Signals and communication Flashcards
What is a signal?
Components
M&H definition (coevolution)
It has 3 basis components: signaller - signal - receiver
Maynard & Harper: “any act which alters the behaviour of other organisms which evolved because of that effect, and which is effective because the receivers response has also evolved”
The signaller and receiver are co-evolving.
Why are signals reliable?
Examples…
Because they can be hard to fake. Only an animal with the quality it is signalling about can express the signal. For example, birds with good neural capacity have complex bird song, large dominant males express this in their physical structure.
Are all signals reliable?
Examples x 2
Some animals are cheats, because probing for cheats extensively can be costly for receivers.
For example, the cuckoo. It fools genetically unrelated parents into feeding them by exploiting their provisioning rules, e.g. the gape width they respond to. As a result, they get more food than their actual chicks would.
Another example is the hover-fly, which is a batesian mimic of bees and wasps - advertises fake defenses
Signal design
Guildford and Dawkins, 2 factors:
They separate a signal into strategic design (content) and tactical design (other factors/pressures that could effect it)
One selection pressure is the environment:
examples from animals and humans
It can effect the sensory modality the signaller uses
E.g. habitat. Rufous collared sparrows have slower trills in forests than open country.
Lizards move quickly or slowly depending on environment.
Man-made environmental change can effect bird song
Human communication parallels e.g. canary islands, use whistle languages. When forests are thick and travel is difficult, whistles travel well and allow communication
Receiver psychology
How can a signal have efficacy?
Signals are selected for their efficacy (effectiveness)
Signals that are better detected, discriminated, and learned & remembered will be selected for
Receivers play a role in increasing the efficiency of information transfer
Receiver psychology
1: detectability
Selection for easy to detect signals
This depends on the visual properties of the environment and the sensory capabilities of the receiver.
Cock O’ the Rock, is highly conspicuous on sunny leks (mating display) but hidden in the shade (hide from predators)
Some animals have private sensory channels, e.g. bats and echolocation, birds and seeing in UV
Receiver psychology
2: discriminability
Selection for easily distinguished signals
E.g. reef fish, species recognition. Might drive the diversity of signal form, to ensure you can identify members of your own species for mating etc.
Receiver psychology
3: learning & memory
Selection for signals that are easier to learn or remember
E.g. aposematism. Advertise defences with conspicuous colouration. Predators learn to avoid toxic prey when they are conspicuous, because they are more easily remembered
Receiver biases
There are 2 types: sensory and learning
Receiver biases
1: sensory
Examples of biases
Sensory biases are by-products of the sensory system, commonly occur in sexual signalling
The predators visual system detects symmetry more easily… conspicuous prey make use of symmetry, whilst camouflage is enhanced by asymmetry
E.g. Tinbergens herring gull chicks- chicks were good at responding to many colours. Responded more to a large spot of red, or red/yellow contrast (supernormal stimuli)
E.g. Female zebra finches prefer red colouration in males
Receiver biases
2: learning
examples of biases, inc. peak shift
Signals evolve in response to learning in many contexts
E.g. bees learn about the profitability of flowers whilst foraging. They develop exaggerated preferences for flowers with lots of nectar, prefer extremes because they are most discriminable. This is called peak shift
E.g. Cate, PS in zebra finches. Mutant finches, painted beak with different colours. Found that parent beak colour effected naive chicks later mate preferences. They had an exaggerated preference for whichever colour beak they were exposed to in the nest
