Table of Contents
Communication in behavioral biology deals with how animals (including humans) exchange information and how this affects their survival and reproduction. In this chapter, the focus lies on communication as a special form of behavior that is shaped by evolution because it increases the fitness of senders, receivers, or both.
What Counts as Communication?
In behavioral biology, communication is usually defined as:
- A sender produces a signal.
- The signal travels through an environmental channel (medium).
- A receiver detects the signal with one or more sense organs.
- The signal causes a change in the receiver’s behavior or internal state.
- The signal has been shaped by natural selection because it affects the fitness of sender and/or receiver.
Important is the distinction between:
- Cues: features or actions that provide information but have not evolved for that purpose (e.g., rustling noise of prey).
- Signals: traits that have evolved specifically to influence the behavior of others (e.g., bird song, pheromone trail).
Only signals in this evolutionary sense are the subject of communication behavior.
Basic Elements and Channels of Communication
Signals can use different channels (modalities). Typical categories:
- Visual signals
Body posture, coloration, bioluminescence, facial expressions. - Acoustic signals
Calls, songs, drumming, substrate-borne vibrations. - Chemical signals
Odors, pheromones, scent marks. - Tactile signals
Touch, grooming, vibrational tapping. - Electrical signals
Electric fields in electric fish.
The same species often uses multiple channels simultaneously (multimodal communication), for example in courtship displays.
Signals, Codes, and Information Content
Signals can differ in how much and what kind of information they carry:
- Discrete signals
Clearly separated states, e.g., “threat” vs. “submission” posture. Suitable for yes/no information: “danger”/“no danger”. - Graded signals
Vary in intensity or frequency, e.g., louder alarm calls for closer predators, stronger odor for more food. - Index signals
Directly linked to physical or physiological constraints (e.g., deep voice only in large individuals) and thus hard to fake. - Symbolic or arbitrary signals
The form of the signal is not physically bound to its meaning (most human words, bee waggle dance direction).
A code is the mapping between signal and meaning (e.g., in bees: angle of waggle run relative to vertical = direction of food source relative to the sun).
Goals and Functions of Communication
Communication exists because it solves adaptive problems. Common functions:
- Mate choice and reproduction
Courtship displays, mating calls, pheromones, signals of fertility or parental quality. - Territory and resource defense
Song to advertise territory, scent marking, threat displays. - Coordination and cooperation
Group cohesion calls, recruitment to food, coordination of hunting or migration. - Alarm and predator defense
Alarm calls, mobbing calls, stotting (jumping) in gazelles as a signal of vigilance and fitness. - Parent–offspring communication
Begging calls, feeding signals, imprinting-related cues. - Dominance and social status
Postures and vocalizations that indicate rank to reduce costly fights.
Often a single signal serves multiple functions or changes function depending on context.
Honesty, Deception, and Signal Reliability
Because communication influences behavior, there is room for both cooperation and conflict of interest.
Why Signals Are Often Honest
Signals often contain reliable information because:
- Production costs:
Some signals are energetically expensive or increase predation risk (bright coloration, loud calls). Only individuals in good condition can afford them. - Handicap principle:
Costly or risky traits can be honest indicators of quality: only high-quality individuals can survive with such “handicaps”. - Indices:
Signals physically linked to body size, strength, or state (e.g., formant frequencies in vocalizations, wingbeat frequency). They cannot be faked independently of the trait.
Selection favors receivers that ignore uninformative signals and senders whose signals effectively influence receivers. This coevolution tends to maintain at least partially honest communication systems.
Deceptive Communication
Despite this, deception occurs when senders benefit by providing misleading information:
- Within-species deception
- False alarm calls to disrupt mating rivals or steal food.
- Mimicking a receptive or submissive state to avoid attack or gain mating opportunities.
- Between-species deception (mimicry)
- Aggressive mimicry: predators or parasites imitate harmless signals (e.g., anglerfish lure, brood parasites using similar begging calls).
- Batesian mimicry: harmless species imitate warning coloration of dangerous species.
Receivers in turn may evolve mechanisms to detect and resist deception, causing an evolutionary arms race.
Signal Design and Environmental Constraints
The environment shapes which signals are effective:
- Light conditions
Visual signals are more effective in daylight and open habitats. In forests or turbid water, bright colors or contrasting patterns are favored; in darkness, bioluminescence or non-visual channels dominate. - Acoustic environment
Dense vegetation absorbs and scatters high frequencies; forest birds often use lower, pure tones. Open habitats allow higher frequencies and rapid modulations. - Range and persistence
- Acoustic and chemical signals can travel far; tactile signals are short-range.
- Chemical signals can persist (scent marks), acoustic signals are transient.
- Medium
Air vs. water vs. solid substrate affects speed and attenuation of sounds and vibrations; some insects use substrate vibrations instead of airborne sound.
Signal form (“design”) is adapted to maximize detectability and contrast against background noise for intended receivers.
Species Recognition and Reproductive Isolation
Communication plays a key role in species recognition, especially where related species live together:
- Species-specific signals
Unique song types, courtship dances, or pheromone blends reduce mating with the wrong species. - Reproductive isolation
Communication barriers (different calls, timings, displays) can contribute to or maintain speciation by preventing gene flow.
Natural selection therefore refines signals so that they are clear and distinctive to conspecifics.
Individual Identity and Social Information
In social species, signals often carry information beyond species identity:
- Individual recognition
Unique voice signatures, scent profiles, face patterns. This enables stable social relationships and kin recognition. - Group identity
Dialects in bird song or whale calls, group-specific odor profiles in ants and mammals. - Status and motivation
Variation in posture, intensity, or acoustic structure can signal dominance, submission, aggression level, or readiness to mate.
Such information structures group life and reduces costly conflicts.
Multimodal Communication
Many animals combine multiple signal channels:
- Redundancy:
The same message is sent in several modalities (e.g., loud call plus conspicuous posture) to increase reliability under noisy conditions. - Complementarity:
Different modalities carry different aspects of information (e.g., visual display shows quality, acoustic call shows location). - Interaction:
One channel can modulate the meaning of another (e.g., facial expression changing interpretation of vocalizations).
Multimodal communication can be especially important in complex social interactions.
Communication and Conflict Within Groups
Communication also structures conflicts and competition:
- Ritualized fights
Threat displays, size exaggeration postures, and vocal challenges can allow assessment of opponents without full combat. - Escalation rules
Sequences of signals (from distant displays to closer threats and only then to physical attack) reduce the risk of injury. - Resolution of dominance
Submissive signals can terminate conflicts, stabilize hierarchies, and reduce long-term stress within groups.
These ritualized communication patterns are adaptive because they minimize costs while still resolving competition.
Communication in Cooperative and Altruistic Behavior
Cooperation often relies on reliable signaling:
- Alarm calls and kin selection
Alarm calls can help relatives and group members, with indirect genetic benefits for the caller. - Recruitment signals
Signals that guide others to resources (e.g., specific calls or movement patterns) can increase group foraging efficiency. - Signaling willingness to cooperate
Displays of grooming, sharing, or “fair” behavior can help establish long-term cooperative relationships.
In such contexts, communication is part of the mechanism that makes cooperation evolutionarily stable.
Human Communication in a Biological Context
Human language is a special case of biological communication:
- It is symbolic, combinatorial, and capable of open-ended expression.
- It uses arbitrary signals (words) and complex grammar.
- It is deeply integrated with other signal channels (gesture, facial expression, prosody).
From a behavioral-biological perspective, language is interpreted as an evolved communication system that builds on more general animal communication principles but has unique complexity and flexibility.
Summary
- Communication in animals is the exchange of information via evolved signals, shaped by natural and sexual selection.
- Signals operate across different modalities and are adapted to environmental and social conditions.
- Communication serves central functions: reproduction, resource use, cooperation, predator defense, and conflict management.
- Honest signaling and deception are both products of evolutionary conflicts and alignments of interest between senders and receivers.
- Complex societies, including human societies, depend on sophisticated communication systems that structure social interactions and increase overall fitness.