Lecture 23 Flashcards
What is Migration?
- Seasonal mass movement
- Long or short distances
- Can occur many times throughout an individual’s life or just once
- Typically involves a switch from one habitat to another
Daily Migration
Golden jellyfish
• Symbiotic relationship with zooxanthallae algae
• Daily migration to ‘sun’ their algae
Some fish, zooplankton
• Daily vertical migration
• Feed at surface at night
• Retreat to depths during day
Migration: Amphibians & Reptiles
• Migrate to aquatic breeding ground (amphibians) or egg-laying site (reptiles)
• Crossing roads is a major hazard
• In some locations, ‘crossing tunnels’ or
culverts have been constructed beneath roads to allow animals safe passage
Migration ‘stars’
Bar-tailed godwit (Limosa lapponica)- One non-stop flight: 11,000 km, 9 days
Bar-headed goose (Anser indicus)-Migrates over the Himalaya less than 10%of oxygen found at sea level
Why Migrate?
- Seasonal changes in the local environment temperature, drought, food availability
- Changing needs at different life stages
- Move to a suitable habitat for reproduction
Preparing for Migration
Migration requires a lot of energy
- Hyperphagia
- Excessive appetite
- intense period of feeding prior to migration
- Fat is stored for the long journey
- Hyperphagia is observed in diverse species including birds, whales, insects, and caribou
- e.g. Birds can double their body weight before migration!
- Many species save energy by taking advantage of wind patterns and water currents
Shorebird Stopover
Many species of shorebirds congregate in Deleware Bay, NJ
• Feast on horseshoe crab eggs • Plentiful
• High in fat
Shorebirds in decline
Horseshoe crabs overharvested
Shorebirds in decline in last 2 decades in Deleware Bay
• 1.5 million to 350,000!
Why migrate to arctic
• most North American species migrate
- Many migrate as far as the arctic. Why?
- Advantages of breeding in the arctic
- Long daylight hours and very productive ecosystem
- Ample resources
- Space (reduces competition)
- Relatively few predators
Migration routes/rates in Birds
Migration routes generally follow set paths, Can be innate or learned
• Some birds travel very fast
• Bar-tailed godwit – 11,000 km in 9 days
• Others travel at a leisurely pace
• Some warblers take 50-60 days to get from Central America to
breeding grounds in Canada
Birds navigate
• chiefly by sight (topographical landmarks)
• Earth’s magnetic field
• Sun and stars
Arctic tern
longest migration of any animal (70,000 km yearly)
• Pole to pole
Over its lifetime (up to 30 years) can migrate 2.4 million km
Costs and benefits of migration
Tropical Resident:
Annual adult survival = High (80%-90%)
Annual reproductive success= low
Migrant:
Annual adult survival = moderate (50%)
Annual reproductive success= moderate
Temperate Resident:
Annual adult survival = Low
Annual reproductive success= High
Migration in freshwater eel
• Endangered species
• Lives in freshwater estuaries and spawns in the ocean
• A panmitic species
• all members of the species mate randomly and are considered to form one large population
Live in freshwater - migrate to the ocean to spawn
Spawn at a depth of 300 m… • …then die
Tiny larvae begin the long migration back to the coast, growing along the way
• takes them 1 year to reach North American estuaries
Salmon migration
- Most salmon are anadromous (running upward)
- Spend adult lives at sea and return to freshwater to spawn
- Atlantic salmon make multiple runs throughout their lives
- Pacific salmon make a single run and then die
- Pacific salmon migrate downstream as juveniles
- Spend 3-4 years in the Pacific ocean (growing)
- Return to spawn in the headwaters of its parent stream
Osmotic Regulation
Maintenance of balance of fluids
• Freshwater fish are hyperosmotic regulators
• Marine fish are hypoosmotic regulators
