The role of dispersal in the population dynamics of snowshoe hares

1985 ◽  
Vol 63 (1) ◽  
pp. 106-115 ◽  
Author(s):  
Stan Boutin ◽  
B. S. Gilbert ◽  
Charles J. Krebs ◽  
A. R. E. Sinclair ◽  
J. N. M. Smith
Keyword(s):  
Population Dynamics ◽  
Small Mammals ◽  
Lepus Americanus ◽  
Population Increase ◽  
Dispersal Rate ◽  
Population Densities ◽  
Control Grid ◽  
Snowshoe Hares ◽  
Kluane Lake

We monitored dispersal of snowshoe hares (Lepus americanus) at Kluane Lake, Yukon, during a population increase, peak, and decline. Dispersal was measured by recording the number of immigrants to a removal grid and by tracking radiocollared individuals. The observed decline was not due to dispersal, as a maximum of 28% of all losses of radiocollared animals was due to dispersal. Dispersal rate (as measured by number of immigrants to the removal grid per individual on the control grid) was negatively correlated (−0.51, P < 0.01) with the rate of population increase. Highest dispersal rates occurred in the winters when hare populations were at peak and early decline densities. Dispersers at this time were lighter in weight than residents. We discuss our results in light of current hypotheses attempting to explain dispersal in cyclic small mammals and conclude that our results are consistent with the hypothesis that food shortage is responsible for increased rates of dispersal at peak population densities Comparison of dispersal, as monitored by radiotelemetry, versus immigration to a removal grid, suggests that removal grids overestimate dispersal, particularly at high densities when removal grids may attract animals because food supplies are relatively favorable there.

scholarly journals Testing predator - prey theory by studying fluctuating populations of small mammals.

1995 ◽  
Vol 22 (1) ◽  
pp. 89 ◽  
Author(s):  
S. Boutin
Keyword(s):  
Population Dynamics ◽  
Small Mammals ◽  
Limit Cycles ◽  
Functional Responses ◽  
Predator Satiation ◽  
Linear Type ◽  
Small Component ◽  
Wide Range ◽  
Fluctuating Populations

Fluctuating populations of small mammals provide an excellent opportunity to study the functional and numerical responses of predators because of the wide range in prey density that occurs. I reinterpret data from six studies that have examined the role of predation in the population dynamics of voles in California, southern Sweden and western Finland, of snowshoe hares in northern Canada, and of house mice and rabbits in Australia. Most studies have measured functional responses by relying on changes in diet as reflected by scat or stomach contents. These methods are probably biased toward showing predator satiation. Contrary to previous conclusions I find that there is little evidence for non-linear (Type 111) functional-response curves or predator satiation at high prey densities. Recent studies indicate that the functional and numerical responses of predators can be rapid and strong enough to initiate cyclic declines, dampen fluctuations, or even cause stable numbers. The exception to this appears to be the irruptions of mice and rabbits in Australia. I propose a general explanation for the role of predation whereby the effect of predation is largely dependent on the entire prey community. When potentially cyclic prey are a small component of the overall prey biomass, generalist predators are able to prevent fluctuations by strong functional or numerical responses. As the prey community becomes dominated by a few species that fluctuate, limit cycles predominate. Limit cycles turn into irruptive population dynamics when seasonal prey reproduction is eliminated because of extended periods of vegetation growth (vegetation flushes following drought). In the future we must test assumptions underlying the way we study predation by telemetric monitoring of prey mortality and by experimentally manipulating predation.

Survival of juvenile hares during a cyclic population increase

1998 ◽  
Vol 76 (10) ◽  
pp. 1949-1956 ◽  
Author(s):  
Elizabeth A Gillis
Keyword(s):  
Cause Of Death ◽  
Food Availability ◽  
Survival Rates ◽  
Lepus Americanus ◽  
Population Increase ◽  
Differential Survival ◽  
Proximate Cause ◽  
Supplemental Food ◽  
Snowshoe Hares ◽  
And Control

Snowshoe hares (Lepus americanus) are multilittered synchronous breeders that produce up to four distinct litters of young each summer. I used radiotelemetry to determine the effects of juvenile cohort (i.e., litter group) and food availability on postweaning survival of hares in the southwestern Yukon during the increase phase of a hare cycle. During the study, I monitored 86 juvenile hares from control areas and areas in which supplemental food was provided. Twenty-eight-day survival did not differ between food addition and control areas for any juvenile cohort, and survival rates of juveniles (all cohorts combined) did not differ significantly from those of adults (juveniles: 0.91 per 28 days; adults: 0.93 per 28 days). However, when examined by juvenile cohort, survival of third and fourth litters was significantly lower than that of adults and first and second litters. These differences were the result of differential survival among the juvenile cohorts during a 3-month period in the fall (September-November). Predation was the primary proximate cause of death for weaned juvenile hares, accounting for 86% of deaths.

What factors determine cyclic amplitude in the snowshoe hare (Lepus americanus) cycle?

2014 ◽  
Vol 92 (12) ◽  
pp. 1039-1048 ◽  
Author(s):  
Charles J. Krebs ◽  
John Bryant ◽  
Knut Kielland ◽  
Mark O’Donoghue ◽  
Frank Doyle ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Forest Succession ◽  
Monitoring Program ◽  
Lepus Americanus ◽  
Snowshoe Hare ◽  
Amplitude Variation ◽  
Regional Monitoring ◽  
Snowshoe Hares ◽  
Existing Data

Snowshoe hares (Lepus americanus Erxleben, 1777) fluctuate in 9–10 year cycles throughout much of their North American range. These cycles show large variations in cyclic amplitude and we ask what factors could cause amplitude variation. We gathered data from 1976 to 2012 on hare numbers in the boreal forest of Alaska, Yukon, Northwest Territories, and northern British Columbia to describe the amplitude of hare fluctuations and to evaluate four possible causes. First, weather could cause variation in amplitude via hare reproduction or survival, but this mechanism does not fit our data. Second, bottom-up processes involving forest succession could explain amplitude variation through changes in winter forage availability, but succession is too slow a variable in our study areas. Third, plant defenses entrained by hare over-browsing in one cycle can produce variation in plant quality and quantity in subsequent cycles. A mathematical model suggests this is a possible explanation. Fourth, predator recovery following the cyclic low is inversely related to hare cyclic amplitude, and the existing data are consistent with this mechanism. A standardized regional monitoring program is needed to improve our understanding of cyclic amplitude variation in hares and the possible role of predators and winter foods in affecting amplitude.

Proximate causes of losses in a snowshoe hare population

1986 ◽  
Vol 64 (3) ◽  
pp. 606-610 ◽  
Author(s):  
Stan Boutin ◽  
C. J. Krebs ◽  
A. R. E. Sinclair ◽  
J. N. M. Smith
Keyword(s):  
Population Density ◽  
Population Increase ◽  
Snowshoe Hare ◽  
Snowshoe Hares ◽  
Causes Of Mortality ◽  
Proximate Causes ◽  
Hare Population ◽  
Kluane Lake ◽  
Predation Rates

We used radiotelemetry to monitor proximate causes of mortality of snowshoe hares during a population increase, peak, and decline at Kluane Lake, Yukon. Predation and starvation rates increased 1.6- and 9-fold, respectively, in the winter of peak population density. Predation accounted for 58% of the losses during the winter of peak densities while losses were equally divided between predation and starvation in the winter following the peak. Starvation and predation rates were lower on a food-supplemented grid than on control grids in the peak winter. In the following spring and winter, starvation rates remained low on the food grid while predation rates increased to equal those on control areas. We conclude that both starvation and predation were the proximate causes of mortality during the hare decline at Kluane Lake.

Zoonoses as factor of evolution, population dynamics, and speciation

2021 ◽  
pp. 153-172
Author(s):  
Igor Evstafiev ◽  
Igor Zagorodniuk
Keyword(s):  
Population Dynamics ◽  
Small Mammals ◽  
Population Diversity ◽  
Crimean Peninsula ◽  
Species Ranges ◽  
Animal Populations ◽  
Tick Borne Encephalitis ◽  
Evolutionary Changes ◽  
Population Numbers

The role of zoonoses in changes of animal populations and communities is considered. The analysis was carried out using examples of population dynamics of small mammals distributed in the Crimean Peninsula, under the influence of the main zoonoses common for this territory, in particular tularaemia, leptospirosis, Marseille fever, viral tick-borne encephalitis, Ixodes tick-borne borreliosis, Crimea-Congo fever, KU fever, HFRS, and many others. Such data were analysed according to databases on the state of small-mammal populations and zoonoses common in these populations, obtained by original studies over the past 40 years. The role of zoonoses as factors of evolutionary changes in populations of small mammals is considered, in particular as a factor of mortality leading to significant reductions in population numbers and fragmentation of species ranges, as well as factors determining co-evolution of pathogens, vectors (arthropods), and small-mammals as hosts. Both groups of factors lead to the formation of population diversity due to changes in character variability and the formation of new characters associated with adaptations to zoonoses.

Snowshoe hare populations in woodlot habitat

1978 ◽  
Vol 56 (5) ◽  
pp. 1071-1080 ◽  
Author(s):  
Lamar A. Windberg ◽  
Lloyd B. Keith
Keyword(s):  
Population Dynamics ◽  
Population Decline ◽  
Lepus Americanus ◽  
Snowshoe Hare ◽  
Population Densities ◽  
Population Growth Rates ◽  
Food Shortages ◽  
Annual Population ◽  
Reproductive Rates ◽  
Lower Population

Snowshoe hare (Lepus americanus) population dynamics were monitored on six woodlots totaling 33 ha in an agricultural area near Westlock, Alberta, from May 1970 to May 1974. Numerical trends in woodlot and nearby forest hare populations at Rochester were similar, but densities were consistently lower in woodlot habitat until the final stages of a general population decline. Annual reproductive rates were greater in woodlot populations in 1971 (11.2 vs. 9.1 young per adult female) and 1973(11.1 vs. 7.4); and similar to forest populations in 1970 and 1972. Consistently low rates of 1st-year survival (4 to 7%) in woodlot hare populations resulted in lower annual population growth rates and hence lower population densities. Browsing-intensity surveys indicated that both forest and woodlot hare populations encountered overwinter food shortages. In addition, woodlot hare populations may have suffered higher rates of predation.

The role of abiotic factors on both mango infestation and Sternochetus mangiferae abundances in mango agroecosystems in Benin

2018 ◽  
Vol 38 (03) ◽  
pp. 232-242
Author(s):  
Anicet G. Dassou ◽  
Désiré Gnanvossou ◽  
Rachid Hanna ◽  
Aimé H. Bokonon-Ganta
Keyword(s):  
Population Dynamics ◽  
Low Temperatures ◽  
Abiotic Factors ◽  
Management Strategies ◽  
The Other ◽  
Population Increase ◽  
First Year ◽  
Agroecological Zones ◽  
Mango Seed

AbstractTo develop management strategies for the mango seed weevil (Sternochetus mangiferae), we surveyed infestation levels of the pest in three agroecological zones of Benin and determined the influences of abiotic factors on mango infestation levels and population dynamics in mango orchards at IITA-Benin from 2009 to 2011. We collected immature and mature fruits from the canopy and fallen fruits from under the canopy from three randomly selected trees per cultivar, per orchard. Samples were examined to determine the number of the mango seed weevil eggs to adults during the rainy seasons of three years of the study. Our results show that the highest abundance of both the weevil and its eggs was from March to May of each year. In the first year of sampling, the cultivar Eldon was more infested than the other two cultivars, while during the second and third years, the cultivar Alphonse was most infested. The occurrence of the weevil was almost nil in the hot agroecological zones, while for the mango cultivars of IITA-Benin the percentage of infested fruit increased or decreased according to the studied variables, such as temperature, rainfall, and relative humidity. We found that the period from March to May with low temperatures and high rainfall was favourable to the population increase of mango seed weevils. We discuss possible implications of our findings for the management of the pest.

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