Migration Flashcards
How do animals know where to go?
Learn it from group members/elders
Specialised abilities - external forces - wind and water current, landmarks, celestial
Internal - Magnetic fields
How do animals know when to migrate?
Internal signals - Hormones - biological rhythms - cicannual, luna, diel External signals - temperature changes - daylight hours - resource level reductions
What are the general patterns of migration?
Return migration - predictably move between 2 places
Migration circuits - similar to return, first gen leads into 2nd, continuous cycle of movement
One way migration - leave and don’t come back, resources gone or population too big
Nomadic migration - species appear to be wandering, breeding at many places during their lives i.e. grazing animals
What are the different types of migration?
Latitude or altitude
long distance or short distance
partial or complete
Describe the latitudinal migration in birds
Regular seasonal movement is South to North in the Spring and North to South in the Autumn
Utilise common flight paths
>180 sp. fly from Europe and Asia to Africa
>200 sp. fly from N.America to the Tropics
75% of 650 bird species in N.America migrate
Which animal makes the longest migration ever recorded?
The Arctic tern
- Flies from the Arctic to the Antarctic anunaly
- 70,000km round trip
Leaves Arctic, Fuel stop over North Atlantic, Feeds on zooplankton and fish, Splits route
Return journey some birds take a 1000km detour
What are the reasons for altitudinal migrations and name some examples of each
Food abundance - frugivorous birds like white-ruffed manakins
Reproduction - bare-necked umbrella birds
Anti-predatory/pest response - elk in America
Anthropogenic -Animals driven higher because of humans (walia ibex)
Describe the return migration of Eidolon helvum
Straw coloured fruit bats
migrate from Congo to Zambia
~5-10 million congregate between Oct-Dec
Largest mammal congregation in Africa, maybe the world
Follows fruit production in the area
Consume 2x bodyweight per night
Responsible for 60% seed dispersal in Africa’s rainforests
Describe the partial migration in starlings
Many are resident and others are migratory
Huge numbers arrive from N.Europe to winter in the UK
Relatively mild therefore easier to find food and appropriate habitat
Arrive in Sept/Oct
Mostly from Scandinavia
Will roost together
Return to breeding colonies in Feb/March
Describe the return migration of whales
In general whales travel to cold waters for feeding and warmer waters to give birth
Larger baleen whales feed on krill - forms dense shoals during summer in cold Antarctic waters
50% weight gain possible - eat enough n 4 months to sustain the rest of year
As winter temps drop pack ice spreads and whales move to warmer breeding and birthing locations
Describe the feeding migration of Rhincodon typus
Whale sharks
worlds largest living fish
Studies have shown they can travel up to 8000km
Gulf of Mexico has had the same sharks returning for up to 6 years
70% are males, females are believed to undergo long migrations to the middle of the oceans, near seamounts and remote islands
Unusual for sharks in that they have nursery areass
Describe the foraging-nesting migration of Dermochelys coriacea
Leatherback turtle
Temperate feeding and foraging areas to tropical breeding grounds
One of the most highly migratory animals >10,000km per year in the hunt for jellyfish
Pineal gland - senses seasonal changes in sunlight via unpigmented spot on crown of forehead
What are irruptive migrations and give an example?
Irregular, not predictable seasonally or geographically
Snowy owl - over-winters in S.E.Canada and New England almost every year
Winter numbers in U.S peak periodically
May link to lemming cycles further North
During irruptive years, snowy owls reproductive output increases and can consume 1600 lemmings
Describe the nomadic migration of the American bison
Plains bison are non-territorial, nomadic
Live in small herds that may be non-migratory and remain in a contained home range
Free ranging, seasonally migratory groups are also found
Move several miles a day when feeding, influenced by biting insects, water and plants
Move to more Southernly habitats in winter, no fixed locations though
Example of seasonal, latitudinal and partial migration
What is DVM?
Diel vertical migration - a pattern of movement in some aquatic organisms
Short, complete migration
Organisms move up to the surface waters at night and back to the depth during the day
Number of reasons - Predator avoidance
- Metabolic advantages
- Dispersal and transport
- Avoid UV damage
