scholarly journals Demography of Microtus pennsylvanicus in Southern Ontario: enumeration versus Jolly–Seber estimation compared

1985 ◽  
Vol 63 (5) ◽  
pp. 1174-1180 ◽  
Author(s):  
Rudy Boonstra
Keyword(s):  
Population Size ◽  
Breeding Season ◽  
Survival Rates ◽  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Vole Population ◽  
Maternal Condition ◽  
Southern Ontario ◽  
Almost All

A meadow vole population near Toronto went through a cycle in numbers from July 1978 to May 1982. The population never reached a density less than 96 voles/ha or greater than 630 voles/ha. Jolly–Seber estimates differed from total enumeration counts by an average of 10.6% in population size and by less than 0.03 per 2 weeks in survival rates for almost all periods. Sharp spring declines occurred in both sexes in both the increase and the peak years, but only among females in the decline year. Dispersal occurred more frequently during the spring of the increase and peak than of the decline, was associated with maturation, and was biased towards males. The breeding season lasted 9 months in the increase and decline but only 5 months in the peak. Survival of adults during the decline summer was no different from that in other years. Survival of young during the increase and peak was moderately high, but was extremely poor during the decline. Since most young failed to be captured in either pitfalls or live-traps, I conclude that they died shortly before or after weaning and suggest that maternal condition was impaired by prior events in the peak and that this may apply to other cyclic microtine populations.

Winter coexistence of voles in spruce forest: relevance of seasonal changes in aggression

1975 ◽  
Vol 53 (8) ◽  
pp. 1004-1011 ◽  
Author(s):  
Brian N. Turner ◽  
Michael R. Perrin ◽  
Stuart L. Iverson
Keyword(s):  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Breeding Period ◽  
Spruce Forest ◽  
Vole Population ◽  
Reproductive Condition ◽  
Interspecific Aggression ◽  
Meadow Voles ◽  
Nonbreeding Season ◽  
Short Period

Beginning in November 1973, numerous meadow voles (Microtus pennsylvanicus) moved onto a spruce forest grid occupied by red-backed voles (Clethrionomys gapperi). A resident meadow vole population resulted, the two species coexisting until April 1974, when most meadow voles disappeared from the grid during a relatively short period. Interspecific aggression levels, as determined from voles temporarily removed from the populations and tested in paired encounters in a laboratory arena, were low during the winter, but increased when males of both species entered reproductive condition in the spring. Microtus was generally dominant in early breeding period encounters, but this dominance declined concurrently with the meadow voles' disappearance from the forest. It is argued that meadow voles did not leave the forest to breed, or because the snow cover melted, since this species will live and reproduce in forest in the absence of Clethrionomys. The results are interpreted as support for an earlier hypothesis that competitive habitat exclusion varies seasonally with reproduction-related aggression. Thus, these species apparently may coexist in either of their preferred habitats when interspecific aggression is low (the nonbreeding season), but this relationship terminates when interspecific aggression levels increase with the resumption of breeding in the spring.

Effect of Orthene® on an unconfined population of the meadow vole (Microtus pennsylvanicus)

1986 ◽  
Vol 64 (1) ◽  
pp. 243-250 ◽  
Author(s):  
David A. Jett ◽  
James D. Nichols ◽  
James E. Hines
Keyword(s):  
Survival Rate ◽  
Population Size ◽  
Weight Change ◽  
Relative Weight ◽  
Reproductive Activity ◽  
Microtus Pennsylvanicus ◽  
Field Application ◽  
Meadow Vole ◽  
Old Field ◽  
Insecticide Treatment

The possible impact on Microtus pennsylvanicus of ground applications of Orthene® insecticide was investigated in old-field habitats in northern Maryland during 1982 and 1983. The treatment grids in 1982 and 1983 were sprayed at 0.62 and 0.82 kg active ingredient/ha, respectively. A capture–recapture design robust to unequal capture probabilities was utilized to estimate population size, survival, and recruitment. Data on reproductive activity and relative weight change were also collected to investigate the effect of the insecticide treatment. There were no significant differences in population size or recruitment between control and treatment grids which could be directly related to the treatment. Survival rate was significantly lower on the treatment grid than on the control grid after spraying in 1983; however, survival rate was higher on the treatment grid after spraying in 1982. Significantly fewer pregnant adults were found on the treatment grid after spraying in 1982, whereas the proportions of voles lactating or with perforate vaginas or open pubic symphyses were slightly higher or remained unchanged during this period. Relative weight change was not affected by the treatment. Results do not indicate any pattern of inhibitory effects from the insecticide treatment. Field application of Orthene® did not have an adverse effect on this Microtus population.

Réponse numérique de l'hermine aux fluctuations d'abondance de Microtus pennsylvanicus

1982 ◽  
Vol 60 (4) ◽  
pp. 542-549 ◽  
Author(s):  
Michel Raymond ◽  
Jean-Marie Bergeron
Keyword(s):  
Local Population ◽  
Microtus Pennsylvanicus ◽  
Density Fluctuations ◽  
Numerical Response ◽  
Meadow Vole ◽  
Strongly Correlated ◽  
Vole Population ◽  
Rodent Population ◽  
Males And Females ◽  
Different Response

The numerical response of two ermine populations (Mustela erminea) to the density fluctuations of the meadow vole (Microtus pennsylvanicus), the dominant mammal in southern Quebec agrosystems, was studied from 1978 to 1980. There is a strong correlation between the densities of the two species, whether or not the fluctuations of Microtus are cyclical. Males and females show a different response, the numerical adjustment of males being strongly correlated to the fluctuations of the vole population while the females do not seem to make particular adjustments. The numerical response of the ermine takes place only a few months after the changes in the rodent population. It is suggested that in areas where preys are small and of similar size the survival of the females is less dependent than that of the males on the density of the dominant prey. As most female ermines seem to participate in reproduction whatever the density of the vole population, the continuity of any local population is insured from year to year by the presence of at least minimal numbers. Survival of the young during the year following their birth seems to depend on the immediate availability of prey, thus determining the characteristics of the numerical response.[Journal translation]

Control of Small Mammals on a Hardwood Plantation by Poison-Bait Feeders

1977 ◽  
Vol 53 (2) ◽  
pp. 96-99
Author(s):  
Arthur M. Martell ◽  
Andrew Radvanyi
Keyword(s):  
Small Mammals ◽  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Low Density ◽  
Meadow Voles ◽  
Southern Ontario

Poison-bait feeder stations were placed on a hardwood plantation in southern Ontario in 1973 to attempt long-term control of a meadow vole (Microtus pennsylvanicus) population by continuous dispensing of poisoned grain. Baiting by means of feeders successfully reduced the numbers of meadow voles and maintained them at a low density, about 3-6/ha (1.2-2.4/acre), through April 1976. During the same period, the density of meadow voles on surrounding unpoisoned areas declined from a 1973 peak to about the same as that found on the poisoned plot by fall and winter 1975-76. Despite that low density, less than 4/ha (1.6/acre), severe gnawing and girdling of young hardwoods occurred during winter. Poison-bait feeders are efficient at reducing meadow vole populations from high to low density, but it cannot be assumed that even those low-density populations will not damage hardwood plantations.

Meadow vole cycles within fences

1984 ◽  
Vol 62 (9) ◽  
pp. 1796-1804 ◽  
Author(s):  
Robert H. Tamarin ◽  
Lawrence M. Reich ◽  
Carol A. Moyer
Keyword(s):  
Microtus Pennsylvanicus ◽  
Major Effect ◽  
Control Population ◽  
Meadow Vole ◽  
Demographic Parameters ◽  
Vole Population ◽  
Demographic Trends ◽  
Vole Cycles ◽  
Vole Cycle

To test the idea that dispersal is necessary for cycling and to develop an enclosure that would permit vole population cycling, we partially and fully fenced grids that included woodland areas (dispersal sinks) that were continually trapped out. We studied three populations of the meadow vole, Microtus pennsylvanicus, in Massachusetts from 1978 to 1982. The control population and both fenced populations exhibited virtually identical demographic trends, which encompassed a vole cycle. Analysis of demographic parameters suggested that the major effect of the fence was to increase survival within. We attributed this increased survival to reduced dispersal because a dispersal sink attracted only 98 dispersers throughout the study, We suggest that there is a continuum of individual thresholds to disperse with only a very few animals motivated enough to enter a woodland dispersal sink.

scholarly journals The spring decline in the meadow vole, Microtus pennsylvanicus: the effect of density

1984 ◽  
Vol 62 (8) ◽  
pp. 1464-1473 ◽  
Author(s):  
F. Helen Rodd ◽  
Rudy Boonstra
Keyword(s):  
Survival Rates ◽  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Breeding Period ◽  
Home Ranges ◽  
Adult Males ◽  
Long Distance ◽  
Mature Adults ◽  
Female Survival ◽  
Reproductive Rates

The densities of six Microtus pennsylvanicus populations were reduced by removing large, sexually mature adults 6 months prior to (fall removal manipulation) and just prior to (spring removal manipulation) anticipated spring declines. When the spring decline on the control grid was a result of short distance dispersal, the manipulations had no effect; when it was a result of in situ mortality and (or) long distance dispersal, the fall removal manipulation produced a significant improvement in the survival rates of adult males. Adult female survival rates were high and unaffected by the manipulations. Adult reproductive rates were high and similar on all grids. The onset of the females' breeding season was advanced by the manipulations in two trials. Home range sizes were similar for all animals during the nonbreeding period. During the breeding period, males and females on the experimental grids had larger home ranges than those on the control grids.

THE DURATION OF THE BREEDING SEASON OF FOUR BREEDS OF SHEEP

1974 ◽  
Vol 54 (3) ◽  
pp. 389-392 ◽  
Author(s):  
J. J. DUFOUR
Keyword(s):  
Sexual Activity ◽  
Breeding Season ◽  
Estrous Cycles ◽  
Progressive Decline ◽  
Daily Exposure ◽  
Almost All

Three breeds of sheep (Dorset, Leicester, and Suffolk) and a crossbred line from these breeds (DLS) were observed throughout 1 yr to determine their sexual activity by daily exposure of the ewes to vasectomized rams. The DLS and Dorset ewes exhibited their first estrus earlier in the year (P < 0.01) and stopped cycling later than the Leicester and Suffolk ewes (P < 0.01). The duration of the breeding season in the DLS ewes was 20 days (P > 0.05) longer than in the Dorsets and 70 and 115 days (P < 0.01) longer than in the Leicester and Suffolk ewes, respectively. The percentage of Dorset and DLS ewes showing one or more estrous periods increased progressively from June to reach 100% in September for both breeds. The Suffolk and Leicester ewes commenced to cycle in late August and by September almost all ewes had shown an estrous period. The progressive decline in estrous activity became evident first with the Suffolk in January, then with the Dorset and Leicester in February and with the DLS in March. The Dorset, DLS and Leicester ewes had longer estrous cycles than the Suffolk ewes. Within ewes, length of estrous cycles was highly repeatable for all breeds. False estrus and silent estrus occurred in 1.0 and 3.9% of the estrous periods, respectively. Over successive estrous cycles, length of estrous cycles increased significantly.

Seasonal Variation in Litter Size of the Meadow Vole in Southern Ontario

1963 ◽  
Vol 44 (4) ◽  
pp. 467 ◽  
Author(s):  
Edward Kott ◽  
William L. Robinson
Keyword(s):  
Seasonal Variation ◽  
Litter Size ◽  
Meadow Vole ◽  
Southern Ontario

scholarly journals Parties between thresholds: State subsidies and party behaviour in post-communist democracies

2017 ◽  
Vol 25 (2) ◽  
pp. 233-244 ◽  
Author(s):  
Fernando Casal Bértoa ◽  
Maria Spirova
Keyword(s):  
Survival Rate ◽  
Political Parties ◽  
Party System ◽  
Survival Rates ◽  
Empirical Support ◽  
State Funding ◽  
Publicly Funded ◽  
State Financing ◽  
State Subsidies ◽  
Almost All

Much has been written about what makes political parties form, persist, change and die. One factor often brought into this discussion is the availability of resources in general and of state financing of political parties in particular. However, an empirical link at the aggregate level is difficult to establish because of various issues of conceptualization, operationalization and measurement. Working at the party level and taking into consideration that state funding provides important resources that make running in elections and achieving a party’s electoral target more likely, this article provides empirical support for the claim that parties who (anticipate to be or) are being funded by the state have a higher chance of forming and surviving in an independent format in the party system. Based on a comparison of 14 post-communist party systems, the main conclusion of the article is that the survival rate for such parties exceeds the survival rate for the non-publicly funded ones in almost all cases. A second, novel and more particular, finding is that parties who find themselves outside parliament, but above the payout threshold, display higher survival rates than parties who are below it.

scholarly journals A fencing experiment on a high-density population of Microtus townsendii

1977 ◽  
Vol 55 (7) ◽  
pp. 1166-1175 ◽  
Author(s):  
Rudy Boonstra ◽  
Charles J. Krebs
Keyword(s):  
Survival Rate ◽  
Breeding Season ◽  
Population Regulation ◽  
Control Area ◽  
High Density ◽  
Low Density ◽  
Vole Population ◽  
Sharp Decline ◽  
Density Population ◽  
Microtus Townsendii

If dispersal is prevented, a low-density vole population will increase to unusually high densities. A mouse-proof fence was constructed around a vole population that had already reached high density and both this population and one on a control area were live-trapped from January 1975 to November 1975. The population on the control remained at peak densities. The enclosed population increased to even higher density once the breeding season had started and had a higher survival rate than the control population. By midsummer the enclosed population had severely overgrazed the vegetation and went into a sharp decline. Dispersal losses from the control were estimated at 32% for males and 31% for females in these high-density populations. Microtus townsendii populations thus responded to a fence in a manner similar to that of other species that have been studied. This experiment indicates the importance of dispersal to population regulation in voles even at peak densities.

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