Proceedings of the Seventh Mountain Lion Workshop

except that attacks by pumas on humans are
rare. We know nothing of bias caused by
missing data. We can speculate that missing
cases may not have been considered
important enough to report; there may have
been nobody to report to; fatal incidents may
have been undiscovered; they may have
been reported and the records lost; they may
have been printed in obscure references that
we did not find; we may have wrongly
discarded some incidents recorded from
word-of-mouth accounts, etc. Thus, we
have a core of strictly defined data that we
treat as a total count. These data are
restricted by the verification criterion in
such a way that the passage of time reduces
opportunity for verification. The core exists
in a matrix of less well-defined incidents,
the statistical properties of which are
unknown.
At a finer level, even the welldocumented
cases have many blank cells in
the data matrix because specific items were
unknown or not reported, and there was no
way to infer the information. In these
situations, we usually cannot assume the
nature of possible biases caused by missing
data, if they exist.
To summarize, we have nearly total
counts of incidents in Beier-quality
categories, missing incidents in others, and
missing data in all incidents. The categories
in which we can assume total counts may be
subject to a time-related bias that may affect
the statistical distribution of the data. We
have little a priori information to guide us.
Therefore, we are restricted mostly to
descriptive statistics and forming hypotheses
that may later be independently verified.
We do use a Chi-square test to explore the
similarity of the distributions in three
different categories, two of which we
assume are total counts.
Statistical Methods
We have no a priori models or
hypotheses. We had believed that most, if
PROCEEDINGS OF THE SEVENTH MOUNTAIN LION WORKSHOP
REDUCING PUMA ATTACKS · Fitzhugh et al. 93
not all, puma attacks were predatory, but
information provided by Sweanor et al.
(personal communication) contradicts that
belief. Thus, our analysis is exploratory,
examining the data to find hypotheses and
descriptive models that may later be
subjected to data collection and statistical
interpretation. In the few cases where
statistical testing was warranted, we report
the test used along with the results, but for
the majority of situations, descriptive
statistics are the only analysis used.
Nevertheless, we feel secure in drawing
some conclusions about how to reduce risk
of serious injury during a puma encounter.
RESULTS AND DISCUSSION
What Can We Tell About the Data?
With respect to counting attacks and
comparing frequencies, we can be a little
more specific about statistical qualities of
the data. Like Beier (1991), we believe we
have a near-complete count of verified fatal
attacks from 1890 to 2003 in the U. S. and
Canada. Authors of new books (Danz,
1999, Deurbrouck and Miller 2001, and
Etling 2001) did extensive new searches,
and failed to find any fatal attacks that meet
Beier’s criteria that were not included by
Beier in his original list, or else occurred
after his publication. The 108 attacks we
analyze that meet Beier’s criteria include 7
fatal and 38 non-fatal attacks that occurred
after Beier published his list, and 9 fatal and
54 non-fatal attacks that meet Beier’s
criteria and occurred between 1890 and
1991. On the basis of additional information
(personal communication, Dale Elliot to
Etling, July 2000), we moved one of Beier’s
non-fatal attacks (Bird and Sieh, Nevada,
1971) to the “provoked attack” category and
added 11 new non-fatal attacks between
1890 and 1991. It is possible that attacks,
even fatal ones, occurred in the U. S. that
were never known, especially during the
depression years of the 1930s and the
various gold rushes in localities in the