Overabundant White-tailed Deer Research Articles

Exclusion of Overabundant White-tailed Deer (Odocoileus virginianus) Results in Shifts in Soil Microbial Communities and Abiotic Soil Condition in a Northeastern Deciduous Forest

Past and current anthropogenic practices have resulted in dramatic alterations to ungulate population densities worldwide. When ungulate populations are overabundant, they can alter the dynamics, structure, and function of ecosystems. White-tailed deer (Odocoileus virginianus), specifically, can occur at densities far greater than their historical records in parts of their native range, which includes forests in the northeastern U.S. They have been shown to alter community structure of native plants, indirectly impact animal communities, and promote the success of invasive species. Despite much research into the effects of overabundant ungulates and deer in particular, less is known about the effects of deer on soil microbial communities. Here, we utilized soil samples from inside and outside of six deer exclosures located in a regional second growth mixed hardwood forest on the Binghamton University campus in Vestal NY, U.S.A. A metagenomic analysis was conducted on DNA extracted from the soil to identify the microbes present. Soil characteristics, including soil organic matter, soil moisture, pH, and electrical conductivity were also measured. Soil samples from inside exclosures had on average lower pH, higher soil moisture and organic matter, and higher electrical conductivity. The microbial communities across all samples were dominated by Proteobacteria, Acidobacteria, and Actinobacteria. However, the structure of the microbial soil community appeared to differ between samples taken inside and outside the exclosures, with those taken outside more closely resembling other outside samples and those sampled inside soils showing more variability in community structure. Overall, our results suggest that overabundant deer may have a homogenization effect on the soil abiotic environment and the soil microbial community.

Spatial factors of white-tailed deer herbivory assessment in the central Appalachian Mountains.

Because moderate to over-abundant white-tailed deer (Odocoileus virginianus) herbivory impacts biodiversity and can alter community function, ecological benchmarks of herbivory impact are needed to assess deer impacts. We evaluated spatial patterns of deer herbivory and their relation to herbivory assessment by evaluating woody vegetation along 20 transects at each of 30 sites spread across a wide range of deer herd densities and vegetative condition throughout the biodiverse Appalachian Mountains of Virginia, USA. Surprisingly, herbivory patterns and the availability of woody forage generally were unchanged among physiographic regions and land use diversity classes. However, some relationships between browsing pattern and vegetation varied with scale. The total quantity of vegetation browsed on a given site and at the transect scale were related positively to the availability of forage, as the proportion of stems browsed decreased as stem density increased. However, this was only true when all stems were considered equally. When stem densities by species were weighted for deer preference, the proportion of stems browsed had no relationship or increased with stem density. Compared to the value from all transects sampled, on average, the mean of ≥ 3 transects within a site was within 0.1 of the browsing ratio and stem densities were within 0.5 stems m-2. Our results suggest that one transect per square kilometer with a minimum of three transects may be sufficient for most browsing intensity survey requirements to assess herbivory impacts in the Appalachian region of Virginia. Still, inclusion of spatial factors to help partition variation of deer herbivory potentially may allow for improved precision and accuracy in the design of field herbivory impact assessment methods and improve their application across various landscape contexts.

Sterilization as an alternative deer control technique: a review

Burgeoning white-tailed deer (Odocoileus virginianus) populations in suburban landscapes continue to impact communities and challenge natural resource managers. Increased deer-related damage to vegetation, ecosystems, and automobiles can exceed the tolerance of local stakeholders. We provide an overview of the potential effi cacy of using surgical sterilization to help manage populations and confl icts associated with locally overabundant white-tailed deer populations. We review theoretical and fi eld studies pertaining to deer sterilization, and provide research priorities to help guide future sterilization efforts. Recent fi eld studies suggest that sterilization of female deer remains expensive, at approximately $1,000 per surgery. Sterilization may provide an alternative management technique for reducing suburban deer herds in communities willing to endure the costs of a long-term effort and where lethal deer removal is unacceptable or impractical. Surgical sterilization is scale-limited based on the ability to capture and sterilize 80% or more of the female deer in a population and maintain that proportion of the population treated over time. Overall success will be greatest for closed or insular deer herds where the effects of immigration can be minimized.

Factors Influencing Trust in a Wildlife Management Agency: A Case Study of Deer Management in Bloomington, Indiana

Overpopulation of white-tailed deer ( Odocoileus virginianus ) is an increasingly common challenge for natural resource managers, especially in the Northeast, Great Lakes, and Midwest regions of the United States. Despite the pervasiveness of the issue, satisfactory resolution remains elusive for many parks, communities, and natural areas. Frequently, social concerns and ecological conditions deteriorate to the point where lethal management techniques are recommended to reduce numbers quickly. However, implementing lethal management strategies to reduce overabundant white-tailed deer populations frequently engenders contentious debate, in part because trust in the managing agency is often low. In such cases, implementation challenges shift from managing deer to affecting and managing public opinion. The purpose of this case study was to examine factors that influence trust in the City of Bloomington (IN) government to properly manage the deer population at a city-owned nature preserve. Results indicated that positive evaluation of the decision-making process and positive evaluation of the science that informed decisions predicted trust in the local city government, while age and preference for hunting predicted distrust. Support for the proposed sharpshooting policy and citizen involvement in the issue, measured by the number of personal and civic actions taken, were not significant predictors of trust in the city. Citizens’ source of information on the issue influenced their evaluation of the science. Specifically, when the local newspaper was the primary source of information, respondents were more likely to agree with the conclusions of a scientific study city managers used to illustrate the deer overpopulation. We recommend natural resource managers identify and use trusted communicators to engage with the public on controversial policies. Trust should be considered a prerequisite to implementation of new policies, controversial or otherwise. Subscribe to JPRA

The joint effects of fire and herbivory on hardwood regeneration in central Texas woodlands

Oaks (Quercus spp.) are not regenerating in forests and woodlands in central Texas and elsewhere. This has been attributed to fire suppression. However, overabundant white-tailed deer (Odocoileus virginianus) can also limit oak regeneration. We hypothesized that both fire re-introduction and protection from deer would increase the number and growth of hardwood seedlings, saplings, and sprouts in a central Texas woodland co-dominated by Texas red oak (Quercus buckleyi) and Ashe juniper (Juniperus ashei). We measured the separate and joint effects of prescribed fire and deer herbivory on the number, size, and growth of Ashe juniper and hardwoods, tree mortality, and canopy cover. We collected data one year before and three years after deer-fence construction and a prescribed fire. Fire stimulated re-sprouting in oak and other hardwoods, but had no detectable effect on their seedlings or saplings, even three years later. Deer exclusion increased the number of seedlings transitioning to the sapling size class. Both fire and deer exclusion together were required to increase average sprout height above the browseline. The apparent adaptations of native hardwoods to fire are the strongest evidence we have for an important role for fire pre-settlement. Our results also indicate that fire suppression in central Texas and other parts of the south-central US is causing a shift, not to more mesic-adapted species as observed in the eastern US, but to juniper (Juniperus spp.), which is at least as xeric-adapted as oak. Therefore, thinking about the “oak regeneration problem” needs to be expanded beyond “mesophication” to incorporate the shift to juniper in drier regions. It is likely that deer control is necessary to allow fire to have positive effects on the regeneration of oaks and other hardwoods in this region and wherever deer are over-abundant. Moreover, the negative effects of deer herbivory on oak growth may partially account for reported failures of single fires alone to promote hardwood regeneration elsewhere.

Structuring Effects of Deer in Boreal Forest Ecosystems

Many deer populations have recently increased worldwide leading to strong direct and indirect ecological and socioeconomical impacts on the composition, dynamic, and functions of forest ecosystems. Deer directly modify the composition and structure of vegetation communities, but they also indirectly affect other species of the ecosystem by modifying the structure of the vegetation. Here we review the results of a research program on overabundant white-tailed deer (Odocoileus virginianus) in the boreal forest of Anticosti Island (Québec, Canada) aimed at identifying deer densities compatible with forest regeneration. Various silvicultural systems and treatments failed to regenerate deer habitat at high deer densities, but planting size-adapted seedlings could be effective at moderate densities. Using a controlled deer density experiment, we found vegetation recovery at deer densities ≤ 15 deer/km2. The same experiment revealed that other groups of organisms such as insects and birds responded favorably to a reduction of deer density. We also found that alternative successional trajectories may occur after a certain period of heavy browsing during early succession. We conclude that one of the most important remaining research gaps is the need to identify habitat-specific threshold densities at which deer impacts occur and then to design effective wildlife and forest management strategies to limit deer impacts and sustain ecosystem integrity.

Individual and interactive effects of Amur honeysuckle (Lonicera maackii) and white-tailed deer (Odocoileus virginianus) on herbs in a deciduous forest in the eastern United States

Invasive Amur honeysuckle (Lonicera maackii) has reduced diversity, growth, and reproduction of native herbs in the Midwest USA. These effects may be compounded by browsing from overabundant white-tailed deer (Odocoileus virginianus). We used experimental treatments of honeysuckle (present, absent, removed) and deer (present, excluded) to measure their independent and interactive impacts on diversity, richness, and abundance of herbs in a deciduous forest in southwestern Ohio, USA. Species diversity and richness of herbs were not affected by honeysuckle or deer. Honeysuckle reduced abundance of annuals, graminoids, spring perennials, and summer perennials; deer decreased abundance of annuals and spring perennials, but increased abundance of graminoids. A deer × honeysuckle interaction showed that when honeysuckle was absent or removed, browsing by deer kept abundance of annuals and spring perennials low. Effects of honeysuckle and deer also were assessed for the three most abundant herbs: honeysuckle reduced abundance of Carex rosea and Sanicula odorata, and deer reduced abundance of Viola soraria. Herb abundance varied seasonally and annually. Honeysuckle and deer reduced number of leaves/stem of Maianthemum racemosum and a deer × honeysuckle interaction indicated that the negative effect of honeysuckle was released only when deer were excluded. Herb abundance and M. racemosum rebounded to or near to control levels after removal of honeysuckle. Our findings revealed that impacts of invasive honeysuckle or overabundant deer were not the same across all levels of biological organization (i.e., individual species, growth forms, community measures of species diversity/richness). Measuring impacts of these species at multiple levels of biological organization, considering deer × honeysuckle interactions, and collecting data for several years to account for seasonal and annual fluctuations will help guide management plans. The rapid response by herbs to removal of honeysuckle demonstrated the resilience of this community and is a hopeful sign for restoration of native understory herbs.

Managing Overabundant White-Tailed Deer: Is it Time to Consider Regulated Commercial Harvest?

Managing Overabundant White-Tailed Deer: Is it Time to Consider Regulated Commercial Harvest?

Are There Too Many Deer in a Large Private Park in West-central Indiana?

Overabundant white-tailed deer (Odocoileus virginianus) can have significant effects on forest understory vegetation, especially in parks where hunting is not permitted. The DePauw Nature Park is a large (210 ha) private park located in west-central Indiana; hunting was prohibited in the park when the park was established in 2003. The park is mostly forest habitat but is surrounded by a rural landscape consisting of a mix of agricultural fields and forest fragments. We assessed the effects of deer on forest understory vegetation in the park using exclosures and control plots and estimated the size of the deer population in the park using infrared digital game cameras. There were almost no changes in forest understory vegetation during the first four years after the exclosures were established. The estimated population size of deer in the park ranged from 46 to 66 deer per km2. Although no observations were made outside park boundaries, we believe that the deer often move in and out of the park, feeding in surrounding fields and returning to the park for shelter. Effects of a large population of deer on forest understory vegetation are mediated by movement of deer in and out of the park as well as hunting pressure outside the park. We conclude that deer are having minimal effects on forest understory vegetation in the park at this time, but we will remain vigilant by continuing to monitor vegetation in the exclosures and control plots during future years.

Benefits to rare plants and highway safety from annual population reductions of a “native invader,” white-tailed deer, in a Chicago-area woodland

Overabundant white-tailed deer are one of the most serious threats to woodland plant communities in the Chicago area. Moreover, the abundant deer in a highly populated area causes economic harm and poses hazards to human safety through collisions with vehicles. The artificial conditions causing the overabundance and resulting consequences qualify the white-tailed deer in the Chicago area to be considered as "native invaders". We examined the benefits of culling deer at a Chicago-area woodland preserve by comparing browse rates on four endangered plant species from years before culling began with years with culling. We also examined deer-vehicle collision and traffic flow rates on area roads from years before culling began and years with culling to assess whether population reductions may have benefited road safety in the area. All four endangered plant species (three orchid species and sweet fern) had lower browse rates in years with culls, although the decreased browsing rates were statistically distinguishable for only two of the species (grass pink orchid and sweet fern). After first verifying that traffic flow rates did not decrease from pre-cull years to years with culls, we analyzed the Illinois Department of Transportation data from area roads based on deer-vehicle collisions causing >US$500 in damage and showed a one-third reduction in deer-vehicle collisions. An economic analysis showed a cost savings during the cull years of US$0.6 million for reducing browsing to just these four monitored plant species and the reduction in deer-vehicle collisions.

Can controlled bow hunts reduce overabundant white-tailed deer populations in suburban ecosystems?

In the northern suburbs of NYC, land managers have begun implementing bow-only hunts to reduce overabundant white-tailed deer (Odocoileus virginianus) herds in an effort to promote forest regeneration. However, there have been no attempts to model the impact of bow hunting on deer population growth. Using harvest statistics from the Mianus River Gorge Preserve in Westchester County, NY we simulated the impact of bow hunting on a population of female deer exhibiting density-dependent growth and explored a range of carrying capacities, immigration rates, and harvest intensities. Simulated bow hunting (adult harvest≥1.8femaleskm−2) was capable of achieving deer densities believed necessary for forest regeneration (2.9femaleskm−2) in closed populations where carrying capacity=13.8femaleskm−2, representing the lower end of deer overabundance. At this carrying capacity and low immigration rates, the impact of bow hunting was more variable, producing population declines ranging from 20 to 70% contingent on harvest rates. Hours per harvest increased rapidly as the deer population declined requiring nearly 5 times the hourly effort as female density approached target levels. Sustaining harvests over multiple decades, particularly as effort per deer harvest increases, is one of the biggest challenges facing bow-only hunts. As controlled bow hunts are executed by volunteer sportsmen, reductions will be determined by hunters’ capacity or willingness to increase effort and efficiency. Bow hunting will therefore likely result in deer densities lower than historical peak values, yet higher than is currently assumed necessary for forest regeneration.

Regulated Commercial Harvest to Manage Overabundant White-Tailed Deer: An Idea to Consider?

Author(s): VerCauteren, Kurt C.; Anderson, Charles W.; Van Deelen, Timothy R.; Drake, David; Walter, W. David; Vantassel, Stephen M.; Hygnstrom, Scott E. | Abstract: Declines in hunter recruitment coupled with dramatic growth in numbers of white-tailed deer (Odocoileus virginianus) have challenged our ability to manage deer populations through traditional methods. We surveyed all state wildlife agencies and estimate the abundance of white-tailed deer in North America currently exceeds 30 million. Traditional methods of population management have been ineffective in reducing numbers of deer sufficiently in some environments. The only way to manage overabundant deer directly, cost-effectively, and in a timely fashion is through lethal methods. States currently are issuing record numbers of permits to hunters to increase harvest of white-tailed deer. Unfortunately, hunter participation has been declining in North America during the past two decades. Regulated commercial harvest would help state wildlife agencies manage overabundant populations of white-tailed deer andallow hunters to sell all orparts of harvested deer. We anticipate that many will criticize regulated commercial harvest of deer and claim that it is contrary to the North American Model of Wildlife Conservation (NAMWC). We can, however,argue that regulated commercial harvest meets all seven of the pillars of the NAMWC: 1) Wildlife is a natural resource of the public trust(state wildlife agencies willmanage deeranddeerwould continue to be a public resource). 2) No commercial use of wildlife [a direct reaction to exploitive and unsustainable market hunting in the 18th and 19th Centuries; commercial markets currently exist for other natural resources (e.g., furbearers, fish, timber); contemporary conservation values would not allow overexploitation; a framework for regulations, monitoring, and enforcement already isin place in every state]. 3) Democratic rule of law to regulate use of wildlife (commercial harvest of white-tailed deer would be highly regulated by wildlife agencies through public processes). 4) Hunting opportunity for all (anyone legally able to hold a deer hunting license would be eligible to apply for a Commercial Deer Harvest License (CDHL), CDHL programs would be implemented only where recreational hunting is proven inefficient or inappropriate). 5) No frivolous use of wildlife (CDHLs will beused to generate of food and other products, management would address risk to human health and safety andlosses ofagricultural resourcesto deer). 6) Wildlife is an international resource (has little to do with our proposed idea of managing overabundant resident populations of white-tailed deer, but a CDHL program may be applicable to any overabundant species, including internationally migratory species,such assnow geese,Chen caerulescens). 7) Science-based wildlife policy (a CDHL program would rely on science and research-based data to estimate densities before, during, and after commercial harvest). A CDHL program should be managed and distributed by state wildlife agencies, issued only to qualified individuals, enable harvest of an allotment of deer in areas targeted for population reduction, and permit the sale of whole carcasses and parts of harvested deer. Administration of a CDHL program will be taxing. State agencies alreadyareunderstaffed, but administrative and enforcement frameworks already exist for commercial harvest of publicly owned natural resources (e.g., furbearers, fish, timber) and the processing and handling of meat (e.g., USDA inspections). Revenue generated by CDHL programs could be directed back toward agencies and personnel who will administer and oversee these programs. Looking forward, we anticipate several issues mustbe addressed for regulated commercial harvestof deer to be accepted by agencies, hunters, and the public. The dogma against commercial use of wildlife may be well established. It may be difficult to mediate changesin attitudes in the wildlife community, stakeholders, and other publics. It will require adoption at all levels. State laws and regulations will need to be reviewed and some will have to be changed. Some will argue that we do not have the strength, stamina, or political will necessary to implement such broad sweeping changes. On the other hand, many wildlife managers will appreciate having an alternative tool for managing overabundant populations of white-tailed deer. We identified several benefits (reduce overabundant populations of deer; source of healthy, natural, green, locally-produced protein; economic growth, entrepreneurship, and market expansion; and public engagement and appreciation) and expected concerns associated with this concept(privatization of wildlife; overexploitation; food safety; competition with existing commodities; law enforcement; challenges of changing laws, regulations, and attitudes). We encourage a professional discussionof regulated commercial harvestto address the issue of overabundant white-tailed deer.

Contraceptive efficacy of a novel intrauterine device (IUD) in white-tailed deer

Overabundant white-tailed deer ( Odocoileus virginianus) pose risks to property, health, and safety of human beings. Public concerns about lethal management can impair efforts to address these issues, particularly in urban settings. Several techniques developed for reducing reproductive output of deer have limited utility because they require repeated dosing to achieve permanent effect and face uncertain regulatory approval for use beyond experimentation. From 10 August 2006 through 30 December 2007, we evaluated the contraceptive efficacy of copper-containing intrauterine devices (IUDs) implanted trans-cervically in white-tailed deer at the E.S. George Reserve in Pinckney, Michigan. Intrauterine devices were implanted before ( n = 9) and shortly after ( n = 10) the breeding season. Post-breeding season IUD treatment was in conjunction with a 5 cm 3 dose of 5 mg/ml prostaglandin F 2α (PGF 2α), delivered subcutaneously. Intrauterine devices reduced pregnancy rates when administered prior to breeding ( P < 0.001) and prevented pregnancy for up to 2 years (the duration of the study). Two of 8 does that received IUDs prior to the breeding season and survived to the end of the study became pregnant (due to loss of the implant) during the second year while all ( n = 16) does without implants conceived. Cervical changes associated with early pregnancy made trans-cervical implantation after the breeding season challenging, and resulted in improperly placed IUDs in 2 treated does. The apparent expulsion of IUDs by pregnant does that received the combined treatment after breeding suggests IUD treatment should be limited to the pre-breeding season. Intrauterine devices show potential as a tool for small-scale deer population management via non-steroidal reproductive inhibition.

Browse Preference and Browsing Intensity of White-Tailed Deer (Odocoileus virginianus) in Allegheny High Plateau Riparian Forests, USA

Decades of chronic browsing by overabundant white-tailed deer ( Odocoileus virginianus Zimmerman) has strongly influenced forest pattern and process on the Allegheny High Plateau Ecoregion of northwestern Pennsylvania, USA. Previous research has found that riparian forests contain the greatest herbaceous plant species richness of regional plant communities but little is known about the impacts of deer browsing on the structure and composition of the herbaceous layer (all vascular plants Aster divaricatus , A. prenanthoides , Chelone glabra , Impatiens capensis , Pilea pumila , Polygonum virginianum and Ranunculus hispidis . We found that plant species richness and composition, and browsing intensity by white-tailed deer, are highly variable across riparian forests of the region. In order to assess or predict deer browsing impacts to regional riparian forests, we suggest that riparian sites be studied individually, perhaps on a watershed basis, as the surrounding landscape and available habitat may influence deer densities and foraging activity in an individualistic manner.

Population growth rate of a common understory herb decreases non-linearly across a gradient of deer herbivory

Overabundant white-tailed deer ( Odocoileus virginianus) are a significant management problem in North America that exerts unprecedented herbivory pressure on native understory forest communities. Conserving understory plant populations requires quantifying a sustainable level of deer herbivory. To date, most population projection models consider only deer presence and absence. To estimate population growth rate along a gradient of herbivory, we focused on Trillium grandiflorum because it is a common understory species and a bellwether of deer effects and forest decline . We used matrix population models, and employed both prospective and retrospective analyses using a regression life table response experiment (LTRE). Deer affect size, stage and population dynamics of T. grandiflorum. Because deer target flowering and large non-flowering stages of T. grandiflorum, these individuals do not produce seed in the year they are browsed and are more likely to regress in stage and size in the following growing season relative to non-browsed plants. Importantly, sustained high browse levels result in populations dominated by small, non-flowering individuals. Our LTRE revealed a significant negative and decelerating relationship between herbivory and λ. This non-linearity occurs at the highest herbivory levels because highly browsed populations become dominated by stages that deer do not consume and are thus buffered from rapid decline. However, population extinction is expected when herbivory is greater than the pivotal value of ∼15%. Our study demonstrates that levels of deer herbivory commonly experienced by forest understory perennials are sufficient to cause the loss of T. grandiflorum and likely other co-occurring palatable species.

Behavioral responses of white-tailed deer subjected to lethal management

Currently, the most effective and cost-efficient mechanism for controlling overabundant white-tailed deer ( Odocoileus virginianus (Zimmermann, 1780)) is lethal removal, most commonly controlled hunting and sharpshooting. Deer subjected to such efforts may behave differently during removal and remaining deer may alter behaviors, potentially limiting future efficacy of removal efforts. Our objectives were to quantify changes in deer distribution in response to controlled hunting and sharpshooting. We immobilized two sample populations of 20 deer (one enclosed and one free-ranging) in central New Jersey, USA, and fitted them with global positioning system collars. The free-ranging herd experienced 11 days of controlled hunting, reducing density from 78 to 27 deer/km2. We subjected the enclosed herd to a 7 day sharpshoot, reducing density from 83 to 7 deer/km2. Hunted deer increased mean home ranges during removal, while deer exposed to sharpshooting did not. Collared doe–doe home-range overlap increased postsharpshoot, suggesting increased social interaction. Behaviors of hunted deer were directly affected by the human threat, while behavioral changes of deer exposed to sharpshooting were linked to population reduction. In the absence of an intact matrilineal social group, unrelated does will seek each other out in what appears to be an inherent need to be social.

Effectiveness of Spayvac® for Reducing White-tailed Deer Fertility

Overabundant white-tailed deer (Odocoileus virginianus) populations have been reported in many urban and suburban communities across the United States. Large populations of deer can potentially increase the risk of human-wildlife conflicts, such as deer-vehicle collisions, transmission of disease to humans, and vegetation damage. In 2003, efforts to control white-tailed deer numbers were initiated at the National Aeronautical and Space Agency's (NASA) Lyndon B. Johnson Space Center (JSC) in Houston, Texas, using the long-lasting, single-dose contraceptive SpayVac. Our objectives were to evaluate the effectiveness of SpayVac for reducing white-tailed deer fertility and determine the partial cost for treatment. Between 2003 and 2004, we monitored 45 adult female deer (34 treated with SpayVac, 11 controls treated with a placebo). Fawning rate over 2 yr for deer treated with SpayVac >30 days prior to the rut was 0% (n=31), whereas the fawning rate for control deer was 78% (n=11). Inoculation 1 mo prior to the breeding season was sufficient time to achieve fertility control. We conclude that SpayVac can effectively reduce the fertility of urban white-tailed deer.

Deer Browse Resistant Exotic-Invasive Understory: An Indicator of Elevated Human Risk of Exposure to &lt;I&gt;Ixodes scapularis&lt;/I&gt; (Acari: Ixodidae) in Southern Coastal Maine Woodlands

We evaluated the relationships between forest understory structure and the abundance of questing adult and nymphal blacklegged ticks, Ixodes scapularis Say (Acari: Ixodidae), in three Maine towns endemic for Lyme disease, 2001-2003. In fragmented New England woodlands, over-abundant white-tailed deer, Odocoileus virginianus Zimmerman, overbrowse palatable species, allowing browse-resistant exotic-invasive species to replace native forest understory structures. We predicted there would be more ticks in plots dominated by exotic-invasive shrubs (such as Japanese barberry, Berberis thunbergii DC) than in plots dominated by native shrubs, ferns, or open understory. We assessed canopy composition and closure, tree basal area, litter composition, percentage of coverage and stem density of understory species, litter depth, soil moisture, and abundance of small mammals and white-tailed deer pellet groups. We used generalized linear mixed model analysis of covariance to determine the effect of understory structure on tick counts, controlling for continuous habitat and host covariates and adjusting for random spatial effects. There were twice as many adults and nearly twice as many nymphs in plots dominated by exotic-invasives than in plots dominated by native shrubs. Both adult and nymphal counts were lowest in open understory with coniferous litter. Adults were positively associated with increasing litter depth, medium soil moisture, and increasing abundance of white-footed deer mice, Peromyscus leucopus Rafinesque, and deer pellet group counts. Nymphs were positively associated with increasing litter depth, moderately wet soil, and mice. We concluded that deer browse-resistant exotic-invasive understory vegetation presented an elevated risk of human exposure to the vector tick of Lyme disease.

Managing an Overabundant Deer Population by Sterilization: Effects of Immigration, Stochasticity and the Capture Process

Fertility control is an alternative to lethal removal for managing overabundant populations. This approach invokes several simplifying assumptions; in particular, that specific individuals can be targeted for sterilization. We evaluated the influence of relaxing this assumption on the likelihood of achieving population control by considering potential sources of variation in the capture and sterilization process in an overabundant white-tailed deer (Odocoileus virginianus) population in Cayuga Heights, New York, USA. Using numerical analysis of an individually based seasonal projection model, including demographic stochasticity, we found that heterogeneity in both sampling, and response to trapping, increased the effort required to achieve population reduction within some acceptable degree of certainty. The inability to precisely control the demographic structure of captured deer required increased capture effort to achieve a given reduction. Trap-aversive behavior following capture improved the efficacy of sterilization while trap affinity reduced it. The efficacy of sterilization as a management tool was reduced dramatically by the presence of net immigration and emigration from the population. We found that sterilization could reduce growth rates of overabundant populations under some conditions, but it is unlikely to be a viable means for reducing populations in general, where there is significant net movement of individuals into the population, and where there is imprecise control over the capture process.

Three-Man Thermal Team (T.T.T.): An Advanced Technique for Control of Overabundant or Nuisance Wildlife

Author(s): Hodnett, Earl L. | Abstract: The Three Man Thermal Team (T.T.T.) is a technique developed within the Fairfax County Virginia Integrated Deer Management Plan in cooperation with the Fairfax County Police Department’s Special Weapons and Tactics (SWAT) unit for control of overabundant white-tailed deer populations within a suburban/urban setting. The technique utilizes a combination of specialized equipment including a hand-held thermal imager, a laser pointer, a 6-million-candlepower MaxaBeam™ searchlight with focusable beam, and a suppressed rifle. T.T.T. allows targeted animals to be located in total darkness. With the use of a night vision or thermal scope in lieu of the light, the entire operation can be conducted in darkness. While this technique was specifically designed for deer, it can be easily adapted for other species.