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Document Type

Thesis - University Access Only

Award Date

2003

Degree Name

Master of Science (MS)

Department

Wildlife and Fisheries Science

First Advisor

Jonathan A. Jenks

Abstract

Knowledge of survival rates, causes of mortality, and information related to movements are essential in understanding the population dynamics of white-tailed deer (Odocoileus virginianus). In addition, proper deer management requires an understanding of fawn mortality from birth to recruitment. No direct information is available on population dynamics of deer in intensively cultivated areas in southwest Minnesota. Primary objectives were to determine seasonal survival rates, seasonal movement, and cause-specific mortality (e.g., hunting, vehicle collision, predation, disease) of white-tailed deer in southwest Minnesota. Secondary objective was to estimate seasonal home ranges. During 2001-02, radio telemetry was used to monitor the movement and mortality of 61 adult (>1 year at capture), 16 fawn (!8 months at capture), and 39 neonate (<1 month at capture) white-tailed deer. From January 2001- August 2002, 6,867 deer locations were collected with a mean 95% error ellipse of 3.83 ha. Deer had two seasonal home ranges, winter and summer. Mean home range size was 5.18 km2 (n = 37, SE = 0.78) during winter and 2.27 km2 (n = 93, SE = 0.18) during summer. Deer occupied summer range for approximately 7 months, arriving from winter range during mid-April and departing to winter range during late November. Mean distance migrated between seasonal ranges was 10.1 km (n = 95, SE = 0.70). Temperature and snow depth were the primary factors influencing seasonal migration in southwest Minnesota. Throughout the study, 14 female deer (10 adults, 4 fawns) died and the overall adult survival rate was 0.75 (n = 77, SE = 0.05). In southwest Minnesota, survival of adult female white-tailed deer was primarily dependent on human factors (i.e., hunting, vehicle collisions). Natural causes of mortality such as predation and disease (14.2%) were minor relative to human related causes (71.5%) for adult female deer. A total of six neonate mortalities (predation = 4, disease = 1, vehicle collision = 1) occurred during the study. Pooled summer neonate survival rate was 0.84 (n = 39, SE = 0.06). Adult female and neonate white-tailed deer populations had high survival and minimal vulnerability to death by natural causes in intensively cultivated areas. These data may be extrapolated to white-tailed deer herds in other highly fragmented regions with intensive cultivation, limited permanent cover, high hunter density, high road density, low predator density, and large fluctuations in seasonal climate. These factors were significant influences on movement and mortality of deer in southwest Minnesota. Data from this study will be used to improve Minnesota’s farmland deer population model and assist wildlife managers with decisions concerning white-tailed deer management. A landscape-level approach is necessary to understand long-term trends and factors influencing deer densities across farmland Minnesota. BROWN 33. High stocking density “mob” grazing is a recent phenomenon that is being promoted by a few practitioners, but has not undergone rigorous scientific testing. Producers have claimed “mob” grazing can generate many benefits in terms of forage production and overall grassland health. The objective of this study was to determine the effect stocking density had on harvest efficiency, forage trampling, and litter decomposition. One experimental site was established in eastern South Dakota. Two separate experiments were conducted. The first experiment examined the effect of stocking density on utilization, harvest efficiency, and forage trampling. The experimental design was a completely randomized design with two replications of 5 stocking densities (50, 100, 200, 400, and 800 1,000 kg/ha of live weight). The second experiment was arranged as a 2x2x2x2 treatment design with 2 replications to examine litter decomposition. The treatments were stocking density (high or low), litter type (fresh or old), placement (surface or buried at 7.5 cm), and origin (high or low stocking litter). Treatments were applied in July and August of 2012 and 2013. Biomass samples were collected throughout July and at the beginning of August. Litter bags were placed directly post-grazing in August and collected the following May. Harvest efficiency across stocking density treatments increased linearly (P<0.08), while trampling had a quadratic response (P<0.05). At a 200,000 kg/ha stocking density a threshold for trampling is reached. Utilization across stocking density treatments increased linearly (P<0.001). Utilization is well above the “take half, leave half” grazing recommendation. In 2012 and 2013 there was no difference in decomposition between surface samples in high and low stocking densities. Overall, the percentage of litter decomposition was less in 2013 (Buried 32% and 35%) (Surface 25% and 26%) vs. (Surface 39% and 41%) (Buried 65% and 57%) in 2012. This was likely due to drier conditions following fall 2013 than fall 2012. High stocking density “mob” grazing increased overall utilization and harvest efficiency, but did not increase litter decomposition rate. Producers with less high quality forage can utilize this grazing technique to increase overall harvest efficiency in grazing pastures. However, high stocking density “mob” grazing may not be suitable for all producers or pasture types. More long-term research is needed to evaluate if high stocking density “mob” grazing effects on plant community composition and production.

Library of Congress Subject Headings

White-tailed deer--Seasonal distribution--Minnesota
White-tailed deer--Minnesota--Mortality

Description

Includes bibliographical references (pages 69-87)

Format

application/pdf

Number of Pages

149

Publisher

South Dakota State University

Rights

Copyright 2003 Todd J. Brinkman. All Rights Reserved.

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