Animal Migration

1. Animal Migration • Leaving an area for part of the year and moving to habitats that are more hospitable. • Migration is • Predictable • Seasonal • Repeated each year

2. Animal Movement NOT Classified as Migration Dispersal: • Animal movement caused by overcrowding • Animal movement away from a group based on sexual maturation. • Example: Young male lions. All the females in a pride are related. As a male reaches sexual maturity, he leaves his pride, and eventually finds another pride he can take over. • Example: Female chimpanzees. Leave natal (birth) communities between the ages of 9-14 years and join unrelated communities. Hypothesis: Why would one gender disperse from a group at sexual maturity?

3. Animal Movement NOT Classified as Migration Irruption: • Animal movement out of an area at unpredictable times due to harsh conditions or limited resources. Example: Lemmings - “the Scandinavian lemming, migrates in a huge group when food becomes scarce. They will run in one direction through meadows, woods and towns. If they come to a large body of water they will swim and swim looking for land.  The stories about lemmings jumping off cliffs are a myth”. www.mnh.si.edu/arctic/html/lemming.html

4. Why Migrate? • To avoid seasonal variations in temperature, snowfall, and water • To take advantage of • Food and essential minerals • Available water • Shelter • Available mates • Available breeding requirements

5. Types of Migration • Latitudinal migration • movement of animals north and south from regions of cold in the winter to warmer regions near the equator. • this movement is reversed in the summer.

6. Types of Migration (continued) • Altitudinal migration: the movement of animals up and down major land features such as mountains. • In the northeast USA, altitudinal migration is not a major factor in the movement of animals. • In the American west, mountains are younger and taller. There are great extremes between conditions on mountain tops (alpine regions) and areas at lower elevation. • Examples: elk and bear move down mountain slopes to where food is more abundant and snowfall is less.

7. Types of Migration (cont) • Reproductive migration is the movement of animals to bear young. • The area may be safer for the young because of fewer predators or more shelter from predators. • An animal requires a different type of habitat when it is young than when it is older. Examples: grey whale, European toad, green turtle, emperor penguin

8. Latitudinal Migration • Why do animals return to their breeding grounds in the spring? • Food, shelter and mates become abundant in their breeding grounds and competition is less than near the equator. • Day length increases at their breeding grounds (up to 24 hours/day), which increases the hours spent foraging. • Day length is 12 hours/day year-round near the equator.

9. Each Type of Migration Can Be: • Complete migration • Occurs when all members of a species leave their breeding range during the non-breeding season. • Many N. American song birds are complete migrants. • These birds winter in South and Central America, the Caribbean, and southernmost parts of USA.

10. Complete Migration • IN WHAT TYPE OF AREAS WOULD YOU EXPECT TO SEE COMPLETE MIGRATION? AND WHY? Most complete migrants breed in northern temperate and arctic areas (such as Alaska) of North America, Europe, and Asia

11. Partial Migration • Some, but not all, members of a species move away from their breeding grounds during the non-breeding season. • This is the most common type of migration Complete: Worksheet on Migration

12. What Triggers Migration? • Trigger(s) one or more of the following: • Shortening day length (end of summer) or lengthening day length (end of winter) • Decrease in food and water supplies • Circannual rhythms – Important for birds wintering close to the equator. At the equator there is no change in day length or food availability year-round.

13. Navigation and Migration • Genetics plays a large role in migratory behavior. Animals inherit migratory routes from their parents. • In short migrations or in altitudinal migrations, animals follow • food or water or • head downhill in winter and back upwards in summer.

14. Navigation and Migration • In longer migrations animals orient movement: • Using the sun’s position in the sky and the time of day (ex. Starlings) • Using the stars of the night sky (mallard ducks) • Using the geo-magnetic field (migratory birds, salamanders, salmon, or hamsters, loggerhead turtles.

15. Navigation and Migration (continued) • Using mental maps based on eyesight (they become familiar with an area) • Using mental maps based on sense of smell – (fish) • Usingsubtle changes in water quality and 'reading' wave and current patterns (aquatic animals) Read: Evidence for a navigational map stretching across the continental U.S. in a migratory songbird, and ANSWER QUESTIONS.

16. Adaptations for Migration (examples) • Birds – hollow bones • Geese – fly in “V” to decrease wind drag • Birds/whales– feed intensively before setting off to lay down fat reserves as fuel – a form of behavior called hyperphagia • Radical physical transformation. Some birds develop larger, powerful breast muscles for flight and shrink non-essential organs prior to migration

17. Surviving migration • How do animals enhance thirability to survive a long-distance migration? They • travel in groups for protection • hitch a lift on ocean currents and winds • stop en route to rest and refuel

18. Specific Examples of Extraordinary Migrations Monarchbutterfly Arctic tern

19. Monarch Butterflies • A monarch butterfly’s life cycle includes four stages: egg, caterpillar, pupa, butterfly

20. Monarch Butterflies • Over the course of ONE year, four or more generations of monarchs are born and die. • The butterflies in most of the generations live only 2-6 weeks. • The butterflies that emerge in August from a chrysalis are the ones which migrate. They live 6-8 months! • Migration begins in late August from eastern USA /Canada and ends in early fall in Mexico. 40-60% die en route.

21. Monarch Butterflies • Navigation: appears to be a combination of the magnetic pull of the earth and the position of the sun among others • While migrating, the butterflies are in reproductive dormancy. Their sexual organs are not fully developed • Upon arriving in Mexico, they settle on oyamel fir trees. • Tens of thousands of monarchs cluster on a single tree to stay warm.

22. Monarch Butterflies • When they arrive in Mexico, they feed and then “hibernate”—low metabolism • As temperatures increase (March), their activity increases, their sexual organs mature, mating begins, and they head north. • Between leaving Mexico and returning to Canada and USA, there will be 2-4 reproductive cycles.

23. Greenland Arctic Terns • Migration route is the longest of all animals • In the summer months of the northern hemisphere, the Arctic tern lives and breeds near the north pole in Greenland. • In the fall, it begins its flight to the shores of Antarctica at the south pole. The terns will reach Antarctica when summer begins there. • Total round trip = 44,000 miles. Antarctica

24. Arctic Tern • On their way from Greenland south, they stop for a month and feed • On their return from Antarctica they follow the winds--even though the trip is longer. • Arctic terns live up to 34 years. Over their lifetime they can fly more than 1.25 million miles • Amazingly each arctic tern has a mass of only 3.5 grams

25. Arctic Tern • Navigation 1) The tern has biomagnetite in its brain. This allows it to sense the surrounding magnetic field and use it as a guide. 2) The tern uses landmarks, such as coastlines, to help guide it. 3) During the night, stars and the moon can guide the birds.

26. Problems for Migrating Animals • Migration routes include multiple countries/continents. Not all of these areas provide safe habitats (wars/construction/habitat loss) • Climate change - has the potential to disrupt the migratory patterns of a wide range of animals. • loss of habitat for birds that breed on small ocean islands. • warmer temperatures may cause a change in the seasonal availability of food for migrating animals.

27. READINGS Choose a Migrating Animal: • Sea turtles • Denali Golden Eagles • Rocky Mountain Elk • Ruby throated hummingbird • Follow guidelines with your group for presenting the material to class.