Behavioral Ecology

Learning Objectives

  • Adaptation

    • Define adaptation and distinguish it from acclimation.

    • Differentiate morphological, physiological, and behavioral adaptations.

    • Explain thermoregulation strategies that allow survival in hot and cold environments.

    • Describe sensory and metabolic adaptations that enable life in dark environments.

    • Explain how animals maintain water and salt balance (osmoregulation) in marine and freshwater environments.

    • Analyze how anadromous fish like salmon transition between salt and freshwater habitats.

    • Identify convergent themes among adaptations to different extremes.

Definitions and Comparisons

  • Adaptation: A long-term, heritable evolutionary change in a population's traits, occurring over generations through natural selection. It involves genetic, heritable change across generations.

  • Acclimation: Short-term, reversible physiological adjustments an individual makes to cope with environmental changes. An example is altitude sickness.

Types of Adaptations

Morphological Adaptations

  • Include physical traits such as:

    • Fur thickness

    • Appendage size

    • Coloration

Physiological Adaptations

  • Include biological functions such as:

    • Antifreeze proteins

    • Salt-excreting glands

    • Metabolic flexibility

Behavioral Adaptations

  • Include activities or behaviors such as:

    • Migration

    • Burrowing

    • Nocturnality

Thermoregulation Strategies

Building Blocks of Thermoregulation

  • Morphological Strategies:

    • Allen's Rule: Animals in warmer climates tend to have longer appendages (like limbs, ears, and tails) compared to their counterparts in colder climates.

    • Bergmann's Rule: Within a broadly distributed group of animals, populations in colder climates have larger body sizes than those in warmer climates.

Physiological Strategies

  • Body-temperature variations observed can range from 34 °C to 41 °C.

  • Physiological adaptations include:

    • Concentration of urine and production of dry feces.

    • Oval-shaped red blood cells.

    • Use of antifreeze glycoproteins (AFGPs).

    • Mechanisms like glucose/sucrose floods.

    • Employing counter-current exchange mechanisms.

Behavioral Adaptations

  • Adaptations to environments include:

    • Desert lizards and insects are active at dawn or dusk.

    • Burrowing techniques to escape heat.

    • Minimizing contact area with the ground.

    • The Namib Desert beetle collects water by standing upside down on sand dunes to catch fog.

Environmental Challenges

Hot Environment Strategies

  • Thermal regulation: Heat dissipation through morphological adaptions (e.g., large extremities, small body size), physiological adaptations (e.g., concentrated urine, oval-shaped red blood cells), and behavioral adaptations (e.g., burrowing, nocturnal habits).

Cold Environment Strategies

  • Thermal regulation: Heat conservation using biological adaptations (e.g., antifreeze glycoproteins (AFGPs), counter-current exchange mechanisms) and physiological adjustments like hibernation and torpor.

Osmoregulation

Types of Osmoregulators

  • Osmoregulators: Actively control internal balance, maintaining a tissue osmolarity different from the environment.

  • Osmoconformers: Match body fluid to the environment, maintaining a similar osmolarity to that of the surrounding environment.

Examples

  • Whitemouth Croaker:

    • Osmolarity: 410 mOsm/L

    • Salinity: 400 mmol/L

    • Urea concentration: <5 mmol/L

  • Seawater:

    • Osmolarity: 1000 mOsm/L

    • Salinity: 1000 mmol/L

    • Urea concentration: <1 mmol/L

  • Leopard Shark:

    • Osmolarity: 1000 mOsm/L

    • Salinity: 600 mmol/L

    • Urea concentration: 380 mmol/L

Anadromous Fish and Their Physiology

Salmon Migration

  • The physiological switch during migration involves:

    • Increased cortisol and growth hormone levels, stimulating chloride cells for salt excretion when migrating to seawater.

    • Upon returning to freshwater, prolactin promotes salt uptake and reduces drinking behavior.

Acclimation vs. Adaptation

  • Difference: Acclimation involves short-term physiological adjustments within an individual's lifetime, while adaptation is long-term, heritable change that occurs across generations. Adaptation is considered reversible, while acclimation is not.

Antifreeze Glycoproteins in Antarctic Fish

  • Function of antifreeze glycoproteins:

    • Inhibit ice crystal formation and reduce the oxygen demand.

Hormonal Changes During Salmon Migration

  • Key hormones that increase during salmon migration to seawater:

    • Cortisol and growth hormone are particularly important during this transition.

Countercurrent Heat Exchange

  • Mechanism helps animals maintain thermal stability by:

    • Transferring heat from cold arterial blood to warm venous blood.

    • Keeping core temperature stable while conserving energy.

Behavioral Ecology Learning Objectives

Key Concepts

  • Define two levels of causation in studying animal behavior.

  • Understand and apply Tinbergen's four questions when studying behavior.

  • Distinguish between two types of behaviors and apply cost-benefit analysis to condition-dependent behaviors.

  • Develop experimental tests of animal behavior.

Ethology, Ecology, and Behavioral Ecology Definitions

  • Ethology: Study of an organism’s behavior as a response to stimuli (Konrad Lorenz & Niko Tinbergen).

  • Ecology: Study of an organism’s interactions with its environment; includes biotic and abiotic factors (Ernst Haeckel).

  • Behavioral Ecology: Study of behavior in relation to the environment (1960-1970s; E. O. Wilson).

The Levels of Causation

Proximate Causes

  • Answers the how regarding behavior; relates to hormonal, neurological, or skeletal-muscular mechanisms.

Ultimate Causes

  • Answers the why regarding behavior; based on historical or evolutionary forces.

Tinbergen’s Four Questions

  1. Causation (Mechanism): What internal or external stimuli trigger the behavior?

  2. Development (Ontogeny): How does the behavior develop throughout an individual's lifetime?

  3. Evolution (Phylogeny): How did this behavior evolve throughout the species' history?

  4. Function (Adaptive Value): How does this behavior contribute to the organism's survival and reproduction?

Fixed Action Patterns versus Condition-Dependent Behaviors

Fixed Action Patterns:

  • Stereotyped behaviors that do not change with conditions; innate responses to stimuli inherited through genetics.

  • Example: Egg-ejection behavior of a newly hatched cuckoo.

Condition-Dependent Behaviors:

  • Behaviors that fluctuate due to learning or environmental conditions; indicative of “decision making.”

  • Example: Imprinting behavior: strong, rapid attachment formed with the first moving object encountered post-birth.

Cost-Benefit Analysis in Behavior

  • Framework utilized by behavioral ecologists to quantify the choices animals make, analyzing flexible, learned behaviors that often involve trade-offs.

Recap of Key Concepts

  • Levels of causation: Proximate and ultimate.

  • Two types of behaviors: Fixed action patterns and condition-dependent behaviors.

  • Use of cost-benefit analysis in animal decision making.