Arthur R. Rodgers

PERFORMANCE OF A GPS ANIMAL LOCATION SYSTEM UNDER BOREAL FOREST CANOPY

An automated animal location system, based on Global Positioning System (GPS) technology, is being used for wildlife research. The GPS is a divergent technology, and positional accuracies vary between millimeters and tens of meters, depending on the system used and operating conditions. Before GPS-based tracking data can be used for habitat analyses, the influence of habitat on GPS-collar performance must be evaluated under various canopy conditions, including the optimal condition of no canopy. We evaluated performance of nondifferentially corrected GPS collars in an experimental forest with mature, evenly spaced trees and on wild free-ranging moose (Alces alces) to determine the influence of canopy on positional accuracy and observation rate. In an experimental forest with mature, evenly spaced trees (henceforth called spacing trial), canopy characteristics of tree species, spacing, height, basal diameter, and canopy closure had no influence on positional accuracy (P > 0.05), but had an influence on GPS observation rate (P < 0.001). Location error was greater if positions were based on 2-dimensional rather than 3-dimensional mode of operation (P < 0.001), with location errors of 65.5 and 45.5 m, respectively. Location error in 3-dimensional mode did not differ from the expected error of 40 m (P = 0.43). As tree density increased, observation rate decreased and the probability of the GPS receiver operating in 2-dimensional mode increased (P < 0.001), resulting in increased location error. With future development of differentially corrected GPS collars, location errors of <10 m are expected. J. WILDL. MANAGE. 59(3):543-551

Woodland Caribou Extirpation and Anthropogenic Landscape Disturbance in Ontario

Abstract The decline of woodland caribou (Rangifer tarandus caribou) has been attributed to anthropogenic landscape disturbances, but critical distance thresholds and time lags between disturbance and extirpation are unknown. Using a database of caribou presence and extirpation for northern Ontario, Canada, geo-coded to 10 × 10-km cells, we constructed logistic regression models to predict caribou extirpation based on distance to the nearest of each of 9 disturbance types: forest cutovers, fires, roads, utility corridors, mines, pits and quarries, lakes, trails, and rail lines. We used Akaikes Information Criterion to select parsimonious models and Receiver-Operating Characteristic curves to derive optimal thresholds. To deal with the effects of spatial autocorrelation on estimates of model significance, we used subsampling and restricted randomizations. Forest cutovers were the best predictor of caribou occupancy, with a tolerance threshold of 13 km to nearest cutover and a time lag of 2 decades between disturbance by cutting and caribou extirpation. Management of woodland caribou should incorporate buffers around habitat and requires long-term monitoring of range occupancy.

Effects of differential correction on accuracy of a GPS animal location system

The location error of uncorrected data from Global Positioning System (GPS) collars range from ca. 45.5 to 65.5 m (Rempel et al. 1995). Improvements that potentially could reduce locational error to <10 m include correcting systematic bias by reference to GPS data collected at a known position (differential correction), increase in the proportion of positions based on ranging 4 rather than 3 satellites (3-dimensional node), and increase in the proportion of positions based on a well-spaced satellite configuration (low dilution of precision). Design changes meant to achieve these results were implemented in the second generation GPS collars we evaluated (Lotek Eng. Inc. 1996). We tested the performance of these collars under the controlled canopy conditions of the Thunder Bay experimental forest. Differential correction caused location error to decrease from 80 to 4 m (P < 0.0001), and the range of 25-75th percentile location error to decrease from 74.3 to 5.0 m. Location error among sample sites was greatest under tall red pines (Pinus resinosa; 15.7 m), possibly because the tall trunks interfered with signal reception, resulting in the acceptance of either 2-dimensional mode positions or positions based on poor satellite configuration (high dilution of precision), or because of multipathing effects caused by signal bounce off the tree trunks. Implementation of differential correction may involve substantial costs to maintain a GPS basestation and data handling, so effectiveness of this enhanced technology must be judged against study objectives and data requirements of the hypotheses being tested.

Timber-management and natural-disturbance effects on moose habitat:landscape evaluation.

We used 16 years of survey data for a moose population, and 3 Landsat satellite scenes, spanning 19 years, to evaluate the hypotheses that Ontarios Moose Habitat Guidelines for timber harvest: (1) mitigate the effects of unmodified clearcuts on moose populations, and (2) create enhanced habitat with greater interspersion of forage with cover and higher habitat suitability indices than areas dominated by unmodified clearcuts. The 5 study landscapes compared were 16,000-91,000 ha, and included landscape disturbance from timber-management and wildfire-burn, and landscapes with and without hunter access. Moose density differed among landscapes, but while neither main effects of hunter access (P = 0.083), nor landscape disturbance (P = 0.31) were significant, their interactions were (P = 0.003), with density increasing if disturbance occurs without hunter access. The habitat suitability index in the wildfire burn was similar (0.80) to both the modified and unmodified clearcut (0.85 and 0.83), and population rate of increase was positive in both the burn (B = 0.153, P < 0.0001) and the unmodified clearcut (B = 0.127, P < 0.0001). The population did not increase in the modified clearcut (B = -0.016, P = 0.9907) because hunter access increased as a consequence of high road density.

Recent Telemetry Technology

Publisher Summary This chapter provides an update on the most significant technological advances of terminology of the past decade along with an overview on the most recent telemetry systems. Telemetry refers to the remote determination of an animals status, which includes the individuals current level of activity, some physiological measurement, and its physical location. Telemetry is used in an extensive array of agricultural, physiological, and medical research activities to monitor the status of individuals. In these studies, measurements are usually made at close range, typically within a few hundred meters. Ecologists, field biologists, and wildlife researchers, on the other hand, generally use “telemetry” to estimate a series of geographic locations for individual animals, often from distances exceeding several hundred meters. Furthermore, since radio signals emanating from a device attached to each animal are commonly used to estimate locations, the technique is often referred to as “radiotelemetry.” Telemetry technology has continued to progress throughout the 1990s. Advances in power management, electronic components, and microcomputers, as well as the emergence of several innovative systems based on the new technology, have all contributed to an ever-increasing variety of telemetry options available to field researchers.

Designating Seasonality Using Rate of Movement

Abstract Traditionally, seasons for animals have been designated based on single external variables such as climate or plant phenology, rather than an animals response to the dynamic environments within which it lives. By interpreting a rate of movement function of cumulative movement through time we established a method that distinguishes transitions between behaviors limited by winter habitat conditions from those present during summer. Identification of these time periods provides temporal definition to subsequent home-range analyses and use–availability comparisons. We used location data from 32 Global Positioning System–collared female moose (Alces alces) to demonstrate the method. We used model selection (Akaikes Information Criterion) to differentiate between candidate rate of movement response curves. Of 32 moose, 29 clearly conformed to an annual movement pattern described by a logistic curve, with increased rates of movement in summer compared to winter. Conversely, 3 aberrant individuals did not alter their movement rate through the year and were best fit with a linear response curve. The seasonal rate of movement model we developed suggests an average summer period of 122 days (median  =  119 days, range  =  96–173 days) for moose in northwestern Ontario, Canada. The rate of movement model we applied to individuals indicated 1 May as the median date for the winter–summer transition (range  =  2 Apr–24 May), and the median transition from summer to winter was 25 August (range  =  1 Aug–23 Oct). Wide variation in timing and duration of summer and winter seasons among individuals demonstrates potential failure of the single external variable approach to capture the suite of factors potentially influencing animal behaviors. By plotting cumulative distance moved throughout the year, we elucidated individual variation in response to known and unknown variables that affect animal movement. Accounting for variability among individuals in designation of biologically significant temporal boundaries is critical to delineation of seasonally important habitats for conservation and sustainability of healthy wildlife populations.

Wolves adapt territory size, not pack size to local habitat quality

1. Although local variation in territorial predator density is often correlated with habitat quality, the causal mechanism underlying this frequently observed association is poorly understood and could stem from facultative adjustment in either group size or territory size. 2. To test between these alternative hypotheses, we used a novel statistical framework to construct a winter population-level utilization distribution for wolves (Canis lupus) in northern Ontario, which we then linked to a suite of environmental variables to determine factors influencing wolf space use. Next, we compared habitat quality metrics emerging from this analysis as well as an independent measure of prey abundance, with pack size and territory size to investigate which hypothesis was most supported by the data. 3. We show that wolf space use patterns were concentrated near deciduous, mixed deciduous/coniferous and disturbed forest stands favoured by moose (Alces alces), the predominant prey species in the diet of wolves in northern Ontario, and in proximity to linear corridors, including shorelines and road networks remaining from commercial forestry activities. 4. We then demonstrate that landscape metrics of wolf habitat quality - projected wolf use, probability of moose occupancy and proportion of preferred land cover classes - were inversely related to territory size but unrelated to pack size. 5. These results suggest that wolves in boreal ecosystems alter territory size, but not pack size, in response to local variation in habitat quality. This could be an adaptive strategy to balance trade-offs between territorial defence costs and energetic gains due to resource acquisition. That pack size was not responsive to habitat quality suggests that variation in group size is influenced by other factors such as intraspecific competition between wolf packs.

Habitat functional response mitigates reduced foraging opportunity: implications for animal fitness and space use

ContextAnimals selectively use landscapes to meet their energetic needs, and trade-offs in habitat use may depend on availability and environmental conditions. For example, habitat selection at high temperatures may favor thermal cover at the cost of reduced foraging efficiency under consistently warm conditions.ObjectiveOur objective was to examine habitat selection and space use in distinct populations of moose (Alces alces). Hypothesizing that endotherm fitness is constrained by heat dissipation efficiency, we predicted that southerly populations would exhibit greater selection for thermal cover and reduced selection for foraging habitat.MethodsWe estimated individual step selection functions with shrinkage for 134 adult female moose in Minnesota, USA, and 64 in Ontario, Canada, to assess habitat selection with variation in temperature, time of day, and habitat availability. We averaged model coefficients within each site to quantify selection strength for habitats differing in forage availability and thermal cover.ResultsMoose in Ontario favored deciduous and mixedwood forest, indicating selection for foraging habitat across both diel and temperature. Habitat selection patterns of moose in Minnesota were more dynamic and indicated time- and temperature-dependent trade-offs between use of foraging habitat and thermal cover.ConclusionsWe detected a scale-dependent functional response in habitat selection driven by the trade-off between selection for foraging habitat and thermal cover. Landscape composition and internal state interact to produce complex patterns of space use, and animals exposed to increasingly high temperatures may mitigate fitness losses from reduced foraging efficiency by increasing selection for foraging habitat in sub-prime foraging landscapes.

Selection for forage and avoidance of risk by woodland caribou (Rangifer tarandus caribou) at coarse and local scales

The relationship between selection at coarse and fine spatiotemporal spatial scales is still poorly understood. Some authors claim that, to accommodate different needs at different scales, individuals should have contrasting selection patterns at different scales of selection, while others claim that coarse scale selection patterns should reflect fine scale selection decisions. Here we examine site selection by 110 woodland caribou equipped with GPS radio-collars with respect to forage availability and predation risk across a broad gradient in availability of both variables in boreal forests of Northern Ontario. We tested whether caribou selection for forage and avoidance of risk was consistent between coarse (seasonal home range) and fine scales of selection. We found that local selection patterns predicted coarse scale selection patterns, indicating a close relationship between the drivers of selection at both spatial scales.

Diel movement patterns influence daily variation in wolf kill rates on moose

Variation in predation can have important consequences for predators and prey, but little is known about associated mechanisms. Diel interactions between predators and prey are commonly assumed to be influenced by movement speeds of both predators and prey individuals, sensu the ideal gas model, but the influencing factors of diel predation dynamics have yet to be empirically examined. In this study, we apply principles of the ideal gas model to predict diel variation in kill frequency of moose (Alces alces) by wolves (Canis lupus) in northern Ontario, Canada based on GPS radio-telemetry data combined with field verification of kills. We used GPS telemetry data from wolves and moose combined with a unique data set on the diel pattern of wolf kills to test whether predator movement rate, prey movement rate, and ambient light condition influence diel variation in kill rates of wolves on moose. Our results indicate that the kill rate between wolves and moose was principally related to the effective movement rate of predators and prey, as predicted by the ideal gas model. We found little evidence that light conditions had any effect on kill rates, but rather the majority of kill rate variation corresponded to wolf movement rate, which was over an order of magnitude higher than that of moose.