Animal Locomotion Strategies

• Locomotion in animals involves strategies for support, propulsion, and stability across diverse habitats.

Learning Outcomes

• Animal movement must be distinguished from animal locomotion.
• Animal locomotion strategies can be described and compared across different habitats.
• Adaptations in animal form provide support, propulsion, and stability.
• Animal locomotion relates to other aspects of anatomy and physiology.

Three Issues

• Support is a key issue in animal locomotion.
• Propulsion is a key issue in animal locomotion.
• Stability is a key issue in animal locomotion.

Medium Influences Movement Strategies

• Animals exhibit airborne locomotion.
• Animals exhibit aquatic locomotion.
• Animals exhibit terrestrial locomotion.
• Animals exhibit fossorial (burrowing) locomotion.

Airborne Locomotion

• There are limited support and propulsive forces in airborne locomotion.
• Thrust and lift are essential, utilizing wings for soaring or gliding.
• Examples of airborne animals include the Andean condor (Vultur gryphus) and the Monarch butterfly (Danaus plexippus).
• Wings function as aerofoils in airborne locomotion.
• Pectoral muscles provide the main power for flight, accounting for ~15% of body mass (BM).
• Hummingbirds are an exception, with pectoral muscles comprising ~25-30% of BM.
• Airborne animals exhibit hollow bones.

Non-Active Flight

• Gliding is a type of non-active flight.
• Parachuting is a type of non-active flight.
• Examples include Wallace’s Flying Frog (Rhacophorus nigropalmatus), the squirrel glider (Petaurus norfolcensis) and the flying fish (Cypselurus melanurus).

Aquatic: Support

• Water resists moving objects.
• Streamlining is used to reduce resistance.
• The high density of water reduces the need for lift.
• Buoyancy is a factor in aquatic support.
• Neutral buoyancy means power is needed for thrust.
• Greater energy is needed to reduce sinking if an animal is denser than water.

Increasing Buoyancy in Aquatic Animals

• Larger animals need to reduce density to increase buoyancy.
• One method of achieving this is by reducing calcium carbonate.
• Animals can increase fats and oils (squalene).
• Gas floats, such as a swim bladder or float, are also used.
• Paired fins or continual swimming can increase buoyancy.
• Examples include Aurelia aurita and Carcharias taurus.

Aquatic: Propulsion

• Antagonistic muscles, such as myomere muscles, increase tail and caudal fin propulsion.
• Anguilliform locomotion involves lateral undulations from the anterior to the posterior body, enabling eels to move.
• Jet propulsion can be used by cephalopods.

Aquatic: Propulsion and Laminar Flow

• Shape can alter laminar flow by minimizing eddy/current production.
• Animal shape can be used to suggest habitat.

Aquatic: Stability

• Aquatic animals experience three stability problems: yawing, pitching, and rolling
• Yawing is the lateral deflection of the front end of the body.
• Pitching is the nose plunging downwards.
• Rolling is the rotation of the body about its longitudinal axis.

Organs Involved in Position Relative to Gravity

• Many animals use a statocyst.
• Statocysts are fluid-filled cavities lined with mechanoreceptor cells.
• Statoliths move to different parts of the statocyst.
• Banded spiny lobster (Panulirus marginatus) uses statocysts.

Terrestrial: Support

• Limbs that act as struts support terrestrial animals.
• Animals maintain a straight posture beneath the body mass as much as possible.
• Early tetrapods had splayed legs.
• Posture and gait influence energetic cost.

Forms of Terrestrial Locomotion

• Terrestrial animals exhibit graviportal locomotion.
• Terrestrial animals exhibit cursrorial locomotion.
• Terrestrial animals exhibit scansorial locomotion.
• Terrestrial animals exhibit saltatorial locomotion.
• Terrestrial animals exhibit ricochetal locomotion.
• Terrestrial animals exhibit fossorial locomotion.
• Terrestrial animals exhibit plantigrade locomotion.
• Terrestrial animals exhibit digitigrade locomotion.
• Terrestrial animals exhibit unguligrade locomotion.

Terrestrial: Vertebrate Locomotion

• Muscle fibre types and orthopaedic structures influence different forms of locomotion.
• Plasticity of the musculoskeletal system enables tissues to adapt according to exercise.

Terrestrial: Propulsion

• Trot uses higher vertical force for propulsion.
• Canter uses higher forward force for propulsion.

Terrestrial: Stability

• Stability becomes an issue for tetrapods.
• The centre of mass is related to balance, for example in rabbits.

Fossorial: Mammals

• Fossorial mammals have adaptations for burrowing.
• An example of a fossorial mammal is Chrysochloris sp (Golden mole).

Fossorial: Reptiles

• Fossorial reptiles have adaptations for burrowing.
• Examples are Leptotyphlops humilis (Western blind snake), and Ramphotyphlops adocetus (blind snake).

The Respiratory – Locomotory Piston

• Breathing is coupled with stride in canter and gallop in horses.

The Visceral – Locomotory Piston

• Crawling caterpillars demonstrate a visceral locomotory system.

Locomotion and Body Size in New World Monkeys

• Small bodied New World monkeys exhibit claw-assisted scansorial and clinging locomotion (e.g., Callithrix, Cebuella).
• Medium sized New World monkeys use quadrupedal walking and running with some leaping (e.g., Cacajao, Chiropotes, Saimiri).
• Pithecia are most saltatory.
• Large bodied New World monkeys use quadrupedal walking, tail-hind limb suspension, or tail-arm brachiating locomotion (e.g., Ateles, Brachyteles).

Conclusions

• Airborne locomotion requires thrust and lift, with reduced support and propulsion and includes non-active flying.
• Aquatic locomotion requires increased buoyancy, methods of propulsion, and strategies to increase stability.
• Terrestrial locomotion relies on appendages as struts for support, propulsion by skeleton and muscles, and various stability mechanisms.
• Fossorial locomotion can be ‘mole’ or ‘snake’ like, with structures to increase propulsion and reduce resistance.