Migration: Animals Getting Around the World

MIGRATION OVERVIEW

  • Definition of Migration:

    1. To move from one country or location to another

    2. The periodic movement from one region or climate to another typically for feeding or breeding.

MIGRATION IN BIRDS

  • Bird Migration Statistics:

    • About 75% of all birds are migratory.

    • An estimated 10 billion birds migrate annually.

  • Notable Migratory Example:

    • Some birds can travel extensive distances, such as flying 23,000 miles.

Types and Examples of Migrating Animals

  • Monarch Butterflies:

    • Migrate from the United States to California and Mexico to escape the colds.

  • Wildebeests:

    • Migrate north in spring following the rains to find grazing grass in the Serengeti, Eastern Africa.

  • Sea Turtles:

    • Live in the ocean but return to land to lay eggs and head to the water after hatching.

  • Arctic Terns:

    • Known for the longest migration, traveling 12,000 miles between the Arctic and Antarctica, experiencing two summers a year.

REASONS FOR MIGRATION

  • Animals migrate for several reasons, including:

    • Avoidance of harsh climates.

    • Follow or find supplies.

    • Searching for abundant food sources or specific food types.

    • Returning to breeding grounds.

    • Escaping parasites.

    • Seasonal movements to safer areas for molting.

OBSTACLES OF MIGRATION

  • Migrating animals face numerous challenges, such as:

    • Physical exhaustion.

    • Predation.

    • Pollution.

    • Natural geographic barriers (oceans, mountains, deserts).

    • High altitudes (up to 29,000 feet).

    • Food and water scarcity along migration routes.

LOSSES DURING MIGRATION

  • Significant mortality rates are common during migration:

    • Approximately 50% of European passerines that migrate to Africa do not return.

    • Harsh conditions, like the harmattan wind in the Sahara, can lead to flocks being blown to sea.

SOCIETY IN MIGRATION

  • Migration can often be a social event, with many individuals traveling together:

    • Provides protection for individuals.

    • Groups form larger flocks or herds for safety.

RESEARCHING MIGRATION

  • Historical observations have been supplemented by modern methodologies:

    • Banding and tagging of birds.

    • Use of radio and satellite tracking.

    • Global Positioning.

ARCTIC TERNS DETAILS

  • Arctic terns are considered the most remarkable migratory birds:

    • Known as sea swallows with a 15-inch wingspan.

    • Journey spans 24,000 miles annually, enduring constant daylight for 8 months.

    • Stay in daylight more than any other animal.

MIGRATION GENETICS

  • Migration behaviors are influenced by genetics as well as environmental factors:

    • Traits influencing migration (migrant vs non-migrant) are affected by environmental and genetically.

WILDEBEEST MIGRATION

  • White-bearded wildebeests \\move together with Burchell’s zebras and Thompson’s gazelles in the Serengeti:

    • Up to 1.5 million migrate slowly throughout their annual cycle.

  • Short grass plains offer nutrition, but as rains begin, they migrate to find phosphorus-rich grazing grounds.

CARIBOU AND REINDEER MIGRATION

Caribou and Reindeer, classified under Rangifer tarandus, are cousins (classified as 2 subspecies):

  • Caribou: large, wild, elk like and in Artic and Greenland.

    • Live on lichens in the winter.

    • Calf can run within 90 minutes of its birth to keep up with the migrating herds.

    • Summer, give birth in NW Alaska and Canada

    • Fall, they move south slowly

    • Unique hairs for insulation and buoyant in water makes them very strong swimmers.

NAVIGATION METHODS

  • Animals utilize various natural mechanisms for navigation:

    • Learned routes through memory of landmarks.

    • Celestial navigation using stars and the sun.

    • Earth's magnetic fields and polarized light.

ANIMAL NAVIGATION MECHANISMS

  • Navigation methods utilized by birds include:

    • Eyes: Imprinting patterns of celestial bodies and using chemical reactions for magnetic navigation.

    • Ears: Utilizing iron concentrations in the inner ear to sense magnetic fields.

    • Beak: Employing olfactory maps for navigation based on scent.

COGNITIVE ASPECTS OF MIGRATION

  • Long-term memory enables migratory warblers to create detailed maps of feeding sites:

    • Migratory warblers have a larger hippocampus than their non-migratory counterparts, enhancing long-term memory maps, and it increases by 12% after first migration.

FORMATION AND EFFICIENCY IN FLIGHT

  • Birds like geese fly in a V-shaped formation, termed "drafting":

    • This formation reduces wind resistance for trailing birds and conserves energy.

CONCLUSION

  • Key questions regarding migration to consider:

    • Why do animals migrate?

    • How do they determine their migration routes and timing?

    • What species exhibit exceptional migratory endurance?