Lecture 16

Question 1

How many sensory modalities are there, & what does it depend on?

Answer 1

6

depends on where the species lives and its lifestyle

signal / cue must be reliable & readily discernable from background noise

Question 2

Distinguish b/w abiotic and biotic changes

Answer 2

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

Question 3

Examples of cues for predators

Answer 3

• 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

Question 4

Features of signals / cues

Answer 4

• 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

Question 5

Signals vs cues

Answer 5

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

Question 6

The 6 sensory modalities (or channels)

Answer 6

chemical
electrical
light
magnetic
mechanical
sound

Question 7

chemical modality (olfaction)

Answer 7

the oldest and taxonomically most widespread sensory channel

production + dispersal of pheromones

pheromones might activate receptors on antennae of mate

Question 8

Electrical modality

Answer 8

• works well in aquatic environments because electricity is more easily transported through water than air
• responds to electrical signals when searching for prey

Question 9

Visual modality

Answer 9

• 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

Question 10

Magnetoreception

Answer 10

• 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

Question 11

Mechanical

Answer 11

• web building spiders use vibrations, transmitted along the flexible silk, to detect the location and size of prey that are arrested by the web

Question 12

Sound frequency

Answer 12

• 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

Question 13

Example of signal in male and female fireflies

Answer 13

flash lights as a SIGNAL to indicate their location for mating

Question 14

Example of a cue

Answer 14

red necked wallabies use the odour of faeces as a CUE revealing the likely presence of a predator

Question 15

Define signal vs cue.

Answer 15

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)

Question 16

Are ant pheromones signals or cues?

Answer 16

• signal for other ants
• cue for adult butterflies (for mating and oviposition)
• cue for spiders (to locate webs where butterflies search)

Question 17

What is meant by signals ‘attenuating’?

Answer 17

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)

Question 18

What else affects the ability of a signal to reach a receiver?

Answer 18

background noise

Question 19

Signals are strategic and efficacious

Answer 19

• strategy –> bright coloration reveals toxicity and this reduces likelihood of predation
• efficacy –> same info, different impact

Question 20

Distinguish bw signals and cues in terms of evolution

Answer 20

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

Question 21

How does an animal KNOW what is a signal or cue and how does it know how to respond?

Answer 21

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

Question 22

Signals benefit both. . .

Answer 22

signaler and receiver, whereas cues do not