Marine Mammals

1
Marine Mammals

• Dolphins and Porpoises

2
Characteristics

• Dolphins and Porpoises are classified as toothed
  whales. They live in both fresh and saltwater.
  There are currently over 40 recognized species.
• sleek, smooth skin lined with blubber
• broad flippers and tails
• They can jump 3X their body length and can reach
  swim speeds of 20-30 mph.
• Keep their teeth their entire lives so age can be
  determined by tooth analysis

3
Senses

• one nostril at the top of their heads less body
  to expose to breathe.
• Special eye adaptations
• Strong eye muscles can change lens for land and
  water viewing
• They can adjust the pupil
• Large pupil deep water
• Slit pupil bright light
• Clear, jelly-like protein that keeps the salt
  from irritating the eye.
• No sense of smell but can taste chemicals in
  the water.

4
Reproduction and Offspring

• Females usually give birth to a single offspring
  after a 12 month gestation.
• Babies are born tail first, 30-45 lbs.
• Females will baby sit the offspring of other
  females by forming playpens - swimming in
  circles around them to protect from predators.
• Young nurse for 2-3 years and can stay with
  mother between 3-6 years.
• Young swim next to mother in baby position

5
Males

• Male dolphins form coalitions.
• A coalition is 2-3 males that form close bonds
  with each other.
• They herd females for breeding and will cooperate
  to feed.

6
Dolphins vs. Porpoises

• Porpoises Dolphins
• Smaller heads larger heads (snout)
• Flat teeth more pointed teeth

7
Dolphins and Tuna

• Dolphins and tuna form a close relationship in
  the open ocean. Fishermen know that to find tuna
  they simply need to look for pods of dolphins.
  They then net the dolphins and are able to
  capture the tuna.
• 1973 144,000 dolphins killed in tuna nets
• 1993 3,605 killed
• Public outcry made them modify the tuna nets and
  companies now advertise dolphin safe tuna.

8
Echolocation a type of hearing

• Steps of echolocation
• Clicks are generated by
• squeezing air in the
• blowhole passage.
• The clicks are reflected
• off the concave skull and focused by the
  melon (the bump on the forehead of a dolphin).
• 3. The melon is made of fat and oil and helps
  concentrate the clicks.
• 4. Once the clicks reach the target they are
  reflected back through the lower jaw and then to
  the inner ear.
• 5. The dolphin is able to determine the size,
  shape and direction of the object by measuring
  the time between the clicks and their return.