Marine Mammal Behavior

1
Marine Mammal Behavior

• Diet and Foraging Behavior
• Health and Maintenance
• Mating

2
Marine Mammal Foraging Ecology

• What an organism eats, where it eats and how much
• Can be very difficult to determine in marine
  mammals
• Some Methods to Analyze what wasn't digested, ie
  hard parts
• Stomach contents
• Can be hard to get
• Feces
• Easier to get
• Serology analysis of serums and enzymes
• Certain enzymes will react with certain foods,
  thus telling you what the organism was eating
• Fatty acids
• Fatty acid composition of the prey influences the
  fatty acid composition of the predator.

3
Role of Marine mammals in Marine ecosystems

• Little is known
• They do eat a lot though
• Sperm whales eat 400million tons of squid/year
• Antarctic
• Our killing off of many whales the feed in the
  Antarctic has made more krill available for other
  animals
• Consequently penguin and seal numbers have
  increased over the last 100 yrs

4
Sirenian Diet

• Herbivores
• Feed mostly on sea grass
• In Shallow areas

5
Pinniped Diet

• Not very specific
• Fish, squid, crustaceans
• Remember, they're like a dog
• Strong preferences though
• Often most of the food is
• Also strong seasonality to prey choice
• Mostly eat fish and squid
• Some eat krill, e.g. the crab eater seal

6
Odontocete Diet

• Odontocetes
• Feed mostly on squid, fish and other large
  animals
• Teeth designed for holding onto fast moving prey

7
Otariid Foraging Behavior

• Considered to be shallow divers with durations of
  2-3 minutes
• Feed mostly on fish in nearshore waters.
• Tend to feed mostly at night or dawn, though the
  California sea lion dives only during the day
• Otariid females forage during lactation

8
Phocid Foraging Behavior

• Phocids Deep divers.
• The deep divers are benthic (bottom) feeders.
• Antarctic fur seal follows the krill. Dives are
  shallow at night because the krill are in the
  surface waters, but are deeper during the day,
  when the krill are deeper in the water column.
• Phocid females, with a few exceptions, fast
  during lactation
• After fasting, Northern Elephant seals will
  forage continuously 70 days for females and 120
  days for males.
• After molting return to sea for 241 days and
  females 296 days.

9
Pinniped Health and Maintenance Behaviors

• Seals have a problem with overheating, so they do
  things to keep cool.
• During breeding females shift their position
  throughout the day so as to stay on cool, moist
  sand, or even move to tide pools.
• Grooming
• Necessary, but not social, meaning that they
  dont groom each other.
• Sea otters (not pinnipeds) groom constantly in
  order to maintain their thick fur coats and
  remove parasites.

10
Pinniped Mating

• The reproductive cycle is annual, synchronous and
  very stable.
• There is a profound annual cycle in males of
  testicualr regression and recrudescence
• The male's cycle is linked to the female's
• Most pinnipeds are polygynous (one male for many
  females)
• Five Tactics of Polygyny
• Males defend resources used by females
• Follow or defend females directly
• Search for receptive females and move on to the
  next
• Sequentially defend single females through mating
• Aggregate and attract mates
• The Northern Elephant Seal
• Males have large harems, which are fought over by
  males in fierce battles. Consequently, the
  largest male tends to have the largest harem.

11
Pinniped Rearing Behavior

• Males tend to offer very little assistance in
  rearing the young
• Three main strategies in maternal care
• Foraging during lactation-Otariids and a few
  phocids, including the harbor seal
• Females acquire a moderate store of blubber
  before coming ashore to give birth
• Fasting during lactation-Phocids
• Females build up large blubber reserves before
  nursing
• Some combination of the two- Odobenids
• Walrus calves travel with their mothers while
  feeding.

12
Pinniped Migration and Social Organization

• Many pinnipeds migrate during the year.
• Coincides with seasonal breeding/foraging cycles.
• Some, such as the harbor seal, have a definitive
  breeding ground from which they disperse, but
  dont actually migrate.
• Social organization is most complex during the
  breeding season.
• Hierarchical dominance forms around harems,
  especially.
• However, these rookeries dont appear to have any
  real order to them, they are just places where
  many individuals congregate.

13
Mysticete Diet

• Very hard to determine diet
• Fecal pellets are rarely available
• Most stomach content data comes from commercial
  whaling or stranded animals
• Can't pump their stomachs
• Different Baleen Types
• Those with coarse baleen feed on swarming
  zooplankton or fish
• Blue whales, humpback whales
• Benthic feeders filter out mud and invertebrates
• Gray whales
• Skimmers have log plates of baleen and feed on
  zooplankton such as copepods
• Right whale, bowhead whale

14
Odontocete Foraging

• Capture single prey, such as fish or squid
• Those with fewer or no teeth tend to eat soft
  bodied prey.
• Feed throughout the year and are therefore tied
  to regions with consistently abundant food.
• Use echolocation to find food.

15
Odontocete Foraging Examples

• Sperm whales
• Deep diving, squid eaters
• Stay under for 1hr to depths 1000m
• Tend to forage in groups
• Orcas
• Capture prey in large teeth at intermediate
  depths
• Tend to feed on school fish and squid, but will
  also eat other marine mammals including large
  mysticetes
• Attack in pods
• Small Odontocetes
• Feed on fish, often in groups
• Can also echolocate fish under the sand and dig
  for it.
• "Fish Whacking" involves hitting a fish with the
  fluke and either stunning or killing it.
• Strand feeding dolphins will chase a school of
  fish up onto the shore and then jump after it.

16
Cetacean Mating Patterns

• A variety of precopulatory behaviors
• Rubbing of bodies
• Stroking pectoral fins
• Rubbing Genitalia
• Copulation
• Bottolenose dolphins the pair orient in the same
  direction, the male mounting the female and
  intromission lasting only a few seconds
• Humpbacked dolphins male displays an erection
  and swims upside down beneath the female,
  repeating this over the course of several hours
• Most cetaceans perform polygamy or promiscuity,
  not monogamy
• Male to male competition
• Narwhals 'joust' with their tusks over females
• In the right whale many males with copulate with
  one female, attempting to flush out each others
  sperm.

17
Cetacean Rearing Patterns

• Parental care occurs over periods of at least
  several months to 1 year, or may last many years.
• Maternal investment includes providing
  nourishment, protection, and learning
  opportunities to calves
• Sometimes other whales aid in the care.
• Mother's milk provides the primary source of
  nutrition
• Many odontocetes form nursing groups, which is a
  cluster of mothers and young