Download Biology 312: February 15, 2002

Biology 360: February 7, 12 & 14, 2007
Migration/Navigation
Detailed outline and study questions for all lectures combined
I.
II.
Introduction
A.
Focus on this topic within the larger theme of “choosing where to live”
B.
What are the key questions/subjects of interest for this topic?
1.
Basic descriptions: Where do individuals/groups move over the course of a
day/month/year/lifetime?
a)
Need to find/study on ecologically relevant time scales.
b)
Methods (briefly)
2.
Why do they move?
3.
What cues do they use for navigation?
Migration: Descriptions
A.
Migration defined: To pass, usually periodically, from one region or climate to
another for feeding or breeding
1.
Temporal cycles: Can occur on daily, tidal, monthly, yearly, multiyear (or
other…) cycles
B.
Some examples of specific migratory patterns
1.
North to south and back
a)
Arctic terns [Fig. 8.13]

Description of migration; wintering and breeding locations
(compare to Antarctic tern)

Longest north-south migration known: 14,000 miles one-way.
2.
Polar to tropical
a)
Pacific grey whale [PP diagram]

Description of migration; feeding vs. breeding grounds

Hypotheses for why they migrate south (rather than just
breeding at their feeding grounds)

For females that give birth/newborns

For non-birthing females and males.
b)
Many North American birds [Fig. 8.19; blackpoll warblers]

Key hypothesis for why they do not breed at feeding grounds.
3.
Migration at same latitude, breeding to feeding grounds
a)
Green sea turtle (other species of sea turtles have similar migrations)
[Fig. 4.45]

Breeds on Ascension Island, only 5 miles wide.

Travels 1200 miles in open ocean between this breeding
location and feeding grounds in Brazil.

Adaptive value of breeding at this site?
4.
Migration between freshwater and seawater
a)
Salmon spend from one to several years (depending upon species and
conditions) in the ocean in order to feed. Probably concentrate in
regions where currents meet, creating “fronts” that contain high
concentrations of food.
5.
Migratory circuits
a)
Wandering albatross [PP, additional figure]
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
b)
III.
IV.
Find food (fish, squid) in the open ocean ; albatrosses caring
for young undertake 10-15 day foraging trips

Circuits are from 1800- 9000 miles (determined by satellite
tracking data)
Monarch butterflies [Fig. 4.42]

It takes several generations for butterflies to complete the full
yearly circuit from feeding to wintering grounds and back.
Costs of migration
A.
Energetic costs: Many migration trips require large energy stores at the beginning;
migrators often severely deplete these energy stores during the journey.
1.
Example: Bristle-thighed curlews have a 2400 mile leg of their journey
over-water, non-stop, during which they do not feed.
2.
Mitigating energy costs: Does the V-formation really work?
a)
Henri Weimerskirtch studies of great white pelicans [Fig. 8.17].
(Worked with the “Winged Migration” project)
b)
Key results of this study?
B.
Predation pressure
1.
In some places, local predators specialize in worn-out, migrating birds
a)
Group travel and over-water routes minimize this risk
C.
Chance of becoming completely lost due to weather.
1.
Which cue can (some) birds detect that will help them avoid bad weather?
Benefits of migration: Why do they do it? (High cost suggests clear adaptive value.)
A.
Food: Net gain upon reaching rich food reserves
1.
Focus: Blue whale migration (Burtenshaw et al., 2004—I have placed a link to the
paper on my website.)
a)
Overview: Vocally distinct population in NE Pacific: Gulf of AK to Central
America

Low frequency, high intensity songs can propagate hundreds of miles

2000-3000 whales in the population (est.)
b)
Methods:

System of fixed hydrophones throughout the NE Pacific were used in
this study to detect the whale calls (US Navy, SOSUS array)

Frequency and intensity of calls used to approximate the blue
whale density in a particular area (pros and cons?)

Satellite imagery used to measure chl a concentration (to estimate
phytoplankton)
c)
Results

Blue whale movement

What appeared to be their pattern of movement?

How did this relate to the pattern of primary production
(phytoplankton)? To the main food type of the blue whale,
which is _ _ _ _ _!

Blue whales eat _ _ _ _ _, not phytoplankton, so what did this
have to do with feeding?
B.
Ideal breeding locations
1.
Food for reproduction (in some cases but not others)
2.
Space for territories and nest sites
3.
Reduced competition (i.e. songbirds migrating to high latitudes)
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C.
V.
VI.
Temperature and other weather conditions (may or may not be breeding
related)
1.
Grey whales (hypotheses for why calving occurs in warm lagoons)
2.
Monarch butterflies: wintering grounds at 3000 m elevations in mountains of
central MX. Have ideal temperature and moisture conditions to prolong
survival time without feeding or drinking [Fig. 8.22]
a)
What role does the forest canopy play? What are the consequences of
deforestation? [Fig. 8.22]
D.
Reduced predation pressure at destination (grey whales?)
E.
Migration as a conditional tactic? [European blackbird, Fig. 8.23]
Overview: How do migrating animals find their way?
A.
Requirement of both a map and a compass. Why?
1.
Compass: Tells you where N, S, E and W (and increments thereof) are.
2.
Map: Tells you where you are in relation to where you need to go.
B.
Cues that may be used for compass and/or map
1.
Celestial bodies (sun and stars)
2.
polarized light (directional)
3.
magnetic cues
4.
barometric pressure
5.
acoustic cues
6.
odors (Controversial: are atmospheric and oceanic circulation patterns are
stable enough to provide consistent cues?)
7.
terrain/landmarks (sensed visually, acoustically, or???)
Sun as a compass
A.
How would a sun compass work?
1.
Need to know the position of the sun at different times of day
a)
Where is the sun at 6 AM? Noon? Six PM?
b)
NOTE Sun moves approximately 15 degrees per hour.
2.
Need to have clock sense both for time of day and time of year.
3.
Examples: A pigeon released south of its loft at noon should orient away
from the sun (sun at its back) to fly north back to its loft.
*NOTE: It would also need to know that it was south of its loft (map sense)
B.
Experiments to test the sun compass [Fig. 4.41]
1.
Methods:
a)
NOTE: All pigeons were raised in the same lofts and initially
exhibited normal homing behavior (I’m not sure I was clear on this
point in lecture.)
b)
Pigeons divided randomly into two groups:

Control pigeons: Normal light cycle matched time of day and
year.

Experimental pigeons: Clock shifted by alteration of light
cycle. (Clock shifted back, so noon was 6 AM for them)
c)
Pigeons taken to test sites east of their loft and released at noon.
Initial “vanishing” bearings recorded. (Shown on video. Blind?)
d)
Results:

Control pigeons: oriented with the sun to their left and
returned (westward) to the loft.
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
Experimental pigeons oriented away from the sun and flew
north.

So, these pigeons knew they were east of their lofts (had
a map sense not involving sun’s position) and flew
appropriately if it had been 6 AM.

NOTE: Other combinations of time and clock-shifting
were done…
C.
Sun compass and dancing bees (Karl von Frisch)
1.
Round dance: food close to hive, within 50 m (no specific directional cues;
vigor of dancing indicates richness of food) [Fig. 7.21]
2.
Waggle dance [Fig. 7.22]
a)
Karl von Frisch’s hypothesis: the waggle dance communicated
direction (based on angle) and distance (based on number of times
performed)

The longer the waggle takes, the farther the food is away.
b)
Experiments/data: trained scout bees to go to sugar water at a
particular angle and distance away; had sugar water “fanned out” at
various locations to test angle, and at various distances to test distance
information [Fig. 7.23]
c)
NOTE: Similar dances occur when hives move or split…
VII. Stars as a compass
A.
Indigo bunting studies (Steve Emlen)
1.
Initial observations: Caged birds exposed to the night sky during migratory
season orient and move in appropriate migratory directions (April and May
orient North; Sept, Oct  orient South)
2.
Planetarium experiments: Inside the planetarium, where star positions could
be altered from magnetic north, orientation occurred according to
appropriate star patterns, regardless of their true positions. (EX: Rotate star
map so than north star is in the east; birds orient eastward instead of
northward in April and May.
a)
Discovered it was the north star and surrounding constellations that
were the cues.
3.
Question: Are the young buntings born with an innate map of the stars in
their head?
a)
Experiment: Emlen exposed newly hatched buntings to either the
normal sky that rotates around the north star or an altered sky that
rotates around the star Betelgeuse.
b)
Results: Those exposed to the altered sky rotation oriented to
Betelgeuse, rather than to the north star
c)
Interpretation: The tendency to orient to the star around which the
others rotate appears to be innate, but the young buntings must learn
the particular pattern of rotation by observation.
VIII. Magnetic field as a cue (sea turtles, monarchs, pigeons)
A.
Experiments with pigeons (Keeton)
1.
Bar magnets attached to pigeons’ heads to disrupt their magnetic sense
2.
Results: comparison of orientation to sunny vs. cloudy days.
B.
Experiments with sea turtles
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1.
IX.
Experiment 1: Hatchlings were placed in an arena (1-m diameter) in the
laboratory and were tethered; able to swim freely in the radius defined by the
tether. The tether electronically tracks the direction they are attempting to
swim. The arena is inside a huge magnetic coil [PP figure]
a)
Normal conditions: Hatchlings oriented to the NE
b)
Reverse magnetic field: Hatchlings oriented to the “new” magnetic
north (south), although they were more scattered.
c)
Possible problems (think about tether system, earth’s own magnetic
field)
2.
Experiment 2: Hatchlings placed in a similar arena, but this one was floating
in the ocean.

Orientation to waves rather than magnetic field (tether,
importance of waves as a cue)
C.
Magnetic field, theoretically, can serve as both map and compass
1.
Inclination angle [Fig. in PP]
a)
Turtles exposed to inclination angle of natal beach swam eastward (normal)
b)
Turtles exposed to an inclination angle corresponding to more northern
latitudes swam south-southwest, and those exposed to an angle characteristic
of more southerly latitudes swam northeasterly [Fig. 4.46, not in PP]
2.
Field strength (used alone as compass)
a)
Similar types of results obtained with alterations of field strength (indicating
that the turtles can detect field strength)
3.
Inclination angle and field strength could work as a bicoordinate map
D.
Hammerhead sharks (Klimley, 1995)
1.
The habitat: seamounts

Site of mating aggregation in hammerheads…
2.
Daily migration patterns
a)
Methods:

Tracked sharks with transmitters

Conducted geomagnetic surveys (magnetometer towed behind vessel)

Superimposed tracks of the sharks with results of magnetic survey
b)
Key results (abbreviated from paper)

Transmitters

Sharks travel away from sea mounts used for mating
aggregations at night; often go to other seamounts whether other
food types (i.e. squid) are available.

Appear to travel on a fixed course; often return along the same
route

Geomagnetic surveys

Distinct valleys and ridges radiate from the seamounts forming
distinct corridors

Superimposed magnetic surveys and shark routes: sharks appeared to
travel along magnetic “corridors”.
c)
Mechanism for magnetic orientation (hypothesized)

Electroreceptors: Ampullae of Lorenzini—numerous jelly-filled
receptors capable of detecting very small changes in electrical strength
Olfactory maps?
A.
Concept of an olfactory landscape [Ch. 5, Fig. 36]
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B.
C.
Experiments testing whether pigeons use olfactory maps (Papi and Bienvenuti et
al., coastal Italy)
1.
Anosmic experiments
a)
Birds deprived of odor homed normally when released from a familiar
site, but oriented randomly at new sites [Ch. 5, Fig. 38]
2.
Altered olfactory environment on journey to release site  pigeons had
difficulty homing
3.
Deflector loft effect: 90 rotation of odor cue using deflector panels [Italian
researchers, Papi and Bienvenuti/Baldaccini, results in PP slide]
a)
Key result: shift of homing orientation (Baldaccini)

Look at the data carefully…was it shifted to the degree
expected?
Challenge to the deflector loft results (Waldvogel and Phillips; Ithaca, NY)
1.
Used deflector lofts to Deflect odor and light in opposite directions (odor
cues shifted 90 counterclockwise, visual cues shifted 90 clockwise)
a)
Homing was altered 90 clockwise, suggesting that polarized light,
rather than odor, was the key factor.
2.
Why the apparent contradiction from the Italian researchers?
a)
The Italian deflector loft experiments could not distinguish between
light and odor cues (both odor and light were deflected), so there
really is no contradiction…
b)
Benzaldehyde experiments conducted by the Italians may have
provided an overwhelming cue that outweighed other cues such as
polarized light.
c)
Pigeons in Italy may be using different cues to orient than pigeons in
Ithaca.

Odor cues may be more important in some places (i.e. coastal
Italy, where sea breezes may carry distinct odors).
Study questions
1.
Define “migration” and describe several possible temporal cycles of migration.
2.
Describe several migratory patterns and provide specific, real examples of each (lecture,
text, prior knowledge). You should also be able to provide basic hypotheses for why the
animals in your examples exhibit the migratory patterns they do to the level described in
lecture. Make sure you are familiar with all examples in lecture.
3.
Describe the key costs of migration. (You should be able to describe at least three…)
4.
What appears to be the function of the V-formation in migrating birds? Discuss the
evidence that supports this hypothesis.
5.
List/describe the major benefits of migration. Also, provide a clear example of an animal
that appears to migrate for the reason stated.
6.
There is a vocally-distinct population of blue whales in the NE Pacific (i.e. west coast of
North America) studied by Burtenshaw et al. (2004).
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NOTE: You can download a PDF file from my website for this paper.
a.
What method was used by researchers to track this whale population?
b.
Describe some problematic aspects of this method (you should be able to think of at
least three…)
c.
Discuss the results of this study, including:

What appeared to be the migratory pattern of these whales in space and time?

What did the researchers suggest was the benefit of this migratory pattern, and
what evidence did they provide to support their hypothesis?

How might you better show a relationship between the whales and their food?
(HINT: Think about what they actually measured compared to what the food
source of this whale is, time lags, water movement, etc…)
7.
Describe two hypotheses for why female grey whales give birth to their calves in the warm
lagoons of Mexico rather than remaining in their northern feeding grounds.
8.
Discuss the migratory pattern of monarch butterflies:
a.
Describe the basic migratory circuit of the eastern population (east of the continental
divide.) Does a single butterfly complete this circuit?
b.
What resource do the monarchs follow during the spring/summer migration? What
creates the northern limit to their migration?
c.
Where does the eastern population of monarch butterflies overwinter, and what
appears to make this an ideal wintering location? (Think about why they would not
winter in regions that are either warmer or colder than this particular site.)
d.
What role does the forest canopy play at the wintering grounds?
e.
Explain why deforestation at their wintering grounds is disastrous for the monarchs.
(Be as specific as possible about how deforestation causes problems.)
9.
Why would a compass-sense be important to migrators? Why would a map sense be
important to migrators?
10.
List several cues that could potentially be useful to an animal in either the map sense or the
compass sense.
11.
Understand how a sun compass works. In other words, understand how the sun moves
across the sky and where you would expect the sun to be at certain times of day.
12.
Why is a clock sense needed in order to use the sun as a compass?
13.
Answer the following questions related to the sun compass and clock-shifting. Assume
you are in the Northern Hemisphere. You will probably find making sketches helpful to
answer these questions.
a.
A normal (not clock-shifted) pigeon is driven to a site due south of its home loft, and
released at noon. In which compass direction is home? Where will it keep the sun’s
position to orient itself directly to home?
b.
A pigeon is clock-shifted back by six hours (so it thinks it is six hours earlier than it
really is) and is, like the above bird, driven due south of its home loft and released at
noon. In which compass direction is home? Where will it keep the sun’s position
(relative to itself) to orient itself to where it thinks home is? In which compass
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c.
d.
e.
f.
direction will it actually orient/fly? (Remember, it does somehow know it has been
moved south of its home.)
A pigeon is clock-shifted forward by six hours (so it thinks it is six hours later than it
really is) and is, like the above birds, driven due south of its home loft and released
at noon. In which compass direction is home? Where will it keep the sun’s position
(relative to itself) to orient itself to where it thinks home is? In which compass
direction will it actually orient/fly?
A normal (not clock-shifted) pigeon is driven to a site due west of its home loft and
released at 6 AM. In which compass direction is home? Where will it keep the
sun’s position to orient itself directly to home?
A pigeon is clock-shifted forward by six hours (so it thinks it is six hours later than it
really is) and is, like the above bird, driven due east of its home loft and released at 6
AM. In which compass direction is home? Where will it keep the sun’s position
(relative to itself) to orient itself to where it thinks home is? In which compass
direction will it actually orient/fly?
NOTE: Make up more questions for yourself like this and be sure you understand!
14.
BONUS: A normal (not clock-shifted) pigeon in the southern hemisphere is driven to a
site due west of its home loft, and released at noon. In which compass direction is home?
Where will it keep the sun’s position to orient itself directly to home?
15.
While the sun compass was emphasized in the pigeon studies, do we know whether
pigeons have a map sense as well? Explain based on the results of the clock-shifting
experiments. (Note: I’m not asking if we know what its map sense is, only whether it not
it has one.)
16.
What are the two key types of information encoded in the waggle dance of bees? Be sure
you can interpret waggle dances (i.e. if provided with a diagram of particular bee dance,
you should be able to determine which direction the bee will fly for food; you should also
know how distance is encoded in the dance.). Also be sure you can interpret graphs
similar to those shown in Fig. 7.23.
17.
In experiments to study orientation of indigo buntings to stars:
a.
What initial observations were made on adult, caged indigo buntings with respect to
orientation during migration season?
b.
How did researchers record which way they the buntings were orienting?
c.
How did the researchers determine that the birds were normally orienting based on
the position of the north star? How did they eliminate the possibility that other cues
were being used for orientation?
d.
How did the researchers test whether the indigo buntings had an “innate” star map
vs. whether they needed to learn a star map? Describe key experiments and results.
e.
What particular experience was required for young birds to properly orient to the
North Star (Polaris)?

How did Stephen Emlen get them to orient to Betelgeuse rather than Polaris?
f.
Which aspect of star navigation is innate? Which aspect of their star navigation is
learned?
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18.
In some orientation experiments with pigeons, bar magnets were strapped to their heads to
disrupt their magnetic sense.
a.
What effect did this have on homing on sunny days? What about on cloudy days?
Why the difference, and what does this tell us about how different cues are used for
homing?
19.
Describe the evidence for the use of magnetic navigation in hammerhead sharks, including
the basics of techniques and results. Also, which sensory structure in sharks is capable of
detecting magnetic fields?
20.
Explain what is meant by an olfactory map, describing how you might use an olfactory
map to find your way. You may include a sketch as well as words in your explanation.
21.
Describe the results for homing by anosmic pigeons that were familiar with their release
site vs. those that were not. Discuss why the results were different for the two situations.
(No “correct” answer for this, but your answer should be logical.)
22.
What is a deflector loft? In what way did deflector lofts alter odor cues? Did they alter
any other potential cues? In the Italian studies, how did pigeons raised in the deflector
lofts home compared to those raised in normal lofts? [Hint: You are basically being asked
to explain, in words, the figure in the PowerPoint titled “Deflector Loft Effect”.] How did
the researchers interpret these results? Look at the vanishing bearings carefully on the
related figure in the
23.
How did the deflector lofts used by Waldvogel and Phillips differ from the Italian
researcher’s deflector lofts? What did this allow Waldvogel and Phillips to test? What
were their key results?
24.
Be sure you understand and can interpret the diagrams used to show “vanishing bearings”
of pigeons (i.e. Fig. 4.41 and Fig. 4.46). For example, you might be provided with similar
diagrams with “bogus” data and asked to discuss whether the data supports a particular
hypothesis, or just to state what the graph tells you about homing/orientation under a
particular condition.
25.
In examining all of the studies as well as thinking about the relative permanence/reliability
of cues, which cues could be considered as “primary” cues and which might provide
supplemental information.
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