Proceedings of the Seventh Mountain Lion Workshop

96 REDUCING PUMA ATTACKS · Fitzhugh et al.
Table 2. The effect of including non-verified puma attack incidents on the non-fatal:fatal attack
ratios before and after 1950, U. S. and Canada.
Data 1890-1949 1950-1999 Difference
Beier-quality only 6 ÷ 4 = 1.5 86 ÷ 12 = 7.2 5.7
Beier-quality & all non-verified 16 ÷ 7 = 2.3 96 ÷ 13 = 7.3 5.0
Beier-quality & non-verified non-fatal only 16 ÷ 4 = 4.0 96 ÷ 12 = 8.0 4.0
fatal attacks did not decrease after that, fatal
attacks increased starting in 1970, bringing
the ratios down. Some of the variation in
Figure 2 is caused by zero values. The nonverified,
non-fatal data (Figure 1) are
approximately of the same value as the
Beier-quality fatal data, and the curves are
very similar, so we may be justified in
combining the non-verified non-fatal data (n
= 23) with the Beier-quality non- fatal data
(n = 86). Four non-verified fatal attacks also
were included with the 15 verified fatal
attacks to be consistent. Ratios for the
periods before and after 1950 (Table 2)
show that adding all non-verified incidents
(fatal and non-fatal) increased the ratios
slightly; ratios were even greater when only
non-verified, non fatal incidents were added.
The non-verified data also reduced the
differences between the earlier and later
periods. If we assume that the underlying
ratio of non-fatal to fatal attacks is
consistent across years, it appears that
excluding non-verified data changes the
ratios. The changes represent bias if we are
justified in using the non-verified data.
Beier’s (1991) calculation of ratios from
1970-1990, to estimate missing non-fatal
attacks prior to 1970, assumed a constant
relationship. It seems logical that we have
detected a larger proportion of the actual
non-fatal attacks in recent years, and the
data seem to indicate that this is so (Figures
1-3). However, some biological,
demographic, and cultural differences may
have caused a change in ratios not related to
PROCEEDINGS OF THE SEVENTH MOUNTAIN LION WORKSHOP
reporting frequency. These changes have to
do with changes in persecution of pumas,
especially before, during, and after World
Wars I and II, the number of people using
puma habitat, changes in the degree of puma
habituation to humans, changes in the
proportion of children versus adults exposed
to pumas, and changes in the inclination or
ability of people to report incidents. We
believe the underlying non-fatal to fatal ratio
may have changed about the middle of the
20 th century, but measurement of this
potential change is confused by changes in
Figure 3. Non-fatal to fatal attack ratios.
Bars represent a 20-year running average
beginning with 1890-1909, 1900-1919, etc.,
except that 1990 represents only 1990-1999.
Included are data that conform to Beier’s
(1991) criteria and non-verified data, both
fatal and non-fatal. The zero value at 1950
represents a 20-year period, 1950-1969,
without fatal attacks. (n = 128; 19 = fatal, 109
= non-fatal.)