Comparing Cats: A Discussion of Similarities & Differences

[Pckts]

Some interesting tid bits from the Captive vs Wild Comparison

"Results
Analyses of Linear Variables
Males and Females are statistically distinct across each of the linear variables (I-XVII), as we hypothesized (H2); males are substantially larger than females in all linear measures (Table 4). However, the sexes do not differ by either of the shape ratios. Those ratios clearly separate lions from tigers as lions have significantly longer rostra and narrower biangular widths – thus supporting H1 as well. Although the upper carnassial (P4) and premolar-molar rows in lions are only slightly longer than those of tigers (35.57 mm vs. 33.79 mm and 68.25 vs. 63.12 respectively), these differences were also highly significant. All of the statistically significant differences including these tooth lengths along with basal skull length (II), two different metrics related to jaw length (V, and X), and the aforementioned mentioned rostral lengths (I and XIV), all relate, essentially, to the lion’s overall longer muzzle while the tiger has a significantly wider rostrum (XV). (Table 4).

Hypothesis 3 (H3) is also supported – there are statistically significant differences between captive and wild pantherines. As has been found by many authors previously [1]–[3], [19], [43], [45], [55], [56] zygomatic arch width statistically differentiates captive and wild lions and tigers with captive specimens having significantly wider skulls. This difference is more than a centimeter on average and the 95% confidence intervals do not overlap – thus the widely acknowledged qualitative observation has clear quantitative validity. However, it is not the most statistically significant differentiator of captive and wild animals; both of the measures of mandibular width – bicoronoid and biangular widths – are also more than a centimeter wider in captive animals with even less overlap between the groups (Table 4, Fig. 2). Thus, not only do the zygomatics flare, as has been previously noted, but so too do the mandibles. Captive animals also have significantly longer alveo-orbital distances, but shorter carnassials, and wider rostra and muzzles. (Table 4, Fig. 2).

When all of the linear variables are entered into a principal component analysis, the first principal component (accounting for 72.7% of the variation), as expected for unscaled values, is strongly driven by overall size (as indicated by the positive sign of all of the eigenvectors; Table 5) and statistically separates the sample only by sex (and not species or captivity status; Table 4). Although the second and third principal components (accounting for 8.3% and 5.2% of the variation respectively; Table 5) both significantly divide the sample according to species and captivity status (and not sex). PC 2 divides the sample more clearly by species (Fig. 3A) while PC 3 divides the population more clearly by captivity status – especially when one outlier is removed (Fig. 3B). (The removal of this outlier does not affect the statistical significance of the findings.) The subsequent principal components (accounting for slightly more than 10% of the variation) do not differentiate any of the groups with any clear pattern

The second principal component of the linear variable PCA is driven, predominantly, by an inverse relationship of the rostral lengths (most substantially the carnassial length and premolar-molar row length) to the skull width variables (most substantially the biangular and zygomatic widths) – as expected for the long muzzles typical of lions relative to the wide skulls more characteristic of tigers. PC 3 is driven most substantially by an inverse relationship between the rhinion to nasion length and the bicoronoid width. Thus, although the minimum convex units (Fig. 3B) visually separate the population according to captivity status, the eigenvectors that drive this axis are somewhat different than the variables that most substantially sort according to captivity status on their own. The fourth principal component, which does not statistically differentiate the sample by any group (Table 4), is driven primarily by an inverse relationship in the rostral and muzzle breadths relative to some of the mandibular metrics. (Table 5)."


I found this very interesting as well

"The first principal component is driven most substantially by the anterior-most points relative to the position of the points that lie most close to the midline of the skull in the lateral view – i.e., the position of the zygomatics and the post-orbital processes (Fig. 6). Given that this axis divides the population by species, it is not surprising that the variables that emerge describe the relatively longer muzzle of lions relative to tigers. What is somewhat contrary to what we would have predicted both the anterior-most and posterior-most points show an anterior shift from the tiger morphospace (represented in Fig. 6– by the dot) to the lion morphospace (represented by the end of the line emerging from the dot). Thus the longer rostra found in lions is driven not by an elongation of the anterior portion of the skull, but by the relatively posterior position of the zygomatics and orbits. In other words, according to this analysis, tigers do not have relatively shorter snouts, but relatively rostral eyes and cheeks"

"The second principal component is driven by a ventral shift in the anterior- and posterior-most points and a dorsal shift in the dorsal-most points (Fig. 7). The lateral-most points are also greatly affected – a finding in accordance with the conclusion that this axis has a strong relationship with captivity status. Some of the other points that shift substantially along this axis relate to the temporalis origin (i.e., points 40–43) especially the location of the antro-superior corner – the most dramatically shifted point other than those of the zygomatic arch. If we take this axis to be most related to captivity status, captive animals have wider skulls that are less domed than their wild counterparts with dramatically differently shaped temporalis origin – suggesting the importance of this masticatory muscle in the overall shape change in this axis." Reply