Migration

Question 1

Migration

Answer 1

Directed locomotor activity of an animal during long distance journeys

Question 2

Periodic migration

Answer 2

Exploration/ population expansion

Question 3

Seasonal migration

Answer 3

Typically involves migration between breeding area and over wintering or feeding area

Question 4

Examples of periodic migration

Answer 4

Lemmings migrate in large numbers when population expands

Question 5

Migratory birds in Ireland include

Answer 5

Bewick’s swan
Corncrake

Question 6

Homing

Answer 6

The ability of an animal to return to a specific set point eg return to nest

Question 7

Why are pigeons used when studying homing

Answer 7

• easy to handle
• not dependent on season

Question 8

Why migrate?

Answer 8

Periodic migrating animals move to prevent overcrowding
Seasonal migrating animals move to track changes in the environment

Question 9

Cost of migration

Answer 9

-Mortality risk: Loss of animals due to exhaustion, predators, storms
- Energetic costs: need to build up body fat by 30-40% before migrating

Question 10

Benefits of seasonal migration

Answer 10

• Energetic benefits: moving south in winter to avoid temperature stresses and associated metabolic costs
• Reduction in competition
• Reproductive benefits: breeding in north, longer day- length for feeding
• Protection from swamp predators

Question 11

Pilotage

Answer 11

Steering a course using familiar landmarks

Question 12

Compass orientation

Answer 12

Ability to head in a particular compass direction without reference to landmarks

Question 13

What can you use for compass orientation

Answer 13

Suns
Stars
Earth’s magnetic field

Question 14

True navigation

Answer 14

Ability to orient towards a goal without landmarks and regardless of direction of goal. Requires both compass sense and map

Question 15

Genetic control of migration in birds

Answer 15

• Whether to migrate
• Direction
• Distance
• Timing of migration

Question 16

Timing of seasonal migration

Answer 16

Modified by:
- External factors eg weather
- energetic condition of bird

Question 17

When do birds learn to use a stellar compass but not the actual patterns of stars

Answer 17

During a sensitive period between leaving the nest and starting the autumn migration

Question 18

How is use of star compass learnt

Answer 18

Young birds learn to recognize constellations that move least

Question 19

Magnetic sense in birds

Answer 19

• Beak region: receptor based on magnetite crystals
• Eye: photochemical system

Question 20

How pigeons use odor map to navigate

Answer 20

• Learn odours at home
• Use odour bouquet and wind direction to locate home when displaced

Question 21

Mechanisms of long distance orientation in birds

Answer 21

• Orientation by landmarks
• Sun compass
• Polarised light
• Star compass
• Magnetic compass
• Odour

Question 22

Where do fish usually migrate to?

Answer 22

• Within seawater
• Within freshwater
• Between sea and freshwater

Question 23

What is smolt transformation

Answer 23

Morphological, physiological and behavioral changes preparing for move to sea. Under control of thyroid hormones

Question 24

How do salmon find their way back to their natal stream?

Answer 24

• Open sea navigation; sun position, polarised light patterns, earth’s magnetic field
• Homing: once at coast locate the exact stream in which they hatched

Question 25

How can salmon learn to recognize their natal river

Answer 25

By smell. During a sensitive period in smolt transformation, salmon become imprinted to the smell of their home river

Question 26

When do fish learn to recognize natal stream

Answer 26

At the time of smolt transformation

Question 27

Requirements for salmon to recognize natal river by smell

Answer 27

• Every stream has a characteristic and persistent odor
• Salmon are able to discriminate between the odors of different streams
• Salmon remember when they return after their time at sea

Question 28

What is the source of distinctive odors

Answer 28

• rocks, soils, plants
• pheromones, mucus or faeces from relatives in stream

Question 29

Sequential imprinting hypothesis

Answer 29

Series of odor bouquets characteristic of different parts of river learnt in sequence as smolts migrate downstream

Question 30

Thyroid hormone increase is induced by:

Answer 30

• developmental processes
• environmental factors

Question 31

Elevated thyroid hormone

Answer 31

• Initiates migration downstream
• increases the tendency to learn local odor features by imprinting

Question 32

How does thyroid hormone influence imprinting?

Answer 32

• influences neurogenesis in the olfactory epithelium
• making the fish more sensitive to odors

Question 33

Advantage of anadromous life cycle

Answer 33

• spawning streams; protected environment, little competition
• sea: food for growth to large size