IMPORTANCE OF VEGETATIVE COVER TO CYCLES OF MICROTUS POPULATIONS

A hypothesis is presented that a site-dependent threshold level of vegetative cover is necessary for a population of Microtus to increase in numbers sufficiently to undergo a multi-year cycle. The hypothesis is supported by results of studies in grassland habitats in the tallgrass prairie of Oklahoma and Minnesota, the mixed grass prairie of South Dakota, and the shortgrass prairie of Colorado. Levels of cover below the threshold sometimes support resident, breeding populations of voles. Levels above the threshold may influence amplitude, duration, and synchrony of Microtus cycles.

[1]  C. Krebs,et al.  Population Cycles in Small Mammals , 1974 .

[2]  F. A. Pitelka.  Some Aspects of Population Structure In The Short-Term Cycle Of The Brown Lemming In Northern Alaska , 1957 .

[3]  E. G. Zimmerman.  A comparison of habitat and food of two species of Microtus. , 1965 .

[4]  C. Krebs,et al.  Population cycles in rodents. , 1974, Scientific American.

[5]  C. Krebs,et al.  Microtus Population Densities and Soil Nutrients in Southern Indiana Grasslands. , 1971, Ecology.

[6]  Dennis Chitty,et al.  POPULATION PROCESSES IN THE VOLE AND THEIR RELEVANCE TO GENERAL THEORY , 1960 .

[7]  A. Mossman.  Light Penetration in Relation to Small Mammal Abundance , 1955 .

[8]  W. R. Eadie.  Response of Microtus to Vegetative Cover , 1953 .

[9]  J. E. Warnock.  The Effects of Crowding on the Survival of Meadow Voles (Microtus Pennsylvanicus) Deprived of Cover and Water , 1965 .

[10]  J. Tester,et al.  A study of certain plant and animal interrelations on a native prairie in northwestern Minnesota. , 1961 .

[11]  C. Krebs,et al.  Microtus Population Biology: Demographic Changes in Fluctuating Populations of M. Ochrogaster and M. Pennsylvanicus in Southern Indiana , 1969 .

[12]  C. Krebs.  Microtus Population Biology: Behavioral Changes Associated with the Population Cycle in M. Ochrogaster and M. Pennsylvanicus , 1970 .

[13]  R. Ogilvie,et al.  Effect of Vegetational Cover of Fence Rows on Small Mammal Populations , 1959 .

[14]  G. O. Batzli,et al.  Influence of Meadow Mouse Populations on California Grassland , 1970 .

[15]  Michael S. Gaines,et al.  Population Cycles in Small Rodents , 1973, Science.

[16]  C. Elton.  On the Nature of Cover , 1939 .

[17]  H. Hopkins.  Effects of Mulch upon Certain Factors of the Grassland Environment , 1954 .

[18]  J. Lobue,et al.  Effect of Habitat Disturbance on a Small Mammal Population , 1959 .

[19]  L. Getz.  Humidities in Vole Runways , 1965 .

[20]  J. Murie.  An Experimental Study of Substrate Selection by Two Species of Voles (Microtus) , 1969 .

[21]  W. Grant,et al.  SMALL MAMMAL ENERGETICS IN GRASSLAND ECOSYSTEMS , 1976 .

[22]  W. Z. Lidicker.  Regulation of Numbers in an Island Population of the California Vole, A Problem in Community Dynamics , 1973 .