Group Living

Question 1

Solitary Species

Answer 1

Something about resources can force individuals to live and forage alone. Resource distribution can prohibit group formation.

Often predators live alone, especially those that take in mainly small prey.

Question 2

Benefits of group living – Predation

Answer 2

• increased vigilance (greater chance of alert before attack)
• confusion effect
• dilution effect (decreases chance that any one individual will be eaten during an attack)
• group defense

Question 3

The Selfish Herd

Answer 3

“Individuals approach others to reduce their domain of danger.”

Tradeoff: exterior positions are better for foraging, and inside positions are better for safety.

Question 4

Costs of group living – Predation

Answer 4

Increased conspicuousness. Larger groups could attract more predators.

Question 5

Benefits of group living – Feeding

Answer 5

• locating food (information centre hypothesis)
• hunting large prey (working together to increase chances)
• more time to feed because there are more eyes scanning for predators

Question 6

Information Centre Hypothesis

Answer 6

Other individuals in a group can be used to determine whether or not to eat a novel food, to estimate patch quality by observing their foraging success, and to discover routes.

ie. Quelea Quelea – after putting groups together overnight, they both flew to the best food source. Some sort of information transfer.

Question 7

Costs of group living – Feeding

Answer 7

• increased competition for food
• increased interference while foraging (prey may be sensitive to sound, and others create noise)

Question 8

Redshanks Feeding

Answer 8

Day – use vision to find prey, feed on shrimp. solitary hunting, as shrimp are sensitive to movement.
Night – sweep mud with bills for snails. because the snails cannot move quickly and they don’t need to worry about disrupting them, they hunt in groups.

Question 9

Benefits of group living – Reproduction

Answer 9

• extra pair copulations
• ability to interfere with others

Question 10

Costs of group living – Reproduction

Answer 10

• Increased cuckolding (both in paternity, and egg dumping)
• Increased probability of cannibalism

Question 11

Costs of group living – Other

Answer 11

Increased disease transmission. Ecoparasitism. Spreads more in groups.

Question 12

Benefits of group living – Other

Answer 12

• hydrodynamic advantage (save energy by taking paths others have taken)
• thermoregulation advantage (roosting together allows warm-blooded animals to save energy by helping each other stay warm)