Winter diet of marten during a snowshoe hare decline

1996 ◽  
Vol 74 (3) ◽  
pp. 456-466 ◽  
Author(s):  
Kim G. Poole ◽  
Ron P. Graf
Keyword(s):  
Northern Region ◽  
Southern Region ◽  
Population Cycle ◽  
Snowshoe Hare ◽  
Corpora Lutea ◽  
Sex Structure ◽  
Winter Diet ◽  
Snowshoe Hares ◽  
Age And Sex ◽  
Prey Items

We examined the winter diet of marten (Martes americana) from northern (65–67°N) and southern (60–62°N) regions of the western Northwest Territories from 1988–1989 to 1993–1994 during a decline in snowshoe hare (Lepus americanus) abundance that started in 1990. We used 4256 marten carcasses collected from trappers to examine changes in diet, productivity, age and sex structure of the harvest, and body and reproductive indices. Arvicoline rodents formed the greatest proportion (41–95% occurrence of total prey items) of the annual winter diet in both regions and snowshoe hares constituted 1–39% of prey items. Snowshoe hares constituted 3–64% of the diet when expressed as biomass. Dietary proportions of arvicolines increased and snowshoe hares decreased with time in the northern region but not in the southern region. Female marten took proportionately more arvicolines and males took more snowshoe hares. Juvenile marten took proportionately more snowshoe hares, while adults took more arvicolines. The proportion of juvenile marten in the harvest declined in both regions between 1991–1992 and 1993–1994. The ratio of juveniles to adult females in the harvest also declined with time in the southern region but not in the northern region. The amount of omental fat declined with time for most age and sex classes. Ovulation rates (as determined by counts of corpora lutea) declined with time among yearlings, and among adults from the southern region but not in the northern region. In utero litter size did not change. We suggest that the snowshoe hare population cycle has a significant impact on marten populations in the northern boreal forest.

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.

Snowshoe hare adrenal weights in relation to population density

1977 ◽  
Vol 55 (3) ◽  
pp. 634-637 ◽  
Author(s):  
E. O. Höhn ◽  
J. G. Stelfox
Keyword(s):  
Adrenal Weight ◽  
Gastric Ulcers ◽  
Population Cycle ◽  
Snowshoe Hare ◽  
Lower Body ◽  
Population Densities ◽  
The Third ◽  
Snowshoe Hares ◽  
Body Weights ◽  
Hare Population

Adrenal and body weights of snowshoe hares from three areas in which hare population densities differed markedly were determined in a search for evidence of adrenal enlargement in the course of the population cycle. In the first area hares were in a sudden decline after a peak. Dead hares were found there in some numbers. Hare populations in the other two areas were still rising (population peaks occurred 18 months after sampling), but hare density was considerably greater in the second as compared with the third area. There were no significant differences in absolute adrenal weight between any of the groups. Relative adrenal weights were also similar, except for significantly higher relative adrenal weights in hares found dead as compared with those shot, but this was apparently due merely to the lower body weights of animals found dead compared with those killed. There was no evidence of significant differences in relative adrenal weight according to sex or age. No gastric ulcers were found in 26 hares taken from a population at the peak of the cycle.

Browse site selection by snowshoe hares: effects of food supply and predation risk

2005 ◽  
Vol 83 (2) ◽  
pp. 280-292 ◽  
Author(s):  
K E Hodges ◽  
A R.E Sinclair
Keyword(s):  
Site Selection ◽  
Food Supply ◽  
Foraging Behaviour ◽  
Population Cycles ◽  
Distribution Patterns ◽  
Pressure Change ◽  
Population Cycle ◽  
Snowshoe Hare ◽  
Snowshoe Hares ◽  
Survival And Reproduction

If snowshoe hares (Lepus americanus Erxleben, 1777) change their foraging behaviour through the population cycle as food supply and predation pressure change, these shifts could contribute to their population cycles by affecting survival and reproduction. We examined whether hares change their foraging movements and browse site selection in response to manipulations of food addition and predator reduction during a cyclic low phase. Snowshoe hares on sites with supplemental rabbit chow ate fewer species per site and preferred to browse in slightly denser cover than unfed hares. Differences in foraging behaviour were linked to season and site characteristics. Snowshoe hares moved similar distances and spent similar amounts of time per browse site in the presence and absence of terrestrial predators. Hares protected from predators used slightly more browse sites in thick cover, but this pattern was partially due to differences in availability. The absence of terrestrial predators had little effect on snowshoe hare foraging behaviour; instead, browse distribution patterns explained most of the behavioural variation. Thus, the predicted patterns in response to the manipulations did not occur, and our results challenge the idea that changes in snowshoe hare foraging behaviour contribute to their cyclic dynamics.

Mammal population cycles: evidence for intrinsic differences during snowshoe hare cycles

2003 ◽  
Vol 81 (2) ◽  
pp. 216-220 ◽  
Author(s):  
A R.E Sinclair ◽  
Dennis Chitty ◽  
Carol I Stefan ◽  
Charles J Krebs
Keyword(s):  
Reproductive Output ◽  
Population Cycles ◽  
Food Shortage ◽  
Population Cycle ◽  
Snowshoe Hare ◽  
Population Densities ◽  
Northern Latitudes ◽  
Snowshoe Hares ◽  
Reproductive Rates ◽  
High Phase

Some mammals in high northern latitudes show regular population cycles. In snowshoe hares (Lepus americanus), these occur every 9–10 years. One hypothesis proposes extrinsic causes such as food shortage or predation. The other proposes intrinsic causes through different morphs that alternate between different phases of the cycle. The morphs should differ in behaviour or physiology. This hypothesis predicts that animal lineages bred from high and low phases of the population cycle should differ in reproduction and survivorship. In a 16-year breeding program, lineages of purebred high-phase female hares had reduced reproductive rates relative to those of purebred low-phase females, resulting in extinction of high-phase lineages. Reproductive output declined with age in high- but not low-phase animals. These lineages also differed in longevity and senescence. These results are consistent with the intrinsic hypothesis and suggest a mechanism for alternating population densities that could work synergistically with extrinsic causes like predation and food shortage.

Does predation risk cause snowshoe hares to modify their diets?

2003 ◽  
Vol 81 (12) ◽  
pp. 1973-1985 ◽  
Author(s):  
K E Hodges ◽  
A R.E Sinclair
Keyword(s):  
Species Composition ◽  
Predation Risk ◽  
Sublethal Effects ◽  
Population Cycle ◽  
Food Supplementation ◽  
Snowshoe Hare ◽  
Supplemental Food ◽  
Snowshoe Hares ◽  
Wide Range ◽  
Mammalian Predators

Snowshoe hares (Lepus americanus) undergo a 10-year population cycle with several years of low densities. Several authors have suggested that snowshoe hares modify their foraging behaviour to reduce predation risk during the low phase, resulting in protein-poor diets and poor body condition. We test that idea by using a factorial manipulation of food supplementation and predator reduction and by examining the species composition, browse size, and nutritional quality of snowshoe hare diets during 3 years of low snowshoe hare abundance in southwestern Yukon. Our results negate the hypothesis that snowshoe hares change their diets in response to mammalian predators during the cyclic low phase. Snowshoe hares on the different treatments had diets that differed in species composition and twig sizes, but protected hares did not have higher protein diets than unprotected hares. Snowshoe hares with access to supplemental food ate more fibrous and lower protein natural browse than unfed hares, showing that they did not choose diets primarily for protein content. Instead, snowshoe hares converted a wide range of forage availabilities into similar intakes of protein and fibre, despite variation in predator presence. Our results suggest that snowshoe hares select their diets to balance the protein and fibre contents. Although sublethal effects of predators may influence cyclic dynamics, our results show that such a feedback does not occur via a nutritional mechanism, counter to previous suggestions.

The Spatial and Temporal Distribution of Lightning Strikes and Their Relationship with Vegetation Type, Elevation, and Fire Scars in the Northern Territory

2007 ◽  
Vol 20 (7) ◽  
pp. 1161-1173 ◽  
Author(s):  
Musa Kilinc ◽  
Jason Beringer
Keyword(s):  
Large Scale ◽  
Vegetation Type ◽  
Northern Region ◽  
Northern Territory ◽  
Southern Region ◽  
Transitional Period ◽  
Geographical Information ◽  
Coastal Regions ◽  
Fire Scars ◽  
Lightning Strikes

Abstract In this paper the authors explore the spatial and temporal patterns of lightning strikes in northern Australia for the first time. In particular, the possible relationships between lightning strikes and elevation, vegetation type, and fire scars (burned areas) are examined. Lightning data provided by the Bureau of Meteorology were analyzed for a 6-yr period (1998–2003) over the northern, southern, and coastal regions of the Northern Territory (NT) through the use of Geographical Information Systems (GIS) to determine the spatial and temporal characteristics of lightning strikes. It was determined that the highest densities of lightning strikes occurred during the monsoon transitional period (dry to wet) and during the active monsoon periods, when atmospheric moisture is highest. For the period of this study, lightning was far more prevalent over the northern region (1.21 strikes per km2 yr−1) than over the southern (0.58 strikes per km2 yr−1) and coastal regions (0.71 strikes per km2 yr−1). Differences in vegetation cover were suggested to influence the lightning distribution over the northern region of the NT, but no relationship was found in the southern region. Lightning strikes in the southern region showed a positive relationship with elevations above 800 m, but no relationship was found in the northern region, which could be due to the low-lying topography of the area. A comparison of lightning densities between burned and unburned areas showed high variability; however, the authors suggest that, under ideal atmospheric conditions, large-scale fire scars (>500 m) could produce lightning strikes triggered by either enhanced free convection or mesoscale circulations.

scholarly journals Anthropological Picture of the Corded Ware Population of the Subcarpathian Region in the Light of Data Obtained from the Sites at Święte, Jarosław District

2018 ◽  
Vol 23 (1) ◽  
pp. 213-228
Author(s):  
Anita Szczepanek
Keyword(s):  
Mortality Rate ◽  
Body Height ◽  
River Valley ◽  
Entire Region ◽  
Anthropometric Data ◽  
Sex Structure ◽  
Males And Females ◽  
Age And Sex

Abstract Twenty Corded Ware graves containing twenty five interments were identified at sites 11, 15 and 20 at Święte, Radymno Commune, Jarosław District. In most of the graves (16), there was only one interment, although there were also three graves with two internments and one grave with three interments. The age and sex structure of buried individuals shows the roughly equal number of females, males, and children at the age of Infans I and II, with the category Maturus (individuals aged 40 to 50) having the highest mortality rate. So far, Rzeszów Foothills and the Lower San River Valley yielded 40 Corded Ware graves containing 51 interments in total. Single burials were predominant. Alike at Święte sites, the highest proportion of burials is recorded for individuals at the age of Maturus irrespective of sex; overall, for the entire region, male graves, however, outnumber female graves. In most cases skeletons are poorly preserved, but scarce anthropometric data are the indication of dolichomorphic crania in both males and females, which phenomenon is already noted for the Małopolska Upland and present Ukraine. The intravital body height for adults varies from 161.3 to 175 cm for males and from 156.7 to 163.1 cm for females.

scholarly journals Comparative Analysis of Effects of Heavy Vehicles on Roads in Southern and Northern Nigeria

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
C. C. Osadebe ◽  
H. A. Quadri
Keyword(s):  
Northern Region ◽  
Design Guidelines ◽  
Traffic Volume ◽  
Southern Region ◽  
Heavy Vehicle ◽  
Heavy Vehicles ◽  
Passenger Cars ◽  
The Road ◽  
Equivalency Factors ◽  
On The Road

The prevalence of flexible pavement deterioration in the country has been adduced largely by highway researchers to trucks or heavy vehicles carrying much in excess of permitted legal limits. This study investigated levels of deterioration of Abuja-Kaduna-Kano road (Northern region) and Port Harcourt-Enugu road (Southern region) caused by heavy vehicles through a 14 day traffic counts conducted at 5 strategic points each in the Northern and Southern regions. Traffic data generated were analyzed with AASHTO Design Guidelines (1993) to evaluate Equivalent Single Axle Loads (ESALs) and Vehicle Damage effects on the road. The Traffic Volume, Average Daily Traffic (ADT), and Heavy Vehicle per day (HV/day) were estimated to be 2,063,977; 147,427; and 12,246 respectively in the Northern region, while in the Southern region they were estimated to be 750,381; 53,670; and 20,951 respectively. Motorcycles, Passenger cars, Mini-buses/Pick-ups, and Heavy vehicles constitute 18.7%, 49.7%, 23.3% and 8.31% of the total traffic volume respectively in the Northern region while in the South they constitute 4.6%, 30.1%, 26.2% and 39.1% respectively. ESALs were estimated according to AASHTO Design Guidelines in the Northern and Southern regions as 547,730 and 836,208 respectively. An average Load Equivalency Factors (LEFs) of 3.43 and 3.02 were estimated for each heavy vehicle plying the Northern and Southern roads respectively and this could explain some failures (alligator cracks, potholes, depressions, linear or longitudinal cracks along the centre line amongst others) inherent on the road.

scholarly journals Roles of Host Species, Geographic Separation, and Isolation in the Seroprevalence of Jamestown Canyon and Snowshoe Hare Viruses in Newfoundland

2012 ◽  
Vol 78 (18) ◽  
pp. 6734-6740 ◽  
Author(s):  
Gregory Goff ◽  
Hugh Whitney ◽  
Michael A. Drebot
Keyword(s):  
Host Species ◽  
Neutralization Assay ◽  
Snowshoe Hare ◽  
Large Mammals ◽  
Content Type ◽  
Neuroinvasive Disease ◽  
Snowshoe Hares ◽  
Jamestown Canyon Virus ◽  
Geographic Separation ◽  
California Serogroup

ABSTRACTCalifornia serogroup viruses, including Jamestown Canyon virus (JCV) and snowshoe hare virus (SSHV), are mosquito-borne members of theBunyaviridaefamily and are endemic across North America. These arboviruses are potential pathogens which occasionally cause neuroinvasive disease in humans and livestock. A neutralization assay was used to document JCV and SSHV seroprevalence using blood collected from a variety of domestic and wildlife host species. These species were sampled in an island setting, Newfoundland, which contains diverse ecoregions, ecological landscapes, and habitats. Seroprevalence rates for each virus differed significantly among host species and within certain species across different geographic areas. JCV was significantly associated with large mammals, and SSHV was significantly associated with snowshoe hares. Seroprevalence rates in the 5 species of animals tested for prior exposure to JCV ranged from 0% in snowshoe hares to 64% in horses. Seroprevalence rates for SSHV ranged from less than 1% in bovines to 55% in all snowshoe hares. The seroprevalence of SSHV differed significantly (P< 0.05) among hares occupying the discrete habitats of watersheds separated by 14 to 35 km. Cattle on farms in boreal forest landscapes displayed significantly higher JCV seroprevalence (P< 0.001) than those on farms located in seacoast landscapes. Lifelong geographic isolation of cattle to insular Newfoundland was associated with significantly lower JCV seroprevalence (P< 0.01) than that for cattle which had lived off-island.

Age and Sex Structure of the Study Population

2017 ◽  
pp. 111-150
Author(s):  
Kim Hill ◽  
A. Magdalena Hurtado
Keyword(s):  
Sex Structure ◽  
Study Population ◽  
Age And Sex
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