Survival of cohorts in a fluctuating population of the vole Microtus townsendii

2009 ◽  
Vol 191 (1) ◽  
pp. 49-60 ◽  
Author(s):  
Terry D. Beacham
Keyword(s):  
Microtus Townsendii

Reproductive correlates of the hip gland in voles (Microtus townsendii)

1977 ◽  
Vol 55 (6) ◽  
pp. 939-941 ◽  
Author(s):  
Gary L. MacIsaac
Keyword(s):  
Reproductive Condition ◽  
Males And Females ◽  
Marking Behaviour ◽  
Highly Correlated ◽  
Microtus Townsendii

The behaviour of hip glands, as gauged by gland length, in Microtus townsendii is shown to be highly correlated with reproductive condition in both males and females. Breeding voles of both sexes are shown to have larger hip glands than nonbreeding voles. It was shown that the hip glands of male Microtus townsendii are under androgen control. The first known observations of marking behaviour in M. townsendii are described.

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.

Breeding characteristics of Townsend's vole (Microtus townsendii) during population fluctuations

1980 ◽  
Vol 58 (4) ◽  
pp. 623-625 ◽  
Author(s):  
Terry D. Beacham
Keyword(s):  
British Columbia ◽  
Sexual Maturity ◽  
Fraser River ◽  
Population Fluctuations ◽  
Peak Density ◽  
Decline Phase ◽  
Early Maturing ◽  
Fraser River Delta ◽  
Peak Phase ◽  
Microtus Townsendii

A 2-year livetrapping study on Townsend's vole (Microtus townsendii) on Reifel Island in the Fraser River delta in British Columbia, Canada, showed that there was an early stop to summer breeding in the peak phase summer compared with the increasing phase summer. Selective dispersal and death of early-maturing voles may account for this result. A delay occurred in the onset of breeding in the decline phase. Voles in peak density populations had the highest median weights at sexual maturity, and males matured at heavier weights than did females.

Fates of disappearing individuals in fluctuating populations of Microtus townsendii

1976 ◽  
Vol 54 (9) ◽  
pp. 1507-1518 ◽  
Author(s):  
Ray Hilborn ◽  
Charles J. Krebs
Keyword(s):  
Natural Populations ◽  
Physical Factors ◽  
Summer Drought ◽  
Factors Associated ◽  
University Of British Columbia ◽  
Live Trapping ◽  
Fluctuating Populations ◽  
The University ◽  
Second Period ◽  
Microtus Townsendii

Fates of disappearing individuals were determined for two natural populations of Microtus townsendii by livetrapping of evacuated areas and marginal habitat, and by marking individuals with radioactive tags to locate carcasses. Two hundred and nineteen out of the 454 individuals that disappeared were radioactively tagged during this 3-year study conducted in the University of British Columbia Research Forest near Haney, B.C. Only 30 radioactive tags were recovered on the live-trapping areas. Most disappearances in this vole population must have been caused by dispersal or predation.Most disappearance from increase and peak populations was due to dispersal. Two summer periods of declining numbers were observed; during one such period many individuals' remains were found on the study areas, but during the other period of declining numbers few remains were found. There was no increase in dispersal rate as measured by the above techniques during either decline period. It is concluded that during the first brief period of declining numbers individuals were dying in their nests from physical factors associated with a severe summer drought and during the second period of declining numbers individuals were either moving long distances without going into traps or being taken by predators.

scholarly journals Efficiency of pitfalls versus live traps in enumeration of populations of Microtus pennsylvanicus

1984 ◽  
Vol 62 (5) ◽  
pp. 758-765 ◽  
Author(s):  
Rudy Boonstra ◽  
F. Helen Rodd
Keyword(s):  
Time Lag ◽  
Microtus Pennsylvanicus ◽  
Pitfall Traps ◽  
First Time ◽  
Two Populations ◽  
Microtus Townsendii

Two populations of Microtus pennsylvanicus were trapped simultaneously with Longworth live traps and pitfall traps over a 3- and a 4-year period. The number of voles enumerated by live traps was usually between 2 and 4 times that enumerated by pitfalls. Of the 3671 new voles caught, 53.7% were first caught in live traps. Pitfalls captured more of the juveniles first (56%) and live traps captured more of the adults first (76%). Animals entering live traps for the first time were about 4 g heavier than those entering pitfalls for the first time. The time lag between entry first into pitfalls and then to live traps was 4–6 weeks; the time lag between entry first in live traps and then to pitfalls was 2–7 weeks. Approximately 18% of all voles never entered live traps. Live traps captured about 83% (N = 747) of all dispersers whereas pitfalls captured about 46%. We conclude that live traps were much more effective than pitfalls in capturing this species. These results are very different from those reported from studies on Microtus townsendii.

Demographic consequences of artificial selection at the LAP locus in voles (Microtus townsendii)

1975 ◽  
Vol 53 (12) ◽  
pp. 1825-1840 ◽  
Author(s):  
Janice LeDuc ◽  
Charles J. Krebs
Keyword(s):  
Population Density ◽  
Demographic Variables ◽  
Control Area ◽  
Experimental Population ◽  
Population Fluctuations ◽  
Genetic Composition ◽  
Gene Frequencies ◽  
Survival And Reproduction ◽  
Altered Gene ◽  
Microtus Townsendii

A number of studies on small mammals have shown that changes in the frequency of alleles at polymorphic loci are correlated with population fluctuations. To determine whether the genetic composition of a population affected its density changes, we altered gene frequencies in two field populations of the vole Microtus townsendii. The fast allele, LAPF, was present in a control population at a frequency of about 35% from July 1971 to July 1973. By removing homozygous LAPS/LAPS voles from one experimental population we maintained an LAPF frequency of about 75%. Removal of LAPF/LAPF homozygotes from a second population resulted in an LAPF frequency of about 25%. We monitored demographic variables of the populations while the selection was being applied. The populations went through increasing and peak phases and then declined sharply during the spring of 1973. Different genotypes had an advantage in survival and reproduction during different phases of population density on the control area, and the selection that maintained the polymorphism on the control area could be correlated with population density. The altered allelic frequencies on the experimental areas did not produce any consistent effects on demography.

Manipulation of Female Behaviour in Field Populations of Microtus townsendii

10.2307/3991 ◽  
1982 ◽  
Vol 51 (2) ◽  
pp. 681 ◽  
Author(s):  
Mary J. Taitt ◽  
C. J. Krebs
Keyword(s):  
Female Behaviour ◽  
Microtus Townsendii

scholarly journals Effect of the parasite Wohlfahrtia vigil on Microtus townsendii populations

1977 ◽  
Vol 55 (6) ◽  
pp. 1057-1060 ◽  
Author(s):  
Rudy Boonstra
Keyword(s):  
Wild Species ◽  
First Record ◽  
Age Classes ◽  
Microtus Townsendii

This paper gives the first record of W. vigil parasitizing a wild species in Canada. The incidence of parasitism of the vole M. townsendii was at a maximum from August to mid-September. Of 1933 voles observed during this time, 5.4% were parasitized, and all age-classes were equally susceptible. Parasitism by W. vigil appeared to be facilitated by the presence of botflies (Cuterebra spp.). Survival of voles parasitized by W. vigil was severely affected, with only 5% living 2 weeks later.

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