Rough draft 
November 24, 1941 
 
 
DEER IREJPTION STUDY 
 
    Aldo Leopold 
 
 
Premise. Irruptions of deer (and elk) are becoming a universal problem, 
 
like forest fire, Studies of irruptions have been so far local and 
 
empirical, i.e., they aim to alleviate the trouble rither than to 
 
find out why it occurs and how to prevent it. The situation parallels 
 
that of fire in 1919. 
 
Proposal. That the Fish and Wildlife Service and the Forest Service 
 
make a Joint attempt to dig deeper into the problem, in cooperation 
 
with some third party not involved in past controversies, commitments, 
 
or history. 
 
     Steps: 1942. Feel-out. Test a selected field worker by having 
                   him gather the history of a typical irruption. 
 
            193-45. Survey.    Gather the history of irruptions in 
                   the United States, Canada, and Mexico. Deduce 
                   "leads", i.e., look for common denominators.

 
            1946. Ixperiments. Start experimental verification of 
                   leads, and tests of preventative treatments. 
 
Strategy. Irruptive population behavior must arise from abnormalities 
 
in the reproductive rate or the mortality rate. There may be secondary 
 
complications in abnormal sex ratios, abnormal sex survival, or 
 
nutritional phenomena. It is certain that predation, as well as 
 
hunting, affects the mortality rate. 
 
     Mortality and predation cannot be studied in confined experimental 
 
deer. Natrition can. Reproductive rate and sex ratios can, except 
 
as they are affected by predation ai nutrition in-the-wild. It is 
 
clear, then, that the problem mest be "shaken down" to one or more

 
simple hypotheses before experimental verifications can begin. This 
 
is the purpose of the survey. 
 
 
J /