Changes in
the abundance of predator species such as Lynx (Lynx
canadensis) and various prey species such as Snowshoe Hare (Lepus americanus)
are documented in records of
the numbers of pelts brought into the Hudson Bay Company.
The cycles are synchronous over a 12~13 year period, where the
lynx cycle peaks slightly later than the hare cycle. This suggests
a hypothesis that an abundance of hares feeds an increase in the
number of Lynx, which subsequently depresses the number of Hares,
and so on. However, hares also cycle in the absence of lynx. It
has also been suggested that species-specific trapping effort may
have varied, such that in the absence of hares in off years, more
effort was invested in Lynx.
The original data set, compiled by Charles
Elton (1925), is notable as one of the longest time series in
ecology.
