Demography and ecology of the arctic hare (Lepus arcticus) in southwestern Newfoundland

1987 ◽  
Vol 65 (4) ◽  
pp. 852-861 ◽  
Author(s):  
Brian J. Hearn ◽  
Lloyd B. Keith ◽  
Orrin J. Rongstad
Keyword(s):  
Survival Rate ◽  
Reproductive Potential ◽  
Home Range Size ◽  
Day Length ◽  
The Arctic ◽  
Adult Males ◽  
Marrow Fat ◽  
Red Foxes ◽  
Arctic Hare ◽  
Hare Population

We determined demographic attributes of an arctic hare (Lepus arcticus) population in the Southern Long Range Mountains of Newfoundland. Twenty-four adult hares were livetrapped, radio collared, and monitored from July 1981 through July 1984. From livetrapping and an aerial census we estimated mean density at about 1 adult/km2. A single litter was born annually and natality averaged 3.0 young/female. Mean dates of conception and parturition were 19 April and 8 June, respectively. Annual survival rate of radio-collared adults was 0.78; calculated 1st-year survival rate of juveniles was 0.15. Natural mortality was mainly from red foxes (Vulpes vulpes). One-year-old individuals comprised 18% of 68 adult hares shot in May. Sex ratios were biased towards males in both trapped and shot samples. Summer home range size of three adult females (52–69 ha) averaged half that of three adult males (116–155 ha). Movements increased in March and April with onset of breeding activity. It is unlikely that winter food shortage affected survival, as hares collected in May had both kidney fat and relatively high levels of bone marrow fat. Annual differences in these condition indices were, however, reflected in several reproductive parameters. We hypothesize that the single litter and small litter size which combine to give Newfoundland arctic hares the lowest reproductive potential of any known hare population are a consequence of (i) the late spring that delays onset of breeding until April, and (ii) the shorter day length in April and hence lower gonadotrophin levels at this southernmost limit of distribution. We believe that predation on juveniles is the paramount limitation on growth of this arctic hare population, and primarily responsible for the stabilization at low densities.

Demography of sympatric arctic and snowshoe hare populations: an experimental assessment of interspecific competition

1989 ◽  
Vol 67 (11) ◽  
pp. 2762-2775 ◽  
Author(s):  
Robert M. Barta ◽  
Lloyd B. Keith ◽  
Shannon M. Fitzgerald
Keyword(s):  
Interspecific Competition ◽  
Home Range Size ◽  
Early Spring ◽  
The Arctic ◽  
Mixed Species ◽  
Marrow Fat ◽  
Weight Losses ◽  
Snowshoe Hares ◽  
Species Population

Geographic distributions of arctic (Lepus arcticus) and snowshoe hares (Lepus americanus) do not overlap on insular Newfoundland, where snowshoes were introduced, or in continental North America, where both species are indigenous. We conducted a field experiment to explore the role of interspecific competition in maintaining this allopatry. In September of 1984 and 1985, single- and mixed-species populations of arctic and snowshoe hares were established as "treatments" on six islands off Newfoundland's southwest coast. Island treatments differed between years. Demographic elements of each species population were monitored as potential response variables. Neither snowshoe nor arctic hares were demographically affected by the sympatry imposed in this experiment. Survival, reproduction, recruitment, habitat use, home range size, and over-winter weight change did not differ between single- and mixed-species treatments. There were, however, major demographic responses when each species was forced to occupy only atypical habitat, i.e., habitat normally used by the other species. Thus, most arctic hares confined to forested islands died from starvation in 1–3 months, after weight losses of 20–30% and marrow-fat reductions to <15%. Such responses occurred during winter and early spring, regardless of whether snow-shoe hares were present. In contrast, arctic hares at similar densities in their typical barrens habitat maintained weight and survived well. Snowshoe hares also maintained weight when restricted to barrens, but unlike those in forest habitat, were rapidly decimated by raptor predation. We believe that lack of suitable food over winter, rather than interspecific competition, has been a major constraint on the arctic hare's ability to populate forested regions of Newfoundland, whereas heavy predation has prevented snowshoe hares from colonizing mountain and coastal barrens.

An experimental study of red fox predation on arctic and snowshoe hares

1992 ◽  
Vol 70 (8) ◽  
pp. 1614-1621 ◽  
Author(s):  
Robert J. Small ◽  
Lloyd B. Keith
Keyword(s):  
Home Range ◽  
Home Range Size ◽  
The Arctic ◽  
Lynx Lynx ◽  
Lynx Canadensis ◽  
Red Foxes ◽  
Snowshoe Hares ◽  
The Status ◽  
Forested Areas ◽  
Experimental Trials

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.

Impact of helminth parasitism on a snowshoe hare population in central Wisconsin: a field experiment

1995 ◽  
Vol 73 (10) ◽  
pp. 1891-1898 ◽  
Author(s):  
Sara E. M. Bloomer ◽  
Thomas Willebrand ◽  
Ingegerd M. Keith ◽  
Lloyd B. Keith
Keyword(s):  
Survival Rates ◽  
Snowshoe Hare ◽  
Marrow Fat ◽  
Proximate Cause ◽  
Risk Of Death ◽  
Snowshoe Hares ◽  
Condition Indices ◽  
Time Specific ◽  
And Control ◽  
Hare Population

We tested the hypothesis that helminth parasitism is demographically significant to a noncyclic population of snowshoe hares (Lepus americanus) near the species' geographic boundary in central Wisconsin (U.S.A.). During November 1988 to December 1991, we injected 93 individuals (≥760 g, aged ≥2 months) with anthelmintics: Ivermectin for nematode and Droncit for cestode infections. We injected 98 control hares with propylene glycol, the common vehicle for both drugs. All treated and control hares were radio-collared with mortality-sensing transmitters and monitored daily to weekly from the ground or air. Prevalence and intensity of lungworms (Protostrongylus boughtoni), intestinal worms (Nematodirus triangularis), and stomach worms (Obeliscoides cuniculi) were markedly reduced by Ivermectin treatment. No other nematodes were found to be present. Treatment with Droncit to remove intestinal cestodes was apparently unnecessary, as prevalence among necropsied untreated hares and controls was just 10%. We compared body-condition indices (mass changes, response to trap stress, and bone-marrow fat), reproduction (pregnancy rate and litter size), home-range sizes, and time-specific survival rates of anthelmintic-treated versus control hares. None of these demographic variables differed significantly between treated and control cohorts, nor was there any evidence that parasitism increased the risk of death from predation, which was the proximate cause of 96% of all natural mortalities. We conclude that helminth parasitism played no detectable role in the dynamics of this Wisconsin snowshoe hare population.

Movement and spatial use patterns of California sea otters

1996 ◽  
Vol 74 (10) ◽  
pp. 1841-1849 ◽  
Author(s):  
Katherine Ralls ◽  
Thomas C. Eagle ◽  
Donald B. Siniff
Keyword(s):  
Movement Patterns ◽  
Extended Period ◽  
Home Range Size ◽  
Adult Males ◽  
Sea Otters ◽  
Daily Monitoring ◽  
Use Patterns ◽  
Radio Transmitters ◽  
Spatial Use ◽  
Short Time

Movement patterns of sea otters (Enhydra lutris) were followed by daily monitoring of 40 individuals with implanted radio transmitters. Otters of all age and sex classes were most often found within 1–2 km of their locations on the previous day. However, individuals often remained within a small area for an extended period and then suddenly moved a much greater distance within a short time period. There were significant differences among age–sex classes, but not months, in the mean monthly distances between successive daily locations and between extreme locations of individual otters. There were significant differences among both age–sex classes and months in the harmonic mean distance deviation. For all three measures, juvenile males tended to move the greatest distances. Adult males tended to be more sedentary than adult females over the short term, but traveled over greater distances in the long term. Individuals within age–sex classes had different movement patterns, and individuals often had different movement patterns during the same month in successive years. Estimates of the area used by individual otters during a single 24-h period (6.9–1166.4 ha) overlapped previous estimates of home-range size based on much longer time periods.

Reproductive potential in parkland- and arctic-nesting populations of mallards and pintails (Anatidae)

1977 ◽  
Vol 55 (8) ◽  
pp. 1242-1251 ◽  
Author(s):  
B. K. Calverley ◽  
D. A. Boag
Keyword(s):  
Clutch Size ◽  
Anas Platyrhynchos ◽  
Reproductive Potential ◽  
Ovarian Follicles ◽  
The Arctic ◽  
Energy Costs ◽  
The Status ◽  
Mackenzie River

We estimated the reproductive potential of mallards (Anas platyrhynchos) and pintails (A. acuta) nesting in the parklands of Alberta and the delta of the Mackenzie River, N.W.T., by recording the number of laying females and the potential clutch size, based on the status of ovarian follicles, in samples of each species collected at the two latitudes. A larger proportion of the ducks collected in the parklands were laying and their potential clutch sizes were larger than in the arctic. Thus, both species exhibited a greater reproductive potential in the parklands than in the arctic. The reasons for these differences are discussed in relation to energy costs to ducks breeding at the two latitudes.

Notes on the Arctic Hare

1947 ◽  
Vol 28 (4) ◽  
pp. 353 ◽  
Author(s):  
Lawrence H. Walkinshaw
Keyword(s):  
The Arctic ◽  
Arctic Hare

scholarly journals Cormorants dive through the Polar night

2005 ◽  
Vol 1 (4) ◽  
pp. 469-471 ◽  
Author(s):  
David Grémillet ◽  
Grégoire Kuntz ◽  
Caroline Gilbert ◽  
Antony J Woakes ◽  
Patrick J Butler ◽  
...  
Keyword(s):  
Visual Cues ◽  
Significant Proportion ◽  
Dive Depth ◽  
Day Length ◽  
The Arctic ◽  
High Latitudes ◽  
Phalacrocorax Carbo ◽  
Polar Night ◽  
Light Levels ◽  
Great Cormorants

Most seabirds are visual hunters and are thus strongly affected by light levels. Dependence on vision should be problematic for species wintering at high latitudes, as they face very low light levels for extended periods during the Polar night. We examined the foraging rhythms of male great cormorants ( Phalacrocorax carbo ) wintering north of the Polar circle in West Greenland, conducting the first year-round recordings of the diving activity in a seabird wintering at high latitudes. Dive depth data revealed that birds dived every day during the Arctic winter and did not adjust their foraging rhythms to varying day length. Therefore, a significant proportion of the dive bouts were conducted in the dark (less than 1 lux) during the Polar night. Our study underlines the stunning adaptability of great cormorants and raises questions about the capacity of diving birds to use non-visual cues to target fish.

Population size and spatial ecology of Blanding’s Turtle (Emydoidea blandingii) in South March Highlands, Ottawa, Ontario, Canada

2015 ◽  
Vol 93 (7) ◽  
pp. 509-514 ◽  
Author(s):  
Caleb T. Hasler ◽  
Kevin Robinson ◽  
Nick Stow ◽  
Shawn R. Taylor
Keyword(s):  
Population Size ◽  
Spatial Ecology ◽  
Road Construction ◽  
Home Range Size ◽  
Adult Males ◽  
Emydoidea Blandingii ◽  
Blanding's Turtle ◽  
The Road ◽  
Gravid Females ◽  
Blanding’S Turtle

Between 2010 and 2011, an arterial road was constructed within provincially significant wetlands in the South March Highlands (SMH) located in Ottawa, Ontario, Canada. The wetlands and adjacent upland areas were determined to be sensitive habitat for Blanding’s Turtles (Emydoidea blandingii (Holbrook, 1838)) during the approval and permitting process, and a population study was required as part of the road construction project. The study consisted of a 4-year mark–recapture program and a movement study of radio-tagged adult turtles. General findings included the identification of 27 adult males and 55 females and a population estimate of 93 adults (95% Cl: 86–118). A 1:2.32 male to female sex bias was also found. Mean home-range size was 19.06 ha and tagged turtles moved, on average, more per observation in 2013 (191.40 m compared with 89.75 and 123.04 m in 2011 and 2012, respectively). Previously reported differences in movement patterns between males, females, and gravid females were not observed. The SMH Blanding’s Turtle population should be closely monitored because urban development continues in the area, which may further reduce the population size. Understanding the biology of imperiled populations across species’ ranges is necessary to promote conservation and adaptive wildlife management.

Effects of adults on the demography of fox squirrels (Sciurus niger)

1985 ◽  
Vol 63 (4) ◽  
pp. 861-867 ◽  
Author(s):  
Lonnie P. Hansen ◽  
Charles M. Nixon
Keyword(s):  
Home Range Size ◽  
Adult Males ◽  
Sciurus Niger ◽  
Age Classes ◽  
Control Grid ◽  
Local Populations ◽  
Adult Females ◽  
Resource Limited ◽  
Fox Squirrels ◽  
Reproductive Rates

As a test of the hypothesis that adult fox squirrels (Sciurus niger) regulate the number of immature and adult squirrels entering a population, each fall from 1979 to 1981 adult males were removed from two grids (male-removal grids, MRGs), adult females from two grids (female-removal grids, FRGs), all adults from one grid (adult-removal grid, ARG), and one grid was maintained as a control (control grid, CG). The number of previously uncaptured juveniles and subadults (both sexes) and yearling–adult females was greater on FRGs than on the CG and MRGs, especially during the fall. The number of new adult males captured during the fall was higher where adult males had been removed. During spring, reproductive rates (percent lactating) were higher on grids from which females had been removed (FRGs and the ARG), but this was not so during fall. Length of residency was shorter for juvenile–subadult and adult fox squirrels and longer for yearling females where adult females had been removed. Movement patterns in response to removal of adults suggested resident adult females influenced home range size of all sex classes and age-classes. We conclude that the presence of adult females is important in limiting recruitment in local populations of fox squirrels and that this strategy likely evolved in response to resource-limited environments.

Demography of barren-ground grizzly bears

2003 ◽  
Vol 81 (2) ◽  
pp. 294-301 ◽  
Author(s):  
Philip D McLoughlin ◽  
Mitchell K Taylor ◽  
H Dean Cluff ◽  
Robert J Gau ◽  
Robert Mulders ◽  
...  
Keyword(s):  
Survival Rate ◽  
Litter Size ◽  
Birth Interval ◽  
Ursus Arctos ◽  
Survival Rates ◽  
Grizzly Bears ◽  
Adult Males ◽  
Barren Ground ◽  
Rate Of Increase ◽  
The Mean

Between May 1995 and June 1999, we equipped 81 barren-ground grizzly bears (Ursus arctos) with satellite radio collars within a study area of 235 000 km2, centred 400 km northeast of Yellowknife, Northwest Territories, Canada. We used data from radiotelemetry to estimate survival rates, reproductive parameters, and the finite rate of increase of the population (λ). The annual survival rate of adult females was estimated at 0.979 (95% confidence intervals (CI) = 0.955–0.998), while the survival rate of adult males was 0.986 (95% CI = 0.942–1.0). The cub survival rate was 0.737 (95% CI = 0.600–0.844) and the yearling survival rate was 0.683 (95% CI = 0.514–0.821). Cub litter size averaged 2.23 (SE = 0.13, n = 35), while yearling litter size decreased to a mean of 1.86 (SE = 0.12, n = 35). The mean litter size of females with 2-year-olds was 1.85 (SE = 0.15, n = 20). The mean birth interval was 2.8 years (SE = 0.3 years, n = 17). The mean reproductive interval, which is calculated by excluding the loss of whole litters from the sample, was 3.9 years (SE = 0.4 years, n = 9). Mean litter size divided by mean birth interval yielded an annual natality rate of 0.81 cubs per adult female per year. The mean age at first parturition was 8.1 years (SE = 0.5 years, n = 10). We believe the population to be currently stable or slightly increasing (λ = 1.033, 95% CI = 1.008–1.064).

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