Animal Migrations

1
Animal Migrations

• Dr. Ouida Meier
• Marine Biology

2
Why migrate?

• To take advantage of food resources, either for
  adults or for young (often not identical)
• To gather in appropriate breeding grounds
• To gather in appropriate egg-laying or calving
  grounds
• Exploit seasonal variations (e.g., temperature)
• To avoid predation (e.g., whales calving in
  warmer areas with fewer Orcas)
• To integrate social, feeding, reproductive
  behaviors with locations and seasons

3
(No Transcript)
4
(No Transcript)
5
Northern Elephant Seal
6

• Northern elephant seals undertake two
  migrations each year to protected beaches or
  rocky shores once to give birth or breed (around
  late December), and again a few months later to
  molt fur and skin.
• Newborn elephant seals are weaned at just 4
  weeks after the moms leave, they hang out on the
  rocks for weeks longer before heading out to feed
  themselves.
• Because of the two long round trips per year,
  northern elephant seals travel the furthest of
  any migrating marine mammal up to 21,000 miles
  per year.
• There are significant differences in male and
  female distributions in the wild larger males
  range further north, and females range further
  offshore to feed.

7
(No Transcript)
8
(No Transcript)
9
Blue Whale

• Suborder Mysticeti
• Size largest mammal, possibly largest animal,
  ever to inhabit the planet. Antacrtic adult
  female to 108 length, 150 tons
• Feeding in summer, up to 4 tons of krill/day (or
  40,000,000 krill/day)
• Migration found in all oceans of the world
  migrate to tropical-to-temperate waters during
  winter months to mate and give birth to calves.
  They can feed throughout their range, in polar,
  temperate, or even tropical waters.
• Factoid Nursing calves can consume 100 gallons
  of milk/day, grow 1 ½ inches/day, and gain 8
  pounds/hour!

10
Population estimates Pre-whaling gt350,000
N. Hemisphere lt4,000 S. Hemisphere
lt10,000
11
Blue Whale
12
Humpback Whale

• Suborder Mysticeti
• Size Adult females 45-50, 25-40 tons
• Feeding consumes 1 ½ tons of krill and small
  fish each day
• Migration Found in all the world's oceans, most
  populations of humpback whales follow a regular
  migration route, summering in temperate and polar
  waters for feeding, and wintering in tropical
  waters for mating and calving.
• Factoid Whales in the North American Atlantic
  population sing the same song, and all the whales
  in the North American Pacific population sing the
  same song. However, the songs of each of these
  populations and of those in other areas of the
  world are uniquely different. A typical song
  lasts from 10-20 minutes, is repeated
  continuously for hours at a time, and changes
  gradually from year to year. Singing whales are
  males, and the songs may be a part of mating
  behavior.

13
Population estimates Pre-whaling 150,000
Current perhaps 40,000
14
Humpback Whale
15
Gray Whale

• Suborder Mysticeti
• Size Adult females 45-48, 30-40 tons
• Feeding small crustaceans such as amphipods, and
  tube worms found in bottom sediments
• MigrationThe gray whale makes one of the longest
  of all mammalian migrations, averaging
  10,000-14,000 miles (16,000-22,530 km) round
  trip. In October, the whales begin to leave their
  feeding grounds in the Bering and Chukchi Seas
  and head south for their mating and calving
  lagoons in Baja California, Mexico. The southward
  journey takes 2-3 months. The whales remain in
  the lagoons for 2-3 months, allowing the calves
  to build up a thick layer of blubber to sustain
  them during the northward migration and keep them
  warm in the colder waters. The return trip north
  takes another 2-3 months.
• Factoid Courtship and mating behavior are
  complex, and frequently involve 3 or more whales
  of mixed sexes. (!)

16
Population estimates N. Atlantic extinct
W. N. Pacific depleted E. N. Pacific
19-24,000
17
Gray Whale
18
(No Transcript)
19
Hammerhead Sharks

• Nine species of hammerheads, 3-20 in length
• Tropical and subtropical oceans
• Schooling sites High daytime densities at
  seamounts, but not for feeding
• Response to magnetic fields in basalt seamounts?
  Electroreceptors at base of head.
• May follow magnetic highways swimming from
  landmark to landmark using seamounts as stepping
  stones.
• Other species?

20
(No Transcript)
21
Sources

• Whale facts and graphics from the American
  Cetacean Society, http//www.acsonline.org/
• National Marine Mammal Lab - elephant seal
  -http//nmml.afsc.noaa.gov/education/pinnipeds/nel
  ephant.htm
• Hammerhead photo http//www.bajadestinations.com/
  fishid/sharkhammer/Roldhamheads.jpg
• Sumich and Morrissey, Introduction to the Biology
  of Marine Life
• Nybakken and Bertness, Marine Biology An
  Ecological Approach