvenile survival may be the most critical component of large herbivore population growth, but how neonate survival changes over time and space is not fully understood. Neonate survival rates are influenced by maternal care, site-specific differences, and are generally characterized by year-to-year variation. Sources of white-tailed deer (Odocoileus virginianus) fawn mortality across North America include predation, natural causes (excluding predation), and both direct and indirect human-caused mortality. The relative frequency of these causes indicates which sources most affect neonate survival and can be easily compared among studies. We used a meta-analysis approach to elucidate spatial patterns in fawn survival at a landscape-scale across North America. However, comparing survival rates across time is not possible when confounded by spatial variation. Therefore, we investigated how fawn survival varied across time by conducting a neonate survival study in central Pennsylvania to compare a current estimate of neonate survival to previous estimates for central Pennsylvania in 20002001. Furthermore, because pre-weaned neonates (<3 months of age) are entirely dependent upon maternal care, maternal behaviors can explain variation in neonate survival rates from year-to-year. The cost, size, and weight of current bio-logging technologies (e.g. global positioning system (GPS) collars) often limit their ability to monitor mother-offspring behavior, even for large herbivores. We conducted a pilot study to evaluate the performance of a behavioral monitoring bio-logger and detail temporally dynamic patterns of maternal behaviors in white-tailed deer. We conducted a meta-analysis of white-tailed deer fawn survival to identify patterns in survival and cause-specific mortality related to landscape characteristics, predator communities, and deer population density. We used fawn survival and cause-specific mortality data from 29 populations in 16 states across North America from studies that reported a survival rate to 36 months of age, sample sizes, landscape descriptions, and cause-specific mortality. We modeled the relationship of fawn survival to percentage of agricultural land cover and deer density. We detected fawn survival increased as the percentage of agricultural land cover increased. We classified cause-specific mortality as human-caused, natural (excluding predation), and predation according to agriculturally dominated, forested, and mixed (i.e., approximately equal parts agriculture and forest) landscapes. Predation was the greatest source of mortality in all three landscape types. Mixed landscapes had greater proportions of human-caused mortalities, and less mortality due to predators, when compared to forested landscapes but not when compared to agricultural landscapes. The proportion of natural deaths was similar among mixed, forested, and agricultural landscapes even though overall mortality rates differed. We failed to detect any relationship between fawn survival and deer density. Since 20002001, surveillance of wildlife populations suggest varying densities of deer, black bear, and coyote populations across Pennsylvania. We assessed differences in current estimates of white-tailed deer neonate survival rates and cause-specific mortality from 2015 to 2016 in central Pennsylvania to estimations reported during 20002001. We collared neonates in 20152016 and monitored survival until 34-weeks of age, mortality, or transmitter failure. We captured 55 neonates in north-central Pennsylvania and 43 neonates in central Pennsylvania. At 26 weeks after capture current fawn survival was 0.504 (95% CI = 0.337 0.621) in an 88% forested landscape in northcentral Pennsylvania and 0.708 (95% CI = 0.5690.848) in central Pennsylvania that contained approximately 15% more agricultural land cover. In 2000, 26-week survival estimates were 0.456 (95% CI = 0.360 0.556) in northcentral Pennsylvania and 0.586 (95% CI = 0.488 0.677) in central Pennsylvania. We failed to detect any long-term change in fawn survival rates or predator abundances in the areas designated as Wildlife Management Units by the Pennsylvania Game Commission that surrounded our study areas. Neonates have the most variable survival in large herbivore species and maternal care influences early survival. We conducted a pilot study to evaluate the performance of a behavioral monitoring bio-logger (separation sensor) and documented temporally dynamic patterns of maternal behaviors in white-tailed deer. We monitored the behaviors of 5 mother-fawn pairs including 3 sets of twins from parturition until fawn mortality or censorship resulting in 5 mothers with 8 total fawns. Given our limited sample size, our ability to discuss the factors that influence maternal behavior is limited; however, we demonstrated the ability of this technology to effectively study maternal behaviors. Using the separation sensor, mothers with twins increased the amount of time spent near their fawn immediately after monitoring began; although we did not observe this pattern in the one mother we monitored who had only one fawn and maternal behavior varied greatly among individuals. Our results suggest the techniques and technology we employed can be valuable to research studying female attentiveness as a measure of maternal behavior to examine ecological questions such as maternal favoritism (i.e., Trivers-Willard theory).
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- Dissertation Note:
- M.S. Pennsylvania State University 2018.
- Technical Details:
- The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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