Effects of Dense Populations

San Juan Islands are overrun by deer, The Island’s Sounder, Sept 27, 2017The lack of understory foliage is indicative of a deer-populated forest, said Milner. An untouched forest in the islands has thick greenery lining the ground. The abundance of [black-tailed] deer has resulted in a depletion of available nourishment for the deer, leaving the population nutritionally deprived. Because of this, the island deer are smaller than their mainland counterparts, grow slowly and have little fat on them. Additionally, there are fewer twins born to island deer, and the mortality rate for twins is about 50 percent.

How to Estimate Your Deer Herd Density with One Trail Camera, RealTree, Aug 23, 2017To obtain accurate fawn-to-doe ratios, camera surveys should be implemented to coincide with increased fawn activity. This is generally around August to September.

Using one camera for your survey provides a random sample of your deer herd but how accurate is it? If your property is 100 acres or less, extremely accurate. In this case, research shows you are photographing around 90 percent of your herd. With one camera on a 200-acre tract of land, you should photograph 70 percent of your herd. Keep in mind, as acreage goes up, percentages of deer observed go down.

Quality vs Quantity: A Closer look at Deer Herd Condition Trends in Ohio, Ohio DNR, 2014?Ohio’s deer program goal has always been to provide enough deer to hunt and enjoy, but not so many that they cause undo economic hardship. In other words, social tolerances for deer, rather than biological considerations have largely driven individual county deer population goals. However, our deer program goal was written when Ohio’s deer herd was small and high quality habitat was everywhere. As a result, herd condition was not a concern at that time. However, deer numbers have increased dramatically since 1961, and the information presented in the following discussion begs the question: “In addition to public opinion, should biologists begin considering deer herd condition when setting population goals?”

The Effects of Population Density on Juvenile Growth Rate in White-Tailed Deer, Environmental Management, 2014Animal body size is driven by habitat quality,food availability, and nutrition. Adult size can relate to birthweight, to length of the ontogenetic growth period, and/or to the rate of growth.

… with the positive correlation between average adult body mass and population-level ontogenetic growth rate established, growth rate can be used to evaluate habitat quality and the efficacy of herd management decisions, and aspects of growth andbody size can better be studied on a population by population basis for purposes of serving quality deer management, sustainable harvest, and/or other management goals. Deer have relatively long reproductive spans and vegetation may take time to recover from intense herbivory (Horsley 2003).

Our experience suggests that though sport hunters desire greater numbers of deer that are easier to find and harvest, when provided with biological evidence that supports management at lower population densities, they are not only interested but also supportive.

The Relationship Between Deer Density, Tick Abundance, and Human Cases of Lyme Disease in a Residential Community, Journal of Medical Entomology, July 2014White-tailed deer (Odocoileus virginianus Zimmerman), serve as the primary host for the adult blacklegged tick (Ixodes scapularis Say), the vector for Lyme disease, human babesiosis, and human granulocytic anaplasmosis. Our objective was to evaluate the degree of association between deer density, tick abundance, and human cases of Lyme disease in one Connecticut community over a 13-yr period. We surveyed 90–98% of all permanent residents in the community six times from 1995 to 2008 to document resident’s exposure to tick-related disease and frequency and abundance of deer observations. After hunts were initiated, number and frequency of deer observations in the community were greatly reduced as were resident-reported cases of Lyme disease. Number of resident-reported cases of Lyme disease per 100 households was strongly correlated to deer density in the community. Reducing deer density to 5.1 deer per square kilometer resulted in a 76% reduction in tick abundance, 70% reduction in the entomological risk index, and 80% reduction in resident-reported cases of Lyme disease in the community from before to after a hunt was initiated.

White-tailed deer population dynamics as influenced by deer density and nutrition in southern Texas, ProQuest Dissertations and Theses Abstract, Cook, Nathan S., Ph.D., TEXAS A&M UNIVERSITY, 2014Population growth rate (λ), Fawn:doe ratios, fawn and yearling growth rate, fawn survival, and adult survival did not display density dependence. Trends in population growth rate (λ) indicated a weak density-dependent relationship and both enhanced and indigenous nutrition populations displayed a constant growth rate over the range of densities analyzed with a 30% higher λ population growth rate in the enhanced nutrition treatments. When modeling the population dynamics in the enhanced nutrition pastures, there was a direct relationship between density and number of trophy bucks produced.

SURVIVAL RATES OF FEMALE WHITE-TAILED DEER ON AN INDUSTRIAL FOREST FOLLOWING A DECLINE IN POPULATION DENSITY, Proceedings of the 18th Central Hardwoods Forest Conference, 2013Our annual survival estimate (0.81, 95-percent CI 0.73–0.89) was similar to what was previously found for this population (0.88, 95-percent CI 0.84–0.93) from 1999 to 2002, when densities were substantially higher (Campbell et al. 2005). Th is result suggests that adult survival rates in this population are robust to changes in population density.

Deer density and disease prevalence influence transmission of chronic wasting disease in white-tailed deer, Ecosphere, Jan 2013. We evaluated the influence of deer density, landscape features, and soil clay content on transmission of chronic wasting disease (CWD) in young white-tailed deer in south-central Wisconsin, USA. We evaluated how frequency-dependent, density-dependent, and intermediate transmission models predicted CWD incidence rates in harvested yearling deer. An intermediate transmission model, incorporating both disease prevalence and density of infected deer, performed better than simple density- and frequency-dependent models. Our results indicate a combination of social structure, non-linear relationships between infectious contact and deer density, and distribution of disease among groups are important factors driving CWD infection in young deer.

THE EFFECTS OF HIGH DEER DENSITY ON FOREST REGENERATION AND CARBON SEQUESTRATION, Environmental Research Journal, 2013The effects of trampling and browsing pressure at high densities can negatively affect seedling recruitment, which is a critical component of forest regeneration and community structure. If the frequency of seedling disturbances is too high, forest regeneration and succession will be negatively affected. This may, in turn, introduce broader impacts beyond forest ecosystems, concerning stand biomass and the rate of carbon sequestration. As forests constitute major sinks for atmospheric CO2, the sizes of terrestrial carbon pools are of particular interest to ecologists, managers, and policy makers in relation to quantifying the amount of carbon sequestration rate.

White-tailed Deer Population at Valley Forge, National Parks Service, 2010?Objective: Students will be able to define key terms related to white-tailed deer populations and forest health and improve understanding of trends in the size of the deer population at Valley Forge National Historical Park, the factors influencing rate of population growth, and deer
management in the park. Using actual park data, students will graph and interpret changes in the deer population over time and calculate deer density and rate of growth over two decades.

Halitat-population density relationships for white-tailed deer in Illinois, John L. Roseberry and Alan Woolf, Wildlife Society Bulletin, 2008White-tailed deer have reached population densities in the agricultural Midwest that would not have been predicted 20-30 years ago. To help explain this phenomenon, we inventoried and analyzed potential deer habitat in Illinois, using classified satellite imagery and a proximity-based habitat model. Statewide prehunt deer densities (ca 1992) were estimated at 4-5 deer per km2 of total area and 30-37 deer per km2 of forest based on population reconstruction and modeling. Habitat suitability indices explained 81% of the variation in deer population densities at the county level. The amount and distribution of deer habitat in Illinois was primarily dependent on intensity of agricultural land use, which in turn was dictated by soil productivity and terrain. We found no evidence that relative use of available habitat at the county level was adversely affected either by habitat fragmentation or human presence on the landscape.

Principles of Population Growth, WP Armstrong, 2001When the population size equals the carrying capacity (N = K) the growth rate is zero (I = 0) or zero population growth. When the population size exceeds the carrying capacity (N > K), I becomes a negative number and the population decreases. In the case of an uncontrolled deer population explosion with insufficient predators, the population declines dramatically because the overbrowsed vegetation simply cannot support the high ratio of deer. Consequently, the deer die from starvation and disease, and the population rapidly declines.

Movements and ecology of a high-density deer herd on a Georgia state park, Charles Henry Killmaster, Master Thesis, U Georgia, 2005When extreme overabundance occurs, disease and starvation leads to the death of individual deer, but only after the ability of the habitat to support deer is drastically reduced (Warren 1991). With continued reproduction and low mortality rates, chronic overabundance will push deer populations beyond acceptable biological, ecological, and/or social carrying capacity (Warren 1991, 1997).

Relative deer density and sustainability: a conceptual framework for integrating deer management with ecosystem management, Wildlife Society Bulletin, 1997This framework replaces the variety of old carry-ing capacity concepts: sustained yield of maximum numbers of deer for harvest and sustained yield of timber. All of these can be expressed in the common currency of RDD, which would help clarify apparent differences when data are collected on landscapes with differing carrying capacities.

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