Animal Behavior: Proximate & Ultimate Causes, Innate vs Learned, Genetics, and Fixed Action Patterns

Proximate vs. Ultimate Causes of Behavior

• Definition review

  • Proximate (HOW?) → Immediate physiological/neurological/environmental mechanisms that trigger or control the act.

  • Ultimate (WHY?) → Long-term evolutionary/adaptive value; how the act increases survival & reproductive success.

Arctic Tern Migration Example

• Longest known migration in animal kingdom.

  • Distance per round trip: 30{,}000{-}60{,}000\ \text{km}.

  • Route: Arctic ⇄ Antarctic.

• Proximate cues

  • Photoperiod change (day-length) signals departure.

  • Magnetoreception → detects Earth’s magnetic field for orientation.

• Ultimate explanation

  • Access to seasonally abundant resources (food, breeding habitat, safe nesting sites).

  • Increases individual survival & overall fitness (number of viable offspring).

• Nature of the behavior: genetically hard-wired (innate) but triggered by environmental cues.

Innate Behaviors

• Present at birth; executed correctly the first time without prior experience.

• Strong genetic control; minimal environmental modification.

• Shared properties

  • Species-specific patterns.

  • Triggered by internal states (e.g., hormonal shifts) or external stimuli.

  • Directly linked to survival & reproduction.

Spider Web Construction

• Every isolated spider still spins a species-typical web.

• Why expend energy?

  • Web captures prey → energy → survival, growth, reproduction.

• Traits: pattern, silk strength, geometric layout are genetically encoded.

Learned Behaviors

• Depend on experience, practice, imitation, and feedback.

• Characteristics

  • Variable among individuals of same species.

  • Improve with repetition and social context.

  • Often built on an innate template that must be refined.

Zebra Finch Song Learning

• Male chicks listen to adult (usually father) song; memorize & practice.

• Isolation ⇒ produce incomplete/abnormal song.

• Adaptive significance: well-formed song = mate attraction & territory defense ⇒ higher reproductive success.

Genetic Basis & Hybridization Study: Lovebirds

• Species compared

  • Fisher Lovebird (FL)

  • Nest material: long strips; carried in beak.

  • Peach-faced Lovebird (PFL)

  • Nest material: short strips; tucked into tail feathers.

Hybrid Offspring Findings

1st breeding season

• Strip length: intermediate.

• Transport: starts to tuck in tail (PFL trait) but fails → carries in beak (FL trait).

Later breeding seasons

• Retains head-turn gesture but ceases futile tucking attempt.

• Illustrates

  • Blended genetic instructions.

  • Subsequent behavioral modification via experience (learning what works).

Artificial Selection & Domestication (Dogs)

• Humans selectively bred wolves for tameness, sociability, obedience ⇒ domestic dog lineages.

• Archaeological evidence

  • Fossil dog jaw dated \approx 14{,}000\ \text{years} before present from German site embedded in human settlement.

• Shows deliberate selection on behavior as well as morphology.

Nature vs. Nurture Continuum

• Gene-environment interactions critical; identical genomes can yield divergent behaviors under different conditions.

• Key principle: genes establish potential; environment shapes expression.

Fixed Action Patterns (FAPs)

• Stereotyped, species-specific sequences executed to completion once triggered.

• Initiated by a sign stimulus (releaser).

Greylag Goose Egg-Retrieval

• Stimulus: any egg-like object outside nest.

• Sequence: extend neck → roll object with bill → return to nest.

• Continues even if egg is removed mid-sequence.

• Responds more vigorously to oversized “supernormal stimulus” (e.g., soccer ball).

• Evolutionary value: ensures all eggs are recovered, maximizing reproductive output.

Herring Gull Chick Pecking

• Sign stimulus: red spot on parent bill.

• FAP: chick pecks → parent regurgitates food.

• Independent of head shape/size/color; spot alone sufficient.

Stickleback Courtship & Territoriality

• Male territorial aggression cued by red ventrum of rival males.

• Courtship zig-zag dance triggered by female’s silvery, distended abdomen (egg presence).

• Model experiments show visual feature alone provokes full behavior.

Sensory Feature Detectors & Supernormal Stimuli

• Groups of specialized receptors/neural circuits that extract critical signal features.

Great Grey Owl Prey Localization

• Relies primarily on audition; hunts under snow or in darkness.

• Adaptations

  • Asymmetrical ear placement.

  • Brain circuits computing interaural time/intensity differences.

  • Enables pinpoint strike on unseen prey.

• Demonstrates interaction of morphology (asymmetry) and neural processing (feature detection).

Supernormal Stimuli Concept

• Exaggerated versions of natural cues elicit stronger responses (e.g., soccer ball for goose; hyper-red bill spot models for gull chicks).

• Illustrates evolutionary algorithm: favor response to cue variants that rarely exceed natural range.

Additional Amphibian Example (teaser from transcript)

• Researchers played assorted recorded frog calls in a crowded pond to determine how females distinguish conspecific males despite acoustic overlap.

• Though details cut off, study underscores role of auditory feature detectors and selective attention to specific frequency/pulse patterns.

Key Takeaways & Connections

• Behavior is molded by BOTH proximate mechanisms (hormones, neurons, sensory systems) & ultimate forces (natural selection for survival/fitness).

• Innate and learned behaviors are not mutually exclusive – many complex actions (e.g., bird song, lovebird nest building) combine genetic templates with experiential refinement.

• Fixed Action Patterns highlight evolutionary efficiency: once a crucial task starts, completing it regardless of distraction maximizes payoff.

• Artificial selection mirrors natural processes, offering direct evidence that behavior is heritable and can evolve quickly under targeted pressures.

• Feature detectors bridge stimulus recognition and motor output, critical for survival in environments where one sensory modality dominates (owls) or where stimuli are subtle (frog calls).

Essential Terms

• Proximate cause

• Ultimate cause

• Innate behavior

• Learned behavior

• Fixed Action Pattern (FAP)

• Sign stimulus / releaser

• Supernormal stimulus

• Feature detector

• Photoperiod

• Magnetoreception

• Artificial selection

• Nature vs. Nurture