Navigation Flashcards
Why do animals need spacial skills?
1) Getting home after displacement
2) Finding something you left behind = target finding
3) Dispersal and migration
What methods are used to navigate?
- Simple rules to stay in environment
- Dead reckoning
- Piloting using map and compass
Give an example of how simple Rules can be used by animals to stay in environment
Woodlice wish to return to a type of habitat – wet and dark. Very simple rule allows this:
Rule : Turn much more in nice habitat
Result : Stay there much longer
What is dead reckoning in navigation?
- process of calculating one’s current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time and course.
Give an example of dead reckoning in navigation?
Desert ant
- Goes on wiggly route out, looking for food.
- Straight line back to nest with the food.
- Works out direction by “Route integration”, i.e. adds all the runs and turns, and calculates direction home.
Describe how animals can pilot by Landmarks
Beewolves (Tinbergen)
Beewolf wasp feeds her grubs paralysed bees in underground burrow among hundreds of others on dune. How does she find it?
Experiment -
put cones round burrow while wasp inside.
Wasp did orientation flight to learn new landmarks.
While she was away, Niko moved the cones.
Wasp searched repeatedly in centre of cones.
Conclusion: must use landmarks to recognise burrow position.
How do the beewolves use landmarks to navigate?
Beewolf forms a mental map of the landmarks
Must be able to adjust map though, when landmarks change.
Beewolf appears to do this on orientation flight when leaving the nest.
More complex in honeybees as many more images remembered.
What animals use landmarks for piloting?
Beewolves
Honey Bee’s
Mice
Food Storing Birds
What different maps are used to navigate?
- Landmark maps
- Current maps
- Sound maps
- Olfactory maps
Describe how animals use current maps to navigate
green turtles
- All born on beaches of Ascention Island
- Drift in current to eel grass beds in Brazil. (Evidence of magnetic sense acting too)
- return when adult to same beach by swimming up the current until close to the island.
- Unknown how they find their original beach though. - probs olfactory map of island
Describe how animals use sound maps to navigate
pigeons and whales use infrasound maps
Sources = breaking waves, wind over mountains etc. make very low frequency sounds called infrasound.
Infrasound travels a very long way with little attenuation so good for maps.
Describe how animals use olfactory maps to navigate
pigeons, shearwaters, eels, salmon
All return to natal river or nest site across apparently featureless sea.
Appear to use local smells as a map for navigation.
How do animals use directional information from celestial cues as compasses for navigation
- position of sunset can give the direction of west, without using an internal clock
- all night as you travel so inaccurate if used alone.
- The north star is the only star that doesn’t move through the night, so also tells you where north is without the need for a sense of time.
- most celestial bodies (sun, moon, or stars), move with time of day, making it difficult to use them as a compass.
- animal must have a clock of some sort to interpret the position of the celestial body, to give direction.
How do we demonstrate that some animals have a clock of some sort to interpret the position of the celestial body, to give direction?
Clock shift experiments
- Keep bird in room with no windows
- Expose it for several days to lights turned on at noon and off at midnight instead of sunrise at 6am and dusk at 6pm
- This confuses its internal clock into thinking it is 6am (dawn) when really it is noon
- When bird is let out at noon, its internal clock thinks it is 6am, and that the sun is just rising in the east. In fact the sun is in the south at noon.
-So the bird, who wants to go south west, flies off in the wrong direction.
Good evidence that direction was assessed by bird using a combination of sun position and internal clock.
Are birds using the sun and clock compass?
- starlings kept in a round loft surrounded by windows
- All orientated in same direction if can see the sun, but at random if sky overcast.
- Put mirrors by windows so reflected light at 90o to sun
- Birds orientated to new “sun position”
Conclusion: birds were using the sun to tell them compass direction
Must be using a clock to interpret the sun’s position too
Is a sense of direction enough to get you home?
Knowing which way is North doesn’t tell you where you are or where your home is. You need a map.
- Having a map is no good unless you know which way you are facing, so need a compass (and probably therefore a clock)
- You also need to know where on the map you are, and where your target is.
- Long distance navigation such as migration may have to be very sophisticated!
What is an emlen funnel?
bird cage shaped like an inverted cone, used to study bird behaviour, in particular birds’ migratory instincts
- Bird stands on ink pad and marks the walls of the funnel as it flutters up.
- After an hour or so, it is clear which direction the bird wants to fly.
