Lecture 4 - mutualism Flashcards
why is reciprocity problematic?
because of delayed repayment
what is the advantage of mutualism over reciprocity?
There is less opportunity to defect in mutualistic interactions (both individuals should get an immediate pay off), although each partner will seek to maximize their own fitness
what is expected to be more common, mutualism of reciprocity?
-Expect mutualism to be much more common and widespread in natural systems than reciprocity
what is the difference between mutualism and mutual benefit?
- Interspecific – mutualism e.g. honey guides and humans
- Intraspecific – mutual benefit e.g. penguins huddling to get warmth from each other
an examples of immediate shared benefits for foraging efficency ?
e. g. wild dogs - hunt in large packs and have really high success rate of 65-70% of all wild dog hunts are successful - much higher than other wild animals
e. g. humpback whales - bubble netting - blow air concentrating shoals of fish within the bubble net and whales come up in the middle and feed
e. g. lions - when hunting small prey they typically do it alone however when hunting large prey they are more likely to work in groups to tackle the prey - but they large size means the food will last them longer
- all reasons why it is important to live in a group - strong selection to get mutual benefits
give an example of a non-imediate benefit involving mating and courtship
e.g. manakins - diverse ways of courting - males cooperate by dancing together
- lek mating system - females visit various mating sites and pick a mate
- males acquire adult plumage at 4yrs
- males display in pairs (alpha and beta)
- alpha monopolises matings (>98%)- in the long run the beta benefits from helping the alpha male • beta always ‘inherits’ alpha status, eventually
• females faithful to lek sites
• beta inherits mating success too
In this case cooperative display is a long term investment to get mating’s
describe how sentinels are another form of mutualism
Many social animals post sentinels to warn of predators
- assumed to be dangerous for sentinels
- used to be explained by reciprocity or kin selection
then Bednekoff (1997) identified that sentinels are actually safer than foragers
- explained by mutualism - ‘safe, selfish, sentinels’
desribe how sentinels work in meerkats
when they dig for food they are very vulnerable to predators so there is always a sentinel standing on a perch to keep an eye out for predators
Conclusions:
- Sentinel behaviour is an optimal activity once stomach is full and no other animal is on guard
- sentinels at low risk
- individuals act as sentinels when well fed
- sentinel behaviour is mutualistic
describe the mutualistic relationship between drongos and pied babblers
babblers feed on the floor - very vulnerable
- drongos get some of the food and babblers get a sentinel
what were interesting findings from the experiment on drongos and pied babblers
babblers less responsive to drongo alarms when the babbler group size increases
- babblers in large groups displace drongos
- Babblers are actually antagonistic to drongos when they live in larger groups - as babbler group size increases the no. of attacks on drongos increases
- Why? - drongos give false alarms and take food from young babblers
- Example of an unstable mutualism - each party is trying to maximise their own success
explain how the babbler and drongo both benefit
foraging benefits = kleptoparasitism - false alarms for food
sentinel benefits = resistance - displace drongos when not needed
what are the 3 solutions for maintaining cooperation?
- Facultative mutualism - each party will only participate in the mutualism when it is beneficial for them to do so if it becomes no longer beneficial, they will no longer participate in the mutualistic interaction e.g. the babblers tolerating the kleptoparasitic behaviour of the drongos only when small group size requires greater viligance
- Punishment/enforcement
- Image scoring/reputation
describe the intersepecific mutualism between cleaners and clients of the blue-streaked cleaner wrasse
- eats c. 1200 parasites (isopods) per day
- inspects c. 2300 fish per day
- some clients visit cleaning stations every 5 mins
Cleaners are tempted to cheat - cleaners prefer fish mucus to ectoparasites
what are the two reasons that the cleaner wrasse cant get away with cheating?
- punishment by chasing cleaner or fleeing cleaner
- similarly to reciprocity - punishment can potentially enforce cooperation
describe the experiment on cleaner wrasse proving reputation as a solution to cheating
Field observations (Bshary & Schaffer 2002)
Clients with a choice of cleaning stations avoid cheats
- 60% return to stations with positive last interaction
- 5% return to stations with negative last interaction
- If as a cleaner fish you can establish a good reputation you will get clients coming back to be cleaned
Followed on with Lab experiments (Bshary & Grutter 2006)
Clients score cleaners’ cooperative image
- choice of cooperative/non-cooperative
cleaners… prefer cooperative
-cleaners more cooperative when being ‘image-scored’ (observed by another fish)
