Cetacean Social & Reproductive Systems

Group Living Benefits Reduced predation risk Enhanced detection/ capture of prey Improved reproduction Reduced harassment Larger prey Costs Share food Increased competition for mates Risk of infection

Evolution of Social Systems Factors Influencing Sociality - 1) Environment 2) Reproduction

Evolution of Social Systems Environment A. Behavior & availability of prey Solitary prey solitary or small groups Widely dispersed, densely clumped prey large aggregations Predator & prey schooling

Schooling Behavior When prey group Confusion effect Dilution effect When predators group Reduces advantage of schooling prey Herd, corral prey Increases detection of patch

Advantages of Schooling

Advantages of Schooling Safety in numbers!

Jack Mackerel study Advantage Predator

Jack Mackerel study Advantage Prey

Jack Mackerel study Advantage Predator

Nat Geo_Dolphin Mud Flat Dolphin Feeding on Mud Flat

Dusky Dolphin Group Foraging

Dolphin Parenting http://www.youtube.com/watch?v=nsk4u0immte&feature=c hannel

Evolution of Social Systems Environment B. Exposure to Predators Coastal or Riverine Pelagic or Offshore increased exposure

Coastal Environment

Pelagic Environment

Evolution of Social Systems Factors Influencing Sociality - 1) Environment 2) Reproduction

Evolution of Social Systems Reproduction A) Offspring dependency B) Location of feeding & breeding sites C) Protection from predators

Reproductive Patterns Odontocetes- 1 calf every 2-8 yrs Weaning 0.5-10+ yrs Feeds during lactation Mysticetes- 1 calf every 1-3 yrs Weaning 5-12 months Fasts during lactation

Odontocetes Highly social, stable Promiscuous Feed on schooling prey Consume single prey Large relative to body size

Odontocetes Highly social, stable Promiscuous Feed on schooling prey Consume single prey Large relative to body size Small body size Males > Females Habitat & Predator Avoidance Large impact on school structure

Role of Environment A) Coastal inshore Tend to be resident Smaller, fluid schools B) Pelagic offshore Cover extensive area Large schools, many sub-units Safety in numbers 7 ± 3 rule

Group Sizes Average Max Delphinus sp. 46 385 650-4000 Pacific Whitesided 11 88 50-6000

Group Sizes Average Max Delphinus sp. 46 385 650-4000 Pacific Whitesided 11 88 50-6000 Pilot whale 12 41 22-230 Killer whale 2 20 5-100

Group Sizes Average Max Delphinus sp. 46 385 650-4000 Pacific Whitesided 11 88 50-6000 Pilot whale 12 41 22-230 Killer whale 2 20 5-100 River dolphins 2 3 8-10 Harbor porpoise 2 7 5-500

Social Group Studies Protection of young (K. Norris) Teacup formation Vulnerable animals in middle Dominant males outside Sleeping behavior (D. Goley) Alternate position within school Sleep in one hemisphere of brain Opposite eye open

Fusion - Fission System Fusion Small groups join for feeding or reproduction Fission Groups split to stable sub-units

Fusion - Fission System Spinner dolphins Small groups join to feed pelagically Maintained by aerial behaviors Groups split to move inshore Rest in coastal bays

Spinner Dolphins

Fusion - Fission System Bottlenose dolphins Strong, stable male alliances (2-3) Pairs join larger groups for mating Super alliances = short term grouping Aggressively separate females from groups

Shark Bay alliance http://www.youtube.com/watch?v=_j2n5ttfbn8&nr=1 Video

Fusion - Fission System Bottlenose dolphins Sarasota, FL: males form bonds (2) or solitary Scotland: no bonds found Differences may be based on body size & sexual dimorphism

Parental Care Females mostly responsible for care & protection Alloparental care taking care of offspring other than your own

Odontocete Grouping Low adult mortality High juvenile mortality Must protect offspring to increase reproductive success

Baird s beaked whales Male & female natal group philopatry Males live longer (up to 30 years) Hypothesized males provide care: protection &/or teaching foraging behaviors offspring from closely related females

Bottlenose Dolphins Social Groups Male Alliances Juvenile Groups Reproductive Groups Fusion - Fission

Female Groups Vary by location & reproductive status Not as strong as male bonds

Sponge Feeding

Unique Odontocete Foraging Sponging Behavior

Sperm whale groups video

Sperm whale groups Matrilineal groups (~10) Interact with other groups for short periods Female bond based on cooperative care of young

Sperm whale groups Males disperse (6 yrs) Increasingly solitary Form loose breeding associations Roam between female groups

Killer whale social behavior

Killer Whales Pacific Social Groups Residents Transients Offshore Group size Diet Vocalizations Echolocation

Killer Whales Pacific Social Groups Group size Residents Transients Offshore Large, stable Small, fluid Large, fluid? Diet Vocalizations Echolocation

Killer Whales Pacific Social Groups Group size Diet Residents Transients Offshore Large, stable Fish Small, fluid Marine mammals Large, fluid? Squid and fish Vocalizations Echolocation

Killer Whale_ Grey Whale Attack

Energy Intake (kcal/kg/day) 180 160 140 120 100 80 60 40 20 0 Optimal Group Size (harbor seal hunting) 0 1 2 3 4 5 6 7 8 9 10 Group Size British Columbia Killer Whales

Killer Whales Pacific Social Groups Group size Diet Vocalizations Residents Transients Offshore Large, stable Fish Group specific Small, fluid Marine mammals Population specific Large, fluid? Squid and fish??? Echolocation

Group size Diet Vocalizations Killer Whales Pacific Social Groups Residents Transients Offshore Large, stable Fish Group specific Echolocation Frequently Small, fluid Marine mammals Population specific Rare Large, fluid? Squid and fish??? Very frequently

Residents Transients & Birth With Mom Sexual maturity With Mom Late teens(+) With Mom

Residents Transients & Birth With Mom With Mom With Mom Sexual With Mom maturity Late teens(+) With Mom

Residents Transients & Birth With Mom With Mom With Mom Sexual maturity With Mom With Mom Leaves Mom Leaves Mom Late teens(+) With Mom

Residents Transients & Birth With Mom With Mom With Mom Sexual maturity With Mom With Mom Leaves Mom Leaves Mom Late teens(+) With Mom With Mom Largely solitary, short associations Forms own pod Returns if unable to reproduce?

Variations in the Antarctic Type A primarily feed on Minke whales Type B found in pack ice, feed on seals Type C feed on fish http://www.2muchmedia.com/orcasfinal2.html

Specialized Foraging

Beaching: Specialized Foraging juveniles participate but rarely catch seals adults sometimes throw live prey to juveniles

Mixed Species Schools Forage with more effective predator Tuna with dolphins Many examples Bottlenose dolphins & pilot whales Right whale dolphins & Risso s or Pacific-white sided

Mixed Species Schools Forage with more effective predator Tuna with dolphins Many examples Bottlenose dolphins & pilot whales Right whale dolphins & Risso s or Pacific-white sided May gain More effective sonar ability Greater food finding ability Predator protection

Sociality Relates to Reproductive Patterns Long gestation, lactation, dependency Large inter-calf interval

Prolonged Development Gestation (months) Age at weaning Tursiops 12 18-20 mo Sperm whale 15-16 Pilot whale 15 2 yr 13 yr (max) 4-5 yr 13-15 yr (max)

Prolonged Development Sperm whales Milk found in stomach (7.5 yo female & 13 yo male) Short finned pilot whales lactate 15 yrs after giving birth 25% females post-reproductive Suggested older females nurse related young

Solitary Promiscuous Mysticetes Feed on schooling prey Consume entire school (one animal) Large body size Females > Males Exception Humpback whales: gregarious feeding

Humpback Feeding

Mysticetes Brought together by breeding habitats Most data from male humpbacks, right whales, & grey whales Not much known about females

Reproductive strategies vary Display: larger/older animals Direct competition Escort Potential for roving & sneaking Humpbacks

Sperm Competition Right whales, bowhead, & grey whales Large testes Multiple copulations Fewer male-male interactions

Summary Odontocetes Highly social Long dependency Structured aggregations Feed on schooling, dispersed prey Promiscuous Mysticetes Solitary to loose aggregations Short dependency Feed on entire prey patches Promiscuous