Dexter P. Hodder

Spatial and behavioral scales of habitat selection and activity by river otters at latrine sites

Abstract Animals interact with their environment at multiple spatial, temporal, and behavioral scales. Few studies of selection for latrine sites by river otters (Lontra canadensis) have considered spatial scale, and no studies have integrated scales of behavior. We used an information theoretic model comparison approach to identify elements of otter habitat that influence the presence, consistency, and intensity of latrine-site activity at 2 spatial scales. We identified and monitored 73 latrine sites in central British Columbia, Canada, during the open-water season in 2007 and 2008. We inventoried latrines and randomly selected sites along the adjacent shoreline, and used those data in the form of a binary resource selection function to model fine-scale selection of latrine sites. At the scale of the landscape, we used a resource selection function and data from geographic information systems to model coarse-scale selection of latrine sites. Drawing on those same data, we used binary and count models to quantify factors that contributed to the consistency (high versus low use) and intensity (number of scats) of otter activity at latrine sites. Fine-scale habitat characteristics were better at predicting the presence of latrine sites when compared to coarse-scale geographic information system data. In general, the presence, consistency, and intensity of latrine activity at the fine scale were influenced by visual obscurity, larger trees, and characteristics of conifer trees. The presence of latrine sites at the coarse scale could not be accurately described by any of the models. The consistency and intensity of activity of otters at latrine sites at the coarse scale, however, was best predicted by habitat characteristics beneficial to fish. These results provide insight into the spatial and behavioral scales of latrine-site activity by river otters that can be incorporated into management, monitoring, and conservation strategies.

Spatio-Temporal Variation in River Otter (Lontra canadensis) Diet and Latrine Site Activity

Abstract: Fluctuations in the distribution and abundance of prey resources are an important influence on the foraging ecology of carnivores. Spatio-temporal variation in the diet of river otters (Lontra canadensis), however, is not well understood. In addition, we have limited knowledge about seasonal changes in otter activity at latrine sites and how these changes may relate to changes in otter diet. We used a combination of scat content and stable-isotope analyses to assess the contributions of different prey items to otter diet. We investigated the spatio-temporal variation in the availability of prey groups as it influenced the composition of otter diet and the number of scat deposited at latrine sites. A combination of fish spawning period, water-body type, and lake best described the presence of salmonidae, minnows, and insects in otter scats. The number of scats was best described by a two-week calendar time measurement and geographic location. Scat deposition was positively influenced by a time period when no fish were spawning (early July) and the kokanee (Oncorhynchus nerka) spawning period (early September). In general, the stable-isotope analysis agreed with the results of the scat content analysis: fish dominated the diet, with lesser contributions from other prey items. The stable-isotope analysis, however, suggested that sockeye salmon, larger species of fish (burbot, lake trout), and birds contributed more than was revealed by scat content analysis. Management strategies require accurate and unbiased information on wildlife distribution and abundance that is often measured from surveys of sign; this study provides some of the critical information needed to interpret surveys for river otters. We also suggest implications for other wildlife species.

Paper birch (Betula papyrifera) shoot selection by moose (Alces alces) following a forest-cleaning experiment

Abstract In order to maximize food intake per harvesting effort and minimize energy expenditures required to move between feeding patches in nature, herbivores such as moose (Alces alces L.) generally select large plant shoots when browsing in winter. To determine moose preferences for shoots of different morphologies, an experiment was conducted in northern British Columbia in which shoots from birches cut at different times of the growing season were fed in 2 consecutive years to eight human-habituated moose in cafeteria-style feeding trials. The results indicate that moose preferred smaller winter shoots of birches regardless of when the parent plant was cut and also appeared to reject larger shoots containing sylleptic branches. It is argued that the preferences for smaller shoots by moose detected in these trials should be observable under natural conditions, but are generally only supported by literature from some parts of Scandinavia. The findings underscore the importance that factors such as mouth filling per harvesting effort, snow depth and consistency, predators and browse patch distribution must have on foraging decisions made by moose while browsing in the wild. Implications of the findings include the significance of cutting time on the size of shoots produced by birch after cutting, how this affects moose browsing birch and, subsequently, how managers can theoretically use cutting time as a tool in forest cleaning operations to direct the foraging efforts of moose towards or away from forest plantations.

Application of a species distribution model to identify and manage bear den habitat in central British Columbia, Canada

Several mammals have adapted to harsh winter conditions by adopting hibernation strategies that enable them to survive periods of unfavourable environmental conditions. At northern latitudes, black and brown bears can be in a state of hibernation for up to seven months. As a result of this prolonged occupation of one small space, bears can be vulnerable to environmental and human caused disturbances. In this study, we developed a predictive model that identifies potential den habitat for black bears that can assist with management planning for industrial land development activities. We identified 40 dens (17 excavated in soil and 23 natural rock cavities) and used fine-scale information to determine how dens were positioned in forest stands. We found that bears denned in areas on mid to upper slope positions and that soil dens were located mainly in clay-loam soil complexes while rock cavity dens were either caves or cavities in boulder piles. Den location was distant from portions of the study area with relatively high road density. We then used resource selection functions to predict where bear dens might be located on the landscape. When applied to the GIS data, the averaged coefficients suggested that 3.1% of the study area had a high suitability ranking as den habitat while 9.1%, 14.6%, and 73.2% had mid, low, and limited suitability, respectively. In our study area, habitat for den sites is reasonably predictable and should be considered during the planning of industrial activities.

The role of demographic and environmental variables on the presence of snow tracks by river otters Lontra canadensis

Unknown causes of heterogeneity in the presence or detection of wildlife tracks and other signs could bias interpretations of population indices derived from surveys. These surveys can be the basis of management decisions for populations of wildlife. However, we know very little about potential biases affecting the presence of tracks in the landscape. We used an Information Theoretic Model Comparison approach to investigate the role of environmental, demographic and behavioural influences on the presence of river otter Lontra canadensis snow tracks in central British Columbia, Canada, from January to March 2008. We repeatedly located five radio-collared otters and recorded the presence of tracks within an estimated 100-m radius of the otters location. We used combinations of five variables to develop logistic regression models that predicted the presence or absence of snow tracks when the location of otters was known. The presence of snow tracks was best described by a model containing covariates for gender and movement distance per day. The probability of detecting snow tracks was higher for male compared to female otters and was positively related to the daily movement distance of the individual animal. Track-sign heterogeneity among individuals could bias surveys that assess and monitor river otter populations, and should be incorporated into the design and interpretation of track surveys.

Timing Moose Pellet Collections to Increase Genotyping Success of Fecal DNA

Abstract Fecal pellets can serve as a noninvasive source of DNA for identifying the distribution of individual animals when conducting population estimates. The quality of fecal DNA, however, can b...

The Use of Stereoscopic Photography to Estimate Browse Use by Large Ungulates

Abstract We developed a stereophotographic technique to estimate browse use by moose. We collected 30 whole plant specimens representing 4 different browse species and placed them in an outdoor compound on the campus of The University of Northern BC. We physically counted all branches on each plant and categorized them as recently browsed, browsed prior to the preceding winter, or unbrowsed. Then, we stereophotographed the plants against a white backdrop in ambient outdoor light. We viewed stereopair prints under a stereoviewer and classified them using the same method as was used in manual counting. We found that this stereophotographic technique tended to underestimate total browse removal, but allowed us to determine browse availability (the number of unbrowsed shoots) and percentage of plant shoots removed by browsing for all species examined. Of the 4 species we examined, we were able to most accurately determine the number of total browsed shoots through stereoscopy on Cornus stolonifera, Acer douglasii and Salix scouleriana while the percentage of newly browsed shoots was best determined on Betula papyrifera, A. douglasii and C. stolonifera. Our findings suggested that estimating browse supply with stereophotography is possible, whereas estimating browse use is more appropriate for some species, but not for others. With adjustments, the method may be useful in reducing field time and costs involved with spring browse surveys.