Lecture 7 Flashcards
Seasons and behaviour
*less sunlight=less food
Benefits and costs of staying put
Benefits:
•Retain occupancy of territories of proven worth
•Avoid energetic costs associated with migration
•Avoid exposure to environmental and predatory risks associated with moving to new ground
Costs:
•Energy expenditure on retaining territory plus risk of injury
•Food or fat stores may not last for the required period
•Extremes of weather may not be survivable
•Reduced opportunities for reproduction
Breeding seasons of Deer mice
High latitude= breeding season restricted to just summer months
-short lifespan of small mammals means that mating must occur whenever costs of lactation can be met
Lactational barrier
=this amount of energy must be available for breeding to take place/produce milk their offspring require
*Enough energy must be available to meet the needs of each stage of reproduction, otherwise the whole process will fail
Arctic terns
- Live in high artic, migration time, fuel stop follow coast of Africa or south America and end up in wintering grounds in the north pole where there abundant plankton – 24hr of day light= more hours to collect food, chicks grow fastest here
- Go south as it gets darks again as the sea freezes 2 month flight, eat sleep and drink at sea
- Back to Antarctica where there is 24hr sunlight again
Monach butterfly
Only lives in a couple of places, go to these places over winter because it doesn’t freeze
Their migration involves 3 or 4 generations of butterfly
Mexico as far as Canada, single super generation that gets all the way there and back
Migration mostly from South to North
- Two thirds of the earths landmass is above the Tropic of Cancer
- Summer in North
Not North to South
- Relatively little land below Tropic of Capricorn but seas rich with phytoplankton
- Summer in south
- Lot of migration from sub Sahara Africa
Green turtles
-tagging has shown movement between nesting at Ascension Island and Atlantic ocean and feeding ground on the Brazilian coast
Grey Whales
- migrate between their summer feeding ground in the north pacific and bering sea and their winter breeding ground in the lagoons of Baja California
- moving in order to reproduce
Piloting
=navigation with references to fixed points in the landscape
eg dolphins follow troughs and ridges
Cranes
use thermals of warm air to glide in direction of migration
Don’t flap wings much
repeat process of finding thermal to spiral upwards over and over throughout the day
Navigation: compasses
**
Eels
- movement during time when the tide is not flowing
- follow direction of north from the tide
Sockeye salmon
- every 4 years return to native spawning grounds in Canada Fraser River
- lay eggs and then die, dead bodies provide nutrients for next generation
- cycle begins anew
Navigation: dead reckoning
**
Celestial compass day
- Clock needed to correct compass reading as it moves across the sky
- Adjust direction according to the time of the day
- Snell’s window: what you see underwater, what the animals in ocean see
Celestial compass night
• Milky way great standout event in sky, dug beetles use
Star compass birds
-night-migrating birds learn and orientate by spatial relationships among the constellations
Star compass
- Open exposure photograph showing apparent rotation of all stars except Polaris, the North Star
- North stays in exactly the same place
- Compass needs correcting for rotation and latitude
Information from other sense organs
- Mechanoreception (wind direction, current)
- Chemoreception (gradients of organic and non-organic chemical concentrations)
- Thermoreception (infrared wavelengths)
- Electrolocation
- Magnetic forces
- Gravitational fields
