Effect of snow depth on wolf activity and prey selection in north central Minnesota

1991 ◽  
Vol 69 (2) ◽  
pp. 283-287 ◽  
Author(s):  
Todd K. Fuller

Wolf (Canis lupus) activity and interactions with white-tailed deer (Odocoileus virginianus) were monitored in north central Minnesota during six winters in which mean January–February snow depth alternated between shallow (19–26 cm) and relatively deep (40–47 cm) and winters (winter severity index; L. J. Verme. 1968. J. Wildl. Manage. 32: 566–574) alternated between mild (71–98) and moderately severe (126–137). Wolves traveled farther and more often and spent less time with other pack members in mild than in severe winters. Radio-marked wolves and deer used conifer cover less, and fewer deer were killed there, when snow was shallow. Similarly, fewer wolf-killed deer were found in and near deer concentration areas during mild winters. Of the 74 deer killed by wolves, the proportion that were fawns (54%) differed from the proportion of fawns in the winter population (27%), but neither varied with winter severity. Few deer killed by wolves appeared debilitated. Carcass consumption was high in all winters, regardless of their severity, but wolves scavenged less in mild than in severe winters (10 vs. 29% of deer carcasses observed). Thus, wolves changed winter activity, movement patterns, sociality, and feeding behavior in response to snow-induced changes in deer distribution and mobility.

2000 ◽  
Vol 78 (1) ◽  
pp. 49-59 ◽  
Author(s):  
R D Hayes ◽  
A M Baer ◽  
U Wotschikowsky ◽  
A S Harestad

We studied the kill rate by wolves (Canis lupus) after a large-scale wolf removal when populations of wolves, moose (Alces alces), and woodland caribou (Rangifer tarandus caribou) were all increasing. We followed a total of 21 wolf packs for 4 winters, measuring prey selection, kill rates, and ecological factors that could influence killing behavior. Wolf predation was found to be mainly additive on both moose and caribou populations. Kill rates by individual wolves were inversely related to pack size and unrelated to prey density or snow depth. Scavenging by ravens decreased the amount of prey biomass available for wolves to consume, especially for wolves in smaller packs. The kill rate by wolves on moose calves was not related to the number of calves available each winter. Wolves did not show a strong switching response away from moose as the ratio of caribou to moose increased in winter. The predation rate by wolves on moose was best modeled by the number and size of packs wolves were organized into each winter.


2012 ◽  
Vol 39 (4) ◽  
pp. 321 ◽  
Author(s):  
K. L. Dawe ◽  
S. Boutin

Context Changes in global climate and evidence of species’ responses to these changes have increased interest in relationships between climate variables and species demography and distributions. Although an important tool for many ecological questions, large-scale climate indices fail to provide the spatial resolution necessary to investigate drivers of change across small spatial scales. Climate variables that describe yearly climate variation at large spatial extents and small spatial grain are needed. Aim Here we develop a model for snow depth using snow water equivalent (SWE) data, which are readily available in a number of formats, to be included in a more general climate index. We use an existing winter severity index (WSI) for white-tailed deer to test the performance of the model. Methods We obtained data for 13 weather stations from north-western Canada, reporting both SWE and snow depth. We accumulated a snowpack from daily SWE of snowfall and then tested two methods for converting the SWE of the snowpack into the snow portion of the WSI. We then generalised the model for application to the northwest forest climate region. Key results Coefficients of determination (R2) relating the actual and predicted snow depth portion of the WSI ranged from 0.41 to 0.78, with only three stations being below 0.50. Coefficients of determination (R2) relating the actual and predicted WSI for the northwest climate region ranged from 0.58 to 0.88. Conclusions The SWE model predicts the snow portion of the WSI well for most stations and, when incorporated into the full WSI, provides a good measure of relative winter severity across space and time for most stations. Implications The method developed here could be applied elsewhere, where snow depth is an important factor in species ecology. The benefit of this approach is a comparatively simple method that maximises the use of widely available SWE data in place of snow-depth data.


2015 ◽  
Vol 54 (8) ◽  
pp. 1693-1712 ◽  
Author(s):  
Barbara E. Mayes Boustead ◽  
Steven D. Hilberg ◽  
Martha D. Shulski ◽  
Kenneth G. Hubbard

AbstractThe character of a winter can be defined by many of its features, including temperature averages and extremes, snowfall totals, snow depth, and the duration between onset and cessation of winter-weather conditions. The accumulated winter season severity index incorporates these elements into one site-specific value that defines the severity of a particular winter, especially when examined in the context of climatological values for that site. Thresholds of temperature, snowfall, and snow depth are assigned points that accumulate through the defined winter season; a parallel index uses temperature and precipitation to provide a snow proxy where snow data are unavailable or unreliable. The results can be analyzed like any other meteorological parameter to examine relationships to teleconnection patterns, determine trends, and create sector-specific applications, as well as to analyze an ongoing winter or any individual winter season to place its severity in context.


2017 ◽  
Vol 83 ◽  
pp. 34-43 ◽  
Author(s):  
Sophie Ståhlberg ◽  
Elena Bassi ◽  
Viviana Viviani ◽  
Marco Apollonio

2021 ◽  
Vol 8 ◽  
Author(s):  
Ignacio Garrido ◽  
Luis Miguel Pardo ◽  
Ladd E. Johnson ◽  
Dirk Schories

Sea stars often function as keystone predators in food webs of intertidal and subtidal communities, especially in temperate and sub-polar regions. In South America the sea star Cosmasterias lurida is distributed along both the Atlantic and Pacific coasts of Patagonia and is one of the most conspicuous and abundant benthic predators in the shallow subtidal zone (<25 m). Its feeding strategy and prey selection are, however, still poorly known. This study describes the feeding behavior of C. lurida at a site in the Seno del Reloncaví (Chile), assessing its abundance, size and prey selection in the field relative to observed prey abundance and size along a bathymetric gradient. We hypothesized that C. lurida is a generalist predator, feeding on suitable prey according to their availability. However, we found that this predator only consumed a limited number (7 of 48) of potential prey species, primarily the slipper limpets Crepipatella spp. and the mussels Aulacomya ater and Mytilus chilensis. Electivity analysis revealed a clear preference for one mussel (A. ater) but not the other (M. chilensis) as well as depth-dependent selectivity for the slipper limpets, which changed from avoidance to preference with increasing depth. Sea star densities varied with depth, peaking between depths of 5 and 10 m, but the size of sea stars and the size of their prey did not vary significantly along a depth gradient. No significant correlations were found with the most commonly selected prey. These results would indicate that while this predator may be a generalist–opportunist, its feeding behavior is context-dependent and its high selectivity for certain species suggests that this sea star plays a key role structuring subtidal benthic communities in Patagonia.


1981 ◽  
Vol 38 (3) ◽  
pp. 275-279 ◽  
Author(s):  
C. Kim Wong

The predatory feeding behavior of Epischura lacustris on Bosmina longirostris and Ceriodaphnia reticulata was investigated. Epischura rarely killed Bosmina > 0.40 mm in length, but below this threshold there was no size selection because predation rates were affected mainly by encounter rate and ingestion probability. When presented with Bosmina and Ceriodaphnia, Epischura fed at higher rates on Bosmina which were more easily captured. Epischura showed no true behavioral preference or switching, and its diet included all the prey it could detect, capture, and ingest successfully. Previous diet had no effect on prey selection. Predation rates on Bosmina were not affected by the presence of algal food.Key words: predatory copepod, predator–prey interactions, size selection, switching, prey defense


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