Animal Migration

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Animal Migration
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What is migration?

• Migration
• Seasonal back and forth journeys between two
  sites
• Migrant vs. Resident

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Which animals migrate?

• Mammals
• Birds
• Amphibians
• Reptiles
• Fish
• Insects

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Why do animals migrate?

• Opportunism exploitation of ephemeral/seasonal
  resources
• Cost benefit ratio

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Types of Migration

• Latitudinal
• Altitudinal
• Reproductive
• Seasonal
• Irruptive

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Types of Migration

• Obligate annual migration
• 1. Latitudinal (north-south)
• Short distance (within a continent)
• Some birds, bats, and whales
• Long distance (between continents)
• Many species of songbirds, shorebirds, waterfowl,
  hawks
• Some bats and whales
• 2. Elevational
• Movement up and down mountain slopes
• Related to weather (especially snow depth) and
  food conditions
• deer, elk, Mountain Goats, Spotted Owls, some
  songbirds

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How do animals migrate?

• Magnetic field
• Landmarks
• Alignment of
• stars in night
• sky
• Olfactory cues
• Combination

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How do we know where animals go?

• Direct observation
• Ex. Broad-tailed hawk

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Photo by B. Webb
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Can estimate general population trends from
number of migrating individuals counted
Photo by B. Webb
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How do we know where animals go?

• Capture, mark, recapture

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How do we know where animals go?

• Radar, radio satellite telemetry
• Radar detection of neotropical migrant birds

Trans Gulf-migrants leaving
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How do we know where animals go?

• Radar, radio satellite telemetry
• Satellite telemetry Radio telemetry

• Signal from transmitter to satellite
• Location downloaded from satellite

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Peregrine Falcon migration routes based on
satellite transmitter data
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Swainsons Hawk migration routes based on
satellite transmitter data
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How do we know where animals go?

• Intrinsic markers
• Stable isotopes
• Elements vary in number of neutrons C, N, H, O,
  S building blocks

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Bird Migration

• Over 5 billion land birds of 187 species migrate
  between Europe and Asia to Africa
• Over 5 billion land birds of over 200 species
  migrate between North America and the New World
  tropics
• 75 of 650 bird species that nest in N. America
  migrate

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Neotropical migrant birds

• 80 of breeding bird spp. in N. America
• Complex annual life cycle
• breeding areas (2-3 mths)
• migratory pathways (2-3 mths)
• wintering areas (6-7 mths)
• Declines in many spp.
• Pattern

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Neotropical Migrant Bird Conservation

• Many species declining
• Loss of multiple habitats
• Breeding
• Migration stopover sites
• Wintering

3 ranges used by the Blackpoll Warbler each year
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Neotropical Migrant Bird Conservation

• Loss and fragmentation of winter habitat
  (tropical forest)
• slash and burn agriculture
• pasture land for livestock production
• commercial and illegal logging

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How declines have been measured

• Breeding Bird Survey
• species-specific studies
• population estimates on breeding and wintering
  grounds

Western meadowlark
Painted bunting
Cerulean warbler
Population trends 1996-2003
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Linkages between annual stages

• American redstart
• link condition on wintering grounds to breeding
  success
• Stable isotope analyses ratios of C13C12
• High quality winter habitat (coastal mangroves
  and lowland forests) wetter and C13 depleted
• Birds from high quality winter habitat
• earlier on breeding grounds
• earlier breeding more
• chicks fledged

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1.3 million wildebeest
350,000 Thompsons gazelles
200,000 plains zebra
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Mammal migration Serengenti
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Dangers Serengeti migration

• Predation
• Land and water
• Rinderpest
• Human population growth
• Land conversion
• Poaching esp. resident animals

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Sea Turtle Migration

• Juveniles hatch on shore and migrate to the open
  ocean
• After years in the open sea, juvenile turtles
  move to specific coastal feeding grounds
• Young loggerhead sea turtles in the North
  Atlantic cover more than 9,000 miles before
  returning to the North American coast!
• Adult turtles migrate between specific feeding
  areas and then back to nesting beaches

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Juvenile Loggerhead Migration

• Orientation during migration
• A variety of navigational cues are used
• Must stay in North Atlantic Gyre for several
  years to grow and develop
• Detect subtle differences in the earths
  magnetic fields to use as navigational markers

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Adult Green Turtle Migration

• Adult Green Turtles captured by fishermen at
  feeding grounds off coast of Nicaragua and
  branded
• Some turtles escaped after boat capsized at FL
  Keys
• Several months later same turtles recaptured in
  same area in Nicaragua
• Turtles use a magnetic compass and have map sense

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Whale Migration

• Pacific Gray Whales
• Longest known migration for any mammal
  10,000-12,000 miles annually!
• Raise calves in nurseries (lagoons) of Baja
  California
• Migrate to feed in the cold arctic seas
• Nearshore migration route allows for easy
  observation, but harassment by whale-watching
  boats may be pushing whales off shore

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Butterfly Migration

• Monarch Butterflies
• Fly up to 3,000 miles each way
• Return to the same winter roosts, often to the
  exact same trees
• Preferred conditions found in oyamel fir
  forests, which occur in a small area of mountain
  tops in central Mexico

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Conservation Strategies

• International cooperation (Partners in Flight)
• Incentives for developing countries to protect
  migratory wildlife and habitat
• Public education consumer choices