Tradeoffs between bite force and gape in Eulemur and Varecia

Area of Science:

• * Primate feeding biomechanics and functional ecology.
• * Vertebrate functional morphology.
• * Paleoanthropology and evolutionary biology.

Background:

• * The relationship between bite force and gape is crucial for understanding feeding systems.
• * In vivo bite force data in primates is scarce, leading to reliance on ex vivo estimations.
• * Previous research established an inverse relationship between bite force and gape without specific muscular adaptations.

Purpose of the Study:

• * To quantify and compare in vivo bite forces and gapes in two distinct strepsirrhine primates.
• * To validate simulated musculoskeletal models for estimating bite force-gape relationships.
• * To investigate feeding biomechanics in Eulemur and Varecia lemurs.

Main Methods:

• * Collected in vivo bite force data across a range of linear gapes in 16 adult lemurs (Eulemur flavifrons, Varecia variegata, Varecia rubra).
• * Utilized simulated musculoskeletal models with architectural data for comparative analysis.
• * Compared maximum linear and angular gapes and recorded maximum in vivo bite forces between species.

Main Results:

• * Varecia exhibited significantly higher maximum linear and angular gapes compared to Eulemur (p = .01).
• * No significant differences were found in maximum in vivo bite forces between Varecia and Eulemur (p = .88).
• * Simulated muscle models accurately estimated bite force-gape tradeoffs, including fiber length and operating ranges.

Conclusions:

• * Varecia lemurs possess wider gapes but reduced bite force capacities relative to jaw length compared to Eulemur.
• * The study validates the simulated muscle approach for estimating bite force as a function of gape in primates.
• * Findings provide insights into feeding adaptations in extant and fossil primates.