POPULATION CYCLES IN SMALL MAMMALS
339
TABLE XIV
The in$wnce of p&rs
on jluctwting populatiolzg of microtinee. The acoo(112t8
vary from impeaaiona of the in$wnce of the p&rs
to attempts to quantify the
percentage of the vole population a c t d y taken. The values given for the peddur
i n $ w m are minimum v a l w since genercclly a worker wa8 concerned with only one
type of predator. The studiee of mrid p & h generally do not c&r
terreatrid
p&h and wice versa
Prey species
Predator species
Predator influence
Author
Microtus
motatanus
Microtus
Ogreeti.3
Microtus
pmnsylvanicus
Microtus
Snowy owl,
Snowy owl,
Snowy owl,
Pomerine jaeger
Pomerine jaeger
Pomarine jaeger,
Least weasel
Snowy owl,
Pomerine jaeger,
Least weasel
Snowy owl
Weasels and raptors
Raccoons
Extensive
Pitelka et al. (1966)
varying
Pitelka (1968)
Density prey > %/acre.
No influence
Density prey < 26/mcre.
Depressing influence
Important during decline. Thompson (1966b)
Weasel influence during
period of low numbers
Ate 8-20y0 spring popln Watson (1967)
Ate 20-3 1 yo summer popln
Little effect
Krebs (1964a)
Maher (1970)
Caused decline
Brant (1962)
Feral cats, raccoons
declining popln
1971)
Kites and shortAte 28% declining popln Stendell
Ate 88, 26 and 33%
Pearson (1964, 1966,
eared owls
(unpublished)
Weasels and ermine Ate 40% decline
Fitzgerald (1972)
2 1 4 7 % low numbers
8% increasing
(winter poplns)
Raptors
Little effect
Chitty (1962)
Elton (1942, p. 192)
Raptors
Ate 26% high density
Craighead and
Ate 22% low density
Craighead (1969,
p. 321)
Short-eared owl
Ate 8-61 yo declining
Lockie (1966)
POPln
POPh
No influence on breeding