Ontogenetic Limits on Locomotor Performance Summary

Ontogenetic Limits on Locomotor Performance

  • Locomotor Activity Initiation:

    • Most vertebrates commence locomotor activity at hatching/birth.
    • Juveniles face predation risks and must navigate environments akin to adults despite limitations due to size and naivete.

  • Allometric Changes:

    • Juveniles may exhibit adaptations such as longer limbs and greater muscular forces to improve performance.
    • For instance, bones of precocial birds/mammals maintain strength through increased cross-sectional diameters during rapid growth.

  • Performance Comparison:

    • Young animals generally exhibit lower stamina and agility than adults, potentially due to being smaller and inexperienced.
    • Increased juvenile mortality suggests strong selective pressures for improved locomotor performance, possibly influencing adult phenotypes.

  • Factors Limiting Performance:

    1. Size Effects: Smaller size adversely affects locomotion and stamina.
    2. Growth Conflicts: Rapid growth may inhibit mature locomotor functions, restricting performance.

  • Acceleration:

    • Juveniles often accelerate more rapidly than adults due to higher relative strength and favorable allometric changes (e.g., black-tailed jackrabbits).

  • Stamina:

    • Young animals exhibit lower stamina mainly due to smaller energy reserves relative to metabolic rates.
    • Cost of running is higher for smaller animals, leading to limited endurance compared to adults.

  • Agility:

    • Young animals appear clumsier, with lack of experience and growth-related challenges contributing to their awkwardness.
    • Possible integration conflict between growth of body parts and effective nervous system control.

  • Implications for Selection:

    • Higher predation on juveniles may result in adult phenotypes reflecting juvenile locomotor performance adaptations.
    • A potential outcome of strong juvenile selection could be accelerated adult growth, impacting body size and shape.

  • Model Examples:

    • Growth of bird wings illustrates how predation pressure and locomotor capability might shape adult morphology, supporting adaptation concepts.