Term 2 Lecture 2: Animal Behaviour - Communication Flashcards
Role of communication
Few animals live in isolation. Even solitary species need to find a mating partner, requiring social interaction with another of the same species (conspecific)
Heterospecific interactions are with animals of other species e.g. predator prey.
Heterogeneous (variable) environments lead to competition -> signal+response= communication
Unequal distribution of food,shelter and mates cause aggregation and non-random interactions amongst individuals e.g. defending territory requires directed signals (sound, visual, olfactory) these displays communicate status eliciting a response from the recipient.
Signal + response = communication
Repeated interactions lead to
Evolution of signals that are less costly
Elements of a communication system
Sender (actor) receiver (reactor)
Display - a signal specifically for social purposes “a behavioural display”
Channel - means by which either signal or display is transmitted, may be visual, auditory, olfactory or rarely electrosensory - such as signals used by electric eels
Context- environmental situation, proximity of individuals & wider environmental context e.g. potential for interference from sender to receiver hindering signal transmission e.g. noise in rainforest or colour shifts in the ocean.
Definitions of biological communication
Communication broad def. :
Sharing something between A & B
Early refined def. Wilson 1975:
“ An action on the part of one organism (or cell) that alters the probability pattern or behaviour in another organism (or cell) in a fashion adaptive to one or both participants”
Modern def. Slater 1983: “ the transmission of a signal from one animal to another such that the sender benefits on average from the response of the recipient”
Involuntary ‘communication’ and misinterpretation
E.g. a vole rustling the grass can attract the attention of an owl and get eaten. It did not intend to communicate its location.
So sender must ‘intend to alter another’s behaviour. However it is difficult to discern the intentions of other individuals let alone those of other species. Risk of anthropomorphism - ascribing human characteristics to non-human animals.
- circular arguments - elephants at a waterhole - did they intend to have a drink because they were thirsty? That’s guessing motivation from outcome of behaviour .
Slaters definition of true communication includes deceit and manipulation.
i.e. purpose of display is not so much as to inform the opponent but to persuade the opponent (e.g. in a fight that they are more dominant/bigger/stronger) so displays evolve to maximise persuasive power - not to maximise info. transfer - as in fighting fish dominance displays
Who benefits from communication?
Value of info to sender/ to receiver
Pos/Pos
True communication - both benefit
Pos / Neg or zero
Manipulating (deceit) sender benefits
Neg or zero/ Pos
Eavesdropping (exploitation) benefits receiver
Neg or zero / Neg or zero
Ignoring (spite) benefits neither
Types of signal: discrete/graded
Discrete: digital (all or none/ on or off) e.g. aggressive or not
- in zebras:
hostile - ears flat
friendly: raised ears
Graded: analog (intensity varies in proportion to stimulus strength)
e.g. how aggressive
-in zebras:
Wider mouth more aggressive
Types of signal: Afferential/referential
Afferential: communicates info about the sender itself e.g. robin song warns other males to keep off its territory by advertising it’s strength and fitness
Referential: communicates info about something in the environment, external to the communicating individual. This enables animals to communicate with one another about their surroundings e.g. alarm calls of ground squirrels on spotting a predator
Most species have 20-40 different displays
According to a study of 6 fish species, 10 bird species and 14 mammal species.
There are other ways to combine or utilise these signals to communicate in a more complex way - composite/syntax/context
Combining signals for complex communication: composite/syntax/context and meta communication
Composite signal: 2 or more signals combined to give new meaning e.g. ear position + how open mouth is to show aggression in zebras
Syntax: changing the sequence of displays e.g. A followed by B has a diff meaning to B followed by A
Context: same signal(s) diff meaning(s) depending on context i.e. what other stimuli are received e.g. a lion’s roar -
Male to male - show of strength
To neighbouring pride - keep distance
To own pride - draw individuals together
Meta communication
-communication about communication
- one display changes the meaning of others that follow e.g. play behaviour in dogs and wolves (canids) is indicated by a play bow which indicates the following acts are play - aggressive/sexual displays are used but understood to be play
Message vs. meaning
Message: what signal encodes about sender (what it is, what it is up to and what it might do next) e.g. I’m dominant, stay out of my territory or I will fight you.
Meaning: what receiver construes from the signal - inferred from receivers response varies depending on recipient
Cost & benefit
E.g. male bird sings
Another male bird of same species - understands it must fight or leave
Hawk - hunts bird
A bird of another species - shares territory but doesn’t compete so won’t make any effort
Economy of effort
Signalling may be a less costly way of manipulating behaviour of another individual than using force e.g. male ground crickets dig burrows shaped to amplify their song that they use to attract females - females must risk walking to find the burrows, males are avoiding risk by hiding in their burrows attracting females to them.
However some signals have high cost e.g. red deer stag roaring contests in rutting season, they often do not eat enough to give them more time to roar then in the winter when forage is scarce they are at risk of dying of starvation BUT this is still less costly than having to physically fight each time for mating opportunities - reduced use of energy and avoiding injury.
Eavesdropping
Behaviour signalling picked up by another individual that wasn’t your intended recipient e.g. Gannett’s will remember if an individual returns to the colony with a full crop (good catch of fish in its throat) and then follow that individual to it’s fishing spot the next time it goes to hunt
Adaptations to reduce eavesdropping
1) signal difficult for eavesdropper to detect or locate e.g. 7khz Freq. If birdsong is easy to hear but hard to locate - safe from predators
2) signal selectively - unavailable to predators e.g. red spots on stickleback fish are used in intraspecific communication and their invertebrate predators are red-blond so cannot detect them
3) direct signal to specific individual(s) e.g. colour change in metamorphoses on surface of cuttlefish can change colour for camouflage on one side whilst producing bright rapidly moving patterns and flashes on the other side to signal to conspecifics such as potential mates
Audience effects
Presence of particular onlookers can make behaviour more or less likely
e.g. domestic rooster will not display (usually) when given food if alone. In the presence of hens the rooster makes a clucking display to show the hens food and show off his food finding ability
E.g. Male vervent monkeys beat up the babies in the absence of females. If the mothers were allowed to view this through a one-way screen on returning to the enclosure they beat up the males - revenge.
What makes a good (useful) signal?
How well suited the signal is to being detected in the receivers environment e.g. wolf howl an auditory signal that travels well in vast quiet territory
Channels and environment
Sound/auditory - most effective in water
Vibration/seismic- e.g. stomping of kangaroo rats and body slap of seals
Visual- bioluminescence, colouration etc.
Tactile- short range
Odour/chemical- scent marking, pheromones e.g. how moths attract a mate
Electric field - electric eel communication
Seal body slap behaviour
Shows dominance by size, larger male = heavier slap. Vibrational and auditory.
Body slap is only performed on close packed wet sand - environmentally specific
Sound degredation
Sound released in dense forest gets degraded and signals may get confused or ignored. Worse for high freq. sounds as they reflect of small objects.
In open meadow sound carries well but can be impacted by wind
Often sound signals have repeated signals as in “trills” in birdsong so that even with interference some meaning should get through
Strategies to reduce sound degredation
Bird calls optimise effectiveness according to surroundings
In forest: low freq (4khz) used and trills avoided unless notes are widely spaced, songs have less variation
In open terrain: trills favoured as repeated elements can be detected during brief periods of good transmission, higher freq used
Temperature impacts sound signals
-Affects sound transmission through environment.
-affects production of sound by the signaller e.g. ectotherms - temp. Affects metabolic rate and neuromuscular mechanisms therefore behaviour e.g. trill rate in 2 tree frog species increase in rate as temp is increased (as pulse increases)
Interference
E.g. biological noise such as song choruses.
Solution: shift sound freq or timing to reduce overlap e.g. frog choruses.
Or use individual variation in vocalisations e.g. in penguin colonies
Background noise interference
E.g. running water, wind etc.
Solution: avoid signalling when/ where there is the problem or adjust signal characteristics to compensate e.g. territorial bird sits at top of tall tree to sing so it’s song is not muddled by leaves - a clear sound field
Best sound freq to use?
Depends on the environment
E.g. blue monkey dawn chorus in forests of Kenya and Uganda - adult males have a special vocal sac that produces a “whoop gobble” call at 200Hz
The calls freq minimises attenuation and stands out from background noise being at a freq at which there is little to no background noise aka a sound window
Multiple channels
Longhorn beetles ignore a black bead without female beetle odour and will attempt to mate with a black bead if it has a female odour. However it will not attempt to mate with a white or transparent bead with a female odour so females communicate by a combination of odour and colour
Summary of a good signal
Detectability- must be easy to pick up e.g. peacock tail fan or bird song
Discriminatibility and memorability -
E.g. toxic organisms communicate their poison via specific bright colouration and patterns to warn predators not to eat them and predators remember these associating them with sickness
Specificity
E.g. moth pheromones only attract male moths of the relevant species
Stereotypy: ritualisation reduces ambiguity of signals.
Unambiguous - clear meaning
Antithesis (Darwin 1872)
Signals conveying opposite meanings often have opposite forms e.g. canine aggressive form is the opposite of their submissive form
