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Dissertation/Thesis Abstract

A Comparison of White-Tailed Deer Recruitment Rates to Relative Predator Abundance in Maryland
by Ness, Eric W., M.S., University of Delaware, 2017, 53; 10643129
Abstract (Summary)

In the late 1990s, Maryland’s deer management plan aimed to reduce and stabilize the state’s white-tailed deer (Odocoileus virginianus ) population. While attempting to achieve this goal through liberalized seasons and bag limits, managers estimated a decreasing fawn recruitment rate and sought to better understand causes for these declines, particularly in the western portion of the state. Fawn recruitment may be impacted by several factors: predation, disease, starvation, malnutrition, parasite-load, and collisions with vehicles and farm machinery. My study’s goal was to better understand the predator-prey relationship within western Maryland. One hypothesis is the predator community reducing the fawn recruitment. In western Maryland, black bear (Ursus americanus), bobcat ( Lynx rufus), and coyote (Canis latrans) are established, but the variation in abundance of these populations has not been well documented. I established 3 study areas focused on 3 publicly hunted state forests (Potomac-Garrett, Savage River, and Green Ridge State Forests). The first objective was to estimate the deer density and fawn recruitment at each study area. I used road-based distance sampling using a forward-looking infrared (FLIR) device to scan the landscape from August-October, 2015 and 2016. I replicated the FLIR survey 6 times on each study area in 2015 and 2016. Once collected, the data were analyzed using a uniform-key function within program DISTANCE. Neither deer density (Potomac-Garrett = 16 deer/km2, Savage River = 6 deer/km 2, Green Ridge = 12 deer/km2) nor fawn recruitment (Potomac-Garrett = 0.56 fawn/doe, Savage River = 0.54 fawn/doe, Green Ridge = 0.52 fawn/doe) changed between years.

My second objective was to estimate a relative predator (black bear, bobcat, and coyote) density among study areas. Each study area contained a systematic grid of 20 cameras spaced 3.2-km apart. This grid created an 8-km 2 buffer around each camera to maintain site independence based on the average home range size of my target species. Cameras were deployed from June-August for a 60-day survey period in 2015 and 2016. Throughout the study, I logged 6,300 camera trap nights during the summer months. To compare predator densities using optimal sampling protocol, I performed an additional 60-day camera survey from December 2016-February 2017, logging 3,300 camera trap nights. I analyzed all data using Royal and Nichols (2004) N-Mixture Model within package unmarked for R 3.0.3 software. Predator densities shared 95% confidence intervals among sites and years. The average yearly mean and standard error of black bear density for each state forest were: Potomac-Garrett: M = 0.35, SE = 0.10 bear/km2, Savage River: M = 0.51, SE = 0.12 bear/km2, and Green Ridge: M = 0.28, SE = 0.07 bear/km2. The average yearly mean and standard error of bobcat density for each state forest were: Potomac-Garrett: M = 0.10, SE = 0.11 bobcat/km2, Savage River: M = 0.13, SE = 0.14 bobcat/km 2, and Green Ridge: M = 0.09, SE = 0.11 bobcat/km2. The average yearly mean and standard error of coyote density for each state forest were: Potomac-Garett: M = 1.84, SE = 1.10 coyote/km2, Savage River: M = 0.88, SE = 0.55 coyote/km2, and Green Ridge: M = 0.19, SE = 0.16 coyote/km2. Finally, I compared fawn recruitment to the predator densities at each of the 3 study areas. The results of our study indicated a stable, albeit on the low side of fawn recruitment but variable predator density across the landscape, suggesting that the predator community is not lowering the fawn recruitment.

Indexing (document details)
Advisor: Bowman, Jacob L.
Commitee: Eyler, Brian, McCarthy, Kyle
School: University of Delaware
Department: Entomology and Wildlife Ecology
School Location: United States -- Delaware
Source: MAI 57/05M(E), Masters Abstracts International
Subjects: Wildlife Management, Natural Resource Management
Keywords: Black bear, Camera survey, Coyote, FLIR survey, Predator-prey ecology, White-tailed deer
Publication Number: 10643129
ISBN: 978-0-355-75729-3
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