1. Navigation and Migration
Finding One’s Way About

2. Focus on the Hippocampus
• The hippocampus is a part of the forebrain, located in the
medial temporal lobe. It belongs to the limbic system and
plays major roles in short-term memory and spatial
navigation (see Alcock, Chapter 4, pages 130-133).
• Humans and other mammals have two hippocampi, one in
each side (hemisphere) of the brain. In rodents, where it
has been studied most extensively, the hippocampus is
shaped something like a banana. In humans it has a curved
and convoluted shape that reminded early anatomists of a
seahorse. The name, in fact, derives from the Greek word
for seahorse (hippos [horse] + kampos [sea monster]).

3. Hippocampus (Cont’d)
• The results of a large number of studies on the
vertebrate hippocampus suggest that this area of
the brain is linked to the ability of the individual
to utilize spatial information.
• Neurobiological studies indicate that specific areas
or cells of the organ provide very specific
information about the location of an individual.
• Lesion studies reveal that damage to the
hippocampus results in impaired spatial ability.

4. Hippocampus (Cont’d)
• Information collected via electrodes from individual cells
within the hippocampus of free-moving rats has revealed a
class of cells now called “place cells.”
• Experimenters have discovered the each of these cells is
sporadically active as the rat navigates its environment.
• However the cells’ activity is far from random: each cell
fires maximally when the rat reaches a particular location.
• The cells don’t appear to respond to location in space, but
to particular landmarks, or combinations of landmarks that
have a particular spatial relationship to the current position
of the animal.

5. Hippocampus (Cont’d)
• In Alzheimer’s disease the hippocampus is one of the first
regions of the brain to suffer damage; memory problems
and disorientation appear among the first symptoms.

6. Enlarged Hippocampi
(Alcock, p. 131-132
• Prediction: human brains, as well as those of food-storing birds,
should possess and enlarged hippocampus that give them the
spatial memory needed to survive.
• London taxi drivers: the average posterior hippocampal size was
larger than in a comparable group of non-taxi-driving men. The
more years of taxi driving (the more navigational experience), the
larger the posterior hippocampus.

7. The Hippocampal Complex in Food-Storing Birds
(D.F. Sherry, A.L. Vaccarino, K.Buckenham, R. Her, 1989)
• Three families of North American passerines - chickadees,
nuthatches and jays - store food. Previous research has
shown that memory for the spatial locations of caches is
the principal mechanism of cache recovery.
• It has also been shown that the hippocampal complex
(hippocampus and area parahippocampalis) plays an
important role in memory for cache sites.
• The hippocampal complex is larger in food-storing birds
than in non-food-storing birds. This difference is greater
than expected.
• Natural selection has led to a larger hippocampal complex
in birds that rely on memory to recover spatially dispersed
food caches.

8. Enlarged Hippocampus
• European marsh tits (Parus palustris) are avid food
hoarding birds that might store 50-100 seeds in a single
morning. These birds can remember where a food item
was hidden, what kind of food it was, and whether or not
the cache has been used.
• The closely related blue tit (P. caeruleus) does not hoard
food and so presumably does not have the same spatial
memory needs (tits are related to chickadees & titmice).
• Juvenile marsh tits and blue tits have similar hippocampal
volumes (as neither stored seeds), but adult marsh tits have
much greater volumes—indicating that hippocampal
enlargement does not happen util the birds begin to
experience food-storing behavior.

9. Food-Caching Birds

10. Hippocampal Injury
Disrupts Navigation
• Rats subjected to hippocampal damage lose the ability to
solve mazes.
• Homing pigeons subjected to such damage also have
disrupted spatial ability.
---Lesioned pigeons released 30+ km from their home loft
were unable to home even if they were familiar with the
release site;
---but the pigeons did set off in the right direction, so the
hippocampus doesn’t seem to be involved in their compass
sense.
---Such results suggest that the hippocampus is involved in
both the acquisition, storage and retrieval of spatial
information.

11. digger wasp Navigation
• Navigation: the science of getting…from place to place;
esp: the method of determining position, course, and
distance traveled. (Merriam-Webster, 1987)
• Niko Tinbergen’s classic experiment involving the digger
wasp:
---the female wasp is able to return directly to her tiny nest
burrow in the ground after a provisioning flight because
she first memorizes the relative positions of landmark
objects;
---NT surrounded a wasp nest burrow with pine cones; then,
after the wasp had emerged from the entrance and flown
away, he moved the ring of cones a short distance away so
that the entrance now was outside the ring.

12. Digger Wasp Experiment
(Cont’d)
---The returning wasp flew directly
to the center of the cone ring, not to
the entrance of the burrow only a
few feet away.
---She searched in vain for the
opening in the middle of the ring.

13. Digger Wasp Experiment
(Cont’d)

14. Digger Wasp Experiment
(Cont’d)
• Wasps of the genus Sphex (commonly known as digger
wasps) are predators that sting and paralyze prey insects.
There are over 130 known digger wasp species.
• In preparation for egg laying they construct a protected
"nest" (some species dig nests in the ground, while others
use pre-existing holes) and then stock it with captured
insects.
• Typically the prey are left alive, but paralyzed by wasp
toxins. The wasps lay their eggs in the provisioned nest.
When the wasp larvae hatch, they feed on the paralyzed
insects.

15. Trail Laying
• Trail laying and trail following as a navigational method
are common throughout the animal kingdom.
• Ants use pheromone trails as a method by which many
foragers can efficiently exploit a new food source.
• When it finds a food source too large to exploit alone, a
foraging ant returns quickly, and by a very direct route to
its nest; as it does so it deposits a pheromone trail on the
ground behind it.
• At the nest the returning individual performs stereotype
behaviors designed to recruit others to the food source.

16. Ants Trail Laying
• By following the pheromone trail these recruits are able to
go directly to the food source, and, as each of them returns,
they too deposit pheromones and the trail is reinforced.
• As the food source is exhausted the ants will stop returning
and no trail reinforcement will take place; the trail quickly
disappears so no ants waste time following it to no reward.

17. Dead Reckoning
• Dead reckoning. 1: the determination without the
aid of celestial observations of the position of a
ship or aircraft from the record of the courses
sailed or flown, the distance made, and the known
or estimated drift. 2: GUESSWORK (Merriam
Webster, 1987).
• Dead reckoning. A corruption of the term
“deduced reckoning” and refers to an individual’s
ability to deduce its current position in relation to
another location by taking into account the
direction(s) and the distance that it has traveled
between the two (G. Scott, 2005).

18. Deduced Direction & Distance
• Ants, in common with a number of other species,
rely upon external cues to guide them to their
ultimate destination.
• Desert ants appear to use global environmental
cues rather than local landmarks by which to
navigate—they use the sun, or more precisely, the
angle between the direction of movement and the
position of the sun relative to the horizontal plane;
they take into account the movement of the sun
across the sky as the day progresses (a kind of
built-in computer system).

19. Desert Ants (Cataglyphis fortis)

20. Japanese Wood Ants
• Japanese wood ants, on the other hand, use visual
landmarks in preference to chemical trails or
celestial cues.
• Researchers, employing various kinds of visual
barriers blocking landmarks, have demonstrated
that Japanese wood ants use features of the skyline
(prominent tree tops, for example) as navigational
guides.
• The ants in the experiments wandered until they
could reach a position whereby they could see
once again the cueing landmarks.

21. Japanese Wood Ants (Formica
japonica)

22. Ant Visual Landmarks
• Ants will regularly stop, turn, and stare at a
prominent landmark feature as they move away
from it during a foraging trip.
• It is thought that during these “learning walks” the
ants commit to memory key objects in their visual
field; on subsequent trips they can compare these
snapshot memories with actual views.
• In this way they are able to deduce information
about the distance and direction of their goal.

23. Japanese Ant Path Directions:
With and Without Obstructions
X = release point N = nest
• X------------------------------------------- N
• X-----------------------<E [obstr. on ground]
• X------<E [obstr. just off ground]E>--N
E------
4. X--<E--------E>[obstr. higher----------N
E------/ off ground]

24. Cognitive Maps
• The ability of an animal to define various
locations within its environment and then
integrate this information is the basis of a
cognitive map.
• Cognitive maps enable animals to plot
routes through their surroundings based
upon information they have stored in the
mental map.

25. Rat Cognitive Map
(R. Morris’ Experiment)
• Rats can be trained to swim through opaque water to the
safety of a platform that is invisible to them because its
surface is just a fraction below water level.
• When a rat is introduced to the water at a novel location,
but the platform is in the same location, it swims directly
to the platform--it has used its cognitive map to deduce
where the platform is still located.
• When the platform is relocated, however, the rat carries
out an exhaustive, wandering search of the area where it
expected to find the platform, before swimming elsewhere
and actually finding it.

26. Swimming Rat
X=Start Point; [ ]=Platform
A. X………
…………………………….. [ ]
B /……………………...[ ]
X……./
/…
/……
G. [ ] …… /……../ /…….X
………/ ../
……../
……/

27. Swimming Rat
(R. Morris’ Cognitive Map
Experiment)

28. Homing and Racing Pigeons
• Homing and racing pigeons are regularly taken by their
owners to release sites hundreds of miles from their home
lofts, and, and, amazingly, the vast majority of the birds
are able to quickly return home without any prior
experience of the journey they undertake (see Alcock,
Chapter 4, pages 133-134, esp. Fig. 4.40).
• To do this they need to determine their current position
and their position relative to home (an internal map sense).
• Next they need to know in which direction to fly and how
far to fly; for this they need an internal compass sense and
a means of measuring distance.

29. Homing (left) & Racing (right)
Pigeons

30. Racing Pigeons & Trophies

31. Homing & Racing Pigeons
(Cont’d)
• Evidence points to the fact that the position of the
sun is used by pigeons as a compass.
• The birds relate the position of the sun in the sky
to their internal body clock and find the compass
bearing that takes them home.
• On cloudy days or at night pigeons are able to use
a magnetic sense by which to orient.
• Attaching a magnet to a pigeon on a cloudy day is
sufficient to disrupt its homing ability (but not on
a sunny day).

32. Effect of Magnets on Pigeons

33. Homing & Racing Pigeons
(Cont’d)
• Regarding the map, pigeons are able to make use of visual
features in the landscape to guide them home, especially if
they are in the vicinity of their loft.
• There is some evidence that pigeons can hear ultra-low
frequency cues radiating from steep-sided topographic
features.
• The most convincing evidence for the basis of the pigeon
map relates to the birds’ sense of smell.
• Pigeons that have be “smell-blinded” are unable to
navigate home over a large distance. Similarly, birds raised
in a loft with air funneled in from a 90 degree direction
from the normal, natural flow learn an inappropriate
olfactory map and are unable to navigate correctly away
from home.

34. Atlantic Salmon Migration
(Reliance on the Sense of Smell)

35. Salmon Life Cycle
• The salmon life cycle
involves traveling 1000s
of miles, from breeding
rivers and fresh water to
saltwater ocean
maturation areas and back
again. Salmon are known
for their sense of smell to
home in on their spawning
grounds.

36. Green Sea Turtles
(see Alcock, p. 137-139, esp. Figs. 4.45 and 4.46)
• Green sea turtles range throughout the tropical and
subtropical seas around the world, with two distinct
populations in the Atlantic and Pacific Oceans.
• Green sea turtles travel thousands of miles from their
nesting beaches to feeding areas on their annual
migrations.
• One population that nests in the middle of the Atlantic, on
Ascension Island, travels westward to feeding zones along
the Brazilian coasts, then back again to Ascension.

37. Green Sea Turtle Migration
(Cont’d)
• Scientists hypothesized that green sea turtles may
be using cues from the earth’s magnetic field.
• Lines of magnetic force could in theory be used by
turtles to construct an internal map.
• Experimental manipulation of the magnetic field
did affect green sea turtle navigation; the turtles
adjusted in a predictable fashion to realignments
of the magnetic field
• Conclusion: green sea turtles are indeed
geomagnetic map navigators.

38. Green Turtle Migration

39. Navigation in Short
• The ability of individuals to navigate over long distances,
including migratory movements, involves using the same
cues as they do during other forms of navigation.
• It is known that the sun, stars, polarized light fields are
used as compasses by birds.
• Salmon employ a keen sense of smell; monarch butterflies
use ultraviolet radiation as well as polarized light.
• Landmark recognition is crucial for many species.
• So, depending on the species, one cue may be predominant
over another in one circumstance, but not another.
• And integration of cues must occur for decisions to be
made on the direction of movement.

40. Genetics of Migration
• The European blackcap warbler experiments indicate that
there are innate components to migratory navigation.
• Southwest German blackcaps southwest migratory
orientation is toward Spain.
• Austrian blackcaps migrate southeast through the Balkans
and Turkey.
• Individual from these two populations were bred together
to produce hybrids: the hybrids migratory orientation
favored a more due south direction, not southwest as in the
case of one set of parents, or southeast in the case of the
other set.

41. European Blackcap Warbler
• Via breeding hybrids
by crossing S.W.
German with Austrian
warblers, Peter
Berthold and Andreas
Helbig demonstrated a
genetic preference to
migratory direction

42. Genetics of Migration (Cont’d)
• During the period of their migration birds exhibit
migratory restlessness or zugenrhue.
• Under confinement some species of birds will
attempt to fly in the direction of their preferred
migratory route if they are kept in funnel shaped
cages with wide tops that provide a view of the
night sky (the starry map by which the birds use to
determine direction).