Social Stress Flashcards
What causes social stress in the natural environment?
Competition for resources
What causes social stress in captivity? How may these be divided into groups?
- Physical or Pychological
Unsuitable housing/husbandry
Inappropriate group composition (aggression)
Inappropriate density (crowding/isolation)
Frequent exposure to unfamiliar individuals (breaking social bonds/lack of control-> anxiety)
Poorly developed social skills (abrupt weaning)
What are the behavioural effects of social stress?
- v social interaction
- v reproductive behaviour
- v exploration
- ^ submissive/defensive behaviour
- ^ anxiety
What are the physiological effects of social stress?
- ^ HPA activity
- ^ BP and HR
- v reproductive acitvity
- v body weight
- ^/v body temp
- immunosuppression
- pain inhibition (SIA)
What do social dominance hierarchies require?
Individual recognition
What types of hierarchy may exist?
> Linear or circular
Fluid (eg. hens when they go off lay move to bottom of pecking order) or static
- may be situation specific
What is the purpose of hierarchies?
Minimised the need for aggression, ^predictability and stability of social relationships
What is stress exposure governed by?
- rank
- type of social organisation
In hierachies, what two types of stress levels is low rank associated with?
In many species, low rank = high stress
> “STRESSFUL SUBORDINATION”
In some species, low rank = low stress
> “NON-STRESSFULL SUBORDINATION”
Give some animals which expiernce stressful subordination
Mouse eared lemur CAPTIVE wolves Pigs Rabbits Babboons
Outline the dominance hierarchy of a group of baboons
Stable hierachy, groups 50-150 Will win 95% of fights with lower rank, and lose 95% with high ranks Maintained by psychological bluff (aggressive displays rather than aggressive attacks) and "displacement aggression" inflicted on ranks below > Subordinate individuals - less control/predictability - limited social support - fewer outlets for frustration => STRESS
Give an example where environmental stress provided a buffer for social stress
1984 - East African Drought
- ^ foraging
- maintained body mass
- v displacement targeting of subordinates by domainants
- > v GC in subordinates
When may dominants in a stressful subordination population show signs of stress?
Instability in the group
- Key individual dies/joins
- Coalition partnership forms/breaks
- > ^ fighting, challenges, “coalition politics”
- > stress
Give examples of animals where dominance is stressful
African Wild Dogs
Mongooses
RT lemurs
Why may dominance be stressful in some species?
Constant reassertion of high rank through overt aggression
Dominancy frequently challenged
Dominance individuals = ^GC
In which species are none of the members stressed?
Egalitarian society - No dominance hierarchy. Small groups of related co-operative breeders
Subordinates reproductively suppressed (“social contraception” by pheromones (relaxed waiting strategy rather than physical enforcement)
Subordinates help out older siblings
Who compared social hierarchies and stress levels?
SAPOLSKY 2005
What are the 5 factors for consideration in social stability?
> Firstly bear in mind fission (WILD) v fusion (CAPTIVE)
1. Age at formation - young and old easy to combine, adults harder
2. Familiarity and genetic relationship - familiarity often reduces hostility eg. inbred mice show reduced hostility but may increase competition as likely to value same things eg. dogs
3. Sex composition
eg. Male rats more stressed in same sex groups than individually
Female rats more stressed alone
- ethnologically males would only share territory with females and young, females would share with male, females and offspring
eg. captive primate groups housed in inappropriate group composition (mixed age/gender) experience abnormal aggression
eg. chimpanzees - risk of wounding more dependent on sex composition than size of group
eg. pig-tailed macaques - more aggression in female only groups than groups with a male
4. Environment
- complexity good
- stability necessary eg. cleaning cage out every day -> ^ aggression in mice
5. Group sizes and densities
- laying hens form dominance hierarchies in small groups and will attack unfamiliar birds, BUT in 100+ groups less aggression shown
- crowding can ^ aggression and v reproduction (farmed deer and lemmings)
What should be considered when evaluating “crowding” of animals?
Is the human definition sufficient?
- usually based on body mass, not sex ratio etc.
- if cages kept close together may still be “crowded” with respect to olfaction
Outline 2 case studies of social instability in commercial rearing
- Pigs
- naturally highly social, live in stable family groups, highly intolerant to strangers
- commercially mixed at weaning, at beginning of grower/finisher period, within groups of gestating sows
> aggression, resource displacement, suppressed immune response, v growth and reproduction
- aggression at weaning not a direct distress response to weaning
- if allowed to mix between farrowing crates v fighting and v fearfulness (though this ^disease risk) - Dairy cattle
- natually cohabit in large herd, new members rarely accepted
- commercially, calves separated from mothers and grouped with other, regrouped according to growth rate, heifers -> milking herd, regrouped according to milk yield, sale
- consequences = aggressive interactions, distress, v feed intake and milk yield
Why may some of the negative effects of social instability not be seen in modern breeds?
Been selected for high reproduction rates so not affected as much
What does the mother-young social bond provide?
- affiliative behaviour eg. allogrooming
- nourishment
- warmth and protection
- information transmission (food/predators)
Outline the social separation process of natural weaning.
Gradual v milk intake and ^ solid
Gradual ^ social independence from dam
Why is early weaning carried out?
- Triggers return to cycling to ^ yield in dairy cows
- Maternal illness/death/lack of care
What does early weaning cause?
- Disruption of social bond, termination of milk supply
- Exposire to social and physical stressors
> distress vocalisation
> v body mass/growth rate
> altered sleep patterns
> suspension of play
> ^GC
> altered HR/temp
Outline 2 case studies of early weaning
- Pigs
- Naturally secluded sow and piglets for a week
- < 5months spends gradually less time with them and integrates into group
> commercially first month intensive interaction with piglets
> week 4 abrupt weaning and mixing - Dairy cattle
- Naturally milk transfer V after first few weeks, weaned at 6-9 months
> commercially separated from cow within hours, bottle fed then weaned onto solid food
> show distress response when separated from cow and weaned from milk
> BUT ^ distress shown if left to form social bond before separation
What is social buffering?
Conspecifics reduce stress associated with maternal separation in foals, piglets and calves
- v stress repsonse
- ^ recovery from distress
> familiarity and emotional status of partner affects effectiveness of social buffering eg. rat footshocks, experience v. naive partner
How may coping with stressful events be affected by personality type? Give 4 examples.
- Ability to form coalition partnerships - social buffering
- Anxiety - Ability to differentiate threatening and neutral interactions (anxious individuals cannot differentiate!)
- Rectivity - Reactive (high GC due to lack of control) v proactive.
- Ability to distinguish win from loss - if can’t distinguish (“pessimist”) have ^GC
