Chapter 12: Ecology of Group Living and Social Behaviour

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20 Terms

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3 main ecological factors for evolution of social behavior

➢Where they give birth - e.g. seal colonies

➢Where they forage - e.g. deep sea / sperm whales: baby sitting

➢What they eat - abundant food (e.g. Fin whales that feed on euphasiid prey)

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Benefits of living in groups

Predation risk

➢Individual avoidance at sea

-> Elephant seals avoid Killer whales by diving deep

-> Nearshore dolphins, Baleen whales hide in river mouths or surf zones or kelp beds Pigmy & Dwarf sperm whale - reddish cloud to confuse predator

➢most important factor to build groups

Dilute predation risks for individuals, e.g. mixed dolphin groups Warning / alert others / defend against predators (e.g. sperm whales "Margarite formation")

➢Non-socially transmitted parasites: Dilution effect (cookie cutter sharks)

➢Cooperative feeding (Killer whales, Humpback whales, Dolphins cooperate with fishermen ...)

➢Environmental factors (keep warm, protection ...)

<p>Predation risk</p><p>➢Individual avoidance at sea</p><p>-&gt; Elephant seals avoid Killer whales by diving deep</p><p>-&gt; Nearshore dolphins, Baleen whales hide in river mouths or surf zones or kelp beds Pigmy &amp; Dwarf sperm whale - reddish cloud to confuse predator</p><p>➢most important factor to build groups</p><p>Dilute predation risks for individuals, e.g. mixed dolphin groups Warning / alert others / defend against predators (e.g. sperm whales "Margarite formation")</p><p>➢Non-socially transmitted parasites: Dilution effect (cookie cutter sharks)</p><p>➢Cooperative feeding (Killer whales, Humpback whales, Dolphins cooperate with fishermen ...)</p><p>➢Environmental factors (keep warm, protection ...)</p>
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Forced aggregations

When resources are clumped- individuals do not necessarily benefit from each other's company!

Examples:

-> Belugas gather in warm tidal creeks during annual moult or Pinnipeds are forced together on small haul-out places

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Costs/risks of living in groups

➢Risk of transmitting parasites socially (e.g. Bacteria infections, parasite fish)

➢Competition for limited resources (share food, haul-out places, mates..)

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Natal Philopatry

Returning to birth place, extreme in pinnipeds - territory of male northern fur seals rarely shift more than 10m!

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Sexually dimorphic philopatry

To avoid inbreeding (e.g. Sperm whales - male dispersion)

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Philopatry

The behaviour of remaining in, or returning to, an individual's birthplace

-> But most aquatic marine mammals have huge home ranges that overlap many conspecifics: Differs between geographic and social philopatry

➢Some geographic but not social philopatry:

Bottlenose dolphins remain in their natal home range but rarely interact with their maternal relatives ➢Both geographic & social philopatry:

Killer whales - no dispersion of either sex, they interact with their relatives throughout their life – but mate outside their kin group

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Affiliative behavior

Friendly

➢Strengthen bonds

➢Mend damaged bonds

➢Reduce tension

➢Need service from another

e.g. grooming

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Affiliative behavior in dolphins/sperm whales

➢Rub body parts, mutual stroking, fin touching, 'greeting

ceremonies' in killer whales, synchrony

➢But also skin / parasite removing

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Aggresion, agonistic displays and dominance

➢Growling, open mouth, head jerking, lunching, charging another

➢Sounds: 'pop' sounds dolphins, growls in seals

➢'Toothrake' marks from fights (male beaked whales, narwhal 3m tusk (but

mostly sensory organ), elephant seals)

➢Headbutting (bottlenose whales, pilot whales)

➢ But most not lethal, except infanticide / killing of Harbour porpoises by Bottlenose Dolphins ➢Agonistic interaction not necessarily aggressive

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Non-receptive sexual behavior

➢Common in marine mammals: fur seals, baleen whales, toothed whales, manatees .. For communication, relationships, bonding ...

➢Dolphin – Bonobos

role dominance or affiliative behaviour / greeting, forming social bonds, conflict resolution and post-conflict reconciliation -> Alliances in male Bottlenose dolphins – dominance / affiliative

➢‘Test the social bonds’

➢Immature animals ‘play or practice of herding others ́

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Matriarchal groups

Female leader in a group with group members are relatives and no-relatives

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Matrilineal groups

Offspring line from one female, several matrilines can be in a group, that are either related (sister groups e.g. Killer whales, Pilot whales) or not (e.g. Sperm whales & Elephants)

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Matrifocal / matrilineal groups

One matriline with a female and her offspring, no offspring dispersal by neither gender: Bisexual philopatry - Killer whales (single matrilines) & Pilot whales (multilevel matrilines)

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Sperm whale bonding strategies

Females: Matrilineal (ca 10 individuals) stable groups in tropical areas but can split after 5-10 years (not all females are related)

Cooperative offspring care, babysitting, communal feeding (allomothering)

Males: Bachelor groups/ old males solitary

– migrate away from females to higher latitudes to feed

- Mature later than females (delay breeding to become larger to compete with others)

– rove alone around females, (but bonds among younger males possible)

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Bottlenose dolphins and bottlenose whales bonding strategies

Roving male alliances, weaker female-female bonds

➢Fission-fusion societies (change in size and composition)

➢Male-male bonds can last for lifetime

➢Male alliances work alone or with other alliances to capture females

➢As strong as mother/offspring bonds

➢Social female bonds – looser network among several females

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Bisexual bonds in killer and pilot whales

➢Matrifocal units (Killer whales: 2-9 individuals, 1-4 generations mother & offspringPilot whales: 60-200 animals, multi-level sister groups)

➢Natal philopatry of both gender

➢Bonds between mothers & sons strong!

➢Bonds between brothers - scouting/mating ➢Bonds between sisters/mother - offspring care

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Adoption of non related animals

➢Killer whales accept non-related animals, even feed them when ill or incapable. Special case in Norway an adopted orphaned handicapped female born 1995 seen with > 5 different groups

➢Crippled Bottlenose dolphin was seen with sperm whales

➢Iceland 2023: Killer whales raised a long-finned pilot whale calf - adoption or abducted?

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Bonding strategies

➢Females bear cost of parental care!

➢Female reproductive and bonding strategies determined by access to food and safety from predators (some cases males: infanticide)

➢Female philopatry (non social factors such as resource

distribution and prey behaviour or social factors such as cooperative defense of offspring or resources)

➢Bisexual philopatry due to low cost of locomotion - large home & feeding ranges in which they encounter other non related mates, e.g. killer whales and pilot whales

➢Cetacean offspring are followers, not tied to a breeding site!

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Male mating and bonding

Determined by distribution of femalesbut also presence of predators:

Bottlenose dolphins in Scotland don't form alliances, shark predation is low compared to Australia, where they form alliances