Section 6 Flashcards
Communication
an interaction in which one individual, a signaller, produces a signal that affects the behaviour of another, a receiver
Animal Signal
an evolved trait that is selected for its effect on the behaviour of a receiver and is adaptive for the signaller and typically the receiver
Research 6.1: Effectiveness of Pheromones in Controlling Damage by Light Brown Apple Moths in Citrus Ocrcahrds
a) Compared two orange groves: one control and one that they released small quantities of apple moth female sex pheromone
b) Each orchard had dozens of individual constrained test females
c) Females in the treatment orchard were almost never inseminated and fruits were less damaged
Research 6.1: Honeybees and The Waggle Dance
a) Honeybees live in colonies and individual workers leave the hive in search of food
b) They use visual and chemosensory systems to find nectar and pollen
c) Once an individual scout finds a rich food source, it flies back to the hive to recruit others to exploit the food
d) This allows the colony to rapidly exploit food resources before others
e) Waggle Dance: scout moves in a figure-eight pattern on the honeycomb, vigorously wagging its body with duration of wagging representing distance to food
f) Every 75 milliseconds of wagging translations into a distance of roughly 100m from the hive
g) Also uses the sun to communicate direction
h) The waggle dance should be providing an accurate signal but travel times are prolonged, why?
i) Some proposed that the waggle dance presents the odour of the food source, suggesting that new recruits fly downwind and search themselves
HONEYBEES & WAGGLE, ODOUR: Research Question
Do bees also use odour to find the food?
HONEYBEES & WAGGLE, ODOUR: Methods
a) Examined flight paths of recruits that viewed the waggle dance from a hive placed in a large, flat, mowed field
b) Field contained few natural sources of nectar or pollen so the only food available was at a feeding station, placed 200m east of the hive, food had no odour
c) Recorded average wind speed and direction to determine effect of bee flight
d) Individual scouts could visit the feeder, their waggle dance indicated that food was located at the feeder due east
e) They captured recruits who never visited the station and placed small transponders on their backs, they were released either at the hive or at one of three locations 200m southwest of the hive
f) All individuals had to fly across the prevailing wind to maintain a due east heading
HONEYBEES & WAGGLE, ODOUR: Results
a) Flight paths of new recruits confirmed the hypothesis of Von Frisch that the waggle dance appears to signal the distance and direction of food
b) Recruits can travel to the area of a novel food source without odour cues
c) The dance signal is not sufficient to allow a recruit to locate a food source precisely, odour helps to finish the task
Research 6.1: Alarm Calls
a) Alarm calls are unique vocalizations produced when a predator is nearby
b) Vervet Monkeys produce different alarm call vocal signals that affect receivers differently, different calls for different predators
c) Each predator is a threat that requires a different response
d) Bark calls are for leopards (monkeys escape via tree)
e) Cough calls are for eagles (monkeys move down from tree tops into bushes)
f) Chutter calls are for snakes (monkeys stand erect and look into grass clumps)
Research 6.1: Titmouse Alarm Calls
a) A small songbird, alarm call is in response to a perched avian predator
b) Titmouse call is composed of three basic notes: Z, A, and D
c) Individuals often vary the number of D notes
d) The call recruits other birds to approach and mob the predator, producing loud vocalizations which is harassment to drive the predator away
TITMOUSE & ALARM CALLS: Research Question
Do alarm calls of titmice differ with the size and degree of threat of a predator?
TITMOUSE & ALARM CALLS: Methods
a) Six treatments, each a different predator and a control
b) Several feeding stations
c) Lifelike models of different birds were placed on platforms a metre away from the feeding station
d) Three models were high-risk predators, two low-risk, and one non-predator control bird
e) Would the titmice produce different alarm call signals?
TITMOUSE & ALARM CALLS: Results
a) Alarm call varied across treatments
b) The number of D notes produced per titmouse was greater in response to small, high-risk predators compared to large, low-risk predators and controls
c) The smaller the predator, the longer the mobbing response
d) Titmice produce different alarm call signals that correlate with varying levels of threat and lead to differences in the behaviour of receivers
Why is the assumption that signals encode specific information problematic?
1) Can imply a language-like meaning of communication which is challenging to document
2) Can encourage attempts to characterize the information encoded in a signal, rather than focusing on factors that shape signal properties
The Environment Influences the Evolution of Signals
a) Chemical signals can be transmitted readily through water or air and are relatively long lasting, travelling great distances, can be deposited as a substrate, strength can be controlled, they can also travel around environmental barriers, but cannot be modified once transmitted
b) Visual signals move rapidly through the environment and can be detected quickly, allowing for a more rapid response, can be perceived over fairly large distances, but this perception requires sufficient light levels and can be blocked by obstacles
c) Auditory signals can bypass obstacles, meaning they can be perceived when visual signals cannot, also can be modified by a sender rapidly, turned on or off, and at different amplitudes, but they lose energy as they move, limiting effective range
Research 6.2: Temperature Affects Ant Chemical Signals
a) Ant scouts travel away from the colony to find food
b) Across species, there’s variation in diurnal foraging activity: some are active all day and some are restricted by warmer temperatures
c) Variation in foraging strategies: some individually search for and bring back food, some find a rich food source and deposit a volatile chemical pheromone to create a trail
d) This chemical signal can persist for 30 minutes or more and allow new recruits to travel directly to the food
e) These ants in the Mediterranean feed on nectar
ANTS & CHEMICAL PHEROMONES: Hypothesis
The persistence of a chemical food trail signal will be negatively affected by surface temperature, which can then affect daily activity patterns
ANTS & CHEMICAL PHEROMONES: Methods
a) Quantified the activity of free-living colonies by counting the number of workers on feeding trails
b) Recorded surface temperature at the colony entrance
ANTS & CHEMICAL PHEROMONES: Results
a) Activity was highest for surface temperatures between 20 and 30
b) Activity declined sharply for surface temperatures above 30
c) No worker activity for surface temperatures above 48
d) Ambient temperature affected foraging behaviour in a manner consistent with the hypothesis but why?
ANTS & CHEMICAL PHEROMONES: Why?
a) Trained lab-housed colonies to feed on a solution of honey and water
b) Workers had to cross two sections of a glass bridge to travel from the nest to food
c) Colony could exploit the food patch to establish a pheromone trail on the bridge
d) Later, the second section of the bridge was removed for several minutes and heated to certain temperatures
e) Basically, they provided two new paths, both new were heated and then cooled
f) Food placed at the end of each and ants could travel anywhere
ANTS & CHEMICAL PHEROMONES: Next Phase Prediction
If the pheromone persisted after the heating treatment, ants would be expected to preferentially use the original bridge
ANTS & CHEMICAL PHEROMONES: New Results
a) For the low temperature treatments, workers preferred the original
b) For the high temperature treatments, there was no significant difference
c) This suggests that surface temperature plays a critical role in food trail persistence and use
Research 6.2: Habitat Light Environment Affects Fish Visual Signals
a) Sometimes, selection favours visual signals that contrast most strongly with the background environment since they can be more readily detected
b) Environments can differ dramatically in both light level and spectral properties
c) Telmatherina sarasinorum, a small fish, males can be either all blue or all yellow
d) Females are grey and male body colour is likely a signal used in communication with females during courtship
e) Males court them in either shallow beaches or deep-water sites
f) These habitats appear to present different light levels and visual backgrounds
SMALL FISH AND VISUAL CUES: Research Question
Do females preferentially mate with males based on the effectiveness of their colour display in each habitat?
SMALL FISH AND VISUAL CUES: Prediction
A male’s reproductive success will be highest in habitats in which his body colour contrasts most strongly with the visual background, since in such conditions, his visual signal should be most effective
SMALL FISH AND VISUAL CUES: Methods
a) 12 transect sits, six in each habitat
b) Analyses of the spectral properties of each morph in each habitat revealed that the blue morph contrasted most strongly with the beach and the yellow most strongly with the root (deep-water)
SMALL FISH AND VISUAL CUES: Results
a) The team first needed to characterize reproductive success of each morph
b) Some males perform active mating displays while others do not and are sneakers
c) Both male morphs use both strategies in both habitats, mating displays and sneaking
d) Each male morph had its highest reproductive success in the habitat in which its morphology contrasted most strongly with the background environment
Research 6.2: Habitat Structure Affects Bowerbird Auditory Signals
a) Comparing vocal signs (advertisement calls) of bowerbirds in different habitats
b) Habitat can range from dense rainforests to open woodlands
c) Males construct a stick bower on the ground from which they display to attract mates
d) Males produce a loud call to attract females
BOWERBIRDS & ADVERTISEMENT CALLS: Research Question
Was variation in geography for advertisement calls due to differences in the vegetation structure across populations?
BOWERBIRDS & ADVERTISEMENT CALLS: Methods
a) To test the prediction that call frequency should be lower in more densely vegetated habitats, they recorded calls from 18 locations that varied in habitat and vegetation structure
BOWERBIRDS & ADVERTISEMENT CALLS: Results
a) Call structure varied across sites and was related to habitat type
b) Minimum frequency and dominant frequency were negatively correlated with tree density: frequency was lower in sites with more trees
c) One possibility is that morphological differences across populations, like body size, could account for this but this was ruled out
d) Another possibility is that juveniles may simply learn those habitat specific calls that they hear best
Signals as Accurate Indicators
Three conditions that favour the evolution of signals as accurate indicators: if the fitness interests of the signaller and receiver are similar, when they can’t be faked, and if they are costly to produce or maintain
Research 6.3: Aposematic Colouration in Frogs
a) Bright colouring that makes them stand out from the environment and indicates they contain chemicals or poisons that make them dangerous prey
b) Species benefit if predators learn to avoid attacking them and predators benefit by learning this association so they won’t waste time hunting unpalatable prey
c) Red and Blue
APOSEMATIC FROGS & BENEFITS: Research Question
Why are dedrobatid frogs brightly coloured?
APOSEMATIC FROGS & BENEFITS: Methods
a) Clay models for a toxic frog and nontoxic frog
b) Placed 800 frog models on either the forest floor or a white piece of paper at 5m intervals along 40 transects
c) White paper was used for brown frogs to balance out the fact that cryptic frogs can be seen so easily so half of them had white paper
APOSEMATIC FROGS & BENEFITS: Results
a) 12% of models are attacked, mostly by birds
b) Brown models were attacked by birds almost twice the rate of cryptic models
c) Supports the hypothesis that bright colouration is a signal to predators that prey are unpalatable
