signalling 1- intro and diversity Flashcards
What is the fundamental definition of animal signalling?
It is the purposeful exchange of information between animals, where one individual (signaller) influences another’s (receiver) behavior through a signal.
What are the core components of a signalling system?
Signaller (actor), Signal (the display or cue), Receiver (reactor), and the Effect/Response (behavioral change).
What is meant by “economy of effort” in signalling?
Signals can influence behavior without requiring direct physical force.
For example, a predator avoids a brightly colored toxic frog without attacking it first.
Why can signals still be costly even if they save energy in other ways?
- Maintaining or producing the signal (e.g., vivid coloration in toxic frogs) often requires significant energy or resources.
- production costs
What are the six key features that define signalling?
- Signals influence behavior
- Economy of effort (no direct force needed)
- Signals can be costly to produce
- Signals are specifically evolved for communication (ritualization)
- Information can be true or false (honest or dishonest signals)
- Individual signals are part of an evolutionarily stable system (ESS)
Why must most signals be honest for the signalling system to remain evolutionarily stable?
Receivers must generally benefit from responding to signals. If too many signals are dishonest, receivers would stop responding, undermining the system’s stability.
What is the significance of the histrionica frog example?
Its bright coloration warns predators of toxicity. This demonstrates that signals influence behavior (predators avoid it) and can be energetically costly to maintain.
what are 4 examples which demonstrate diversity of signals
- honey bee dance signals: directional and resource signals
- blue headed wrasse: mating or agressive/competitive signals
- monket call signals: cooperative and anti-predatory
- gazelle stotting: anti-predatory
What is the basic role of the honeybee dance language?
It allows foraging worker bees to recruit others by communicating the direction, distance, and quality of a food source.
How do honeybees use the “round dance” versus the “waggle dance”?
- Round Dance: Used for food sources within ~100m, featuring short waggles and circular runs.
- Waggle Dance: Used for more distant sources, featuring a longer waggle run and specific return paths.
- integration of two dances are actually more like a continuum
How do honeybees encode distance, direction, and quality in the waggle dance?
- Distance: Duration of the waggle run.
- Direction: Angle of the waggle run relative to the comb’s vertical, mimicking the sun’s position.
- Quality: Number of dance circuits and vigor of the movements.
What environmental cues help bees maintain accurate directional information in the waggle dance?
They use the sun as a compass (adjusting ~15° per hour for its movement), gravity for orientation on the comb, and even sky polarization when it’s cloudy.
In what other scenario (besides foraging) do honeybees use the waggle dance?
New nest-site selection. Scout bees advertise potential sites by dancing, and the colony uses quorum sensing to decide on the best site.
How does quorum sensing work in honeybee nest-site selection?
Multiple scouts dance for different sites; when enough scouts converge on one site (reaching a threshold), the colony collectively chooses it, and a piping signal prompts the move.
Why is the honeybee dance language considered an example of complex animal signalling?
It conveys multiple pieces of information (distance, direction, quality), adapts to environmental changes, and plays a crucial role in collective decisions.
Summary of Key Concepts
Signalling involves signaller, signal, receiver, and effect.
While signals save direct conflict, they can still be costly.
Most signals must remain honest to keep the system stable.
Honeybee dances showcase a highly evolved signalling system that encodes distance, direction, and quality of resources, crucial for colony success.
What is notable about the two distinct morphs of the Blue Headed Wrasse?
Terminal phase males (blue head, green/blue tail) are larger and dominant, while initial phase fish (both males and females) have a yellow top and greyish stripe.
found in carribean
How do Blue Headed Wrasse transition between phases?
All start in the initial phase; some males can change to the terminal phase, with males gaining dominance and changing coloration.
Females can also switch sex under certain conditions.
Why do Blue Headed Wrasse perform a circling display during mating?
Terminal phase males use this circling display to court females, increasing speed of pectoral fin movement as spawning nears, to coordinate precise timing for gamete release in open water.
How do pectoral fin movements function as a signal in Blue Headed Wrasse?
Males flutter their fins along their midline stripe, with the movement rate increasing as spawning approaches, acting like a countdown for simultaneous gamete release.
What role does aggressive signalling play for Blue Headed Wrasse males?
Dominant males defend prime breeding territories through conspicuous darting, chasing, and color changes to deter rivals and attract mates.
Why do not all male wrasse become “super males”?
Breeding territories are limited, so many males remain in the initial phase with lower mating success, while only a few transition to dominant terminal phase status.
Vervet Monkeys & Referential Signalling
Vervet monkeys produce specific alarm calls for different predators (leopards, eagles, snakes), each triggering a distinct, adaptive response.
How do vervet monkeys signal the presence of a leopard, and what is the response?
They emit a bark call, causing other monkeys to climb into trees for safety.
What call do vervet monkeys use for aerial predators, and what is the effect?
A cough call alerts the group to run for cover in bushes, indicating an eagle threat overhead.
What call do vervet monkeys use for snake predators, and what is the effect?
- chutte call
- signals other monkeys to look upward and alert the group about the threat on the ground.
How do we know vervet monkey alarm calls are referential signals?
Playback experiments showed each recorded call elicited the same specific response, even without the actual predator present.
What does research show about young vervet monkeys’ alarm calls?
They initially misuse calls (e.g., calling for a vulture instead of an eagle), but learn correct usage through adult feedback and reinforcement over time.
What is “stotting” (or pronking) in gazelles like the Springbok?
It’s a series of high, energy-costly leaps when threatened by predators, even though it briefly slows the gazelle down.
Why is stotting considered an honest signal of strength?
The gazelle demonstrates its energy and endurance, deterring predators by showing it can likely outrun them.
* costly signal - handicap so more reliable
What experimental findings support stotting as a predator deterrent?
Studies show predators, like wild dogs, are less likely to chase gazelles that stot vigorously, and more likely to pursue those with weaker displays.
Key Takeaways from Part 2
• Blue Headed Wrasse: Sexual signalling, phase transitions, and aggressive displays for territory.
• Vervet Monkeys: Referential alarm calls with learned accuracy, plus grunt calls for contact.
• Gazelle Stotting: Honest signal of endurance deterring predation through costly displays.
How do the four example systems (honeybees, wrasse, vervet monkeys, gazelles) illustrate signal diversity?
Each system uses different modalities, costs, and purposes:
* Honeybees: Cooperative dance (motion + pheromones) to share resource info.
* Wrasse: Circling (mating) and aggressive color changes (competitive).
* Vervet Monkeys: Alarm calls and grunts (auditory) for group coordination.
* Gazelles: Stotting (visual) to deter predators by signaling strength, anti predatory signal
In what way do honeybee dance signals differ from wrasse mating signals?
Honeybee dances provide environmental resource information (direction, distance, quality), whereas wrasse signals communicate the signaller’s own status (mating readiness, dominance).
Why are wrasse aggressive signals considered costly?
They involve vivid color changes and high-energy displays, requiring extra metabolic resources to maintain coloration and perform intense movements that deter rivals.
What does gazelle stotting (or pronking) communicate, and who is the intended receiver?
It signals the gazelle’s strength and endurance directly to predators, deterring pursuit by demonstrating high energy and fitness.
What is the key difference between signals and cues?
- Signals: Specifically evolved to convey information and influence behavior (e.g., bright coloration of toxic frogs).
- Cues: Incidental by-products not evolved for communication (e.g., human CO2 emission attracting mosquitoes), but exploited by others
what is the evolution of signalling systems?
- Sensory systems evolved to extract information from cues, and later used for signalling
* (e.g., visual, auditory, olfactory, mechanosensory, electro sensing),
*Allowing evolution of signals - Evolutionary Implications:
* The necessity to extract and use information drives both the evolution of sensory systems and the diversification of signalling systems.
* different sensory system optimised for different kinds of environment to extract information
why are signalling systems divers
- they are diverse because originally evolved different sensory systems to extract different kinds of information from different envrionments (cues)
- that led to diverse sensory systems
- the diverse sensory systems were then adapted to be used as communication methods and created diverse signalling system
in which 2 ways are sensory systems diverse
- can detect sensory cues in environment
- have diverse taxa: evolutionary history and diverse morphological structures to detect sensory information
Why is magnetoreception rarely co-opted for animal signalling?
Although many species can sense Earth’s magnetic field, animals cannot easily produce or manipulate magnetic fields, making it impractical as a communicative signal.
How do diverse sensory systems drive signal diversity?
Each sensory modality (vision, audition, olfaction, electrosensing) provides unique channels for communication.
As these senses evolve to detect different cues, corresponding signals evolve to exploit them.
What is an example of how the transmission medium affects signal design?
Birds in dense forests use lower-pitched songs to carry better through foliage, whereas birds in open grasslands favor higher-pitched calls for long-range clarity.
How do black-capped chickadees adjust their songs in response to anthropogenic noise?
They increase the frequency and decrease the duration of their calls to compensate for traffic noise, ensuring their signals remain detectable.
what are 4 sensory drivers of signal diversity
- sensory modality
- sensory sensitivity/range
- signaller physiology
- Transmission medium
what is sensory modality and how does it drive signal diversity
- sensory modality ios the type of senses which can extract info: i.e visual, olfactory, electrosensing, auditory
- For every sensory system (apart from magnetoreception) a signalling system has evolved to produce the signal and receive/detect the signal
o Exception - magnetoreception, organisms cant create their own magnetic fields so cant really be used for communication and signalling - i.e electrosensing in gymnotifers = production of short electrical pulses used short distance communication. They likely exploited electro signals and then evolved to produce and detect them
what is sensory sensitivity and how does it drive diversity in signals
- (aka sensory range)
- Because different sensory modalities in different animals can produce and detect different ranges, giving different types of signalling, adding to signal diversity
o Auditory Examples and Physiological Constraints:
1. Different sized animals can produce different frequency sound waves
2. Vocal ranges of animals impact the type and range of sound they can produce
3. Linked to signaller physiology
what is signaller physiology and how does it drive diversity in signals
o Leads to variation in how modalities develop
o Leads to diversity in method used to produce signal
Size and Frequency:
Insects: Call frequency is inversely related to body size (smaller insects produce higher frequency calls).
Mammals: Highest audible frequency is inversely related to head size (measured via interaural delay time – measure of distance between ears).
what is transmission medium and how does it drive diversity in signals
The transmission medium (air, water, or solid substrate) is diverse
And this drives the diversity of signal design, signals need to be specific to the medium its travelling through
Visual Signals of Wrasse in marine environments
The green coloration in some aggressive displays transmits more effectively through Caribbean seawater due to their wavelength
o External Factor:
The medium is external and does not coevolve with signal production, yet it imposes physical constraints on how signals can be effectively transmitted.
What are the four categories of signals according to Bradbury and Birmingham?
Aggressive Signals, Mating Signals, Social Integration, environmental signals
How would you categorize each of the lecture’s examples under this scheme?
• Honeybee Dances: Environmental signals (resource info).
• Wrasse Circling: Mating signal; Wrasse Aggressive Displays: Aggressive signal.
• Vervet Alarm Calls: Environmental (predator warning); Vervet Grunts: Social integration.
• Gazelle Stotting: Anti-predator (environmental) signal focusing on pursuit deterrence.
What four questions offer a more nuanced way to classify signals?
- How are signals processed? (sensory modality)
- How are signals produced? (signaller physiology)
- How are signals transmitted? (medium)
- What information do they convey? (content)
Why is “information” central to understanding signal evolution?
Signals evolve to reliably convey information that changes receiver behavior. This informational exchange underpins feeding, mating, avoidance of predators, and social coordination.
Key Takeaways from Part 3
• Signal Diversity: Influenced by modality, cost, and context (cooperative vs. competitive).
• Signals vs. Cues: Evolved intent versus incidental by-products.
• Sensory Systems: Drive how signals are produced, transmitted, and received.
• Classification: Multiple frameworks (e.g., Bradbury & Birmingham) reveal complexity.
• Information Rules: The flow of reliable information is the cornerstone of signalling systems.
