Animal Migration

What is migration?Migration: Seasonal back and forth journeys between two sites

Migrant vs. Resident

Which animals migrate? Mammals Birds Amphibians Reptiles Fish Insects

Why do animals migrate?Opportunism exploitation of ephemeral/seasonal resources

Cost benefit ratio

Types of MigrationLatitudinalAltitudinalReproductiveSeasonalIrruptive

Types of MigrationObligate annual migration1. Latitudinal (north-south)Short distance (within a continent)Some birds, bats, and whalesLong distance (between continents)Many species of songbirds, shorebirds, waterfowl, hawksSome bats and whales2. ElevationalMovement up and down mountain slopesRelated to weather (especially snow depth) and food conditionsdeer, elk, Mountain Goats, Spotted Owls, some songbirds

How do animals migrate?Magnetic field LandmarksAlignment of stars in night skyOlfactory cuesCombination

How do we know where animals go?Direct observationEx. Broad-tailed hawk

Photo by B. Webb

Photo by B. WebbCan estimate general population trends from number of migrating individuals counted

How do we know where animals go?Capture, mark, recapture

How do we know where animals go?Radar, radio & satellite telemetryRadar detection of neotropical migrant birdsTrans Gulf-migrants leaving

How do we know where animals go?Radar, radio & satellite telemetrySatellite telemetry Radio telemetry Signal from transmitter to satellite Location downloaded from satellite

Peregrine Falcon migration routes based on satellite transmitter data

Swainsons Hawk migration routes based on satellite transmitter data

How do we know where animals go?Intrinsic markersStable isotopesElements vary in number of neutrons C, N, H, O, S building blocks

Bird MigrationOver 5 billion land birds of 187 species migrate between Europe and Asia to AfricaOver 5 billion land birds of over 200 species migrate between North America and the New World tropics75% of 650 bird species that nest in N. America migrate

Neotropical migrant birds80% of breeding bird spp. in N. AmericaComplex annual life cyclebreeding areas (2-3 mths)migratory pathways (2-3 mths)wintering areas (6-7 mths)Declines in many spp. Pattern

Neotropical Migrant Bird ConservationMany species decliningLoss of multiple habitats:BreedingMigration stopover sitesWintering3 ranges used by the Blackpoll Warbler each year

Neotropical Migrant Bird ConservationLoss and fragmentation of winter habitat (tropical forest): slash and burn agriculture pasture land for livestock production commercial and illegal logging

How declines have been measuredBreeding Bird Surveyspecies-specific studiespopulation estimates on breeding and wintering groundsWestern meadowlarkPainted buntingCerulean warblerPopulation trends: 1996-2003

Linkages between annual stagesAmerican redstart link condition on wintering grounds to breeding successStable isotope analyses: ratios of C13:C12High quality winter habitat (coastal mangroves and lowland forests): wetter and C13 depletedBirds from high quality winter habitatearlier on breeding groundsearlier breeding = more chicks fledged

1.3 million wildebeest200,000 plains zebra350,000 Thompsons gazelles

Mammal migration: Serengenti

Dangers: Serengeti migrationPredationLand and water

RinderpestHuman population growthLand conversionPoaching esp. resident animals

Sea Turtle MigrationJuveniles hatch on shore and migrate to the open oceanAfter years in the open sea, juvenile turtles move to specific coastal feeding groundsYoung 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

Juvenile Loggerhead MigrationOrientation 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

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

Whale MigrationPacific 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

Butterfly MigrationMonarch 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

Conservation StrategiesInternational cooperation (Partners in Flight)Incentives for developing countries to protect migratory wildlife and habitatPublic education: consumer choices

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