Social Behaviour Flashcards
What are the 3 types of social groups in animals?
Asocial
Social
Eusocial
Describe ASOCIAL animals
- have little interaction with conspecifics (members of same species)
- usually solitary for most of life
- may come together to reproduce
Describe SOCIAL groups
- Monogamous pair or polygamous groups (hierarchical) – alpha dominance
- can be unstable or stable groups
What is an example of a stable social group?
Wolf pack
Baboons
Lions
Chickens
= highly organised, stable.
What is an example of an unstable social group?
Shoal of fish
= movements, changes etc are all in flux - no hierarchical organisation
Describe a EUSOCIAL species
- highly social
- labour is divided
- sacrifice of reproduction is often made to benefit whole group
Give some examples of eusocial species
Bees
Naked mole rats
ants
termites
Name 3 advantages to group living
Any: – Heat (thermoregulation) – Predator avoidance – Predator protection – Defence – Feeding – Locating food – Defence of prey – Reproduction and mating systems
Name 3 disadvantages to group living
Any from: – Increased competition for food – Increased disease transmission – More obvious to predators (pheromones) – More risk of parasitism/cannibalism of young – Reduced reproductive success
How does group living reduce risk of predation
o More eyes can detect a predator earlier = more vigilance (meerkats)
o As group size increases, individuals can decrease own vigilance
o Spend more time foraging and/or save energy
- groups can also confuse predators (zebras)
- communal defence
Give an example of when group living reduces predation risk
Meerkats (Suricata suricatta) - have a sentinel to look out for predators and warn the group
Zebras - confusion defence from markings
Give an example of predator confusion in social groups
zebras - groups stripes confuse predators
Give an example of increased predator vigilance
birds flocking
Meerkats: Suricata suricatta
Give an example of communal defence
Buffalo grouping to defend against an attacker
How do Harbour seals show increased vigilance in groups?
When they haul out offshore sandbanks/ beaches, scanning behaviour is observed to look out for predators.
The bigger the group, the more time spent scanning
What are sentinels
They act as look-outs and signal alarm calls in presence of danger
Give an example of a sentinel
Meerkats
What did Bedenkoff (1997) conclude about unselfish behaviour (4 points)
o Individuals more likely to become sentinels when satiated
o Sentinels detect predators first and also flee first (increased survival)
o Sentinels change in the group as the sentinels become hungry and are replaced by foragers
o Observations that even solitary individuals become sentinels when satiated
What does the presence of pups cause in meerkat behaviour?
When on foraging trips, both male and female meerkats increase sentinel behaviour when pups were with them.
Consequently, females found less food (because more time spent on look out)
What is the dilution effect?
The dilution effect is the idea that the chance of an individual being captured by a predator decreases as group size increases. This is because the predator only takes a single or a limited amount of prey in each attack
How do you calculate an individuals risk of predation, according to the dilution effect?
1 individual = 100%
10 individuals = 1/10
12 individuals = 1/12
n = group size risk = 1/n
What is the selfish herd effect/ principle? (Hamilton, 1971)
the idea that each individual in the herd will try to be at the group centre to avoid predation.
What effect can explain the constant movement in flocks and shoals?
selfish herd principle
What is the trade-off for the selfish herd principle?
o Exterior positions may be better for foraging but greater exposure to predation. Trade off between predation risk and foraging benefit.
How does the confusion effect protect groups?
- In large groups predators have difficulty focusing on a single target
- Difficult to focus on individual stimuli at the same time = sensory overload for predator = confusion effect
What is the confusion effect?
The effect is based on the fact that it is difficult to focus on multiple stimuli at the same time. Predators have a hard time focusing on a specific individual, when many other animals are escaping from them at the same time
What does the Neill & Cullen (1974) study show about the confusion effect?
o Attack success declined with increasing prey shoal size, regardless of attack mode
o Based on 4 aquatic predators (squid, cuttlefish, pike = ambush predators; perch = chasing predator)
Aquatic predators were less successful at catching prey in bigger groups
What is the odd prey effect?
- Idea is that if an individual differs from the rest of the group, it is more likely to be attacked and captures
What can make an individual in a group more likely to be predated?
If it differs from the rest of the group
i.e: odd-coloured, weaker, deformed etc…
The odd effect.
What is communal defence?
When prey may actively defend themselves by attacking a predator
Give an example of communal defence in birds
Artificial nests of fieldfares (Turdus pilaris) placed near colonies survived better than those placed as solitary nests.
What do fieldfare birds do to protect themselves?
They make artificial nests around the colony, even though solitary, as a form of communal defence (appear more abundant)
How does social living benefit foraging?
- Less time looking/ locating food (golden shiners fish)
- Capture prey too difficult for an individual to capture (lions)
Give a species that demonstrates co-operative hunting
Lions
African Hunting Dogs
Which position do lionesses adopt when group hunting
wing or centre positions
wings stalk prey
centres ambush and kill
Why do lionesses use preferred positions when hunting
their hunts are more successful
Centre positions are filled by the usually larger individuals = better ambushers
What did Creel & Creel (1995) find about African Hunting Dogs?
showed that hunting success, prey mass and the probability of multiple kills increased with number of adult hunting dogs
More dogs = better/ more kills
How does co-operative hunting help African Hunting Dogs?
Dogs weigh ~25kg
Buffalo weighs ~250kg (10x more)
By hunting together, they can kill prey much bigger than themselves
How does information sharing benefit a social group?
Groups can find food more efficiently
Stay away from predators/ danger
How does information sharing benefit colonies and roosts
o Unsuccessful birds may follow successful foragers without any signalling (eavesdropping).
o Successful birds may communicate where food is to others and recruit them.
= more efficient foraging & less predation risk
How do Ravens (Corvus corvax) use information sharing?
- A territorial pair of ravens finds food source (i.e: a carcass)
- Defends carcass against juvenilles
- Pair will give up food when confronted by a gang of 6 or more juvenilles
- Juveniles then call out loudly to others to recruit them and feed on the carcass
How does group living impact parental care?
- Help defend young against predation
- Help raise young
- more food availability/ foraging
- Créches
Give an example of a species that uses group living to defend young from predation
Nesting black-headed gulls
- will mod crows that try to steal eggs and chicks
Give an example of a species that uses creches
LIONS
How do lion creches work
- Lionesses have 1 to 6 cubs in a litter.
- Mothers of similarly aged cubs form a crèche and remain together for 1–2 years.
- Crèche-mates often nurse each other’s cubs
- More protection against infanticide
How does group living benefit thermoregulation
- Maintenance of internal body temperature within a range
- Need to conserve heat
- Solitary animals may find it difficult to cover the cost of this
- Social animals share the cost of keeping warm between them
What are 2 ways animal groups conserve heat
Huddling
Clustering
How does huddling conserve heat?
Reduces surface area to volume ratio
Assumes that both sides in contact are the same temperature, therefore there is no heat loss.
Name a species that uses clustering to conserve heat
Slugs
How does clustering conserve heat?
Bodies pack together to reduce evaporation
Name a species that uses huddling
Emperor Penguins (Aptenodytes forsteri)
What did Gilbert et al (2008) find out huddling in emperor penguins?
- Huddling behaviour allows male penguins to save energy while fasting during their incubation period’
- Estimated to save 38% of metabolic energy by reducing exposure of body surface and production of a microclimate within the group
Give a species that supports the desiccation hypothesis
North American Lepidopterans
Cluster eggs tightly normally. In Tropical areas they lay the eggs singly or in loose monolayers to avoid too much humidity
What is the desiccation hypothesis?
Clutch size and hatching success in eggs vary at different humidity levels
Name a study on the confusion effect
Neill & Cullen (1974)
Prey catching success of squid, cuttlefish, pike and perch decreased as shoal size increased
