bystander effects

Bystander effects

• Ok, lots of support for winner and loser effects• How about bystanders?• What affect does seeing another win or lose

have on YOUR chances of winning or losing?• What does watching give you?

Swordtail fish

• If you see an aggressive encounter, you can learn valuable information for the future.

• Test for these effects with control where bystander could not see outcome of combat

• Treatment where bystander could see but combatants couldn’t

What happens when you now pit bystander against winner or loser?

Outcomes

• Where bystander could see outcome, tended to avoid contest with winner more than bystander that could not see contest.

• AND not escalate as often,

Outcomes

• Bystanders that saw outcomes and those that did not, treated losers about the same way.

• But length of aggressive encounter made a difference.

• Initiated more against losers that left contest quickly.

What does this mean?

• Bystander can use information to its advantage.

• Judges fighting skills of both combatants based on not only on who wins or loses but how escalated the fight becomes.

• Future aggressive actions then affected by this information.

Audience Effects

• Here we are looking at how onlookers affect the outcome of the conflict.

• Chimpanzees: Aggressor screams and victim screams.

• In mild encounters, victims don’t scream any longer with or without audience

• In severe encounters, victims scream longer and louder with an audience.

Outcome

• Who is in the audience makes a difference!• If there was an equal or higher ranking

individual to the aggressor, was present.Why?intervenes and breaks up fight.

Summary

• In this case combatants seem aware of who is in the audience and adjust their behavior accordingly.

• Area rich in research possibilities to see not just how they may adjust behavior but how audience might alter outcome.

• Would you fight harder depending on who is watching??

Aggression summary

• Aggression behavior is over resources• Is linked with testosterone and various other

hormones.• Can be modeled with game theory where

outcome depends on value of the resource and the costs associated with trying to get that resource.

• Outcomes often decided on physical advantage but also depends on how each combatant values the resource.

Aggression summary

• Can result in an “ordering” of society but not a peaceful one.

“Pure behavior”

• Before we move on to behavioral ecology, a few other behavioral categories to cover.

• First of these is disease and animal behavior. (Chap 16).

• As we will see with other “threats” to health and life, many animals have developed behaviors aimed at reducing their chances of catching diseases.

• Here we will look at a few of them.

Avoidance of disease

• Avoidance of habitats -Tree frogs: were able to determine presence

of snails (intermediate host of trematode parasite) and avoid laying eggs in these ponds.

Avoidance of individuals

• Bullfrogs: In tadpole stage, evidence that uninfected individuals preferred to associate with other uninfected ones, avoided inflected individuals.

• How did they tell?• Seems chemical cues were used.• Others? Often see avoidance of “unhealthy”

individuals. Part of the sexual test is a health check!

Self - medication

• Seems we are not the only ones who like to self medicate!

• Two broad categories• 1) Preventative• 2) Therapeutic

Preventative medicine

• Many species use potentially anti-bacterial plant substances in their nests.

- Starlings add fresh herbs – led to higher body weight of fledglings.

- Many primate species eat clay, dirt, and rocks to reduce indigestion, as an antidiarrheal agent, absorb dangerous plant compounds

Preventive medicine

• “Anting” by birds and mammals: rubbing crushed ants on feathers and fur. Formic acid aids against tick infections

• “Fur rubbing”: many primates rub fruits, leaves, and vines on their fur, which have antimicrobial effects.

Therapeutic self-medication

• Use of leaves by Chimpanzees against tapeworms.

• Other primate do the same.- Dogs and cats eating grass.

Summary

• Growing evidence that many species self medicate,

• Obvious evolutionary advantage to individuals who “discover” the use of these medicines.

• Often with similar substances we commonly use today. In fact, starting to try and identify others that are being used that we might be able to use!

Next: Personalities!

• Used to consider people who thought animals had “personalities” were them selves “personalities”!!!

• But more and more research is demonstrating that indeed there are individual differences in behaviors or personalities.

• Not surprising in that we have been talking about natural variation in most behaviors.

How do personalities differ?

• One common way is Boldness vs Shyness• Boldness: tendency to take risk in familiar and

unfamiliar situations• Shyness: reluctance to take such risks or

reluctance to engage in unfamiliar activities at all.

Why would we find both?

• IF we think of evolution as the survival of the fittest, often hard to see why we would have a range of any trait.

• IF we consider survival of the adequate, then in some cases being shy has advantages and some cases being bold.

Evidence for boldness and shyness

• Do we really find these personality differences?

• Pumpkinseed sunfish: • Trapped vs seined• Trapped bolder willing to investigate

Were they?

• Trapped adjusted more quickly

Guppies

• Boldness and predator inspection:• Found there were consistent differences• Always bold• Always shy• Bold are colorful

Why be bold?

• It seems to impress the females!

Is she really??

• Will mate with bold males regardless of color

Other than boldness and shyness?

• What other traits vary regarding personalities?• Gosling (1998) found five aggregate traits in Hyenas:• 1) assertiveness• 2) excitability• 3) Human-directed agreeableness• 4) sociability• 5) curiosity

Octopus??

• Turns out they have personalities!• 1) Active vs inactive• 2) anxious vs calm• 3) bold vs inhibited.

Ruffs

• Personalities related to physical differences.• “independent” males vs “Satellite” males• Dark and larger vs light and smaller• Independent set up territories.• Satellites needed to attract females.

Last: Coping styles

• Related to bold and shy but relative to how they respond to stress in the environment.

• Proactive vs reactive• Proactive: likely to remove negative stimuli

from their environment• Reactive; more likely to hide from new

negative stimuli

Lab rats

• Can breed for proactive vs reactive• Proactive more likely to show aggression

toward intruder, reactive will hide• Proactive rats will try to remove or neutralize

a negative stimulus, reactive ones will just avoid the area where the stimulus is.

Summary

• Good evidence that personality differences exist: boldness/shyness most studied

Fear• Recognize it in humans• TV, Movies, Books, etc. play upon our fears!• We love to be scared!!

• But what about other animals?• Often reluctant to recognize it: too

anthropocentric!

Fear• Talked about aggression

as a behavior

• Widely accepted as a behavior of animals, no anthropocentric overtones.

But why does aggressive behavior work?

• Needs reciprocal reaction or behavior!• Call it submissive behavior

• But it is FEAR!

Intraspecific conflicts

• Why does one win and another lose?• What makes the one back down? …..Fear

If not…. fight to the death!

Imagine if someone was trying to kill you!

• Would we call it submissive behavior?

What is it?

• No other way to describe it except… Fear!

One of the most prevalent behaviors

• Considering what we have talked about regarding aggression and what we will talk about regarding predation…

• Fear is probably THE one most likely behavior an organism will experience!

• Also, as you will see, is probably the most influential behavioral force in ecology

So fear exists

• Many felt it was too anthropocentric to ascribe fear to animals:

• Talked about “escape” and “avoidance behaviors”

• But these are the behaviors that are produced by fear.

Today?

• More acceptable to talk about fear in animals• Still not mainstream• No mention of it in most behavioral texts.• Yet whole chapters devoted to aggression!• So lets look at fear as a behavior

Definitions

• Two important concepts regarding fear (from psychology)

• 1) motivation

• 2) personality

Motivation

• Fear and anxiety: emotional states that are induced by the perception of any actual danger (fear state) or potential danger (anxiety state) and which are characterized as a feeling of insecurity

Personality

• Fearfulness: personality or temperament trait defining the general susceptibility of an individual to react to potentially threatening situations. (Just how fearful or anxious you will be)

Five basic questions

• Survival function “What good is it”• Immediate stimuli “what causes it”• Development “How does it develop”• Phylogeny “How does it change”• Ecological function “How does it affect others”

Evolutionary advantage?

• Fear definitely has survival value to wild animals!

• Most important threats of injury and death individual encounters are from predators and competing/attacking conspecifics.

• Defensive reactions increase the chances of survival.

• If you don’t fear your predators, your dead!!

What causes fear response?

• Classic is there is a stimulus associated with behavior

• What is nature of frightening stimuli?• Gray in 1979 classified fear-producing stimuli

into 5 subdividsion

Subdivisions of fear stimuli

• 1) dangers related to evolutionary history• 2) dangers related to novelty• 3) stimuli you learn are related to danger• 4) Intensity of the stimuli• 5) stimuli arising from interactions with

conspecifics.

1. Evolutionary history

• “Innate” fear responses• Usually specific stimuli that are related to

ecology of species, many cross species boundaries

• Physical dangers: fear of heights, fear of darkness, fear of dead things.

• Fear of predators: silhouettes of hawks illicit responses in nestlings

2. Novelty

• Apart from established innate fear stimuli• Exposing animals to a novel object has been

found to be most potent stimulus leading to negative emotional response.

• Behavioral reaction similar to that induced by negative stimuli such as electric footshocks!

• Animals are inherently afraid of NEW things!

3. Learning

• Obvious learning would be a part of developing the fear process

• Identifies new sources of danger (if you live to tell about it!).

• Yellowstone elk and wolves• Identifies new SITUATIONS of danger,

important in ecological aspects of fear.

4. Physical characteristics of stimuli

• Intensity, movement, duration, proximity, etc.• All can become associated with fear response• A flying hawk will illicit a response while a

perched one will not.• Distance the predator is: prey know “safety

range”, e.g. animals in Serengeti• Behavior of predator: prey can detect if

predator is serious.

5. Interactions with conspecifics

• Can be combinations of previous• Here conspecific is the “predator”• Novelty: new animal may provoke fighting

response.• Learning what are the dangers from others• Lack of social contact: afraid to be alone!

Ok your scared!

• What do you do now?• Adaptive response to danger: two

complementary pathways.• 1) Neuroendocrin adjustments to maintain

homeostasis.• 2) psychobehavioral changes to neutralize

effect of stimulus

First the neuroendocrine aspects

• Pure neurological responses obvious: Fight or flight reactions are direct responses of muscles to nervous responses.

• However, what produces this nervous response is at the root of how danger leads to fear leads to the response.

• As we saw earlier, interaction between neural and endocrine systems plays a big role in many behaviors.

What is going on when you get scared?

• Needless to say complex and would be more appropriate for course in neuroendocrenology

• Object here is to indicate major players and some insight as to what they do.

• Two major complexes known to be sensitive to “environmental challenges”

Anatomy of fear

• Sympathetic Adrenal Medullar system• Hypothalamo-Pituitary-Adrenal Axis• These are the structures/areas of nervous

system.• What do they do?

What happens when you get scared?

• Back in 1935, noted that emotional reactions such as fear and rage threaten the integrity (homeostasis) of the body

• In response, body attempts to maintain internal environment.

• In BRIEF, Fear stimulus causes release of adrenal medullary catecholamines and the ACTH (Adrenocorticotrophic hormone) to Glucocorticoids route we saw earlier

Familiar ground

• Saw earlier that these secretions help organism to react behaviorally rapidly.

• Inhibit glucose uptake and fatty acid storage• Stimulate release of glucose, amino acids,

fatty acids• Shunt blood flow from nonessential body

areas.• All aimed at enabling muscles to react rapidly

Response is graduated!

• Fine and good but fear response is not an “all or nothing” reaction.

• What factors control the extent of the response to fear?

• Why are we more scared sometimes??• How do we control our fear??

Counter balances to fear response

• Sex hormones affect reactions: females respond less to challenges than males

• BUT testosterone injected into female cattle reduces fear reactions.

• Prolactin secretions increase with exposure to challenges and may lower reactivity to challenges.

More?

• Endogenous opioids (endorphins) reduce intensity of response to challenges.

• So not all or nothing but animal does seem to have some control over how much it will react.

• What are factors that help animal modulate this reaction?

Adjusting fear response

• Prior experience: rats place in area where they received shock before, while have greater fear reaction than naïve rats. (likely works other way too)

• Controllability: Degree of control animal can exert over situation will affect degree of response. Perceives danger is under its control, reduces intensity of response

Controllability

• Examples: Availability of familiar environments will lower fear response to novel environment.

• Chewing on nonedible objects seems to help in mice. (fingernails!!??)

• Being able to move in general helps to reduce fear reaction.

Adjusting fear response

• Predictability: ability to predict when challenge will occur helps reduce reaction

• Repeated exposure to novel objects becomes reduced IF it is done on a regular basis

Result is biological response to a challenge is not stereotypic but influenced by psychological factors and behavioral strategies

More?• Negative feedback in the neuroendocrine system:• Glucocorticoids exert negative effect on own

secretions and other fear-activated neural circuits.• So system itself has built in safeguards to excess

reactions!• And can aid animal in controlling fear reaction,

depending on its ability to cope with it, as above.

End effect?

• Fear-producing stimuli and fear-related responses function interactively.

• Result of:• 1) properties of threatening event• 2) possibility of controlling the danger• 3) neuroendocrine state of the individual

here

Variations in Fearfulness

• Have seen that individual can vary its response• Question is does Fearfulness vary across

individuals?• personality or temperament trait defining the

general susceptibility of an individual to react to potentially threatening situations.

• Are some more prone to be scared than others?

Some do scare easier than others!

• Not surprisingly the answer is yes!• Variation in test results support this variation

in response to fear.• In fact, have been able to select for strains of

mice and rats based on their reactivity to fear stimuli

• Basically selecting for the control of the neuroendocrine responses.

How do we measure fear?

• Difficult to measure the emotional state of fear itself.

• Things we have talked about, psychobiological reactions to fear stimuli are only indicators.

• But, give that, how do we measure them?

• Forkman et al. 2007 provides a review of various tests used, primarily on domestic animals.

I am sure you all read it!!

• Don’t want to go into detail on any one method.

• Just provide an overview of how we can go about testing for fear responses.

• 1) Novel arena/object tests: area where subject enters and behavior noted or its reaction to the appearance of a novel object.

• Also called open-field test

• 2) handling tests: Human interactions/handling. Record reaction of animal to various forms of handling from soft to hard.

• 3) Restraint tests/tonic immobility: used in birds, simulate predator and bird goes immobile or “feigns” death. Length of time it does so is used as a gauge of fear.

More?

• Various others, often modifications of previous ones.

• How good are they? • Each has strengths/weaknesses

• One recent one that is used with wild animals is the level of vigilance.

• Usually related to predation risk.

Summary

• Fear exists: strong evolutionary force• Complementary behavior to aggression• Produces many of the outward behaviors we

see: submission, • Neuroendocrine basis• Interactive with the extent and property of

the fear stimulus• Is measurable on a variety of levels

Summary

• Is one of the most prevalent groups of behaviors

• Is important factor in many of the organism-environment interactions….or

• BEHAVIORAL ECOLOGY.• Will run into it again….

Behavioral ecology

• What is it?• Obvious: blending of behavioral and ecological

theory• Why?• Only in the laboratory do animals “behave” in a

vacuum: environment is the medium.• Most behaviors occur in real-life situations• Behaviors often have feedbacks on ecological

processes.

here

Behavioral ecology• So, behavior and ecology cannot be separated.• Eluded to behavioral ecology every time we

talked about how individuals interacted with environment, e.g. nesting habitat and parenting behavior, or with other species, e.g. predator-prey

• Now need to address it fully • In many cases, will be looking at behaviors we

are now familiar with but in relation to ecology

Lets begin!

• Where do we begin??• Basics: behaviors aimed at keeping your

energy machine alive!

• First of these is getting the energy you need: Foraging (Chap 10)

Foraging behavior

• Obvious important set of behaviors!• If you don’t eat, you die!• But…what do you eat?• …and why?• Where do you look for it?• Just a few questions concerning foraging

behavior.• Answers to these shape behaviors we see

What do you eat?

• Actually two basic questions.• One is deciding what food to eat.• The other is determining what a specific food

type looks like.

• Lets look at distinguishing among possible foods first

Search image theory

• One suggested hypothesis on how animals distinguish among food types:

• Animal encounters food type repeatedly, they form a representation (image) of that food type.

• Representation becomes more detailed with experience.

• Animal gets better at finding this food type

What are they keying in on?

• Some debate:• Some say: keying in on one or two attributes of

the food (color, pattern, movement)• Others say: more total image of entire food

item.

• In both cases: learning something relevant (stimulus-response) and helps to be more efficient in finding more.

What do they eat?

• Ok, they can develop skill in identifying specific food types but which one(s) should they choose and why?

• Lots of descriptive studies• In 1960’s developed theory as to making food

choices:• Initially based on the concept of optimization

Optimization

• Idea was that there should be selection pressure for organisms to optimize their energy gain from their foraging efforts.

• Basically the ratio between energy gains and costs.

• Those who did so, ate more, raised more young, etc. …were the fittest.

• From this logic came Optimal foraging theory

Initial works

• 1966: McArthur and Pianka/ Emlen.• Proposed energetics important and costs.• Idea of ranking foods• Idea of optimization in food choice • Basics: as food becomes abundant, you

specialize• There will be a limit to the number of food

types used: cost/benefit of adding new items

Arguments against optimizing

• Optimizing means eventually leading to the BEST way of doing it.

• Kind of like Evolution’s “survival of the fittest”• Should lead to one “optimal” form.• Better is: survival of adequate• And: Adaptive foraging theory.• Semantics? Reflects individual’s constant

adjustment to changing conditions.

Optimal (adaptive) foraging theory

• A theory based on looking at animal decisions (the decision making process then is the initial behavior, the need for food is the stimulus driving the behavior)

• What decisions?• Besides deciding what to eat, OFT also

attempts to explain other foraging decisions.

Basic foraging decisions

• When foraging, animals have to often make decisions:

• What to eat (Which is the best)• Where to eat (food not uniformly distributed)• How long to forage in a certain area• Where do you go next?

What to eat?

• Two levels: what is food providing • Which food provides it better?

Foraging rules: what should we select for?

• Diet selection: what factors to take into consideration?

• Caloric value: obviously, this is the principle gain.

• More calories the better!• Will see later, also other nutrition

considerations, not just all Kcals.

Costs?

• Counter that with costs: how much does it cost you to get that energy?

• May not be as simple as maximum Kcals • Ease of handling: Pecans vs hickory nuts vs

acorns; deer vs cow, • Risk: of being killed… of being injured.• Ease of finding: the best may not be the

easiest to find! (search times)

Search times

• Because looking for a food source costs you, must decide from different “quality” sources (kcal basis) based on relative abundance of each.

• Major area of investigation in food choice part of foraging theory.

• A high energy but low abundance food may actually be less efficient than a lower energy but more abundant one.

But how do you decide?

• The main problem here is when to decide to switch from one food source to another, based on their respective cost/benefit ratios when the benefits are fixed but costs can change.

• When is it cost efficient to switch?

Initial models

• Rules: Forager can’t search for/handle more than one item at a time.

• Fixed number of foraging hours (the clock is ticking)

• Each food item has its own unique set of inherent benefits (currency: kcal) and costs (handling times)

• Search time is a cost and is variable depending on abundance, prey encountered sequentially

Ranking food items

• The third rule allows a ranking of food items from highest to lowest: A >B>C> D etc. on their “inherent” value. This is idea of McArthur and Pianka

• Now need to see what happens when their “relative value” changes with search times.

Results

• Mathematical treatment• Results in a Type II feeding response• Forager can only eat so much!• But more important regarding food type 2

Diet rules

• Basically, should broaden diet when principle prey 1 drops below a certain level.

• Considered “optimal” strategy.

General predictions• Should rank food types relative to profitability• Should always include most profitable prey

and only expand to less profitable when 1st does not meet needs

• Thus decision to switch is based on abundance of most profitable not less profitable

• All or none response: either always accept or never accept them.

Does it hold?

• Great tits: offered differing proportions of high value (large food item) and lower value (small food item).

• Bluegill sunfish: offered three different prey items.

Results: great tits

Results: bluegillshere

Do they hold?

• Works the best for herbivores or predators of sessile prey

• Not so well with predators and mobile prey• Also not so well under predation risk.• Does not include other needs e.g. minerals,

proteins, etc. Not just all Kcal!

Other dietary requirements

• Not just all Kcals• Water intake: animal may alter diet from

“ideal” to eat a lower Kcal but higher water content food.

• Trace minerals: Zinc, etc., animals will again, purposely consume less than ideal to satisfy need.

Salt

• One big one for many herbivores is salt.• Need Sodium for body functions• Many terrestrial plants low in sodium• Some species, like the moose, will supplement

with low Kcal but high salt, aquatic plants.• Some will travel extensively to salt licks,

forgoing foraging opportunities.

Predators?

• Perfect food: body constituents similar to themselves! >90% water!

• Handling time becomes most important• What is involved?• Size: return on investment, too small to deal

with.• Size: chance of injury becomes important.

Predators?

• WHERE you forage becomes important• Habitat mediates risk and success of foraging

in predators, will look at more later

• Illustrates next question regarding foraging:• Where do I eat?

Patch selection

• First we have to remember that the distribution of food resources is not uniform

• Habitat heterogeneity is pretty much accepted.

• So we can talk about habitat or food patches on a landscape scale.

Patch characteristics

Size

Shape

Configuration

Juxtaposition

Patch quality

• All these add to patch quality: ratio between benefits and cost

• Benefits: kcals• Costs: getting to patch, foraging within patch• So one of the major decisions regarding where

to forage is whether patch provides what is needed at a favorable ratio.

Landscape of opportunity

• So, regarding the question of where to eat, we can envision the landscape as offering varying choices, each with their unique ratio of costs and benefits.

• So through the eyes of the forager, we envision a landscape of opportunities.

• Forager makes decisions on where to go.

Now your there, eating happily but..

• How long do you stay???

• Fixed food level: more you eat, less there is left!

• Do you stay until you have eaten it all?• Or do you leave sometime before then &

when?• What is the best strategy?

Cost/benefits

• Benefit of staying: known food source• Cost of staying: diminishing returns/ may be

better patch out there.• Benefit of leaving: finding patch with higher

resource value• Costs: travel costs, may find patch of lower

quality!• What to do, what to do???

Are there leaving rules? (exit strategy)

• Charnov (1976) proposed the marginal value theorem as a possible leaving strategy

• What is it based on?• Again, variation in patch quality over

landscape

Patches of different qualities

2

5

1

3 24

1

3

Average = 3

Enters patch with quality 4: how long should it stay?

#’s = food intake rates, e.g. # 2 means can find and consume 2 items/time

Marginal value theorem

• Should stay until marginal value rate of food intake, equal to average food intake across all patches.

• Enters patch with #4 rate but as consumes, rate drops: 3.8,3.6,…etc.

• Eventually reaches 3.0• Then it should leave:

Why??

• On average, if searches randomly, has a good chance of finding higher value patch.

• Confounding factors:• Travel costs: higher the travel costs, longer

should stay (again cost benefit ratio)• Leads to last question

Where do I go?

• The last of the 4 questions: when I do leave, where do I go next?

• Obviously requires some knowledge of foraging landscape: basic premise in behavior!

• Given that animal has some information on resource levels (time since visit, etc.), which patch should it select?

Travel time

• Obvious: should avoid below average patches• Biggest determining factor is travel time

RELATIVE to patch quality.• IF all possibilities above average but different,

then net gain depends on costs of getting there!

• Should be willing to travel further for a higher quality patch/visit lower quality one if it is close.

Other factors?

• Variance of food quality and where to go next?

• Example: two types, one consistently has a given level of food.

• Other ½ the time may have none or may have twice as much! This is not known at the time.

• Which do you choose?• On average, value is the same.

Risk sensitive foraging

• Risk in the sense your betting (taking a risk) that if you go to the variable source, it will have food. If not, you loose!

• What should you do?

• What would YOU do?

Depends on your hunger state!

• Three possibilities: three outcomes• 1) each item of equal value: In this case, really

no concern if you lose or not, if you lose, you move on.

• So, should show no preference for either patch

2 ) What if your satiated?

• Each has value but each additional one has less. So no advantage to take the chance for a higher reward and should actually prefer the lower but constant food patch.

• Referred to as Risk-averse: not willing to take the risk on an uncertain food source.

3) If your starving?

• Here each additional food item has increasing value: one more further from starvation.

• What to do?• Should select the variable food source!

• Why?

Risk-prone foraging

• Should take the most variable because:• Known consistent food source may not be

enough, you know it is there but is just not enough.

• IF you win, payback is sufficient to “pull you from the brink” of starvation.

Evidence?

• First tested in juncos (Caraco et al. 1980) and found to apply.

• Hungry birds more likely to choose tray with variable but higher # of seeds.

• Since found in variety of species birds, mammals, invertebrates

Group size and foraging behavior

• Ok, Optimization or at least adaptive strategies seem to be taken into consideration

• Apart from the four questions, what other considerations are there?

• First is group foraging• Again, would seem counter productive, having

to share!

here

When to forage in groups

• However, many species do it.• IF we assume foraging is honed by natural

selection, the truism is that in these cases, benefits must outweigh costs!

• But how? • Need to look at factors regarding group

foraging to understand better.

Role of group size?

• Basically, increasing the foraging group increases amount of food each forage receives, to a point!

• Bluegills:

Why?

• More eyes/more efficient capture.

Public information

• Another advantage to group foraging is the sharing of public information

• Basically: gather information about food resources from actions of others in the group.

• Sources of food/quality of food patch, etc.

Predictions

• If this information is being transferred, predict that social foraging individuals should leave poor patches sooner than solitary foragers

• Basically use success of co-foragers to make decisions

• Support: Individual without or with co-feedersLeft poor feeder faster when with others.

More

• If naïve bird paired with one that had total information on cups, left the fastest.

• Evidence that 1) information was transmitted• 2) influenced foraging decisions.

Caching behavior

• One thing, find food patch, eat and leave• Another thing, find food patch, eat, store

“excess”• Reason for behavior: • Pulsed resources: type that can be stored• Harsher, less productive environments.

Food abundance

• Chickadees• Less food more

caching.- More caching less search

time.

Common behavior

• Squirrels, we know about

• Many bird species do it

• Acorn Woodpecker

• Caching behavior is two behaviors: • Idea of “planning ahead” –for the future• Second is remembering where you put it!!• Remembering seems related to volume of

Hippocampal region of the brain: spatial memory.

Evidence

• Data from 6 species of birds

Planning for the future

• The big question: do animals plan for the future?

• When they cache food, is this considered planning for the future?

Criteria for planning

• Two requirements recognized to demonstrate planning for the future

• 1) Must be a novel behavior, not a manifestation of innate action, such as migratory behavior

• 2) must NOT be tied to current motivational state of animal but to an anticipated one in the future

Test for planning

• Western Scrub Jay• Caches• Has great memory: specific events, where the

cache food and who might have watched them do it!

• Do they plan for the future?

The Test!

• Over 6 days exposed to one of two compartments: one contained ground-up pine nuts and the other nothing.

• Fasted night before test• Test was exposure to area with the

compartments but now area had bowl of whole pine nuts (cacheable items).

• Cache sites added to each compartment• What did they do?

The results

• Jays cached more nuts in compartment that had been consistently empty before.

• Suggested they were planning ahead for when those compartments would be empty as before.

• So evidence that caching behavior does involve planning ahead.

Return to foraging strategies

• The four basic questions:• What to eat• Where to eat• How long to eat• Where to go• All these ideas developed regarding caloric

value of the food (the common currency) also food being plants (herbivores) or prey being sessile (predators).

How about predators?

• But for a large percent of the predators, prey are mobile. How does this change things?

• First lets look at the predator

• How does an actively mobile prey affect the foraging strategy of the predator?

A predator and its landscape

• Predator also has to look for food –found in “resource patches”

• However, unlike herbivores, food moves AND does not like to be eaten!

• So, as we saw earlier, need to incorporate not just abundance or availability of prey but their catchability.

• This varies across habitat types!!

Need to talk about lethality

• So unlike prey where how much you eat depends on how fast you can bite and chew or how rich the food patch is, a predator has to be able to catch its food.

• Predator lethality: basically how efficient it is in catching a prey. If your good, your lethal, if not….

• What is predator efficiency?

Predator efficiency

• Definition: # successful captures/total attempts

• Difficult to quantify in the wild• Rarely ranges over 30%

• Average probably around 20%

• Is quite variable

Reasons for variability?

• Health of prey: - Young, sick, and old more vulnerable so

hunting efficiency would be higher for these groups

• Mid-aged healthy prey can defend themselves

• But their ability to do so varies with habitat

Habitat and predator efficiency

• Each predator has strengths/weaknesses

• Wolves: Adapted to run prey down, attack from behind.

A moose in trouble!

• Go to video

here

Cougars and deer

• Cougars stalk their prey.

• Need to get within 20-25 meters to have a chance.

• Need cover

Cougars and deer• Cougars are predators of the forest and edge!• More than 80% of the time• in one or the other.

Habitat use by cougars

Habitat type

Open Edge Forest

Pe

rce

nt

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ObservedExpected

• And they are successful!

Open Edge Forest

NU

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ER

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ES

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45

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75%

Patch quality for predator

• So high quality patches for predators are ones where they have a good chance of making a kill.

The landscape of opportunity

• So through the eyes of the predator, the landscape is one of a mixture of successful and less successful patches.

Return to our habitat patches

Now each has a success value to it for predator. Based on lethality of predator.

How about the prey?

• Had said prey selected on level of resources.• It is within this framework of predator

lethality that the prey must make their foraging decisions!

• So…. Becomes not as simple as selecting the patch with the highest food resources.

• Need to balance food resources and predation risk.

Which is more important?

• In the past, placed most (if not all) emphasis on resource levels.

• How long does it take to starve?• How long does it take to get killed by a

predator?

• Food is important but not if your dead!

Predation risk

• So the risk of being killed (predation risk) becomes overlying factor in how a prey will use the habitat.

• What are its options? • 1) use dangerous areas less/safe ones more• 2) If you have to go, spend little time/use

vigilance to offset dangers/reduces feeding efficiency

Two principle lines of investigation

1. Changes in habitat

2. Changes in the amount of vigilance.

Where risk is high: - Use the most secure areas

Where risk is low: - Use all parts of habitat

2. Changes in Behavior. -Time foraging vs surveying.

Where risk is low: - eat more and survey less.

Where the risk is high: - survey more and eat less.

Since the 1980’s – lots of studies:Mech, L.D. 1977. Wolf-pack buffer zones as prey reservoirs.

Science 198:320-321.

Edwards, J. 1983. Diet shifts in moose due to predator avoidance.Oecologia 60:185-189.

Stephens, P.W. and R.O. Peterson. 1984. Wolf-avoidence strategiesof moose. Holarctic Ecology 7:239-244.

Hunter, L.T.B. and J.D. Skinner. 1998. Vigilance behaviour in Africanungulates: the role of predation pressure. Behaviour. 135:195-211.

Scrimegeour G.J. and J.M. Culp. 1994. Foraging and evading predators: the effect of predator species on a behavioural trade-off by a

lotic mayfly. Oikos 69:71-79.

And more.…

All indicate that the prey are

adjusting their behavior

because of the risk of predation.

Our studies:

Wolves-elk: Laundré et al.

Puma-deer: Altendorf et al.

Hernández and Laundré 2005

Supported these predictions.

Elk -Wolf

Towns and Tourist sitesGrand TetonNationalPark

YellowstoneNationalPark

Lamar Valley

Wolf Pack locations (96-97)

N

Madison Junction

Old Faithful

20 km

West Yellowstone

Gibbon Meadow

Hayden Valley

Swan Lake

Mammoth

Flat

Wolf Pack expansions (98-00)

Yellowstone Park

Visual Observations

Amount ofFeeding

Amount ofVigilance

Effects on Feeding Behavior

Level of vigilance of females with calves before and afterThe reintroduction of wolves in Yellowstone.

Number of years after wolf reintroduction

0 1 2 3 4 5 6

% V

igil

ance

10

20

30

40

50

60

70

Females with calves in area with wolves

Females with calves in areas originally without wolves

Elk

Predation Risk and Habitat Use.

Pellet group Counts

Effect of predation risk onTime Allocation.

Distance from Forest Edge (m)

-100 0 100 200 300 400 500 600

Num

ber of Pellet G

roups/10m2

0

1

2

3

Lamar valleyNon wolf areas Y = 1.9 - 0.002 X

r2 = 0.657, P = 0.001

NS

a

1998

Distance from Forest Edge (m)

-100 0 100 200 300 400 500 600

Num

ber of Pellet G

roups/10m2

-1

0

1

2

Lamar ValleyNon wolf areas

b Y = 1.06 - 0.002 Xr2 = 0.68, P = 0.003

NS 1999

Number of pellet groups per 10 m2 sample plots

located at 50 m intervals. Plots started 50 m into

the forest and were located every 50 m up to 500 m

into the open.

Mule Deer - Puma

Giving Up Densities

OpenEdge

Forest

Graph of Giving Up Densities for two forest types

Habitat type

Giv

ing

up

den

siti

es (

kg)

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Open areasEdgesForest area

Douglas Fir Mountain Mahogany

Habitat UsePellet surveys

Mean deer pellet groups per 10 m

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4

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6

Open Edge Forest

Juniper Fir Mahogany Aspen1st Yr 2nd Yr 1st Yr 2nd Yr 1st Yr 2nd Yr 1st Yr 2nd Yr

Deer pellet groups per 10 m2

So:Predators

not only killtheir prey…

They Scare Them!!!

So what do we have?

• Predator that has varying lethality• Prey that responds to this by avoiding high

risk/lethal areas

Large ungulates1. React behaviorally

a. Increased vigilanceb. Reduced feeding

2. Change their foraging strategiesa. Spend more time in “safe” areas

3. Have a poorer quality diet a. Any shift in use will be to poorer area

In Response

All this made us think of what might be

the basic force to explain these

reactions of prey to their predators.

as they move about the landscapeto reduce predation risk.

Fear of predation changes how theyuse the landscape

is seen through their eyes as a landscape of differing levels of risk or fear

Thus a landscape of physical features

Or

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02

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8

Pred

atio

n R

isk

Dist

ance

in X

Pla

ne

Distance in Y Plane

The Landscape of FearA Landscape of Fear

And the game goes on

• Given all that, lets return to the predator!• Given that it scares its prey • Its prey respond by using safe areas more (low

lethality of the predator)• Where should the predator hunt relative to

prey densities??

here

Developing views

• Commonalities in physiological and behavioral responses to DANGERS within and among species.