POPULATION CYCLES IN SMALL MAMMALS
276
theory. For some purposes these faults are not critical, but when
information about rates of change in density is required, the proper
techniques should be used.
B. D O P O P U L A T I O N C Y C L E S R E A L L Y OCCUR?
There are few long-term data on vole and lemming populations and
the longer the time series, the more unreliable the data. Elton (1942)
summarized the bulk of the historical data on voles and lemmings.
Table I gives the peak years for the Norwegian lemming in south
Norway for almost 80 years. Peak years tend t o recur at three- or
four-year intervals. Figure 2 shows fur returns for the arctic fox
TABLE I
Peak years for the Norwegian Lemming i n South Norway, 1862-1938.
(After Elton, 1942)
1862-3
1883-4
1906
1930
1866
1887-8
1909-10
1933-4
1868-9
1890-1
1918
1938
1871-2
189P5
1920
1879-80
1902-3
1926-7
1876-6
1897
1922-3
I"'""'""'""'""'""'""'""'""'""'""'""'
1
1870 1875 1880 1885 1890 1895 1900 1905 1910
1915
1920 1925
PEAK
* * * * * + * * * * * * w 9 *
YEARS
FIG. 2. Fur return statistics for the arctic fox in Ungava District, 1868-1924.
(Data from Elton, 1942, pp. 415-416.)