Category Archives: population density

Habitat-population density relationships for white-tailed deer in Illinois


Habitat-population density relationships for white-tailed deer in Illinois

John L. Roseberry and Alan Woolf, Wildlife Society Bulletin, 2008

White-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.

THE EFFECTS OF HIGH DEER DENSITY ON FOREST REGENERATION AND CARBON SEQUESTRATION

THE EFFECTS OF HIGH DEER DENSITY ON FOREST REGENERATION AND CARBON SEQUESTRATION
Environmental Research Journal, 2013

The 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.

Deer density and disease prevalence influence transmission of chronic wasting disease in white-tailed deer

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 Population Density on Juvenile Growth Rate in White-Tailed Deer

The Effects of Population Density on Juvenile Growth Rate in White-Tailed Deer
Environmental Management, 2014

Animal body size is driven by habitat quality,food availability, and nutrition. Adult size can relate to birth weight, 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.

Deer eating the future of Pennsylvania’s Forests!

Special Issue: Deer eating the future of Pennsylvania’s Forests!,
U Penn., no date

Deer population levels, when the earliest European settlers arrived, have been estimated at 9-11 deer per forested square mile. Today levels of 30-80 deer per forested square mile are not unusual and in some urban/suburban sites they are even higher.

The Relationship Between Deer Density, Tick Abundance, and Human Cases of Lyme Disease in a Residential Community

The Relationship Between Deer Density, Tick Abundance, and Human Cases of Lyme Disease in a Residential Community
Journal of Medical Entomology, July, 2014

Howard J. Kilpatrick, Andrew M. Labonte, and Kirby C. Stafford, III

ABSTRACT

White-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.

Citations
Full document

In a long-term experimental demography study, excluding ungulates reversed invader’s explosive population growth rate and restored natives

In a long-term experimental demography study, excluding ungulates reversed invader’s explosive population growth rate and restored natives
Proceedings of the National Academy of Sciences of the United States of America, vol. 111 no. 12, Mar 25, 2014
Susan Kalisz, p. 4501–4506.

In a long-term experimental demography study, excluding ungulates reversed invader’s explosive population growth rate and restored natives.

The study was long-term, over six years in a PA woodland with a deer population of 20-42 deer per km-sq (51-107 mi-sq), a population similar to some areas of Washtenaw County. There’s a lot of data and statistics in the report, and it shows that the garlic mustard population “explodes” (their “technical” term) where deer had access, but declines where deer were excluded. The ability of native plants to successfully compete with garlic mustard was dependent on the extent of deer browse. Deer never browsed on the garlic mustard, but selectively browsed the native plants.

For our natural areas to sustain the native plants that support a community of other wildlife, the PA study shows that the deer need to be managed at a level where the native flora can survive.

Excessive Deer Populations Hurt Native Plant Biodiversity, Pitt-Led Study Says

Excessive Deer Populations Hurt Native Plant Biodiversity, Pitt-Led Study Says
University of Pittsburgh News, March 10, 2014

The study, initiated in 2003 at the Trillium Trail Nature Reserve in Fox Chapel, Pa., concludes that an overpopulation of deer (density of deer in the United States is about four to 10 times what it was prior to European settlement of North America) is the primary reason garlic mustard is crowding out native plants, such as trillium, which are preferred food for wild deer.

Washtenaw County Parks and Recreations, Status Report: Deer Population Trends and Impacts in County Parks

Washtenaw County Parks and Recreations
Status Report: Deer Population Trends and Impacts in County Parks, February 2014
,
Shawn Severance, county naturalist

The deer population in Washtenaw County is elevated and increasing – The proposed DNR goal for Washtenaw County is 28 deer per square mile. Washtenaw County as a whole is currently 25% over the goal at 35 deer per square mile. The deer population in Washtenaw County has been steadily increasing over the last 15 years. Washtenaw County seems to be a magnet for deer due to a higher percentage of forested land than many of the adjacent Counties