Antipredator strategies of caribou: dispersion along shorelines

1985 ◽  
Vol 63 (6) ◽  
pp. 1324-1329 ◽  
Author(s):  
A. T. Bergerud

A small herd of 15–31 caribou (Rangifer tarandus) inhabited a shoreline strip of habitat along Lake Superior from 1972 to 1983. By remaining near the shoreline, they were spaced away from the major distributions of wolves (Canis lupus) and lynx (Lynx canadensis) that hunted mainly inland for moose (Alces alces) and snowshoe hares (Lepus americanus), respectively. Lake Superior also provided a means of escape from wolves, and offshore islands constituted safe parturition sites. The persistence of this herd is consistent with the hypothesis that viable caribou populations cannot survive on ranges frequented by high numbers of wolves (maintained mainly by moose prey) unless there are special habitat features providing escape for cows with young calves.

1970 ◽  
Vol 48 (6) ◽  
pp. 1287-1293 ◽  
Author(s):  
Carl C. Bursey ◽  
Michael D. B. Burt

Examination of 129 bobcats (Lynx rufus) from New Brunswick, Nova Scotia, and Maine and 14 lynx (Lynx canadensis) from Newfoundland revealed the presence of adult Taenia macrocystis (Diesing 1850) in 86% of the bobcats and in all the lynx. Concurrent examination of snowshoe hares (Lepus americanus) showed that a high proportion of adult hares were infected with cestode larvae of the strobilocercus type. Scolices of these larvae were identical with scolices of T. macrocystis adults recovered from wild cats.Experimental infection of domestic cats with fresh larvae from hares yielded adult taeniids, within 42 days, which were identical with the adult T. macrocystis found in wild cats.Experimental infection of laboratory-reared snowshoe hares with eggs of these cestodes produced fully developed, infective strobilocercus larvae within 14 weeks, thus establishing that Lepus americanus acts as an intermediate host in the life cycle of T. macrocystis in northeastern North America.


1982 ◽  
Vol 28 (4) ◽  
pp. 403-405 ◽  
Author(s):  
M. B. Akerman ◽  
J. A. Embil

A serological survey showed antibodies to Francisella tularensis present in 1.55% of snowshoe hares (Lepus americanus struthopus) and 1.06% of moose (Alces alces americana Clinton) sampled in Nova Scotia. No antibody-positive hares were found in Prince Edward Island, however. We believe this to be the first report of antibodies to F. tularensis in the moose.


2021 ◽  
Vol 134 (4) ◽  
pp. 342-352
Author(s):  
Arthur T. Bergerud ◽  
Brian E. McLaren ◽  
William Dalton ◽  
Lo Camps ◽  
Heather Butler ◽  
...  

Observations from 1974-2016 of Caribou (Rangifer tarandus) on the archipelago that comprises Slate Islands Provincial Park allowed us to infer direct and indirect effects of the arrival of Wolf (Canis lupus) pairs in winters of 1993-94 and 2003-04. Wolves created conditions that led to the near demise of Caribou from the islands, including some, but not all, behavioural changes in Caribou consistent with avoiding predators. Caribou on SIPP did not appear to return to calving locations near shoreline areas, nor use them to escape from Wolves by entering water. Shorelines and locations of Patterson Island near a Wolf-occupied Red Fox (Vulpes vulpes) den were the most common Caribou kill locations. Wolves also functionally shifted the ecosystem in Slate Islands Provincial Park via direct and indirect effects on North American Beavers (Castor canadensis), Red Foxes and Snowshoe Hares (Lepus americanus).


1992 ◽  
Vol 70 (8) ◽  
pp. 1614-1621 ◽  
Author(s):  
Robert J. Small ◽  
Lloyd B. Keith

We tested the relative vulnerability of arctic (Lepus arcticus) and snowshoe (Lepus americanus) hares to predation by red foxes (Vulpes vulpes) in experimental trials on three islands off Newfoundland's southwest coast. Arctic hares were significantly more vulnerable than snowshoe hares to fox predation: they were killed at a higher rate, and though the probability of death increased slightly for arctic hares over a trial period, it decreased for snowshoe hares. Rates of fox predation on arctic hares were inversely related to home-range size and nutritional status, whereas predation on snowshoe hares was inversely related to the percentage of home-range core areas with dense understory cover. We believe the arctic hare's greater vulnerability to fox predation, found in this study, coupled with its apparent inability to utilize food resources in forested areas that support snowshoe hares, which we found in an earlier study, largely accounts for the current restriction of arctic hares in Newfoundland to certain mountain and coastal barrens. The status of arctic hare populations before the introduction of snowshoe hares is unclear. However, distribution and abundance likely decreased as red foxes and lynx (Lynx canadensis) increased and began to cycle with snowshoe hares. Dispersal of foxes, and perhaps of lynx, from forested areas following snowshoe hare declines would have periodically intensified predation on the barrens.


2014 ◽  
Vol 92 (9) ◽  
pp. 789-794 ◽  
Author(s):  
M.V.A. Ewacha ◽  
J.D. Roth ◽  
R.K. Brook

Snowshoe hares (Lepus americanus Erxleben, 1777) are keystone herbivores supporting many boreal-forest predators. Understanding habitat use of hares can help predict how hares and their predators will be affected by disturbances such as climate change, which will have a particularly strong effect at tree line. We examined hare activity at arctic tree line near Churchill, Manitoba, using fecal pellet transects established in August 2012. We counted all hare fecal pellets at two plots per transect and measured plant abundance and vegetation structure surrounding the plots, then used model selection to determine the combinations of habitat features or plant species that best explained hare activity or presence. Hare pellets occurred at a higher density where tall shrub cover was high. Pellet density also increased with increasing canopy cover, tree size, tree density, visibility, and small shrub cover, but was negatively correlated with medium-sized shrub and herb cover. Hares preferred areas with willow (genus Salix L.) and avoided areas with unpalatable black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.). With climate warming, tree line is expected to advance northward and the increased tall shrub and willow cover predicted with increasing temperatures should benefit hares by providing greater predator protection and food.


2013 ◽  
Vol 91 (8) ◽  
pp. 562-572 ◽  
Author(s):  
Charles J. Krebs ◽  
Knut Kielland ◽  
John Bryant ◽  
Mark O’Donoghue ◽  
Frank Doyle ◽  
...  

Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9–10 year cycles throughout much of their North American range. Regional synchrony has been assumed to be the rule for these cycles, so that hare populations in virtually all of northwestern North America have been assumed to be in phase. We gathered qualitative and quantitative data on hare numbers and fur returns of Canada lynx (Lynx canadensis Kerr, 1792) in the boreal forest regions of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe synchrony in the time window of 1970–2012. Broad-scale synchrony in lynx fur returns was strong from 1970 to about 1995 but then seemed to break down in different parts of this region. Hare populations at 20 sites in Alaska, the Yukon, and Northwest Territories showed peak populations that lagged by 1–4 years during the 1990s and 2000s cycles. The simplest hypothesis to explain these patterns of asynchrony in hare cycles is the movement of predators from British Columbia north into the Yukon and then east into the Northwest Territories and west into Alaska. A traveling wave of these cycles is clearly seen in the lynx fur returns from western Canada and Alaska from 1970 to 2009. One consequence of a failure of synchrony is that hare predators like Canada lynx and Great-horned Owls (Bubo virginianus (Gmelin, 1788)) can move from one adjacent area to the next within this region and survive long enough to prolong low densities in hare populations that have declined earlier.


2003 ◽  
Vol 117 (3) ◽  
pp. 360 ◽  
Author(s):  
Kim G. Poole

The Canada Lynx (Lynx canadensis) is the most common and widespread member of the cat family in Canada. Lynx are distributed throughout forested regions of Canada and Alaska and into portions of the northern contiguous United States, closely paralleling the range of its primary prey, the Snowshoe Hare (Lepus americanus). They are most common in the boreal, sub-boreal and western montane forests, preferring older regenerating forests (>20 years) and generally avoiding younger stands, and occupy roughly 95% of their former range in Canada. Lynx population size fluctuates 3–17 fold over an 8–11 year cycle, tracking the abundance of Snowshoe Hares with a 1–2 year lag. During increasing and high hare abundance, lynx have high reproductive output and high kit and adult survival. The decline phase is characterized by reproductive failure, increased natural mortality, and high rates of dispersal. Dispersal distances of over 1000 km have been recorded. During the cyclic low, kit recruitment essentially fails for 2–3 years, and is followed by several years of modest reproductive output. Reproductive parameters in southern lynx populations appear similar to those found during the cyclic low and early increase phase in more northern populations. Trapping is a significant source of mortality in some areas. Field studies have documented from 2–45 lynx/100 km2 at various times in the cycle and in various habitats. Although the amplitude of the cyclic fluctuations in lynx numbers may have decreased somewhat in recent decades, there is no evidence to suggest a significant decline in numbers in Canada. Lynx are managed as a furbearer in Canada, with harvest regulated primarily by seasons, quotas, and closures. The harvest over the past decade has declined concurrent with declining pelt prices, and is currently a fraction of historic levels. Lynx are fully protected in less than 2–3% of their range in Canada. There is no evidence to suggest that overall lynx numbers or distribution across Canada have declined significantly over the past two decades, although loss of habitat through increased urbanization and development and forestry is likely affecting lynx populations along the southern fringe of its range. Its high potential to increase in numbers and propensity to disperse long distances suggest that the species is relatively resilient to localized perturbations and reductions, given time and removal of the factors that cause the initial decrease. Lowered lynx harvests, coupled with a greater awareness of the need for proactive lynx management, suggests that the overall future of lynx in Canada is secure.


2011 ◽  
Vol 89 (6) ◽  
pp. 509-516 ◽  
Author(s):  
N.P. McCann ◽  
R.A. Moen

We used location data from radio-collared Canada lynx ( Lynx canadensis Kerr, 1792), pellet-count data from snowshoe hares ( Lepus americanus Erxleben, 1777), and cover-type data from satellite imagery to evaluate the relationship between the scale of habitat measurement and the potential for persistence of lynx in northeastern Minnesota, USA, at the southern extent of their range. We counted hare pellets at transects throughout northeastern Minnesota to index hare abundance in cover types. Pellet counts were highest in coniferous forest, regenerating–young forest, and shrubby grassland, and these cover types were greater inside lynx use areas than outside of them. Proportions of regenerating–young forest were greater at scales ≥5 km2. We used these results and satellite imagery to map potential lynx core areas. We predicted that 7%–20% of the study area was suitable for lynx. Areas that we predicted to be suitable for lynx corresponded with known core areas, including those withheld from analyses. To maintain habitat for lynx persistence, forest management should retain current levels of 10- to 30-year-old coniferous forest and include ≥5 km2 areas containing 40% of 10- to 30-year-old coniferous forest. Mapping of potential core areas would be improved if cover-type data from satellite imagery identified conifer regeneration.


2015 ◽  
Vol 129 (2) ◽  
pp. 139 ◽  
Author(s):  
Daniel S. Licht ◽  
Ron A. Moen ◽  
D. Paul Brown ◽  
Mark C. Romanski ◽  
Robert A. Gitzen

In the 1930s, the Canada Lynx (Lynx canadensis) was extirpated from Isle Royale, a 535-km2 island located in western Lake Superior, 22 km from the Ontario and Minnesota shorelines. The first half of the 20th century was a time of change on Isle Royale as Caribou (Rangifer tarandus) disappeared, Coyotes (Canis latrans) briefly appeared, Moose (Alces americanus), Grey Wolves (Canis lupus), and Red Foxes (Vulpes vulpes) became established, and the habitat was altered by fire, logging, and over-browsing. Although these changes may have contributed to the demise of the Canada Lynx, our results suggest that over-harvest was a primary cause. Assuming a peak carrying capacity of 75 Canada Lynx and harvest rates comparable to those reported from 1890–1935, a population viability analysis indicated that the island population had a 0% chance of surviving 50 years. The analysis also indicated that, even in the absence of harvest, the population had only a 14% chance of persistence for 250 years. However, when 10 Canada Lynx were added to the modeled population every 10th year, the probability of persistence increased to 100%. Our analyses suggest that the island’s Canada Lynx population maintained itself by periodic immigration across an ice bridge; therefore, natural recolonization should be possible. However, the probability of ice-bridge formation has declined from 0.8 in the winter of 1958–59 to 0.1 in 2012–13, likely as a result of climate change. The Isle Royale situation exemplifies another impact of climate change and the possible need to augment populations to mitigate the loss of connectivity.


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