Variation in the sacroiliac joint in Felidae

Area of Science:

• Comparative anatomy
• Functional morphology
• Evolutionary biology

Background:

• Felidae exhibit diverse hunting strategies and prey sizes.
• Subduing prey involves unique behaviors and biomechanical challenges for felids.
• Pack hunting may reduce individual risk compared to solitary hunting.

Purpose of the Study:

• To investigate the role of the sacroiliac articulation in stabilizing felids during prey capture.
• To correlate the inter-iliac angle with felid body size, hunting strategy, and ecological factors.

Main Methods:

• Computed tomography (CT) scans of 59 felid coxal bones were analyzed.
• The angle between the iliac articular surfaces (inter-iliac angle) was calculated.
• Correlations between the inter-iliac angle and body size, hunting style, and habitat were assessed.

Main Results:

• Body size significantly impacts the inter-iliac angle; smaller cats have wider angles than larger cats.
• Arboreal felids possess significantly wider inter-iliac angles than cursorial, scansorial, or terrestrial species.
• Felids hunting large prey have smaller inter-iliac angles compared to those hunting small or mixed prey.
• Pack-hunting lions exhibit a larger inter-iliac angle than solitary-hunting felids within the Panthera lineage.

Conclusions:

• Two distinct felid groups based on inter-iliac angle: ~40° (small, pack-hunting, arboreal) and ~30° (solitary, large-prey hunters).
• A tighter sacroiliac articulation likely aids large cats in high-speed pursuits and controlling large prey.
• Pack hunting in lions may have lessened the selective pressure for extreme adaptations related to large prey capture.