Snowshoe Hare Population Response to Artificial High Densities

1976 ◽  
Vol 57 (3) ◽  
pp. 523-553 ◽  
Author(s):  
L. A. Windberg ◽  
L. B. Keith
Keyword(s):  
Snowshoe Hare ◽  
Population Response ◽  
Hare Population

Experimental analyses of dispersal in snowshoe hare populations

1976 ◽  
Vol 54 (12) ◽  
pp. 2061-2081 ◽  
Author(s):  
Lamar A. Windberg ◽  
Lloyd B. Keith
Keyword(s):  
Lepus Americanus ◽  
Snowshoe Hare ◽  
Lower Body ◽  
Population Densities ◽  
Population Response ◽  
Partial Removal ◽  
Resident Population ◽  
Body Weights ◽  
Sex Ratio Imbalance ◽  
Hare Population

Dispersal was investigated in snowshoe hare (Lepus americanus) populations near Rochester, Alberta, from May 1970 to May 1974. Ingressing hares (dispersers) were removed every 3 to 4 weeks after removal of the initial resident population from an 11.3-ha study area. Dispersal into this vacant habitat occurred during all seasons of each year. The highest rates of ingress were recorded during the winter of peak population densities (1970–1971). There was a higher proportion of short-yearlings among ingressing hares than among residents. During two winters of known food shortage (1970–1971 and 1971–1972) dispersing hares had lower body weights than residents. Lighter adrenals and a higher incidence of scarring were also found among ingressing hares during winter 1970–1971.During winter 1971–1972 the resident hare population was removed from another area. Comparable recapture rates between marked immigrants on this area and hares on unmanipulated study areas indicated that ingressing individuals had settled in the vacant habitat.Hare population response to sex-ratio imbalance, created by partial removal of each sex on different areas, was studied during 1970 and 1971. Pregnancy rates declined significantly only on the male-removal area. Movements by adults during the breeding season and by predominantly juveniles over winter tended toward rebalancing population sex ratios.

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.

Influence of forest herbicide on snowshoe hare population dynamics: reproduction, growth, and survival

1996 ◽  
Vol 26 (1) ◽  
pp. 112-119 ◽  
Author(s):  
Thomas P. Sullivan
Keyword(s):  
Body Mass ◽  
Demographic Parameters ◽  
Snowshoe Hare ◽  
Growth And Survival ◽  
Physiological Processes ◽  
Adult Females ◽  
Breeding Condition ◽  
Glyphosate Herbicide ◽  
Hare Population ◽  
Treatment Population

This study was designed to assess the influence of forest applications of glyphosate herbicide on reproduction, growth, and survival in snowshoe hare (Lepusamericanus Erxleben) populations in control (reference) and treatment habitats near Prince George, B.C. Proportion of adult hares in breeding condition and number of successful pregnancies showed no consistent differences between control and treatment populations. Recruitment of hares was generally similar except for significantly more juvenile females entering the control than treatment population at one study area. At a second study area, total recruitment was significantly higher in the treatment than control population for both sexes in 1990 and for adult females in 1991, the 2 post-treatment years. There was little difference in survival of hares between control and treatment populations. Lack of significant differences in mean body mass and growth rates suggested that this herbicide treatment had little or no effect on metabolic or general physiological processes in the development of young hares. Similar profiles of body mass distribution between control and treatment populations indicated that comparable levels of biomass of hares were available as prey for predators. Use of this forest herbicide did not measurably affect demographic parameters of snowshoe hare populations.

Demographic Parameters of a Snowshoe Hare Population

1968 ◽  
Vol 32 (4) ◽  
pp. 812 ◽  
Author(s):  
E. Charles Meslow ◽  
Lloyd B. Keith
Keyword(s):  
Demographic Parameters ◽  
Snowshoe Hare ◽  
Hare Population

Reproductive change in the 10-year cycle of snowshoe hares

1979 ◽  
Vol 57 (2) ◽  
pp. 375-390 ◽  
Author(s):  
John R. Cary ◽  
Lloyd B. Keith
Keyword(s):  
Pregnancy Rate ◽  
Litter Size ◽  
Weight Change ◽  
Ovulation Rate ◽  
Population Cycle ◽  
Snowshoe Hare ◽  
Cyclic Variation ◽  
Reproductive Parameters ◽  
Snowshoe Hares ◽  
Hare Population

Reproduction was monitored during a 16-year study of snowshoe hare (Lepus americanus) populations near Rochester, Alberta. Pregnancy rate, ovulation rate, and litter size changed markedly between successive litters within the breeding season; these parameters were thus further categorized by litter in our analyses. Most reproductive components varied significantly between years; a significant '10-year' periodicity was the dominant source of this variation. The cyclic fluctuations of reproductive parameters were broadly synchronous and tended to precede the population cycle by about 3 years, thereby producing a range in potential natality annually of 7.5 to 17.9 young per female. The year-to-year variability of pregnancy rate, ovulation rate, and litter size was markedly larger in the later litters than in the early ones. Paunched weight, mean age, incidence of endoparasites, liver and spleen weights, and midwinter-to-spring weight change also possessed significant 10-year cycles; paunched weight cycled directly with the hare population, but the others cycled either directly with or counter to reproduction. We believe that the correspondence between midwinter-to-spring weight change and reproduction implicates winter nutrition as the primary cause of the cyclic variation. Onset of spring accounted for a significant amount of variability in onset of breeding, adding to that due to the periodic change.

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