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Animal navigation 1 – Basic navigation techniques used by animals
NB – Lecture 1 + 2 – Navigation over 2 dimensions/surfaces (i
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no vertical component)
Manx shearwater example
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Breed on an island off the SW coast of Wales → Migrate via W coast of Africa and across the Atlantic → Overwinter
in S Argentina (abundant food) → Migrate via E coast of Americas and back across Atlantic to breeding grounds

Aims of navigation vary but all require information on current location and target location
•

Search for – (1) Food/water (2) Overwinter survival (3) Mates/Offspring (4) Refuge (5) Home territory/range

Achieved through many different mechanisms with varying sophistication/scale/utilisation of sensory systems
NB – Lecture 1 mechanisms are only applicable to familiar environments – Not ‘true’ navigation
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Random search
Simplest form – Similar to Brownian motion (random motion of liquid-suspended particles resulting in collision)
Usually over short periods – Inefficient
No processing of information by sensory systems – Rare (most environments have gradients/cues)
Directional search
More sophisticate – Sensing and movement along chemical (e
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taste or smell)/light/pressure/magnetic/vision
gradients (e
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towards food or away from predators)
Neurophysiological understanding and representation of surrounding environment as a ‘map’
Involves knowledge of places previously visited and the direction travelling in
Often demonstrated empirically in mice and rats
NB – Multiple mechanisms are often used in conjunction to successfully navigate
E
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Navigation towards overwintering ground Vs specific burrow/mate differ

Levy flights – Biased random search
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Studied widely on small (e
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bacteria/protozoa) and large (e
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basking sharks) organisms
Advantages – Able to be implemented when sensory information is limited to forage for sparsely distributed food
Involves foraging in numerous small sections with significant distances between them
- E
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Basking sharks will feed within a prey-rich section until depletion (making
sharp turns within the section to catch prey), then travel over a long distance
in a particular direction until a new prey-rich section is found, then forage there
- Long tail distribution – Most movements are short/sharp, long distances are
only made when a given section has been foraged to depletion
• Limitations – Only utilises gradients or internal clock (search time)
Systematic search
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Demonstrated in desert ants in displacement experiments
Search in circular motions spiralling out from a start position
Advantages – More efficient that random search → Allows coverage of large areas/minimises retracing of steps to
forage for randomly/sparsely distributed food
Limitations – Inadequate to relocate home range/nest site

Homing – Most studied element of navigation
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Important for relocating particular locations
Very testable predictions – Manipulation of (1) navigating animal (2) route (3) signals is easy

Trail following – Simplest form of homing
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Involves following information left on an outward journey – Usually chemical cues
Many examples with varying levels of sophistication
1
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Gastropods (e
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snails, limpets)
Leave a physical slime trail for homing to a consistent rest spot
3
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Termites/ants
Release pheromone trails on outward journeys to aid navigation of themselves/nestmates to and from food
sources
Directionality of trail following is not fully understood BUT widely accepted that chemical gradients are used, likely
translated by anterior and posterior sensory systems
Gradients are thought to provide directional indication and have a limited lifespan (→ decay)
Limitations
(1) Inflexible – Unable to deviate from trail
(2) Unreliable – Disruption → disorientation – Require supplementary (random/levy/systematic) search
mechanism
(3) Inefficient route home

Route-based orientation
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Involves remembering/recording a series of pieces of information (e
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landmarks) on an outward journey and
reversing their order on the homeward journey
Similar to trail following BUT no ‘physical’ trail is left
Involves use of various sensory systems – (1) Touch (2) Smell (3) Vision – E
...
landmarks, polarised light detection
(4) Mechanosensory information to detect fluid flow (5) Wind direction
Some more easily manipulated under natural conditions than others – E
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landmarks surrounding an animals
nest/foraging sites can be moved/removed (if moved, ants still demonstrated to follow in new direction) Vs
polarised light (must be manipulated in under laboratory conditions)
E
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Golden hamsters
Travel between nest and foraging sites during active periods (dawn and dusk)
Demonstrated to use senses (e
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smell) to locate objects encountered on an outward journey when on the
homeward journey under IR light, but expectedly navigated the most direct route (straight line) under visible light
Limitations
(1) Inflexible – Requires visiting all outward landmarks to navigate home
(2) Unreliable – If landmarks are moved
(3) Inefficient – Might require zigzagging along the outbound route when homebound

Path integration (aka dead reckoning)
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Internally based navigation system first proposed by Darwin – Used widely
in animals
Involves calculating one’s current position by using a previously
determined position, and advancing that position based upon known or
estimated speeds over elapsed time and course
Taking the most direct route home – Integrated path
Requires 2 pieces of information
1
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g
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g
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Distance of travel
One theory – Use of an ‘odometer’ to measure distance travelled in a cumulative way
Every step taken is recorded as ‘one distance’, providing length of step is regular

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E
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The desert ant (contradictory findings below??)
Easy to manipulate → Used extensively in research
Demonstrated to use a more efficient homebound route (113m) than
outward foraging route (345m)
Also demonstrated to use ‘odometer’ in navigation – Foraging ants were
collected and manipulated (stumps/stilts) then allowed to return to nest
Stilted ants overshot the nest, stump ants undershot the nest (then initiated random search) and control ants
found the nest
The ants were then allowed to complete a whole foraging journey – All of which completed it correctly – Leg
length was irrelevant – Ants were using an internal odometer to count outward journey steps, then repeat that on
the homebound journey
Limitations
Odometer is error-prone – Potentially severely disrupted by displacement → Inaccurate (e
...
if an individual is
blown by wind or falls off a rock)
If disrupted → Initiates random or systematic search → May result very far from intended target
Limited to navigating to a known home/nest site – Unsuitable to locate novel habitat patches

Animal navigation 2 – Complex navigation strategies between true navigation
‘True’ navigation
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True navigation = Navigation to a point outside of an individual’s sensory range (e
...
Manx
shearwaters long distance overwintering)
• Well-studied discipline of animal behaviour – Tested in many animals (especially birds)
• Involve displacement experiments both in field + laboratory experiments
- Movement to an unfamiliar area (outside of sensory range) to determine an ability to
determine location and navigate in the right direction from there
- E
...
Displacing a migrating bird to test whether it (1) Adjusts its trajectory to reach the
intended location or (2) continues along their vector navigation at the same bearings as
before displacement
Requirements for true navigation
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Could be the result of several different mechanisms combined
1
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Internal compass (direction – simpler concept) – Knowledge of the bearing (i
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direction of travel) of a goal
- Sun, star, magnetic
• (1) + (2) are often translated using global sensory systems
‘Time-compensated’ sun compass
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Position of the sun in the sky at certain times of day provides indication of direction
Used by many day-navigating animals (e
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bees)
Individuals learn (1) when to forage (2) which specific plants to forage by calculating the
angle between the sun and intended (reward) foraging site, based on time of day
Practical example – Do bees use a sun compass to navigate?
Tested using clock-shift experiments under artificial laboratory conditions (i
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controlled
light exposure to stimulate different times of day)
Bees trained to forage at 9am
At 6am (not clock-shifted) – Bees successfully reach intended foraging site, despite angle
being different (by using sun compass correctly)
Clock-shifted 3hr back – Bees ‘think’ it is 6am (under artificial light) when it is in fact 9am
(under natural light), resulting in utilising the 6am angle and navigating to an
unrewarded flower (by using sun compass correctly)

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Hypothetical example supported by empirical study – Do pigeons use a sun compass to navigate?
Artificial sunrise/sunset maintained the same as natural sunrise/sunset (control) – When released at 6am, 9am,
12pm, and 8:30pm (first 4 graphs), pigeons are able to calculate the time of day using the angle of the sun to
navigate at a particular angle and arrive successfully at their target
Sunrise/sunset clock-shifted 3hr back (right graph) – Pigeons ‘think’ it is 6am when in fact they are released at
9am, implementing the ‘6am angle’ to reach home and navigating in the wrong direction
Similar pattern demonstrated for clock-shifting forward 6hr – Forward/backwards and time of clock-shift irrelevant
Further evidence supporting the use of a sun compass in navigation

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Just as the position of the sun changes the day, the function of its angle also changes throughout the seasons
Animals must keep track of the time of year as well as time of day
This is supported by empirical study, but there is less certainty over the mechanisms driving it

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Star compass
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Similar to sun compass BUT not time compensated
- Other stars are much further away → Little shift in star movement at night → Considered stationary
• Used by many animals – Especially nocturnal/night foraging animals
- Well studied/demonstrated in birds – Emlen funnel experiments
- Developing evidence in newts + salmon but more difficult to test
• Early experience appears vital – Captive-bred chicks not exposed to night sky proven incapable of utilising star
compass as adults
Emlen funnels
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Developed in 1960s and still used widely today
A circular funnel with an inkpad at the base and blotting paper up the side
Operates under the assumption birds caught mid-migration and placed in
the funnel are trying to escape and navigate to their intended target (e
...
by
following a star compass)
- Emlen funnel can be kept under artificial conditions within a planetarium
with other factors controlled (e
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olfactory, magnetism)
- Bird movement can then be recorded in response to fake stars (indicating direction) manipulation
• Provides indication of which direction birds are attempting to navigate
- Extensive empirical study demonstrates the ability to utilise star compass to navigate in a particular direction
Magnetic compass
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Emlen funnels can also be used to test use of magnetic compasses – I
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use of magnetic field to navigate
Wiltschko and Wiltschko conducted one of the first experiments to test this ‘nonsense’ concept in 1972 (below)
One way (of several) to test this theory is using a Helmholtz coil (surrounding an Emlen funnel)
Used to manipulate Earth’s natural magnetic field under laboratory conditions
Simplest form – 2 bands of coiled isolated copper … More complex forms – Additional band in each direction
Electronic current can be manipulated (i
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ran through at different
wattage) to alter the magnetic field surrounding an Emlen funnel
4 elements to Earth’s magnetic field (Simplified diagram on right)
1
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Inclination angle – Of the arrows around the globe
Angle at which the magnetic field is coming off Earth’s surface

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Changes around the globe’ surface
Angle changes with latitude – Nearly horizontal at geomagnetic equator (black line) → Steeper until geometric
north (nearly right angle) → Shallower until horizontal at equator → Steeper until geomagnetic south → etc
3
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g
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g
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g
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Cluster N in the eye – Where cryptochrome was predicted to interact with the retina facilitating visualisation
of the magnetic field
➢ Three groups – (a) Control – Operation did not disrupt cluster N (b) Operation did disrupt cluster N (c) Birds
eyes covered (i
...
not receiving visual information from magnetic field)
➢ Results (a) Robins well orientated (b) Robins were disorientated (c) Robins were disorientated
➢ Key point – If (b) robins were able to use another sensory system (e
...
sun compass in this study), they were
able to re-orientate navigation
2
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g
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g
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g
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g
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g
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g
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g
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g
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g
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e
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The local ecology/environment – Flat topography → Effectively 2D (e
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desert ants), with the small amount of
3D being filtered out/not recorded (e
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by internal odometer)
2
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g
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g
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g
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g
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g
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e
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g
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e
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g
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e
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Fish were trained to swim in a particular direction (e
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up and left)
During probe trials in which the maze had been rotated to be horizontal, fish were then
tested whether they retained the learnt behaviour
• Results – (Middle) = Mean proportion of correct + incorrect choice during probe trails
- Fish consistently were able to learn horizontal information and extract that independently
from their 3D route?????
Question #4 – Fish are very visual animals
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g
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e
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g
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Physoclist (e
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eels) – Lack connection between gas bladder + alimentary canal → Fast rising not possible
(swim bladder would burst)
2
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g
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e
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e
How do fish represent space when swimming freely?)
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Experimental set up:
(1) Standard Y maze
(2) Adapted Y maze, lacking arms – Allows free movement of fish once
through the initial start box
Cameras fitted within tank to record/reconstruct individual fish 3D
position within space of (1) and (2)
Fish were trained to swim through (1) under constrained conditions (red)
Movements were then tested through (2) under unconstrained
conditions (blue)
Results – Even when free movement was permitted (under 2), fish still
closely followed the trajectory of their trained movement (under 1)
Demonstrates a high accuracy in retracing 3D learnt routes
The deviation between training and test trajectories were analysed to determine what exactly the fish were doing
and how important vertical information was to that
3 further experiments were set up and tested, against the associated null hypotheses
1) Training trajectory with no vertical component – How far does the true 3D test trajectories deviate?
2) Training track with no horizontal component (only vertical movement)
3) Straight ahead vector – How accurate are fish at reproducing the training trajectory learnt?
Results – In all cases, fish’s test trajectory was closer to their training trajectory when 3D information was
involved/considered
➢ Loss of any aspect of 3D information → Loss of accuracy
➢ Demonstrates the importance of vertical information
Subsequent experiments demonstrated fish ability to remember/repeat angle of release accurately
Overall, there was near equal error between horizontal and vertical dimensions
➢ Measured in mm deviation of test trajectory from training trajectory
➢ Demonstrates that, despite being achieved separately by different mechanisms, horizontal and vertical
movement are completed with equal accuracy in 3D space
This is widely accepted that this is achieved by fusing two pieces of information into one coherent navigation
strategy, BUT it is not known at which point this is achieved
(1) Possibly taking place in the brain
(2) Possibly sensor fusion = Combination of hydrostatic pressure (vertical) information with horizontal information

Conclusions
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Rats (2df translational, but 3df overall including yaw
High horizontal resolution and prefer horizontal movement
• Fish (3df translational, but 6df overall with added rotation)
- Accurately encode 3D spatial information
- Use horizontal + vertical information equally when navigating freely – Similar error in accuracy
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Sexual selection 1 – Polyandry: Why do females mate with multiple males?
Key point – Utilise material/examples from research discussed in lectures
History of polyandry
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Minimal research until 1970s – Now researched extensively
Good review – Pizzari and Wedell (2013)
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Phil trans
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Why was polyandry a contentious issue? – Victorian attitudes, Bateman curves, anisogamy
2
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Is polyandry adaptive for females? – Forced copulations, coevolution, multiple mates/matings
4
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What are the consequence of polyandry for individuals and populations?
Changes from ‘old school’ sexual selection attitudes

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Attitudes have changed over time – Victorian → Bateman curves → Anisogamy
Victorian attitudes (e
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Darwin predicting males of all mammals eagerly pursue all females, whilst females are more
picky) unravelled as not being entirely true
Bateman principle (1948) – Remains influential, but re-analysis in subsequent
years predicts curves are not as steep/flat
Bateman curves – Consequences of differing number of mates for males on
females on fertility
Predicts male fertility was dependent on how many offspring they produced
BUT females couldn’t increase fertility any more by mating with 2+ males
Anisogamy = Sexual reproduction involving fusion of gametes
Males and females invest differently to mating
Eggs often (not always e
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Drosophila 6cm sperm) bigger than sperm →
Females investing more per gamete – Asymmetrical costs for M + F?
Not necessarily – Other male costs must be considered (e
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seminal fluid
production, search time, courtship displays, STDs, increased predation risk)
On the whole, males and females often face similar costs of mating (in different ways)
Post-1980s
Geoff Parker – Studied dung fly mating → Suggested polyandry is ubiquitous in insects and causes sperm
competition leading up to, during and after mating
Bill Eberhand – Polyandry might be beneficial to females, allowing cryptic choice of which male to father offspring
(i
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which sperm to use
Advances in understanding since the 1970s as a result of Molecular Parentage Analysis

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Previously unfeasible to accurately predict an individuals’ mating pattern (e
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required
24/7 surveillance)
Previous predictions consequently vastly underestimated extent of polyandry (e
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on
10% of bird species)
Molecular parentage analysis allows inferences to be made about an individual’s
mating patterns using paternity analysis
Based on analysis of microsatellites profiles
Microsatellites = Short repeated DNA sections – One copy inherited from each parent
Moderate mutation rate – High enough for variation to exist between individuals but
low enough for alleles to be easily identified
Different peaks → Different gene loci
Allows for parents and offspring to be genetically linked
DNA samples taken from (1) Female/mother (2) Offspring (3) Potential male partners
Determines how often the female mated (and to which father) in producing offspring
E
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Allele 276 is inherited from mother and allele 298 is inherited from father

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This is conducted across multiple loci to reliably detect the offspring father(s) / Identify how many fathers were
involved in producing a clutch of offspring
• BUT doesn’t necessarily predict how many times a female has mated
- Processes are often in place to allow females to mate with more males than those that father their offspring
How often do females mate? – Gryllus bimaculatus field cricket case study (Bretman & Tregnaza, 2005)
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Female field crickets have a spermatheca – Sperm storage organ
Mated crickets can be collected in the field and sampled to genotype (1) stored sperm (2) offspring
½ were kept and left to lay eggs to genotype offspring (nymphs)
½ were preserved and dissected to genotype stored sperm
Results
On average, 2 males represent a clutch of nymphs
On average, 3
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e
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e
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Male seed beetles provide nuptial feeding (of water) to females → Survive/reproduce for longer
2
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Male water striders and ducks can be very determined in mating → Submitting to reproduce with multiple
males may be less damaging/harmful than resisting and result in reduced harassment
4
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Males of many species offer different extents of parental care to offspring
BUT many of these direct benefits could arguably be gained by mating multiply to a single male
Indirect benefits of polyandry – Genetic quality of offspring indirectly increases female fitness
1
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g
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Results in increased variation amongst offspring
E
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Polygamous pygmy grasshoppers have different colour polymorphisms adapted to different environments →
Increased collective ability to avoid predators
3
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g
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g
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campestris and (2) G
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e
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pseudoobscura carry a selfish genetic element (SR) on their X chromosome
Males carrying SR only produce X-bearing sperm because SR kills Y-bearing sperm → Only female offspring
produced
Reduces female fitness directly (receives fewer sperm) and indirectly (only produces daughters – when sons are
consequently more valuable in this sex-biased population)
Under laboratory and field conditions, there is a mechanism in place resulting in female flies in lines with SR being
more likely to remate than in lines without SR – I
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SR → Increased polyandry
By mating multiply, females can avoid having offspring with SR males even if they accidently mate with them
This is achieved by setting up sperm competition – SR males are poor sperm competitors
Males without SR gain more paternity + father more offspring
Lines with SR under monogamous conditions → Increasingly female biased → Eventually go extinct after several
generations due to loss of males in the population

Summary
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Polyandry is widespread and we now have the tools to measure it in the wild
There are many adaptive explanations for polyandry – (1) Direct (2) Indirect benefits
- Some explanations are supported by good evidence BUT there is likely not one general evolutionary driver of
polyandry
• Whether or not adaptive, polyandry has many individual, population and species level ecological and evolutionary
consequences
- Should the real question be, why are so many species monandrous?
Consequences of polyandry
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Lecture 2 + 3
Sperm competition + cryptic female choice
Sexual conflict – Decoupling of male and female interests
Relatedness, effective population size, gene flow
Speciation

Cited journal articles
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Bretman and Tregenza, 2005, Mol Eco, 14, 2169-2179 …/… Bretman et al
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2015, Nature, 522, 470 …/… Price et al
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What kind of traits have evolved under the selection pressure of sperm competition?
- Sperm morphology/number (huge variation between species), testis size, genital plugs, sperm displacement
mechanisms
2
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Response to varying levels of competition
Traits evolved under selection pressure of sperm competition

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1
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Removal or displacement of sperm (already deposited in the female)
Achieved with specialised genitalia that can ‘scrape’ out previous male’s
sperm (e
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spiny penis in damselflies)
3
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g
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g
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e
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e
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e
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Favoured role
Perhaps the 1st mated male has a greater chance of ‘winning’ than the 2nd or 3rd etc
2
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Female role

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Female characteristics might affect the outcome of sperm competition and influence rate of polyandry
(1) Dumping sperm (2) prioritised storage in spermatheca (3) Spermicidal reproductive tract (4) Aggression
Might factor into the Evolutionary Stable Strategy (ESS) for particular mating systems
NB – Sometimes male driven (e
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ducks)
Response to varying levels of competition

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Two properties that influence an individual male’s response in investing in reproduction
1
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g
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Intensity = Average number of ejaculates (/individuals) in competition
Isolated (i
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no competed males) → 0 expenditure
Expenditure peaks when in competition with one other male
3+ competing males (i
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increasing intensity) → Individual return on investment
decreases with each additional male → Reduced effort
Theoretical curves developed by Parker and tested in recent years

Phenotypic plasticity
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Phenotypic plasticity = A genotype can produce multiple phenotypes dependent on
the environment
- Considered an adapted strategy IF the species is adapted to particular environment
• The sexual environment is dynamic in the natural world – Local sex ratios can vary quite rapidly
- If males are able to assess changes in the environment and predict future levels of sperm competition, they can
adjust their investment (e
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pre/during/post mating behaviour, developmental tissue investment) accordingly
- Many examples in the natural world of males expressing plastic traits in relation to reproductive investment
Developmental responses to threats of competition – Field crickets (and D
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g
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e
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Premating
- (1) Increased guarding of females (2) Changing courtship effort – E
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Singing (3) Aggression towards other males
2
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After mating
- (1) Guarding mated females to prevent remating (2) Produce/invest more into mating plugs
• Reviews on (1) Strategic ejaculation – Wedell, et al 2002 (2) Behavioural plasticity – Bretman et al 2011
Pre-mating responses to threats of competition – Guarding in Soapberry bugs in the USA
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Populations exist in (1) Oklahoma and (2) Florida
In (1) → Males + females overwinter differently → Variation in sex ratio – Increased male density in winter
In (2) → Males + females overwinter the same → Stable year round sex ratio
Lab-based study
(1) males increased mate guarding behaviour under male bias conditions
(2) males did not alter guarding under male bias conditions
Findings demonstrate
The ability of soapberry bugs to utilise cues from the environment and respond with plasticity to behaviour
An underlying genetic basis drives this – (2) populations did not respond similarly

Effects of competition on mating in D
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e
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g
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g
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melanogaster?
Results – Indicate males exposed to competition do transfer more sex peptide
How does sperm production/transfer differ under competition in D
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melanogaster – Only able to produce one type of sperm (fertilising)
Conclusions – An ejaculate response often accompanies a behavioural response (e
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increased mating duration)
Both responses are costly to the male and should only be invested in if long term competition is anticipated

Is there evidence in a trade-off in resources when responding to competition?
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Males must invest limited resources wisely into various factors enhancing reproductive fitness (e
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ACP production)
A plastic response should therefore theoretically have (1) associated benefits AND (2) associated costs
• Experiments have also studied the associated costs of reproduction on males
1
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Mating success compared between males (1) isolated for entire lifespan (2) exposed to a rival for entire
lifespan
- Results – (1) Invested less effort into each mating → Lived/reproduced longer
– (2) Invested more effort into each mating → Aged faster + died younger
– Similar overall offspring production – Demonstrates trade-off in resources
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How do males assess competition?
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Varies between species – Extensive evidence of:
Smell (cuticular hydrocarbons) – E
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Voles, newts, mealworms, beetles
Song – E
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Field crickets
Combination of cues – E
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D
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melanogaster
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Studies have been conducted on the impact of sensory input on observed fitness output/behavioural change
Involve combination of (1) genetic (2) physical manipulation to remove male’s ability to detect sensory cues from
other males
Removal of song → (1) Preventing rival producing song by removing wings (2) Using mutants that couldn’t hear
Removal of smell → (1) Stimulate presence of a rival using cuticular hydrocarbons (2) Use of mutant lacking smelldetection odorant binding protein (3) Removal of 3rd antennal segment
Removal of vision → (1) Kept in darkness (2) Using mutants with vision defects
Removal of touch → (1) Separating males by nets
Individual/independent removal of cues → Males still able to respond – Suggests uses of multiple cues
To determine importance of each dependent cue, cues were taken away in pairs
I
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Exposure to smell and hearing but not touch and vision, etc
Results
Control (unmanipulated) males exposed to all cues AND any paired manipulation involving vision → Males still
able to respond – Suggests vision is unimportant
All other combinations → Males unable to respond significantly to presence of a rival male – Suggests males use
complex interactive touch, smell, and hearing cues to assess competition in their environment

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Studies currently underway to determine how particular gene expression is driving these processes
Involves comparison of mRNA of (1) isolated males (2) males
exposed to rivals for varying amounts of time between:
a
...
ejaculate response (abdomen/testis/accessory glands)
- Results – Gene expression in (a) and (b) was found to be
upregulated in (2) compared to (1) demonstrating
sensitivity to competitive environments – See figure for
changes in (2)
• Individual gene types can be identified and their expression
changes (related to competition over time) resulting in
particular responses can be determined
What is the role of memory in initiating particular responses to
competition threat in D
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g
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melanogaster – Apparent that males can identify if females have previously mated or not
BUT it is not clear what associated behaviour they initiate → Contradicting case studies
• Studies in other species are more conclusive
- E
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Bedbugs utilise traumatic insemination to fertilise females – There is evidence that suggests males can detect
whether females have been previously inseminated by another males sperm, and displace it if so
Summary
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If females mate more than once, males will face sperm competition and must infest finite resources accordingly
The ESS for resource allocation depends on various factors (e
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rate of polyandry, level of competition, sperm
storage, male status)
• Many traits are thought to have evolved under sperm competition
• Level of competition can vary – Males use plastic strategies to cope with this uncertainty
- (1) Juveniles alter investment into reproductive tissues (2) Adults alter behaviour and/or use strategic ejaculation
• Competition can be signalled through presence of rival males, or the mating status of females
• Best studied example to date – D
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e
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Intralocus conflict (might drive sex-biased expression and constrain evolution)
The same gene (or set of genes) is controlling a trait expressed in both sexes
E
...
(1) Zebra finch bill colour and (2) human height
2
...
g
...
melanogaster and (3) Antennal graspers in
water striders

Interlocus conflicts
•

•
-

•
-

-

-

To demonstrate this conflict is happening we must:
1
...
e
...
e
...
Demonstrate that Ms and Fs have different optimal values for the trait (i
...
correlation between trait and fitness
is opposite in either sex)
E
...
Zebra finch bill colour
Males generally have much redder bills → A sexually selected (and costly) trait
Criteria was met
1
...
Negatively phenotypically correlated – Intensity of bill colour determines offspring output (unresolved conflict)
➢ For males, darker bill → Increased offspring output
➢ BUT for females, darker bill → reduced offspring output (costly but not beneficial)
E
...
Human height
Males are generally taller than females → A (somewhat) sexually selected trait
The reproductive output for relatively taller + relatively shorter pairs of siblings was studied
Criteria was met
1
...
Negatively phenotypically correlated
Height determined offspring output
➢ Shorter siblings → Females had more offspring BUT males had less
➢ Taller siblings → Males had more offspring BUT females had less
And conflict remained unresolved
➢ Taller offspring → Sons more reproductively fit
➢ Shorter offspring → Daughters more reproductively fit

•
•
-

Intralocus conflict is also seen in offspring fitness of crickets
Predictions – (1) High quality males → High quality sons but low quality daughters (2) Vice versa
Experimental set up – Reproductive success (i
...
mate attraction + offspring output) of males was measured
Results – In line with predictions
Consequences of intralocus conflict
Constraint to (/slow down) evolution – Trait under ‘tug of war’ → Unable to evolve towards M or F optimum
Evolution will attempt to resolve this through:
➢ Evolution of sex specific gene expression/recruitment of genes to the sex chromosomes → Taken out of conflict
(e
...
Evidence in Drosophila – Rate of gene recruitment to male Y chromosome is 10x higher than gene loss)
➢ Evolution of new sex chromosomes

Interlocus conflicts (might drive co-evolutionary arms race)
•

•
•
•
-

•
-

To demonstrate this conflict is happening we must:
1
...
Find the paired (defensive) trait in the opposite sex
3
...
g
...
melanogaster
Male production/transfer of sex peptide:
1
...
Increases female egg laying rate (increases male + female offspring output)
3
...
e
...
g
...
elegans)
Able to self-fertilise BUT non-self sperm outcompetes self-sperm
Mating increases brood size BUT also reduces lifespan
Interrupting the process of sexually antagonistic co-evolutionary arms race by enforced monogamy
Holland and Rice (1999) tested this concept on D
...
Bean weevils – Correlation demonstrated between spiny-ness of penis (offensive trait) Vs thickness of female
reproductive tract walls (counter-adaptation/defensive trait to prevent internal damage)
2
...
Identify tissue specific expression and compare sequences of these genes across species
2
...
g
...
e
...
e
...
, A
...
Chapman
...
Sexual Conflict
...
400-415 in D
...
Westneat, and C
...
Fox, eds
...
Oxford University Press, Oxford
...
, G
...
Bangham, and L
...

Social learning 1 – Imitation
Possible exam questions
Concept
Methodology

Broad

Specific

Can non-human animals learn by imitation?
How can you test for imitation in non-human animals?

Only examples – Chimps, quails, blackbirds
Probably no specific questions on imitation

Introduction to social learning
•
•
•

Course text available online – Hoppitt & Laland (2013)
Broad topic covering many disciplines – (1) Psychologists (2) Anthropologists (3) Economics (4) A
...
(5) Zoologists
Key focus of lectures – (1) Does social learning occur? (2) How can we test for social learning?
- There are general principles to follow when addressing such questions
• No right or wrong answer in exam – Questions marked on (1) Demonstrating understanding of how to test for social
learning (2) Using evidence to justify an argument
• Be specific in answering the question asked
Key terminology (chapter 1)
1
...
Social transmission – Acquisition of a behavioural trait (T) by one individual (A) exerts a positive causal influence
on the rate at which another individual (B) acquires or performs (T)
3
...
Culture – Group level behaviour patterns shared by members of a community that rely on socially learned and
transmitted information
5
...
g
...
g
...
g
...
1)
•
•
•

Continuum of methodologies used to study social learning (figure)
‘Traditional’ laboratory studies – (1) High reliability/control (2) low validity
Observations in natural environment – (1) Low reliability/control (2) high validity
- E
...
Humpback whales and lobtail feeding
- E
...
Bottlenose dolphins and shells
- E
...
Chimpanzees and water collection techniques
• In between – Mid-range (1) reliability/control and (2) validity

-

Transmission chains, field experiments (in captivity or natural habitat if studied easily), open diffusions

Traditional experiment – Demonstrator-observer paradigm
•

•
•
-

Detects whether an individual has the capacity for social learning under unnatural conditions BUT doesn’t provide
information about the applicability of social learning in their natural environment (e
...
unknown ability to witness
under natural conditions?)
Hypothetical example – Lever pushing rats
Train a caged rat to press a lever to receive a reward (demonstrator)
Place an observer rat in a cage (1) next to the caged demonstrator
and (2) next to an empty cage with a lever (control)
After a period of time, place (1) and (2) in a cage with a lever – Tests whether the
observer rat witnessing the demonstrator’s behaviour learns the behaviour faster (/more likely) than the control
Practical example – Treadle pressing quails (2 action test)
Train a caged quail to press a treadle to release food (demonstrators)
2 sets of demonstrators – (1) steps on treadle (2) pecks at treadle
Place an observer quail in a cage next to (1) the demonstrator’s chamber (2) an
empty chamber with a treadle
After a period of time, place (1) and (2) in a cage with a treadle
Results – Step observers more likely to step, peck observers more likely to peck

Traditional experiment – Multiple demonstrators
•

Traditional demonstrator-observer paradigm can be expanded and modified
E
...
Differing the combination of (1) Demonstrators (2) Observers in the system
• This may influence learning rate
- E
...
Guppies separated from food by a wall with (a) red hole (b) green hole
- One demonstrator → No difference in choice of (a) or (b)
- Increasing number of demonstrators → Difference in choice of (a) or (b) based on
demonstrator preference
- Evidence of behaviour being transmitted, learned and repeated
• Other studies have looked at the impacts of other factors – E
...
Prestige
-

Linear transmission chain (chapter 3
...
1
...
g
...
2
...
2)
•
•
-

Is a learnt behaviour retained in a population experiencing
gradual turnover? – More representative of natural environment
I
...
Loss of informed individuals, gain of uninformed individuals
E
...
Diet preference in rats (Galef & Allen, 1995)
Two populations of 4 demonstrator rats were trained to eat different diets flavoured
with (1) Cayenne pepper – Circles (2) Japanese horse radish – Squares
A replacement chain was then initiated – Each day, one individual would be taken
out and another put in → After 4 days, no ‘original’ demonstrators present
Results – Preference remained statistically significant for 14 days

Open diffusion (chapter 3
...
2)
•
•

Populations of animals free to interact naturally – Studied in (1) the wild (2) captivity
E
...
Captive chimpanzee populations and pan pipes (Whiten et al, 2005)
- 2 separate groups provisioned with a foraging task that can be solved in 2 different
(but arbitrary) ways, both resulting in release of food –
(1) Poking (2) Lifting with a stick
- One demonstrator from each group is taught how to perform (1) / (2)
- Results – Technique preference of observers was found to correlate to
the choice of the group’s respective demonstrator when studied after
10 days and 2 months – Stable tradition

General scientific process of answering questions
1
...
g
...
Identify what patterns are consistent with the hypothesised process
3
...
e
...
Design a procedure of collecting data that allows the target process to be
distinguished from any alternatives
5
...
Develop and apply these techniques to test social transmission in natural animal populations and assess
whether the target process is operating
IMITATION (Chapter 2
...
Social facilitation (chapter 4
...
5)
The mere presence of a (conspecific) demonstrator affects the observer’s behaviour (e
...
increased activity levels)
in a way that increases its probability of finding/pressing the lever randomly, thereby accidently discovering the
yielded food reward → Repeat behaviour
2
...
1
...
g
...
Local enhancement (chapter 4
...
2) – A debatably separate sub-set of (2) → Can lead onto further learning
After or during a demonstrators presence, or interaction with objects (e
...
lever) at a particular location, an
observer is more likely to visit or interact with objects at that location, thereby investigating the area surrounding
the lever and accidently pressing it to discover the yielded food reward → Repeat behaviour
4
...
1
...
g
...
g
...
Response facilitation (chapter 4
...
4)
Presence of the demonstrator performing an act (e
...
paw pushing action) increases the probability of the
observer repeating the same act (in any context), without any association made between the act and the
lever/food reward – When in the test phase, the observer is more likely to perform that act on the lever to release
food, thereby learning the association → Repeat behaviour
6
...
1
...
g
...
g
...
1
...
1
...
1)
•

Directly through observing a demonstrator perform an action in a specific context, an observer becomes more likely
to perform that action in the same context
- I
...
Animal is learning to perform a familiar action in a novel context
• Focus of lecture
Production imitation – Overcomes the problem of ‘no single action component is novel’ (chapter 4
...
6
...
e
...
g
...
e
...
g
...
2
...
4 + 2
...
1)
•
•
•
-

More difficult to define than imitation – Different researchers differ in opinion as to whether it should:
Require teaching and imitation – Very difficult to pinpoint
Require human specific traits – Rules out animal culture entirely
Maintain a broad definition – Best opinion for understanding animal culture in relation to human culture
Culture = Group typical behaviour patterns spread through members of a community by social transmission (p4)
Essential properties
(1) Socially transmitted information/behaviour (2) Group typical behaviour patterns

Do chimpanzees have culture? (chapter 6
...
g
...
Genetic differences between groups
2
...
g
...
g
...
2
...
g
...
2
...
g
...
Basic method of exclusion – Simple, but untrustworthy
2
...
2
...
2
...
e
...
g
...
2
...
2
...
2
...
3)
•
•

Analysing every mechanism of genetic inheritance for plausible influence is not often possible
Model fitting approach – An alternative to this, in which there is some measure of genetic, ecological, social and
behavioural similarity (or dissimilarity in example below) between individuals, which can be analysed to distinguish
significance in driving the behaviour

•
-

-

-

-

Best approach available to review static repertoires
E
...
Measure of social similarity → a social network (i
...
how often individuals interact) – Proposed by Whitehead
(2009) but previously utilised in other studies
Madden et al (2004) implemented a model fitting approach in researching spotted bowerbirds (chapter 6
...
2)
Male birds create bowers = Stage area of mating display to attract females
The type of material used to create bowers differed geographically – Possibly a
result of culture? – Do males create their bowers based on those of other
successful males?
This was determined by measuring and quantifying:
1
...
Ecological dissimilarity – Building materials e
...
flowers
3
...
Social dissimilarity – Geographical distance between individuals (less distance → more likely to learn)
Results
➢ No relationship between ecological and behavioural dissimilarity
➢ Persistent relationship between social dissimilarity and behavioural similarity, even when genetic dissimiarlity
was accounted for – Strong evidence for social transmission
➢ Weak evidence for genetic dissimilarity when social dissimilarity was controlled
Conclusions
➢ Similarity in bower composition are products of local tradition either (1) culturally transmitted by neighbouring
males who regularly inspect neighbours’ bowers (social learning) OR (2) as a localised response to variable
individual female preferences (an ecological factor that could not be ruled out)
➢ 2nd conclusion emphasises difficulty in ruling out every ecological aspect when attempting to detect culture

Repertoire based methods Vs diffusion data
•

Ruling out every possible ecological explanation is often very difficult using repertoire based methods
- Where the repertoires of individuals in different locations are analysed in a static snapshot and asking whether
that pattern suggests social learning is driving the behaviour, rather than genetics or local ecology
- There are clearly problems in getting definite answers from that data
• These problems may be resolved using diffusion data
- Involves collecting data on the spread of a novel behaviour through a population of animals, then determining
whether the pattern shown could be driven by social transmission
Methods of analysing diffusion data
•

-

-

•
•

1
...
0 = All individuals have learnt the behaviour)
(a) Asocial learning is responsible for spread of a behaviour
r shaped diffusion curve – Individuals acquire behaviour at a
constant rate BUT as more become informed, fewer are learning
(b) Social transmission responsible for spread of a behaviour
s shaped diffusion curve – When few individuals know the
behaviour, there are few individuals to learn from (low % informed) BUT as the number of potential individuals to
learn from increases, there is an accelerated rate of learning
BUT this isn’t as clear-cut when the population is non-homologous
Social learning can result in r curves
Asocial learning can result in s curves
2
...
g
...
e
...
8, what is the probability of getting the order
observed in the real data?
Once the function that provides the likelihood for a given value of ‘s’ is
determined, the MLE can be calculated – Equates to the value of ‘s’ that
miminises the negative log-likelihood (y axis on bottom graph)
In this hypothetical example, ‘s’ = 1
These experimental results can be fitted to a model in which (1) Social
transmission is occurring (2) Asocial transmission is occurring (i
...
in this
example, ‘s’ = 0)
It can then be determined which model fits the data better, in order to
estimate the importance of social transmission in a behaviour (e
...
lobtail
feeding) spreading through a population
The evidence was highly in favour of social transmission occurring
For every unit of connection to an informed lobtailer, an uninformed
observer was 31x faster at learning this behaviour than by asocial learning alone

Applying NBDA to chimpanzee culture (Whiten et al, 1999; Hannien, 2013)
•

The same principles were applied through video surveillance of a particular population of chimpanzees (Sonso)

•

•
•

•

•
•
-

Discovery of mineral rich water holes in trees within their habitat triggered the innovation of 2 novel watercollection techniques that appeared to spread through the population within days, branching from the historic
behaviour of using leaf sponges to collect water
1
...
Using moss sponges, instead of leaves
Hobaiter et al (2014) generated re-use and moss variant
maps to illustrate the order of spread of (1) + (2)
(2) showed a pattern following a social network more
closely than (1)
Time-structured data was also compiled to demonstrate
observer acquisition of behaviour following observation
of a demonstrator
5 NBDA social transmission models were generated to
take into account this time-structured data
1
...
Same social transmission effort – (1) and (2) passed on by ST to the
same degree
3
...
ST of moss sponging only
5
...
g
...
g
...
g
...
(2013) Science 340: 485-488 / Hobaiter et al
...
(2010) J
...
Biol
...
N
...
(2006) The animal cultures debate
...
et al
...
N
...
(2007) Trends in Ecology and Evolution, 22: 7

Social learning 3 – Teaching
Possible exam questions
Broad
Do non-human animals teach others of the same spp?
Concept
Methodology How can you test for teaching in non-human animals?

Specific
Likely not a specific animal example
How can Caro and Hauser’s criteria be used to detect
teaching?

Step 1–4 (chapter 4
...
Cognitive perspective – More difficult
Tutors actively gage the intelligence of their pupils and alter teaching accordingly
2
...
e
...
g
...
4 –p153)
•

3 criteria that must be met to distinguish the target process and rule out inadvertent learning
1
...
Tutor must pay a cost or at least gain no immediate benefit as a result of the behavioural modification
3
...
2
...
g
...
g
...
Tutor does modify behaviour to pupil
Probability of being fed an intact scorpion increases with pup age
Doesn’t require sophisticated cognition – Helpers simply associate age of pup call with type of prey provisioned
2
...
Pupil does acquire skill/knowledge more effectively/faster
Experiment set up involving provisioning 3 groups of pups for 3 days with (1) 4 dead scorpions (2) 4 live, stingless
scorpions (3) Hard-boiled egg (control) – Tested on day 4
Results – (1) 4/6 success rate (2) 6/6 success rate (3) 2/6 success rate

Tandem running in ants – Primitive alternative to pheromone trails (Franks & Richardson, 2006)

•

Ant finds a food source → Returns to nest → Guides another ant to that food source, maintaining contact on the
journey
1
...
Costly to tutor – Takes longer to reach food source than travelling independently
3
...
g
...
g
...
Tutor modifies behaviour – Purr call only emitted with young and in particular circumstances
2
...
Pupil acquires skill/knowledge – Nestlings conditions to purr call, associating it with food

Summary of teaching
•
•

Teaching is likely a common phenomenon BUT it is often difficult to collect data to establish strong evidence
Other examples of teaching from referenced paper – Table below (NB – 4th column related to loophole)

Key reading
•
•

Sections of the book – 5
...
2 (don’t worry about technical details, just underlying logic), 4
...
2
...
(2008) Lessons in Animal Teaching
...
Whether animals can imitate AND developed a procedure of testing for that
2
...
Whether animals are capable of teaching others of the same species in a functional sense



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