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

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.

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.

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.

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.

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.

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.

Species compared
- Fisher Lovebird (FL)
- Nest material: long strips; carried in beak.
- Peach-faced Lovebird (PFL)
- Nest material: short strips; tucked into tail feathers.

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).

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.

Gene-environment interactions critical; identical genomes can yield divergent behaviors under different conditions.
Key principle: genes establish potential; environment shapes expression.

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.

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.

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

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).

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.

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.

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).