Cetacean Social & Reproductive Systems

Transcription

1 Cetacean Social & Reproductive Systems

2 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

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

4 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

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

6 Advantages of Schooling

7 Advantages of Schooling

8 Advantages of Schooling Safety in numbers!

9 Jack Mackerel study Advantage Predator

10 Jack Mackerel study Advantage Prey

11 Jack Mackerel study Advantage Predator

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13 Nat Geo_Dolphin Mud Flat Dolphin Feeding on Mud Flat

14 Dusky Dolphin Group Foraging

15 Dolphin Parenting hannel

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

17 Coastal Environment

18 Pelagic Environment

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

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

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

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

23 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

24 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

25 Group Sizes Average Max Delphinus sp Pacific Whitesided

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27 Group Sizes Average Max Delphinus sp Pacific Whitesided Pilot whale Killer whale

28 Group Sizes Average Max Delphinus sp Pacific Whitesided Pilot whale Killer whale River dolphins Harbor porpoise

29 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

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

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

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33 Spinner Dolphins

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35 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

36 Shark Bay alliance Video

37 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

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

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

40 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

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

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

43 Sponge Feeding

44 Unique Odontocete Foraging Sponging Behavior

45 Sperm whale groups video

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

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

48 Killer whale social behavior

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

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

51 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

52 Killer Whale_ Grey Whale Attack

53 Energy Intake (kcal/kg/day) Optimal Group Size (harbor seal hunting) Group Size British Columbia Killer Whales

54 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

55 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

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

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

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

59 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?

60 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

61 Specialized Foraging

62 Specialized Foraging

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

64 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

65 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

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

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

68 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

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

70 Humpback Feeding

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

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

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

74 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

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