Proceedings of the fifth mountain lion workshop: 27

PROCEEDINGS OF THE FIFTH MOUNTAIN LION WORKSHOP 63
1984) to address whether available morphometric data
supported a taxonomic distinction for this population, and to
assess the accuracy of Merriam's original claim that P. c.
browni could be distinguished from conspecifics on the basis
of tooth size.
RESULTS AND DISCUSSION
For clarity, we will consider the 3 lines of evidence
(ecology, morphology, genetics) separately for the Yuma
mountain lion, and then provide a conclusion synthesizing all
3 sources of information.
Ecology
We located 6 published range maps for this subspecies
(McIvor et al. 1995); no consensus exists regarding the
probable range of P. c. browni. Only the maps of Hall (1991)
and Young and Goldman (1946) appeared to coincide, and Hall
(1981) cited Young and Goldman (1946) as his source of
information for P. concolor. We found that none of the authors
satisfactorily explained the derivation of their maps, thus there
was little basis for choosing one over another. We elected to
use Duke et al.'s (1987) map because it encompasses the largest
geographic area, and thus represents the most parsimonious
approach to conserving biological diversity.
Personal interviews and requests for information, as
well as our review of the literature, produced 272 sighting
reports of mountain lions within P. c. browni's published range.
Of these reports 142 could not be confirmed, 17 were reports
of specimens, and the remaining 113 reports were categorized
as confirmed (McIvor et al. 1994). The densest grouping
(43.8%) of sighting accounts occurred in the vicinity of Ajo
and Organ Pipe National Monument (OPNM), Arizona. This
clustering is an artifact of OPNM's systematic record keeping,
the efforts of B. Broyles (pers. commun) to collect sighting
accounts in the area of Cabeza Prieta National Wildlife Refuge,
and the movement of mountain lions in the Ajo and Sauceda
Ranges outside the eastern boundary of P. c. browni's range.
The remaining accounts were scattered fairly uniformly across
the range described by Duke et al. (1987).
Interpretation of sighting reports and their implications
is problematic (Van Dyke and Brocke 1987). Mountain lions
appear to be seen with modest frequency throughout the study
area, however, the frequency of sightings decreases as the core
range (the area around Yuma) is approached. The distribution
of sightings, particularly near OPNM, and the home range data
collected by Peirce and Cashman (1993), indicate that the range
boundaries delineated for P. c. browni have no biological
relevance, and in many areas do not correspond to any isolating
geographic barriers.
Merriam (1903), based on his perception that the teeth
of P. c. browni are smaller than those of conspecifics,
hypothesized that the Yuma mountain lion subsisted on smaller
prey than other subspecies. The larger body of literature
documenting the importance of deer in the diet suggests that
mountain lions in North America are dependant on some form
of large prey for long-term population maintenance (Anderson
1983, Shaw et al. 1988). A study conducted on the eastern
boundary of P. c. browni range also found deer to be the most
frequently occurring prey item in mountain lion diets
(Cashman et al. 1992). Finally, the food requirements of
females with young (Ackerman 1982, Weaver 1982,
Ackerman et al. 1986) suggests breeding populations of
mountain lions may not be able to exist in the absence of large
prey (Ackerman et al. 1984).
Morphometry
We located 17 specimens (10 M, 4 F, 3 unknown).
Nine were officially cataloged in museums and 6 specimens
were held in private collections (McIvor et al. 1994). Contact
with museums revealed an additional animal collected from
the Hualapai Mountains of Arizona, as well as a specimen
collected on the Kofa National Wildlife Refuge in 1944
(Halloran 1946), that had not been cataloged as specimens of
this subspecies.
Partly because opinion varies between researchers
regarding the important characters to measure, complete data
for all skulls were not available from the literature (Table 1).
Some skulls were incomplete, usually because of damage
inflicted during collection, and dynamic terminology also
contributed ambiguity to some measurements (e.g., "braincase
height" and "greatest depth" were used interchangeably).
Early analysis of mountain lion skulls and variation
in pelage were based on subjective criteria. Powerful
statistical tools are a relatively recent development unavailable
to early taxonomists. CVA generates n-1 uncorrelated linear
combinations of variables that maximize separation among a
priori designated groupings (Bookstein et al. 1985). These
variates, which are linear combinations of the original
variables, provide a useful framework for displaying the
magnitude of the interrelationship between the populations,
and can be plotted and studied on a two dimensional graph
(Reyment et al. 1984). Furthermore, each component (i.e.,
original variable) is assessed for its contribution to the
separation between populations. CVA has the advantages of
being easy to interpret, and only one statistical test is
conducted, avoiding the ambiguities associated with a multiple
test approach and protected alpha levels. However, CVA is
highly sensitive to heterscedasticity, and to sparse data; a
single missing variable results in the loss