Lecture 23

Question 1

What is Migration?

Answer 1

• 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

Question 2

Daily Migration

Answer 2

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

Question 3

Migration: Amphibians & Reptiles

Answer 3

• 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

Question 4

Migration ‘stars’

Answer 4

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

Question 5

Why Migrate?

Answer 5

• Seasonal changes in the local environment temperature, drought, food availability
• Changing needs at different life stages
• Move to a suitable habitat for reproduction

Question 6

Preparing for Migration

Answer 6

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

Question 7

Shorebird Stopover

Answer 7

Many species of shorebirds congregate in Deleware Bay, NJ
• Feast on horseshoe crab eggs • Plentiful
• High in fat

Question 8

Shorebirds in decline

Answer 8

Horseshoe crabs overharvested

Shorebirds in decline in last 2 decades in Deleware Bay
• 1.5 million to 350,000!

Question 9

Why migrate to arctic

Answer 9

• 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

Question 10

Migration routes/rates in Birds

Answer 10

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

Question 11

Arctic tern

Answer 11

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

Question 12

Costs and benefits of migration

Answer 12

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

Question 13

Migration in freshwater eel

Answer 13

• 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

Question 14

Salmon migration

Answer 14

• 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

Question 15

Osmotic Regulation

Answer 15

Maintenance of balance of fluids
• Freshwater fish are hyperosmotic regulators
• Marine fish are hypoosmotic regulators

Question 16

Osmoregulation

Answer 16

Euryhaline species can survive in a range of salinities
• Freshwater: low salinity
• Brackish water: medium salinity
• Found in estuaries (where rivers meet the ocean)
• Saltwater: high salinity

Two types of euryhaline species of fish:
• Catadromous: migrate downstream to spawn e.g. American eel
• Anadromous: migrate upstream to spawn e.g. Pacific salmon

Question 17

Migration in Marine Mammals

Answer 17

• Many marine mammals migrate
• Spend summer eating in Arctic
or Antarctic
• Breed in tropics

Question 18

Migration in Terrestrial Mammals

Answer 18

More difficult for terrestrial mammals than for birds, fish, or marine mammals
• Terrestrial locomotion is more energetically costly than swimming or flying

Few terrestrial mammals migrate
• have a defined home range
• Notable exception: caribou

Question 19

Biodiversity

Answer 19

Biodiversity = biological diversity • At its most simplistic…

• biodiversity = a ‘simple’ counting of the number of species in an ecosystem
• 3 levels of Biodiversity:
• Genetic diversity
• Species diversity
• Ecological diversity

Question 20

Distribution of Species

Answer 20

• High biodiversity
• Tropical rain forests • coral reefs
• Low Biodiversity
• Arctic regions

Question 21

Endemic Species

Answer 21

Distribution limited to small area (ie galapagos species)

Vulnerable to extinction

Question 22

Types of Extinction

Answer 22

• Background extinction
Gradual loss of species in a natural population as conditions
gradually change.

• Mass extinction
Loss of a large number of species during a short period of time due to a natural catastrophe (e.g. volcano, meteor impact, prolonged drought)
Can eliminate nearly all (or all) species in a region

• Anthropogenic extinction
Loss of species due to human activity.
Rate of extinction is currently far above background levels

Question 23

Threats to Biodiversity

Answer 23

• Habitat Loss and Fragmentation
• Invasive Species
• Overexploitation
• Others (e.g. pollution, climate change…)

Question 24

Habitat Loss and Fragmentation

Answer 24

Habitat loss and habitat fragmentation threaten biodiversity

ex:
•Cowbird is a “brood parasite” – lays eggs in the nests of other birds
• When the patches of forest are small, Kentucky warblers are more likely to be parasitized by brown-headed cowbirds
• Example of how fragmentation can put pressure on a species

Question 25

Invasive Species

Answer 25

* Exotic species * Any species that is not native to the ecosystem • Also called ‘alien’ or ‘non-native’ species * Invasive Species * exotic species that has a negative impact on the ecosystem * Invasion of new ecosystems is a natural process * greatly accelerated through human intervention (purposeful and otherwise)

Question 26

Why is invasive species the Second most important threat to biodiversity

Answer 26

* Cause disease * Act as predators or parasites * Act as competitors * Alter habitat * Hybridize with local species

Question 27

Invasive species examples

Answer 27

Brown tree snake- eliminated 11/12 native bird species | Eastern grey squirrel -threatens native populations of squirrels in Europe