Distribution: The gray wolf, Canis lupus, is one of the most widely distributed members of the family Canidae (Fritts et al., 1997). Although its distribution is restricted to the northern hemisphere, the gray wolf is found on all continents in the northern hemisphere within temperate, boreal, tundra, and arctic ecoregions (Fritts et al., 1997; Singh & Kumara, 2006). Figure 1 illustrates the global distribution of the gray wolf while Figure 2 illustrates the distribution within the province of Ontario. Canis lupus is absent from southern Ontario where the only large canids are the eastern wolf, Canis lycaon, and the coyote, Canis latrans (Mladenoff, Haight, Sickley, & Wydeven, 1995).
Figure 1: Global distribution of the gray wolf, Canis lupus. Although it is restricted to the northern hemisphere, Canis lupus is found on all continents north of the equator (Base map: ESRI 2015; Distribution modified from National Geographic, N.D.).
Figure 2: The gray wolf, Canis lupus, is found throughout northern Ontario and absent from south eastern, south central and south western Ontario (Base map: ESRI 2015; Distribution modified from National Geographic, N.D.).
Habitat: Gray wolves have adapted to live in a variety of habitats including temperate forest, grassland, boreal forest, tundra, and arctic habitat (Blanco & Cortés, 2007; Mech, 2014; Mladenoff et al., 1995; Singh & Kumara, 2006). Habitat selection is influenced primarily by prey availability with a secondary influence of the requirement for the alpha female to have a suitable denning site (Bergstrom, et al. 2009; Blanco & Cortés, 2007; Singh & Kumara, 2006). Dens are generally located on hillsides that provide both cover and a vantage point for the wolves to view the surrounding area for both potential prey and potential threats. Soil conditions are generally suitable for the wolves to excavate a large den into the hillside that is large enough to accommodate the alpha female and her litter of wolf cubs. Dens are also situated somewhat centrally within the home range of the wolf pack to facilitate the provision of food for the alpha female and cubs. During the summer, Ontario wolves spend more time in mixed and deciduous forest habitats while in the winter they are in primarily coniferous forest(Mladenoff et al., 1995). Mapping the habitat use and preferences of moose in this region of Ontario reveals that it is in fact the movement and preference of the moose that dictates the areas frequented by gray wolves.
Potential for Infestation: Gray wolves exhibit the typical reproductive strategy of K-strategists. They are among the largest and longest lived canids with moderate litter size and significant parental/pack investment in raising the young. Population growth is generally slow and recovery from a population bottleneck takes 15 to 20 years. Key elements of wolf biology that support their classification as K-strategists are summarized in table 1.
Table 1: Summary of the reproductive characteristics of the gray wolf, Canis lupus. Note that the gray wolves align best with the reproductive characteristics of K-strategists (Adapted from Rickleffs, 1990)
|Mortality||Variable and unpredictable||More constant and predictable||Not variable – constant|
|Lifespan||Short||Long||Longest of the Canids|
|Litter Size||Large||Small||Moderate – 4-6 cubs|
|Parental Investment/Care||Very little if any||Required||Entire pack assists with care of cubs|
|Frequency of Reproduction||Once to multiple times over short time period||Multiple times but over a prolonged period||Once a year for multiple years|
|Additional Factors||Most reproductively mature individuals reproduce successfully||Few reproductively mature individuals or only some reproduce successfully||Only alpha female and alpha male reproduce. Several individuals in the pack that are capable of reproduction but do not|
Survivorship: Gray wolves have a relatively even probability of survival throughout life which designates them as a species with a Type II survivorship curve (see Figure 3). The success and survivorship of individuals is closely linked to the pack because multiple animals contributing to the survival of both pack members throughout life. If an individual is cast out or left without a pack, survivorship is significantly reduced.
Dispersal and Vectors: Wolves migrate and move throughout the landscape on foot. Their energy conserving, loping gate, permits them to travel hundreds of kilometers in a relatively short time. While rivers and lakes do not form significant a barrier to dispersal there are some consistent barriers related to human activity. Gray wolves are significantly affected by major road ways as are many species of terrestrial vertebrates. A study conducted in and around Algonquin park and a similar study in Minnesota found that the presence of wolves in any given area is inversely related to road density (Mladenoff et al., 1995). Once road density hits a specific threshold, wolves are absent from the landscape. Therefore, dispersal of wolves is over land, across rivers, lakes, and even the ocean when ice is present. A pack or individual wolf can travel great distances over a few days yet roads and dense human populations are the most significant barriers to dispersal.
Special Considerations: Wolves are pack animals. Working as a pack they are able to capture and kill prey that is much larger than if they were to work alone (Vaughan, 1986). Territoriality is a common characteristic of pack animals and it is a trait that gray wolves exhibit. Each pack will generally exclude other packs and individual wolves from entering their territory or home range to reduce competition for food resources (Alcock, 1993). The size of the territory/home range is directly related to the food resources in the area. That is, if the food resources are plentiful, wolves will have a smaller territory because they can obtain enough food without having to travel long distances (Alcock, 1993; Vaughan, 1986). Higher densities of wolves are observed in areas where there are higher densities of prey. Conversely, if the food resources are scarce and unpredictable, the territory of the pack will be large and wolf density will be low.
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