Michael J. Wisdom

Understanding Ungulate Herbivory—Episodic Disturbance Effects on Vegetation Dynamics: Knowledge Gaps and Management Needs

Abstract Herbivory by wild and domestic ungulates is a chronic disturbance that can have dramatic effects on vegetation dynamics. Herbivory effects, however, are not easily predicted under different combinations of episodic disturbance such as fire, timber harvest, drought, and insect defoliation. This lack of predictability poses a substantial obstacle to effective management of ungulate herbivory. Traditional models of vegetation transition in forested ecosystems have ignored the influences of ungulate herbivory, while research on effects of herbivory have typically excluded other disturbances. Of the 82 contemporary studies on ungulate herbivory we examined, only 15 (18%) considered the interactions of herbivory with episodic disturbances. Moreover, only 26 (32%) evaluated vegetation response to ungulate herbivory beyond the simplistic treatment levels of herbivory versus no herbivory. Only 31 (38%) used a repeated-measures design of sampling responses over 3 or more time periods. Finally, just 7 (9%) explicitly made inferences to large landscapes such as watersheds, which are often used for management planning. We contend that useful landscape research on herbivory must examine the interactions of ungulate grazing with other disturbance regimes at spatial extents of interest to forest and rangeland managers and under varying ungulate densities and species. We identify herbivory models that could accommodate such information for forested landscapes in western North America. Such models are essential for identifying knowledge gaps, designing future studies, and validating relations of ungulate herbivory on landscapes where episodic disturbances are common, such as those of western North America.

Experimental Design for Radiotelemetry Studies

Publisher Summary Design studies that use radiotelemetry require careful consideration of the goals of a project and the resources available to meet those goals. Success in meeting the research goals depends on thoughtful planning of field methods and ancillary data collection, selection of telemetry equipment appropriate to the study animal and budget, careful execution of the field protocols, and creative analysis of the data. Some of the most important design factors include consideration of the studys purpose; degree of experimental manipulation, controls, and replication; selection of an efficient yet unbiased sampling scheme; definition of the sample unit; calculation of sample size requirements; identification and removal of sources of bias; and clear specification of biological significance. This chapter emphasizes the need to integrate univariate metrics of animal choice, such as estimates of home range size and resource selection, with metrics for the demographic consequences of these choices, all of which can be generated from radiotelemetry. Radiotelemetry is an essential tool in modern studies of movement, migration, and dispersal of most vertebrates. Its use has dramatically increased the amount and detail of information available for estimating movements of larger animals, and provides extremely valuable additions to information from studies that use tagging, banding (ringing), and other forms of marking for smaller animals. In addition, radiotelemetry studies are an important complement to recent approaches that use genetic markers.

Behavioral Responses of North American Elk to Recreational Activity

Abstract Off-road recreation on public lands in North America has increased dramatically in recent years. Wild ungulates are sensitive to human activities, but the effect of off-road recreation, both motorized and nonmotorized, is poorly understood. We measured responses of elk (Cervus elaphus) to recreational disturbance in northeast Oregon, USA, from April to October, 2003 and 2004. We subjected elk to 4 types of recreational disturbance: all-terrain vehicle (ATV) riding, mountain biking, hiking, and horseback riding. Motion sensors inside radiocollars worn by 13 female elk recorded resting, feeding, and travel activities at 5-minute intervals throughout disturbance and control periods. Elk fed and rested during control periods, with little time spent traveling. Travel time increased in response to all 4 disturbances and was highest in mornings. Elk travel time was highest during ATV exposure, followed by exposure to mountain biking, hiking, and horseback riding. Feeding time decreased during ATV exposure and resting decreased when we subjected elk to mountain biking and hiking disturbance in 2003. Our results demonstrated that activities of elk can be substantially affected by off-road recreation. Mitigating these effects may be appropriate where elk are a management priority. Balancing management of species like elk with off-road recreation will become increasingly important as off-road recreational uses continue to increase on public lands in North America.

Mitigating spatial differences in observation rate of automated telemetry systems

Wildlife ecologists are increasingly interested in determining spatial distributions and habitat use of ungulates from locations estimated from both conventional and automated telemetry systems (ATS). If the performance of an ATS causes spatial versus random variation in probability of obtaining an acceptable location (observation rate), analysis of habitat selection is potentially biased. We define observation rate as the percentage of acceptable locations (i.e., those that meet signal strength, signal-to-noise ratios, geometric dilution of precision criteria) of the total locations attempted. An ATS at the Starkey Experimental Forest and Range (Starkey) in Oregon tracks movements of elk (Cervus elaphus), mule deer (Odocoileus hemionus), and cattle. We detected localized variation in observation rate of stationary radiocollars in 1993. Subsequently, we devised a method to estimate observation rate at various spatial scales using animal location data over 4 years (1992-95 ; n = 907,156 location attempts) to determine if the variation was spatial or random. We formulated 5 variants of a general linear model to obtain estimates of spatial variation in observation rate. All 5 models assumed spatially correlated error terms estimated from isotropic semivariograms. Three models included environmental variables as covariates correlated with observation rate. Models then were compared based on mean error, coefficient of determination, and residual plots. Random variation accounted for 47-53%, and spatial variation accounted for 38-45% of the variation in observation rate. One model was selected to demonstrate application of the correction to mitigate spatial bias in observation rate. Our results demonstrate the utility of semivariograms to detect and quantify spatial variation in observation rate of animal locations determined from an ATS.

Effect of Sample Size on the Performance of Resource Selection Analyses

Publisher Summary Assessing resource selection is one of the main objectives of many wildlife radiotelemetry studies. Methods for determining resource selection vary from the widely used χ 2 analysis for categorical data to complex statistical modeling using continuous data. This chapter conducts an evaluation with elk location data generated from an automated tracking system, which allowed collection of a substantially larger dataset than what could be collected with conventional methods of radiotelemetry. These data are used to estimate baseline patterns of resource selection for a population of elk and use resampling methods to simulate the effects of varying numbers of animals and varying numbers of locations per animal on the accuracy of resource selection estimates. The chapter calculates the percentage of correct conclusions (accuracy) for 1000 simulations for elk selection of six resource types (aspect, distance to open roads, distance to cover, distance to forage, % canopy closure, and vegetation) under varying levels of resampling for the two methods of resource selection. In general, the accuracy of resource selection increased with an increasing number of animals and an increasing number of observations per animal for all resource variables.

Validation of elk resource selection models with spatially independent data

ABSTRACT n Knowledge of how landscape features affect wildlife resource use is essential for informed management. Resource selection functions often are used to make and validate predictions about landscape use; however, resource selection functions are rarely validated with data from landscapes independent of those from which the models were built. This problem has severely limited the application of resource selection functions over larger geographic areas for widely distributed species. North American elk (Cervus elaphus) is an example of a widely-distributed species of keen interest to managers and for which validation of resource selection functions over large geographic areas is important. We evaluated the performance of resource selection functions developed for elk on one landscape in northeast Oregon with independent data from a different landscape in the same region. We compared predicted versus observed elk resource use for 9 monthly or seasonal periods across 3 yr. Results showed strong, positive agreement between predicted and observed use for 2 spring and 3 late summer-early fall models (3-yr r = 0.81–0.95). Predicted versus observed use was negatively or weakly positively correlated for 3 summer models and 1 mid-fall model (3-yr r = -0.57–0.14). Predicted and observed use correlated well when forage was limited (spring and late summer or early fall), corresponding to important biological stages for elk (parturition and breeding seasons). For these seasonal periods, model covariates such as rate of motorized traffic and canopy closure often were effective predictors of elk resource selection. The models we validated for spring and late summer-early fall may be used to evaluate management activities in areas with similar landscape characteristics.

Log sampling methods and software for stand and landscape analyses.

We describe methods for efficient, accurate sampling of logs at landscape and stand scales to estimate density, total length, cover, volume, and weight. Our methods focus on optimizing the sampling effort by choosing an appropriate sampling method and transect length for specific forest conditions and objectives. Sampling methods include the line-intersect method and the strip-plot method. Which method is better depends on the variable of interest, log quantities, desired precision, and forest conditions. Two statistical options are available. The first requires sampling until a desired precision level is obtained. The second is used to evaluate or monitor areas that have low log abundance compared to values in a land management plan. A minimum of 60 samples usually are sufficient to test for a significant difference between the estimated and targeted parameters. Both sampling methods are compatible with existing snag and large tree sampling methods, thereby improving efficiency by enabling the simultaneous collection of all three components--snags, large trees, and logs--to evaluate wildlife or other resource conditions of interest. Analysis of log data requires SnagPRO, a user-friendly software application designed for use with our sampling protocols. Default transect lengths are suggested for both English and metric measurement systems, but users may override default values for transect lengths that better meet their specific sampling designs. SnagPRO also analyzes wildlife snag and large tree data.

Chapter 19 – Habitat Networks for Terrestrial Wildlife: Concepts and Case Studies

A habitat network is defined as a spatially explicit portrayal of environmental conditions across large landscapes that can be used to understand the status and trends of species of conservation concern, particularly in relation to how species needs are met through management of habitat abundance and distribution. Habitat networks are specifically designed to account for and summarize spatial information across landscapes compatible in size and arrangement with the targeted species activities and movements. Habitat networks provide several potential benefits, including conditions for large numbers of species of conservation concern can be addressed efficiently across space and time; a wide variety of habitat characteristics can be holistically integrated; and ecological characterizations provided as part of the network do not dictate a particular form of management, but rather provide the basis for development of a variety of follow-up on management strategies and options. Habitat networks exemplify spatial relationships in wildlife ecology; habitat patches are not only defined and located, but also mapped in relation to each other. Mapping habitat networks in a GIS thus allows for “spatial depictions of theoretical constructs,” such as core habitat and linkages.

Habitat networks for terrestrial wildlife: concepts and case studies

A habitat network is defined as a spatially explicit portrayal of environmental conditions across large landscapes that can be used to understand the status and trends of species of conservation concern, particularly in relation to how species needs are met through management of habitat abundance and distribution. Habitat networks are specifically designed to account for and summarize spatial information across landscapes compatible in size and arrangement with the targeted species activities and movements. Habitat networks provide several potential benefits, including conditions for large numbers of species of conservation concern can be addressed efficiently across space and time; a wide variety of habitat characteristics can be holistically integrated; and ecological characterizations provided as part of the network do not dictate a particular form of management, but rather provide the basis for development of a variety of follow-up on management strategies and options. Habitat networks exemplify spatial relationships in wildlife ecology; habitat patches are not only defined and located, but also mapped in relation to each other. Mapping habitat networks in a GIS thus allows for “spatial depictions of theoretical constructs,” such as core habitat and linkages.

Habitat Networks for Terrestrial Wildlife

A habitat network is defined as a spatially explicit portrayal of environmental conditions across large landscapes that can be used to understand the status and trends of species of conservation concern, particularly in relation to how species needs are met through management of habitat abundance and distribution. Habitat networks are specifically designed to account for and summarize spatial information across landscapes compatible in size and arrangement with the targeted species activities and movements. Habitat networks provide several potential benefits, including conditions for large numbers of species of conservation concern can be addressed efficiently across space and time; a wide variety of habitat characteristics can be holistically integrated; and ecological characterizations provided as part of the network do not dictate a particular form of management, but rather provide the basis for development of a variety of follow-up on management strategies and options. Habitat networks exemplify spatial relationships in wildlife ecology; habitat patches are not only defined and located, but also mapped in relation to each other. Mapping habitat networks in a GIS thus allows for “spatial depictions of theoretical constructs,” such as core habitat and linkages.