Communication allows organisms to detect conspecifics, coordinate interactions, and respond to threats or opportunities. This page focuses on the major signal types and how they are produced, transmitted, detected, and interpreted.

Core idea: signals and information transfer

Organisms communicate when a sender produces a signal that changes the receiver’s physiology or behavior after detection and neural/hormonal processing.

Effective communication depends on:

• Signal production (structures or secretions that generate the cue)

• Transmission through a medium (air, water, substrate, direct contact)

• Reception by sensory receptors (photoreceptors, mechanoreceptors, chemoreceptors, electroreceptors)

• Transduction and processing (conversion to electrical impulses; integration in nervous/endocrine systems)

• Context (time of day, habitat, background noise/odors, distance)

Visual signals

What they are and how they work

Visual communication uses light-based information: color, pattern, posture, movement, or bioluminescence. These signals are detected mainly by photoreceptors and processed in the nervous system.

Key features

• Best in well-lit environments; limited by obstacles and turbidity

• Can be rapid and precisely directed (line-of-sight)

• Often involves:

  • Body coloration (pigments or structural colors)

  • Displays (posture, gestures, locomotor patterns)

  • Bioluminescence (light produced by biochemical reactions, common in marine systems)

Typical examples (mechanism-focused)

• Pattern changes via chromatophores in cephalopods (fast neural control)

• Postural displays that alter perceived size (muscle-driven)

Audible (acoustic) signals

What they are and how they work

Acoustic signals are vibrations transmitted through air or water. Receivers detect them using mechanoreceptors (e.g., hair cells) and interpret features such as frequency, amplitude, and timing.

Key features

• Useful in low visibility habitats (dense vegetation, nighttime)

• Can travel around obstacles, but attenuates with distance and is distorted by wind/water flow

• Production mechanisms include:

  • Vocal cords/syrinx in vertebrates

  • Stridulation in insects (rubbing body parts)

  • Drumming on substrates (percussive signaling)

Information content

• Frequency can reflect body size or species identity

• Temporal patterning (pulse rate, rhythm) supports individual recognition and coordination

Tactile signals

What they are and how they work

Tactile communication requires direct contact and is detected by touch/pressure receptors. It is common in social animals where close-range interaction is frequent.

Key features

• Highly reliable (low environmental interference), but short-range

• Often used for:

  • Coordination (movement, group tasks)

  • Affiliative interactions (social bonding, hierarchy maintenance)

  • Parent–offspring communication

Mechanisms

• Antennal contact in insects (mechanoreceptor-rich antennae)

• Grooming/contact behaviors that trigger measurable physiological changes (stress reduction via neuroendocrine pathways)

Electrical signals

What they are and how they work

Electrical communication involves electric fields generated by specialized organs or ion channel activity. Receivers detect these fields using electroreceptors, common in some aquatic vertebrates where water conducts electricity well.

Key features

• Works in dark/turbid water

• Can be species- or individual-specific based on waveform properties

• Often integrated with electrolocation (sensing objects) but can also function as true communication when signals convey information to other organisms

Mechanisms

• Electric organ discharges (EODs): coordinated depolarisation of electrocytes

• Receiver nervous systems decode pulse timing and signal shape

Electric fish generate species-specific electric organ discharges (EODs) that can be visualized both as head-to-tail voltage waveforms and as spatial maps of electric potentials around the body. The figure contrasts continuous “wave” EODs with discrete “pulse” EODs, illustrating how waveform shape and timing differ among species. These differences provide information that electroreceptors and neural circuits can use for communication and electrolocation. Source

Chemical signals

What they are and how they work

Chemical communication relies on molecules detected by chemoreceptors (olfactory and gustatory). Signals may be airborne, waterborne, or deposited on surfaces.

Major modes

• Pheromones (within a species)

• Allelochemicals (between species; e.g., deterrents, attractants)

• Scent marking: persistent chemical “messages” in the environment

Key features

• Can persist over time (useful for territory or trail information), but is influenced by:

  • Temperature and humidity (volatility)

  • Wind/current direction (plume structure)

  • Microbial degradation and UV exposure

Mechanisms

• Binding of molecules to receptor proteins triggers signal transduction pathways, generating neural responses; some chemicals also act via endocrine effects after absorption.