Lecture 16 Flashcards
How many sensory modalities are there, & what does it depend on?
6
depends on where the species lives and its lifestyle
signal / cue must be reliable & readily discernable from background noise
Distinguish b/w abiotic and biotic changes
abiotic changes - temperature, humidity, sunlight, altitude, longitude, substrate for mobile organisms
biotic changes - temporal and spatial variation in the abundance of food, competitors, natural enemies (predators, parasites, pathogens), & reproductive partners
Examples of cues for predators
- inside of eggshell is conspicuous (the closer broken egg shell is to intact egg, the more likely the intact eff will be taken)
- black-headed gull parents remove the broken eff shell immediately after their chick has hatched
Features of signals / cues
- have no intrinsic meaning
- must be recognizable
(selection must favour the evolution of the sensory mechanisms that allow the signal or cue to be detected)
chemicals (signals & odours) transmit info
Signals vs cues
Signals are an evolved means of actively conveying information and influencing the behavior of receivers.
In contrast, cues are passive, non-evolving biological and environmental traits that inherently provide the observer with information
The 6 sensory modalities (or channels)
chemical
electrical
light
magnetic
mechanical
sound
chemical modality (olfaction)
the oldest and taxonomically most widespread sensory channel
production + dispersal of pheromones
pheromones might activate receptors on antennae of mate
Electrical modality
- works well in aquatic environments because electricity is more easily transported through water than air
- responds to electrical signals when searching for prey
Visual modality
- visual acuity (the ability to see) varies across species and may depend upon eye size
- the ability to detect a signal (a natural decoration on a spider’s web) varies with distance and species
Magnetoreception
- bacteria and many animals detect and respond to the magnetic field, allowing them to orient over long (i.e. migration) and short (i.e. homing) distances
Emlen funnel - used to record the direction the bird attempts to escape
Mechanical
- web building spiders use vibrations, transmitted along the flexible silk, to detect the location and size of prey that are arrested by the web
Sound frequency
- bat sonar operates at frequencies of 20 - 200 kHz
- objects in space are located by directing sounds at them and detecting the echoes
- the longer the time interval until the echo is detected, the further away the object
Example of signal in male and female fireflies
flash lights as a SIGNAL to indicate their location for mating
Example of a cue
red necked wallabies use the odour of faeces as a CUE revealing the likely presence of a predator
Define signal vs cue.
Signal - any act or structure that influences the behaviour of other organisms (receivers) and which evolved specifically because of that effect
Cue - an incidental source of info that may influence the behaviour of a receiver, despite not having evolved under selection for that function (e.g. dog faeces)
Are ant pheromones signals or cues?
- signal for other ants
- cue for adult butterflies (for mating and oviposition)
- cue for spiders (to locate webs where butterflies search)
What is meant by signals ‘attenuating’?
signals, & the info they provide, may not reach their intended receiver because they attenuate as they travel through the environment (it is more difficult to discern colour patterns of hear sounds the further from the source)
What else affects the ability of a signal to reach a receiver?
background noise
Signals are strategic and efficacious
- strategy –> bright coloration reveals toxicity and this reduces likelihood of predation
- efficacy –> same info, different impact
Distinguish bw signals and cues in terms of evolution
signal - evolved as a vehicle for info bc it benefits both the individual that produced the signal AND the receiver that detected it
selection will favour greater distinctiveness in the signal and greater ability of the receiver to detect it
cue = has not evolved as a vehicle for info, but rather it inadvertently provides useful info to the receiver
selection may favour greater detection abilities in the receiver, but will not act on the cue, unless it disadvantages the source of the cue
How does an animal KNOW what is a signal or cue and how does it know how to respond?
The source of ‘info’ that allows animals to behave:
INNATE
LEARNED - a behaviour that is modified as a result of the animal’s experience of its env
Signals benefit both. . .
signaler and receiver, whereas cues do not
