Proceedings of the Seventh Mountain Lion Workshop

94 REDUCING PUMA ATTACKS · Fitzhugh et al.
Table 1. Calculations of non-fatal attacks by pumas in the U.S. and Canada between 1890 and 1969
that might not have been detected.
Source
Beier (1991)
1970-1990
Our data
1970-2001
Ratio NF/F
from 1970
onward
× Fatal
attacks 1890-
1969
= Calculated
non-fatal
attacks
− Attacks
detected
1890-1969
PROCEEDINGS OF THE SEVENTH MOUNTAIN LION WORKSHOP
= Calculated
attacks not
detected
31÷5 = 6.2 4 25 13 12
69÷12 = 5.75 4 23 21 2
western U.S. It is certain that attacks
occurred in Latin America for which no
records are available. Written accounts of
attacks occur in some obscure publications,
not susceptible to easy location. One
example is the killing of Henry Ramsey in
1876 (Hunter 1922:110). That account was
found by scanning the table of contents of a
county history that was in a fund-raising
auction of “white elephant” donations. All
of these missing accounts would, of course,
fail Beier’s criterion of verification, and
perhaps other criteria as well. We believe
we can use the 16 fatal attacks that meet
Beier’s criteria as a complete count, not
requiring statistical measures of variability.
The 92 Beier-quality non-fatal attacks
probably include a large majority of all nonfatal
attacks (Table 1). They should be
representative, and probably can be treated
as a complete count. However, they were
not sampled according to a statistical design.
The remaining 116 attacks and 155
encounters have unknown statistical
properties, with variable report quality and
amounts of information.
Beier (1991) estimated that he might
have missed finding 12 non-fatal accounts
between 1970 and 1990. He did this by
assuming that he found all the accounts from
1970 to 1990, and multiplying the ratio of
non-fatal to fatal attacks during that period
by the number of fatal attacks from 1890 to
1969. We discovered 8 of the 12 missing
accounts, and also 3 more between 1970 and
1990, so we recalculated the potentially
missing non-fatal accounts (Table 1). These
were calculated through 2001, as the 2002
data are yet incomplete. The analysis in
Table 1 assumes a constant rate of attacks
across years. Puma populations, prey
populations, and the number, age, sex, and
group size of people at risk may have
changed considerably since 1890. These
factors may affect the attack rate. Thus, the
calculation may be invalid to the degree that
these parameters have changed.
Even if the analysis in Table 1 is valid,
the number of fatal attacks is small enough
that a change in even one attack can alter the
calculation of non-detected non-fatal
attacks. Because there is a chance that we
may have missed some fatal attacks prior to
1970 (and especially prior to 1950 as
discussed later), this is a tentative
calculation that serves only to illustrate that
there likely are some incidents we have not
found, but that number is relatively small.
We will return to this topic later with respect
to possible bias caused by Beier’s
verification criterion.
Comparing Verified and Unverified Data
Figure 1 shows the relationship through
time between the 15 Beier-quality fatal
attacks, the 86 non-fatal attacks, and the 27
non-verified, non-fatal attacks, 1890-1999.
The Beier-quality non-fatal attack curve