Migration and Dispersal Flashcards
(22 cards)
What is migration?
Relatively long-distance (outside of the animal’s habitat), two-way (cyclical) movement.
Most migrations are on an __________ cycle. What’s another name for these migrations?
Annual.
Also called latitudinal migrations, which involve changing latitudes throughout the migration.
What is anadromous and catadromous migration?
- Anadromous = freshwater —> ocean —> freshwater
EX: Salmon - Catadromous = ocean —> freshwater —> ocean
EX: Freshwater Eels
Many mesopelagic fish have daily __________ migration. How does it work?
Vertical.
They swim up to shallow waters (getting food) and then back down to deeper waters (staying away from predators).
What are the possible benefits of migration?
1) allows the exploitation of seasonal resources.
2) allows animals to stay in a favorable climate.
3) allows animals to avoid competition, especially in high-density tropical regions.
4) may allow animals to more easily find mating partners.
5) may allow animals to avoid predators.
What are the possible costs of migration?
1) Represents of huge energy cost!
2) You have to move through unpredictable weather and unfamiliar territory.
3) Predators may be attracted by large groups of migrating animals.
What is partial migration?
Some individuals migrate, others stay resident.
- This is often sex-biased!
What is variable migration?
Individuals migrate some years but not others.
- This is often based on condition (good-conditioned individuals and bad-conditioned individuals).
Is being sedentary(staying in one place) or migratory (moving from one place to another) ancestral?
Default Assumption: Having a behavior is going to be the derived condition. Not having a behavior is the ancestral condition.
- However, if we look within particular groups, we see different patterns.
- EX: Some groups show migratory behavior as ancestral.
What is the Northern Home Hypothesis?
Ancestral non-migratory species started from the north and began moving their wintering range more and more southward.
What is the Southern Home Hypothesis?
Ancestral non-migratory species started from the south and began moving their wintering range more and more northward.
How do first-time migrants know where to go?
1) It may be innate - Organisms know the correct direction to travel just from birth
2) It may be learned - Young organisms follow older and experienced individuals and learning the migration route themselves.
What is dispersal?
Relatively short-distance, one-way movement
What is natal dispersal?
A permanent relocation away from the birthplace.
- In other words, it’s organisms (usually juveniles) moving away from wherever they are born.
What is philopatry?
Staying at the birthplace as an adult.
What are the possible benefits of natal dispersal?
1) Dispersal allows individuals to avoid inbreeding depression.
2) Dispersal also reduces competition for mates (especially in polygynous species).
3) Dispersal reduces competition when density is high and/or resources are low.
4) Dispersal specifically reduces competition with relatives.
A possible benefit of natal dispersal involves avoid inbreeding depression. What kind of pattern does this avoidance lead to?
Leads to “sex-biased” dispersal, which is when one sex disperses and the other is philopatric.
- Gender can go either way with dispersers and those who are philopatric.
- Significantly avoids inbreeding since different genders are going to different locations (either staying or leaving).
What are the possible costs of dispersal?
1) Dispersing takes time and energy that could be allocated to other things.
2) Dispersal means dealing with a habitat that is unfamiliar and potentially unsuitable.
What is breeding dispersal?
Adults moving to a new breeding territory.
What is site fidelity?
Staying in your breeding territory over repeated years.
- Most adults exhibit site fidelity regarding breeding dispersal.
How is breeding dispersal determined?
Determined by a “win-stay lose-switch strategy.”
- If you do well on your breeding territory (win), you’re going to stay and remain faithful in subsequent years.
- If you don’t do well on your breeding territory (lose), you’re going to undergo breeding dispersal in subsequent years.
Breeding dispersal decisions may also be made based on ________ information.
Public
*Just to understand this statement - “You could be basing your decision on whether to switch territories or not on how well others in that habitat are doing, instead of basing that decision on how YOU do.”
