Animal Migration What is Migration Migration is the

Animal Migration

What is Migration? Migration is the regular movement of animals from one location to another. v Prerequisites for migration: 1. Sustained movement 2. Physical endurance 3. Mechanisms for storing energy 4. Designated food sources on the migration route v Migration ensures animals will have adequate food supplies & will be able to reproduce.

Types of Migration v Migration may occur: § As a round trip § As a return migration • Corresponds with the seasons v Some require a lifetime to complete: § Ex: Pacific salmon • Born in freshwater streams • Travel to the ocean • Return to the stream where they were born • Spawn and then die

Knowing When to Migrate v How do animals know when it is time to migrate? v. Internal signals § Hormones trigger an overwhelming urge to… • eat, mate & reproduce v. External signals (clues) § Temperature change § Daylight hours § Scarce food supply

Migration Destinations v How do animals know where to go? v Specialized abilities to navigate v External forces § Ex. : wind & water currents v Landmarks: § Ex. : coastlines, mountain ranges, river valleys & distinctive odors v Sun: § Track the passage of days and months § Track their position in relationship to the sun

Migration Destinations (cont. ) v Internal Clues v Are sensitive to a mineral known as magnetite § Found in many animals, including humans § Allows animals to use the earth’s magnetic field as a guide. v Ex. : Gray whales § Large amount of magnetite in their retinas • Helps them navigate their 10, 000 mile journey

Migration: Behavior or Instinct? v Monarch butterfly § Migration is instinctive § Fly without guidance or previous experience § Use little or no directional clues v Learning migration behaviors for most animals is critical to their survival.

Migration Behaviors v Most animals must learn their migratory routes. v Older members of the group teach the younger animals: § The route traveled § Valuable strategies and/or behaviors v Humans teach younger animals, too. § Ultra-light aircraft • Taught various species of cranes their migration routes v Animals who are not taught these behaviors will not likely survive.

Why Migrate? v. Most animals migrate for two reasons: § Food & water: • Will migrate to find these resources § Reproduction: • Safe environment for bearing & nursing offspring. • Abundant food sources

Hazards of Migration v Two categories: § Natural hazards: • • • Climate changes Drought Food Supply Predators Physical demands of migration § Man-made hazards: • Barriers (fences, dams, & skyscrapers) • Water, aircraft, & fishing practices