MARB 403 Lecture 8

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Guest Lecture tomorrow

Dusky Dolphins (Lagenorhynchus obscurus)

Occur right inside the Peru / Humbolt current

Most closely related to Pacific White-Sided Dolphins (Lagenorhynchus obliquidens):

• a long ago (during the ice age), Duskies traveled north to become this species
• some Phocoena (Phocoena spinipidus [sp?]) moved north as well and formed the now-most-endangered California harbor porpoise

Orange ruffy is very overfished...

Large expanse of relatively shallow water (200 m) in Argentina (similar to what we have here in Galveston)

Patagonia

The Würsig's favorite place

• Lesser rhea (flightless bird)
• Guaco (llama-type)
• Gray foxes
• 2 species of armadillo (long and short)

Darwin started his Evolutionary history reserach here

Tide is 10 m, 2nd highest on Earth

Field trip!

Foraging Strategies: Argentina

Fission/fusion society in a shallow water environment

Study area: Golfo San José around 42° 20' S, 64° 20' W

Early AM rest time

Carrying capacity of bay is about 300 dolphins.

Predator pressure: orcas

• Dolphins try to hide in surf zone

Breakfast

Later in morning, groups wake up. Breakfast time!

• "clean"; head-first re-entry leap: efficient breathing from at depth (overshoot surface and use gravity to get back down)
• "side-slap", "noisy-leap", "belly-slap": attract more dolphins to feed
  • the more animals, the longer feeding continues (easier to lose bait ball when fewer animals)
• multi-species aggregations: gulls, Magellanic penguins, seals

After Meal Play

• bouts of acrobatic leaps: backflip with a half-twist, frontflips, high leaps
• sex... umm... hetero and homo?
  • female over male
  • social bonding (not just procreation)
• According to Würsig, "it's very much a party attitude."

Summary

1. before feeding: noisy leaps and clean leaps
2. during feeding: less noisy, a few acrobatic, and clean leaps
3. after feeding: mostly acrobatic leaps

All dolphins have stages of feeding:

• before, they don't want anything to do with boats
• after, they'll dash to a boat. They want to have fun!

Evening fission

Rest near shore in shallow water

Foraging Strategies: New Zealand

Kaikoura Canyon: deep ravine off coast of New Zealand.

Feed at night on mesopelagic DSL creatures

Whitlow Au: acoustics

• array of multiple sonar devices to image the deep scattering layer
• dolphins show up as a large dot (lungs)

During day, dolphins stay near surface

At night they dive to deep scattering layer when it's closer to the surface, but they don't like to dive any deeper than they have to

Subgroups are larger when they feed at shallower depth

Light affects DSL location, so darker = shallower feeding

Summary

In shallow water,

• feed on schooling fishes
• cooperate to herd prey during daytime
• Fission-fusion society
• Intense social bouts after feeding

In deep water,

• Midwater fishes and squid
• at night
• do not cooperate closely?
• Disperse social activety throughout day and night
• unlike fin whales, who are energy maximizers, these dusky dolphins are time maximizers (don't like to hold breath long; spend more time with prey)

Tracking Vocalization

Lots of vocalization in bait-balling

Background

Calculating the speed of sound underwater:

• 1826
• Mathematician/engineer and oceanographer
• name? "Baron"
• Bell underwater, cymbal above water, and signal light (gunpowder) all go off at same time
• Sound travels 4.5 times as fast in water as it does in air: ${\tfrac {1500}{340}}=4.41$

Today

3-hydrophone array:

• William A. Watkins
• William E. Schevill

Triangulation of location based on time delay

• Overlaid with video
• Able to discriminate between individuals' vocalizations (i.e. who is making the sound )
• Dr. Michiel Schotten

Other Work

• Common Dolphins (Delphinus spp.) in the Sea of Cortez
• Spinner Dolphins (Stenella longirostris) near shore in Hawai'i: deep water DSL feeding

Questions

• Different roles during herding?
• Adjust techniques by prey type and size of ball?
• Feed more when they herd as a group (call more together)?
• cheaters in society?

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Culture and Conservation of Whales and Dolphins

What is culture?

• defined by both behavior and genetics
• "hitchhiking" ?
• Broadest definition: Culture is information or behavior shaped by a population or subpopulation, acquired from conspecifics through some form of social learning
• Doesn't have to be thoughtful or mindful, but here's a mindful one: (from some univ in 1930s) when beams of great hall become beetley, go harvest this grove of trees that was planted for this purpose

Types:

vertical

Learning from parents or other elders

stable (e.g. Relation,language)

transmission similar to genes

can inhibit survival (not willing to change)

horizontal

learning from peers

"pop culture", "fads" (e.g. musical tastes, clothes)

usually short-lived, but can last longer like humpback whale songs

helps with adaptation and survival

oblique

learning from someone a non-relative, but longer-lasting than horizontal

learning piano from the lady down the street.

Culture in whales and dolphins

• Junk-food dolphins
• Culture and environmental change
• Food fads and ecosystem shifts

Conservation

• Of non-human biodiversity (genes)
• Of elements of human culture (art, architecture, languages, aboriginal cultures)
• Of non-human culture?

Cultural units:

• compare to when one culture of humans dies out (due to extirpation or natural causes)
• Can be very significant loss

In Cetaceans

1. Long lives and prolonged parental care
   • 100+ years for bowhead whales
   • suckle for 4+ years
2. Large Brains
3. Advanced cognitive abilities (T. truncatus pass mirror-mark test)
4. Complex social structures (two levels of male alliance formation in bottlenose dolphins)
5. Mobile and not territorial (makes culture more ecologically and evolutionarily significant)

Note: Roughtooth dolphins are the brightest thing in the sea

Evidence of culture is remarkably strong given the difficulty of study:

• Orcas: stable, sympatric, multifaceted culture
• Bottlenose dolphin: variation and imitation

Humpback Whale Songs

• Long, elaborate, circular set of vocalizations
• sung by males on breeding grounds
• All males sing same song
• slowly evolves
• all populations follow same rules (except for "Australian revolution")
  • In 1997, South Pacific singers switched to song sung by males on Australian west coast (Indian Ocean) song
  • One male changed everything

Sperm Whale Codas

• Short patterns of 3–40 broadband clicks
• Sperm whale clans have different codas
  • Killer whales, sperm whales, and bottlenose dolphins are the only known species that can distinguish individuality
  • Many (smaller) delphinids do not whistle (e.g. Dusky dolphins, phocoenids, orcas).

Killer Whales

1. Population
2. form/type: (main foraging strategy; transient/mammal-eaters, resident/fish-eaters, offshore/mixed)
3. Community: (North Alaska, North BC, South BC) - differentiating by greeting ceremonies
4. Vocal Clan: dialect
5. Pods: dialect and foraging specializations
6. Matrilines

Junk-Food Dolphins

Two types of bottlenose dolphins in Moreton Bay, Australia: trawler foragers, non-trawler foragers

• Ranges overlap
• socially isolated
• What happens when fishing is restricted? Some youngsters may not have learned to forage for wild food...

Culture and Climate-Change

• Sperm whales in E Pacific are affected by El Niño phenomenon:
  • reduced feeding success
  • large movements
  • (further) reduced calving rate
• "Global warming"
  • produces El Niño-like conditions
  • increases frequency of El Niños

Some may be better-equipped to survive in changed climates: Bottlenose dolphins are very adaptable (can adapt to noisy environments, eat different foods)