Population and Habitat Analysis
A new insight for monitoring ungulates: density surface modelling of roe deer in a Mediterranean habitat AM Valente, TA Marques, C Fonseca, RT Torres - European Journal of Wildlife …, 2016
... In this study, we combined density surface modelling (DSM) with line transect survey to predict roe deer density in northeastern Portugal. This was based on modelling pellet group counts as a function of environmental factors while taking into account the probability of detecting pellets and conversion factors to relate pellet density to animal density. We estimated a global density of 3.01 animals/100 ha (95 % CI 0.37–3.51) with a 32.82 % CV. Roe deer densities increased with increasing distance to roads as well as with higher percentage of cover areas and decreased with increasing distance to human populations. This recently developed spatial method can be advantageous to predict density over space through the identification of key factors influencing species abundance...
Movement patterns, survival, and sightability of mule deer in central and western South Dakota [PDF] KA Robling, SL Griffin, S Stolz, SD Pierre - 2014
... our objectives were to construct logistic regression models to estimate mule deer sightability and evaluate factors contributing to visibility bias during spring and winter survey flights in the grasslands habitats of central South Dakota and the rugged river
break habitats of western South Dakota...
DNA research transforms deer pellets into 'libraries' April 1, 2013 Alaska, KCAW
... Todd Brinkman is a researcher with the Institute of Arctic Biology in Fairbanks. Jon Martin is an assistant professor of Biology at the University of Alaska Southeast. The two scientists make the case that DNA is revolutionizing the study of Sitka black-tailed deer... Read an article by Todd Brinkman in Fairchase, his scientific writing on estimating deer populations, and his work on hunting systems. ...
Explanation of the Wisconsin Deer Estimation Methods which include survey input from the people of the state
Estimating White-tailed Deer Abundance at the Blue Hills Reservation using Distance Sampling Mass.Gov
.QDMA Deer Management Report - 2012
Getting the Lay of the Land, GIS September 22, 2012 West Virginia, WVGazzette
Division of Natural Resources officials have made high-quality color topographic maps available on the agency's website... , biologists who want to establish deer-population level guidelines might study satellite-generated GIS data on forest cover and agricultural crops to determine how much food is available in a given area... Visitors to the DNR's website, www.wvdnr.gov, can access the maps by going to the site's Hunting section and clicking on the "New WMA Topo Maps" link ...
Estimating occupancy and predicting numbers of gray wolf packs in Montana using hunter surveys LN Rich, RE Russell, EM Glenn, MS Mitchell, JA Gude… - The Journal of Wildlife …, 2013
... Montana Fish, Wildlife and Parks (MFWP) conducts annual telephone surveys of >50,000 deer and elk hunters. We explored how survey data on hunters' sightings of wolves could be used to estimate the occupancy and distribution of wolf packs and predict their abundance in Montana for 2007–2009... Overall, estimates of the occupancy and distribution of wolf packs were generally consistent with known distributions... Our results indicate that multi-season occupancy models based on public sightings can be used to monitor populations and changes in the spatial distribution of territorial carnivores across large areas where alternative methods may be limited by personnel, time, accessibility, and budget constraints ...
Density estimation in wildlife surveys by J Bart - 2004 - Aug 30, 2010 - Title: Density estimation in wildlife surveys. Author: Bart, Jonathan; Droege, Sam; Geissler, Paul; Peterjohn, Bruce; Ralph, C. John. Date: 2004 ...
Habitat guidelines for mule deer - Colorado
Participatory GIS for collaborative deer management February 9, 2012 A slidshow presentation by Justin Irvine.
Background to the issue. Constructing a GIS model. Participation in GIS. Validating GIS predictions. Using GIS to address local NRM conflicts
Spatially explicit models for inference about density in unmarked or partially marked populations RB Chandler, JA Royle - The Annals of Applied Statistics, 2013
... Recently developed spatial capture–recapture (SCR) models represent a major advance over traditional capture–recapture (CR) models because they yield explicit estimates of animal density instead of population size within an unknown area. Furthermore, unlike nonspatial CR methods, SCR models account for heterogeneity in capture probability arising from the juxtaposition of animal activity centers and sample locations... Our paper challenges sampling and analytical conventions in ecology by demonstrating that neither spatial independence nor individual recognition is needed to estimate population density—rather, spatial dependence can be informative about individual distribution and density.
Deer Habitat Management: Getting Started January 22, 2013 New York Corning Leader
... In numerous cases the process of improving a particular woodlot cannot start with a commercial cut, so the first phase of work is Timber Stand Improvement. The genetically best species that are preferred by deer and other wildlife will be left for seed production. The Timber Stand Improvement process before a future commercial cut can be conducted should focus on removing; autumn olive, multiflora rose, buckthorn, barberry, prickly ash, hayscented fern, New York fern, hopehornbeam, ironwood, beech and aspen...
PR Krausman, VC Bleich - International Journal of Environmental Studies, 2013
... Contemporary management of the ungulates evolved through three stages: exploitation, concern for survival and conservation through wise use. The success of conservation of ungulates has been attributed to the merger of biology, an understanding of habitat and the role of human dimensions. This triad of wildlife management has been effective. Most ungulate populations in North America have been restored; viable populations exist. Challenges to the conservation of large mammals remain, however, including increased human population growth, climate change and sources of funding...
Food Plot Strategy For Whitetails April 13, 2011 Habitat North American Whitetail MagazineWith the right plan, your food plots can meet the nutritional needs of the deer on your land and provide some excellent hunting opportunities! By Dr. James C. Kroll When I began my work in deer management, here in eastern Texas hunting clubs practiced ..
Growth in Deer Herds Contributes to Forest Biodiversity - Research from France
Texas Study Finds Deer Density Correlated with more Birds, June, 2011 "Effects of deer overabundance on avian abundance, diversity, and reproductive success in Central Texas" by Jinelle H. Sperry, Ph.D.
Contrary to our predictions, there were significantly more birds (t = 2.86, P < 0.01; Fig 1) and bird species (t = 2.46, P = 0.01; Fig 1) detected per point on the BCP [Balcones Canyonland Preserve, not deer managed, higher deer density] compared to the ranch sites.. We found that nest survival was slightly lower on the BCP sites (model averaged estimate = -0.44) although the 95% confidence intervals encompassed zero (-1.10, 0.23), indicating a weak effect [not statistically significant].
Best way to count white-tailed deer populations in tropical forests June 27, 2011 Population Estimation Mongabay.com
In the new issues of mongabay.com's open access journal Tropical Conservation Science, researchers look at the most accurate way to count white-tailed deer (Odocoileus virginianus) in central Mexican forests. The white-tailed deer is not considered an endanagered species, but local extinction can occur. ...The researchers write that in order to conduct any accurate count, "two crucial factors are required: pellet decomposition rate and daily defecation rate." ..Researchers tried four different methods of pellet counting to find the best way to compile population density: two ways to count pellet groups in circular plots known as FSC or FAR, strip transects, or line transects. They found that average density estimates were similar in all four counts, but recommend that line transects were the best method. Second was strip transect and last FSC.
Deer Nutrition - Part 1 Energize Your Deer Management September 24, 2011 Whitetaildomains.com
Carbohydrates and fats are the two primary sources of energy for deer... Acorns and whole cottonseed are examples deer foods that may be high in fat and thus are good energy sources...[a study found] that the months in which energy was most limiting were May-August, when fawns are being produced and antlers are growing... Deer are typically fattest during autumn and lose fat throughout the winter, even with unlimited access to high quality food.... - female deer may be in poor condition during autumn...because they successfully raised fawns. Providing milk for fawns requires tremendous amounts of energy. ..
Local study published on developmental malformations in deer ...
November 3, 2011, Montana, Bitteroot Star, By victoria1
This long-term study was done with no funding, as a public service.... Underbite makes it difficult for a grazing animal to procure enough nutrition, the primary reason many of the females are unable to produce viable young and young animals fail to grow properly and gain weight after weaning... The authors attribute the widespread deformations to endocrine disrupting chemicals in the environment that are associated with fetal thyroid dysfunction that results in such deformations... The study concludes that underbite and the other serious symptoms of fetal hypothyroidism are likely a significant factor in the decline of wild ruminant populations in Montana and other western states. [Gary Haas of Big Sky Beetle Works, and Dr. Pamela Hallock, a researcher and professor at the University of South Florida, recently published in the journal Wildlife Biology in Practice]
Human Activity Displaces Predators More Than Prey March 3, 2011, ScienceDaily
... Faculty of Environmental Design, Department of Geomatics in the Schulich School of Engineering and the Faculty of Veterinary Medicine. ... Their results showed that prey were three times more abundant on roads and trails used by more than 32 humans a day, but predators were less abundant on roads and trails used by more than 18 humans a day. ... "The research shows that humans might displace large mammalian predators," says Tyler Muhly ...
Large predators limit herbivore densities in northern forest ecosystems April 2012, William J. Ripple and Robert L. Beschta, EUROPEAN JOURNAL OF WILDLIFE RESEARCH, DOI: 10.1007/s10344-012-0623-5
There is a lack of scientific consensus about how top-down and bottom-up forces interact to structure terrestrial ecosystems. This is especially true for systems with large carnivore and herbivore species where the effects of predation versus food limitation on herbivores are controversial. Uncertainty exists whether top-down forces driven by large carnivores are common, and if so, how their influences vary with predator guild composition and primary productivity. Based on data and information in 42 published studies from over a 50-year time span, we analyzed the composition of large predator guilds and prey densities across a productivity gradient in boreal and temperate forests of North America and Eurasia. We found that predation by large mammalian carnivores, especially sympatric gray wolves (Canis lupus) and bears (Ursus spp.), apparently limits densities of large mammalian herbivores. We found that cervid densities, measured in deer equivalents, averaged nearly six times greater in areas without wolves compared to areas with wolves. In areas with wolves, herbivore density increased only slightly with increasing productivity. These predator effects are consistent with the exploitation ecosystems hypothesis and appear to occur across a broad range of net primary productivities. Results are also consistent with theory on trophic cascades, suggesting widespread and top-down forcing by large carnivores on large herbivores in forest biomes across the northern hemisphere. These findings have important conservation implications involving not only the management of large carnivores but also that of large herbivores and plant communities.
Peaceful Coexistence with Deer — Bay Nature Institute (History of Deer in the Bay Area and speculation about the population size) feral deer farther up the hill in Wildcat Canyon and Tilden Regional Parks, ... Bay Area Hiker: Waterfall Loop Big Basin Redwoods State Park ...
A Deer Population Model for California
MODELING ARTIODACTYL POPULATION DEMOGRAPHICS UNDER HUMAN PREDATION, SCA Proceedings, Volume 22 (2009), ADRIAN R WHITAKER, DEPARTMENT OF ANTHROPOLOGY, UNIVERSITY OF CALIFORNIA, DAVIS
This paper will attempt to identify the critical variables of population dynamics for deer (Odocoileus sp.) through the modeling of deer populations both under and free from hunting pressure. The dynamics of these models, combined with modern ecological studies, will demonstrate the robust nature of deer populations and the overall ability of deer to withstand fairly substantial losses from human hunting. The paper will conclude with a discussion of the implications of the findings for arguments regarding resource conservation by prehistoric Californians.
Tooth Aging as a Management Tool
E Vander Wal, FM van Beest, RK Brook 2013, The Journal of Wildlife Management
... We used group size data from a population of elk in Manitoba, Canada, that was experimentally reduced from 1.20 to 0.67 elk/km2 between 2002 and 2009. Our results indicated that functional responses of group size to population density are sex-specific. Females showed a positive density-dependent response in group size at population densities ≥0.70 elk/km2 and we found evidence for a minimum group size at population density ≤0.70 elk/km2. Changes in male group size were also density-dependent; however, the strength of the relationship was lower than for females. Density dependence in male group size was predominantly a result of fusion of solitary males into larger groups, rather than fusion among existing groups...
Spatial factors related to mortality and population decline of endangered mountain caribou CD Apps, BN Mclellan, TA Kinley, R Serrouya, DR Seip… Journal of Wildlife Management, 2013
Mountain caribou are an endangered ecotype of woodland caribou ... The decline in caribou is thought to be due to apparent competition where increases in early-seral conditions stimulate a numerical response in primary ungulate prey and their predators and these incidentally kill an unsustainable number of caribou... Wolf predation occurred primarily at low elevations at the broader scale and in association with roads at the finer scale. Our results indicate that caribou vulnerability to predation was a function of both static (e.g., terrain) and dynamic (e.g., overstory conditions) factors, but we did not find evidence that localized habitat fragmentation due to forest harvest influenced predation on caribou...
Modelling and Habitat Analysis
From Deer wars: science, tradition, and the battle over managing whitetails in Pennsylvania:
"At the beginning of the [19th] centruy Pennsylvania's forests had been young and brush, sprouting from the hilssides that had been clear-cut only a decade or so earlier They offered lots of browse and could support one deer on every eight to ten acres Two decades later, it took twenty-five acres of forest to suport a single deer, Latham said, because the state's forests had entered the "pole timber" stage, when trees are too small to produce large amounts of mast but too larger to provide browse. "
Habitat management influences overwinter survival of mule deer fawns in Colorado EJ Bergman, CJ Bishop, DJ Freddy, GC White… - … of Wildlife Management, 2014
... many pinyon pine (Pinus edulis)–Utah juniper (Juniperus osteosperma) woodland habitats reach late seral stages that encroach into forest openings. This encroachment typically occurs at the expense of browse species that are preferred by mule deer ... documented changes in deer vital rates in response to habitat manipulations are lacking. ... . Our study provides evidence that habitat management on winter ranges can positively influence a key vital rate for mule deer in pinyon pine–Utah juniper ecosystems ...
Climate change and fire management in the mid-Atlantic region KL Clark, N Skowronski, H Renninger, R Scheller - Forest Ecology and Management, 2013
... Prescribed burning is the only major viable option that land managers have for reducing hazardous fuels in a cost-effective manner, or ensuring the regeneration and maintenance of fire-dependent species.
Habitat Issues and the Wyoming Range Mule Deer Herd Initiative [This link wild download a powerpoint slideshow, one slide below]
Just Add Water for Fawns?
A Long-Term Assessment of the Variability in Winter Use of Dense Conifer Cover by Female White-Tailed Deer June 17, 2013 GD DelGiudice, JR Fieberg, BA Sampson - PLOS ONE
... Consistent with our findings reported elsewhere that snow depth has a greater impact on deer survival than ambient temperature, herein our population-level results highlight the importance of dense conifer cover as snow shelter rather than thermal cover. Collectively, our findings suggest that maximizing availability of dense conifer cover in an energetically beneficial arrangement with quality feeding sites should be a prominent component of habitat management for deer...
SPECIAL PROBLEMS OF FORESTS AS DYNAMICALLY COMPLEX ECOLOGIC-ECONOMIC SYSTEMS JB Rosser Jr - 2013
... deer maximize in population about 8 years after a clearcut, turkey and quail
(and overall biodiversity) maximize at around 25 years after a clearcut, whereas bears maximize after the forest reaches about 60 years in age, bears preferring old growth forests with large trees (especially fallen ones).
The Role of Vegetation and Supplemental Feed in Deer Management
[PowerPoint slides] David G. Hewitt. Caesar Kleberg Wildlife Research Institute, March, 2012
Fast Deer Facts, By The Numbers November 30, 2014 Grand View Outdoors... 907 Acres: The average fall home range size of mature bucks in a University of Georgia GPS-collar study in unfragmented hardwood forest in northern Pennsylvania. The average core area size, or the area where a buck spends at least half of its time, was only 142 acres...
How does climate change influence demographic processes of widespread species? Lessons from the comparative analysis of contrasted populations of roe deer
JM Gaillard, AJ Mark Hewison, F Klein, F Plard… - Ecology Letters, 2013
... Roe deer are income breeders, with high levels of allocation to reproduction, and are hence strongly constrained by the availability of high quality resources during spring. We investigated how recent climate change has influenced demographic processes in two populations of this widespread species. Spring began increasingly earlier over the study, allowing us to identify 2 periods with contrasting onset of spring. Both populations grew more slowly when spring was early. As expected for a long-lived and iteroparous species, adult survival had the greatest potential impact on population growth. Using perturbation analyses, we measured the relative contribution of the demographic parameters to observed variation in population growth, both within and between periods and populations. Within periods, the identity of the critical parameter depended on the variance in growth rate, but variation in recruitment was the main driver of observed demographic change between periods of contrasting spring earliness. Our results indicate that roe deer in forest habitats cannot currently cope with increasingly early springs. We hypothesise that they should shift their distribution to richer, more heterogeneous landscapes to offset energetic requirements during the critical rearing stage.
Getting the biggest birch for the bang: restoring and expanding upland birchwoods in the Scottish Highlands by managing red deer AJ Tanentzap, J Zou, DA Coomes - Ecology and Evolution, 2013
... High deer populations threaten the conservation value of woodlands and grasslands, but predicting the success of deer culling, in terms of allowing vegetation to recover, is difficult. Numerical simulation modeling is one approach to gain insight into the outcomes of management scenarios... Our results show that managers interested in maximizing tree regeneration cannot simply reduce deer densities but must also improve ground cover for seedling establishment, and the model we develop now enables managers to quantify explicitly how much both these factors need to be altered. More broadly, our findings emphasize the need for land managers to consider the impacts of large herbivores rather than their densities.
The Effects of Extreme Drought on Native Forage Nutritional Quality and White-Tailed Deer Diet Selection
MA Lashley, CA Harper - Southeastern Naturalist, 2012
Forage availability is often used as a measure of habitat quality for Odocoileus virginianus (White-tailed Deer; hereafter “Deer”). Many studies have evaluated treatment effects on forage availability, but the effects of other abiotic factors, such as drought, on native forages and Deer diet selection are poorly understood. We measured diet selection and nutritional quality of commonly occurring forages following extreme drought (2007) and normal rainfall years (2008) in 4 closed-canopied hardwood stands in the Central Hardwoods region. Deer selected 6 forage species in both years of the study. Within these 6 species, crude protein (CP) and acid detergent fiber (ADF) were not different, and neutral detergent fiber (NDF) increased during the year of normal rainfall. Thirteen other commonly occurring forages showed a different trend, with CP negatively affected by drought and ADF and NDF unaffected. Less-selected species in the drought year and a greater selection-index cut-off value suggest Deer were more selective of species consumed during extreme drought because fewer plants met their nutritional requirements. Our data support the selective quality hypothesis, predicting Deer become more selective of plant species to meet nutritional requirements when resources are limited. Our data suggest more frequent and intense droughts predicted as a result of global climate change may influence diet selection of deer and decrease forage quality enough to limit lactation during the late-summer stress period in the Southeast.
Deer can be too many, too few, or just enough for healthy forests March 31, 2012 NRS Research Review, No. 16, Spring 2012
... they found that deer population levels at or below 20 per square mile allowed undergrowth to recover. The study surprised scientists, though, when there was some regrowth even at very high deer densities.... one species of small tree/shrub, pin cherry, that had become overabundant at the lowest levels of deer density (10 per square mile in that study). They soon realized that this phenomenon was early evidence of such a thing as too few deer... this research suggested that the levels of deer were just right for the West Virginia landscape where the study occurred because the mix of disturbances experienced by these forests historically—ground fire, canopy gaps, and some deer—increased diversity...
dynamics and Conservation Management of a Wooded Landscape under High Herbivore Pressure AC Newton, E Cantarello, N Tejedor, G Myers - International Journal of Biodiversity, 2013
... We present the use of a spatially explicitmodel of woodland dynamics (LANDIS-II) to examine the impacts of herbivory in the New Forest National Park, UK, in relation to its management for biodiversity conservation.The model was parameterized using spatial
data and the results of two field surveys and then was tested with results from a third survey. Field survey results indicated that regeneration by tree specieswas found to bewidespread but to occur at low density, despite heavy browsing pressure.The model was found to accurately predict the abundance and richness of tree species. Over the duration of the simulations (300 yr), woodland area increased in all scenarios, with or without herbivory. While the increase in woodland area was most pronounced under a
scenario of no herbivory, values increased by more than 70% even in the presence of heavy browsing pressure. Model projections provided little evidence for the conversion of woodland areas to either grassland or heathland; changes in woodland structure and
composition were consistent with traditional successional theory.These results highlight the need for multiple types of intervention when managing successional landscape mosaics and demonstrate the value of landscape-scale modelling for evaluating the role of herbivory in conservation management.
Impacts of White-tailed Deer on Forests May, 2012 Ohio State Universit
For an interactive tool for determining the level of deer impact in a forest, visit http://www.deerandforests.org/home/habitat .
The loss of plants and plant diversity due to over browsing by deer can reverberate up through the food chain, especially to insects and birds. ... It's important to note that while too many deer can be a problem, so can too few deer. Eastern forests have evolved with white-tailed deer and depend on their browsing as a disturbance, which can lead to an increased diversity of plant species. In Pennsylvania, researchers found an overabundance of pin cherry in areas of the forest with low deer numbers (10 deer per square mile). Pin cherry has the ability to out compete other tree seedlings when highly abundant, and deer browsing can effectively keep such species under control, allowing for more diversity.
Forage resource evaluation system for habitat—deer: an interactive deer habitat system March 24, 2012 Alaska
Author: Hanley, Thomas A.; Spalinger, Donald E.; Mock, Kenrick J.; Weaver, Oran L.; Harris, Grant M. Date: 2012 Source: Gen. Tech. Rep. PNW-GTR-858. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 64 p Station ID: GTR-PNW-858
Description: We describe a food-based system for quantitatively evaluating habitat quality for deer called the Forage Resource Evaluation System for Habitat and provide its rationale and suggestions for use. The system was developed as a tool for wildlife biologists and other natural resource managers and planners interested in evaluating habitat quality and, especially, comparing two or more patches of habitat or the same patch at different seasons or under different conditions. It is based on the quantity (of biomass) and quality (digestible energy and digestible protein) of the habitat’s food resources in relation to user-specified metabolic requirements of deer (which differ with species, age, sex, season, and reproductive status). It uses a linear programming algorithm to determine the suitable forage that can sustain deer at the specified requirements. Output includes the number of deer days (1 deer day equals one deer for 1 day) per unit area that the available food resources are capable of supporting, the species composition of the solution set to the linear programming problem, and the relative importance of biomass versus nutritional quality as limiting factors of the habitat for deer. The system is accessed via the Internet (http://cervid.uaa.alaska.edu/deer/home.aspx) and consists of a Web-based application for analysis at the patch (or “stand”) scale and a geographical information system (GIS)-based application for analysis at the landscape scale, which includes spa
tial effects of patch sizes and their shapes and locations in relation to deer home ranges. Although the system was developed for Sitka black-tailed deer (Odocoileus hemionus sitkensis) in southeastern Alaska and illustrated with examples for them, it also can be applied for other species of deer (with the exception of very large species such as moose, Alces alces) elsewhere in the world.
Keywords: Black-tailed deer, Odocoilius hemionus, Alaska, habitat evaluation, carrying capacity, nutrition, forest planning
Setting Time Limits for Hunting and Fishing May Help Maintain Wildlife Populations ScienceDaily (May 14, 2010) — Hunting and fishing quotas limit the number of game animals or fish an individual may take based on harvests from the previous year. But according to a new study co-authored by University of Minnesota ecologist Craig Packer, this strategy may jeopardize wildlife populations.
Photo Album Tells Story of Wildlife Decline ScienceDaily (Aug. 31, 2010) — With a simple click of the camera, scientists from the Wildlife Conservation Society and Zoological Society of London have developed a new way to accurately monitor long-term trends in rare and vanishing species over large landscapes.
The ecological role of fire in Sierran conifer forests:: Its application to National Park management BM Kilgore - Quaternary Research, 1973 - Elsevier ... A model for a small forest fire … to simulate burned and burning areas for use in a detection model.
Forest Science 17 2, pp. 163–169. Lawrence, G., 1966. ... Effect of forest manipulation on deer habitat
in giant sequoia. Journal of Wildlife Management 36 2, pp. 595–605. ...
Modelling habitat suitability for black-tailed deer (Odocoileus ... by BB Boroski - 1996 -
Within this extent, habitat suitability classed based on feeding and cover produced the grain size for black-tailed deer (mean 0.44 ha, range 0.06–7.79 ha). ...
Wildlife Online - Risk Factors and Mortality of Black-Tailed Deer ...... managers attempting to manipulate habitats to benefit deer populations. Keywords: black-tailed deer, Cox proportional hazards, forest management, ...
Modeling black-tailed deer population dynamics using structured ...We used cohort analysis to reconstruct the female segment of a Columbian black-tailed deer.
Does Hunting Increase Deer Populations in some environments?
Current game management practices are designed to artificially propagate selected game species for hunters.
A text titled "Wildlife Ecology and Management" by William Robinson states quite clearly: "The general theory of harvesting animals is based on the premise that when animals are not harvested at all, growth and recruitment are balanced by natural mortality and that the average growth rate of a population at its carrying capacity is zero. Harvesting reduces the population size, but the reduction results in an increase in the growth rate of the population. This increase in growth rate is brought about because of higher birth rates and lower death rates resulting from decreased competition for resources. This increased growth rate provides a surplus of individuals above the number required to replace the population, and this surplus can be harvested."
Hunting only lowers deer numbers on a temporary basis. A study by Richter & Labisky, "Reproductive Dynamics and Disjunct White-tailed Deer Herds in Florida," in The Journal of Wildlife Management, determined that the "incidence of twinning was 38% on hunted herds and 14% on nonhunted sites."
'Smart Collar' in the Works to Manage Wildlife Better August 30, 2011 New York Times
The collars, in development in academia and intended for commercial production in the next few years, use a combination of global positioning technology and accelerometers for measuring an animal’s metabolic inner life in leaping, running or sleeping....“What you end up with is a diary for the animal, a 24-hour diary that says he spent this much time sleeping, and we know from the GPS where that was,” said Terrie Williams, a professor of biology at the University of California, Santa Cruz, and one of three co-investigators on the project.
Reconstructing historical snow depth surfaces to evaluate changes in critical demographic rates and habitat components of snow-dependent and snow-restricted species August 30, 2011 Jeffrey A. Manning, Edward O. Garton.
Methods in Ecology and Evolution
1. Climate change models consistently predict snow depth declines across the Northern Hemisphere. Snow depth has been linked to the demography of numerous species, and snow depth reduction is expected to affect the demography of some northern species. As many demographic studies depend on long-term population data that extend back beyond available sources of spatially continuous snow depth data, reliable hindcasting of snow depth surface maps is needed.
2. We developed a two-stage regression modelling approach to reconstructing historic snow depths using an existing and readily available spatiotemporal data set of daily meteorological variables across a large, heterogeneous landscape in North America from 1982 to 2003. The final model accounted for ecoregional differences and predicted snow depth as a function of elevation and total snowfall accumulation.
3. Model validations showed that the estimated snow depths were spatially and temporally accurate.
4. We demonstrate how to apply this model with ArcGIS to hindcast monthly and yearly sequences of high-resolution, spatially continuous surfaces of historic snow depths. We also illustrate the utility of the modelled snow depth surfaces for informing predictions of how changes in snow depth may influence the demography and habitats of snow-dependent and snow-restricted species by assessing the spatiotemporal stochasticity of snow conditions that potentially benefit wolverine Gulo gulo and the winter ranges, net energy costs and population growth of mule deer Odocoileus hemionus.
5. This model can be used to hindcast snow depth surfaces across similar regions; our simple two-stage modelling approach can be applied to other regions where equivalent climate data are available. The resulting spatiotemporal snow depth surfaces estimated from this model can be linked to existing long-term wildlife population data sets to investigate the extent to which snow depth declines may regulate or limit populations.