MARB 403 Lab 4
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Orcas
Most distinguishing feature is coloration
Transient
Little seasonal change in range
Mammal-eating, no fish
Resident
Seasonal movement in coordination with fish migrations
fish-eating
Other marine mammals do not avoid them
Activity states
- traveling
- foraging
- resting
- socializing
mammal-eating: only eat
- tongue
- lips
- blubber
transient spend most time traveling and foraging
specialization from passed-on feeding strategies (probably caused division between types)
Third sympatric form: "Offshore orca"
Three antarctic ecotypes: A, B, and C
Resident Unit
- Matrilinear society
- strong group
- linked by maternal descent
- female, calves, and daughter's offspring
- 1 to 4 generations
Pod
- matrilines with recetn common ancestor
- 1-3 matrilines
- travel apart
Clan
- defined by acoustic behavior of pods (similar dialect)
- multiple pods
Community
- Associating pods
Transient Unit
- Same basic unit, but smaller
- juveniles leave and wander
Foraging
Resident: Carousel Feeding: tail lobbing, bubbles, and flashing ventral sides will herd fish into balls at surface
Transient: acoustically quieter hunting, trap cetaceans against shore or debilitate prey before drowning it Purposefully beach themselves to grab seals
Antarctic Type B: wash seals off ice floes
Baleen/sperm whale: only eat
Sperm Whales
Males and females have same diet: Cephalopods (Squid) and mesopelagic fish, but males eat larger stuff
Compete with beaked whales and elephant seals for food.
K-selected animal: live long (50 yrs), but slow birth, gestation, and maturation rate
Loudest animals in world
"Codas" for social communications
Males have slow clicks
Swim at 4 km/h
Social Structure
Females stay in groups of about 12
Alloparenting
Males are more solitary
Form loose aggregations around (4-21 yrs) and then separate
Behavior
75% of time spent Foraging
only other behavior is Social/Resting
.5 to 1 sec. interval echolocating clicks
Deepest-diving animals: 9800 ft.
Moby Dick was a Sperm Whale
Heterogeneous Social Associations within a Sperm Whale Unit Reflect Pairwise Relatedness
Interactions between pairs of individuals
Understanding socail structure requires knolwedge of individuals' relatedness to others
We know more about intra-group social structure than intergroup
Females and immature males live in "units"
- long-term stable relationships
- multiple units join to form groups
- 2-ary benefits: foraging and defense
Equivalence Model has only two possiblilty : Unit Member or Outsider
- If true , unit members would treat each other equally (preferred associations)
Three types of association
- obligate association (mother-calf)
- unidirectional one wants, other doesn't care
- mutualistic both care
Methods
Well-studied "group of seven" sperm whales observed for 40 days
Picture quality (1=poor, 5=high) for ID
- Computer matching program
- Calf identified using fin and body markings
Considered to be associated if in same cluster at surface Cluster is within 3 adult body length chain rule
2-hour sampling period
DNA extraction from sloughed skin
Results
7 individuals
Calf had 2 associations: mother and babysitter (otherwise with juvenile male Mother associated with calf and babysitter Babysitter was only member to associate with all members All were from same matriline
Discussion
Little known about sperm whale social behavior prior to experiment
Sperm whales prefer associations with kin, but predation may influence non-kin associations (weaker bonds)
- Unit # in Pacific doubles
- increase = more social opportunities
Cause for association: Predation pressure and protection of young (latter may be cause of sociality)
Individuals differ in sociality:
- Age: Older females have decreased interaction
- Social role: mothers need to produce milk and must forage more often
Discussion
Modern major general dolphin species song
Peter Tyack on TED
Research Paper Topics
- Odontocete communication and intelligence
- Brain-to-body ratios: most of mass is blubber, which does not need nerve endings. What is the brain to muscle ratio?
Look for these authors:
- Whitlow Au
- Peter Tyack
- Manger - dolphins may not be intelligent; rebuttal by Marino, et al
TED Video
Sound used in echolocation and communication
- Stay in touch
- Reproductive meanings
Underwater so foreign to us:
- we rely on sight, but light doesn't go that far
- marine mammals rely on sounds
Captive dolphins can imitate human sounds
Dolphin signature whistles are radically different (c.f. primate ID sounds)
Mother and calf use it to keep in touch, and rate is directly proportional to distance (> 100 m = 100%)
"Loving dolphins to death"
Sound and tourism noise really affects marine mammals
Sound can travel halfway around the world in the ocean
Blue whales communicate and travel over hundreds of miles
Shipping sound frequencies overlap with whale communication frequencies
- Whales shift their calling frequencies to higher frequencies
- Whales can wait for silence
- Whales can "speak" louder
Setting standards for quieting ships: better propeller design and isolating motor from hull; going slower