SOLENT &
SOUTH NEWS - an event report by Graham Purchase
On February
2nd, Royal Lymington Yacht Club hosted a joint meeting with our RIN
Branch: “An Evening with David Barrie CB FRIN”.
Rather than a giving a lecture, David answered questions from Dr Clare
Stead & the audience.
David is a retired diplomat and is the author
of 2 critically acclaimed books: “Sextant”, the story of how the sextant and
its predecessors were used to map the world’s oceans; and “Incredible Journeys”
which chronicles many amazing discoveries and research projects about Animal
Navigation.
David said
that he went to school in Lymington and is a former member of RLYC. One of his
teachers was a keen entomologist and used his moth trap to interest pupils in
moths and butterflies. David remembered being presented with the chrysalis of a
Monarch Butterfly; a species which is now the most famous of insect navigators.
“What
attracted you to research the Monarch Butterfly?”
Decades
after my school days, I looked into the science of the extraordinary migration
of Monarchs between as far North as the Canada/USA border in the Summer and a
small area of just a few hectares in a remote, mountainous region to the West
of Mexico City in the Winter; where they congregate in their millions. It is
even more amazing that the migration involves several generations of the
butterflies during the journeys. If they just followed the sun, they would fly
a curved course; but to be able to fly a steady course, the Monarchs must have
a ‘time-compensated sun-compass’ sense, with a sort of clock in their antennae.
“Incredible
Journeys covers a wide range of creatures, but which animal’s migration &
navigational methods impresses you most?”
Animal navigators face the same challenges as humans, and to
start navigating one needs to know: Where am I now?... What is the location of
the destination?... Then one can set a course to get there. The book
distinguishes between two main categories: using a ‘map’-based sense; or, more
commonly, using some other technique. A simple non-map method might be using
‘beacons’, which could involve eyesight, or perhaps the sense of smell or even
hearing. A more complex method might be ‘Path Integration’, also known as Dead
Reckoning or DR, which involves measuring how far and how fast one is
travelling and in what direction; while taking account of changes while en‑route.
However, DR accuracy get worse with time. The most impressive and best studied
animal user of DR is the Desert Ant, which lives in burrows in bleak, desert
salt-pans. They come out to hunt in extreme heat, looking for live or dead
prey, zig-zagging all over the place over 10s of metres; then carry the prey in
a straight line back to their very small burrow entrance. The ants have been
found to have a special part of their eyes that detects the polarization
patterns of sunlight, and they do use a time-compensated sun-compass sense, but
this would not locate their nest; so, they seem to have an odometer sense too,
as they now how far they have gone. They have a keen sense of smell, can detect
the wind direction and are also brilliant at landmark. The ants achieve all
this with a very small brain containing perhaps 400 thousand neurons! (For
comparison, a human brain has roughly 85 billion neurons).
“What other experiments caught your imagination?”
One of my favourite researchers that I interviewed is Eric
Warrant, an Australian working at the University of Lund in Sweden, He and his
colleague Marie Dacke are famous for their research with nocturnal insects, and
especially the nocturnal African Dung Beetle. On finding a dung heap, the
beetles grab some dung and sculpt it into a sphere; then, grasping the ball in
their rear legs, roll it backwards to a place where they can lay eggs in the
ball and bury it. However, they have a competitive streak, and often ‘mug’
others and steal their balls of dung!
This means that the beetles need to move quickly, and despite it being
night, they go in a straight line – but how do they manage this? It has been
shown by experimentation that the beetles can detect the polarization patterns
of moonlight. However, it was discovered later that they can still get straight
to their nests when there is no moonlight. Then, it was realised that given the
unpolluted air in the Kalahari Dessert, the Milky Way is usually visible.
Further experiments conducted in an observatory, confirmed that the beetles
were using its orientation to navigate.
“Turning to your book ‘Sextant’: when was the earliest
known use of Heavenly Bodies for navigation?”
Evidence from prehistoric times suggests that the earliest
navigators must have been using the Sun and stars in some way. During
scientific expeditions in the Pacific in the 2nd half of the
eighteenth century, Bougainville, Cook and others were very impressed by the
navigational skills of Polynesian islanders. Research in the 60s & 70s
showed that they could travel in the order of 2000 miles in their large canoes
and still be able to locate a small island without recourse to any navigation
tools or charts. These expert navigators could remember the rising points on
the horizon of many stars, and used these to enable them maintain a steady
course at night. They were also using other clues like swell patterns in the
sea caused by islands over the horizon; and even the type of birds they were seeing.
Their skills were truly remarkable.
“You made your own journey across the Atlantic Ocean on a
small yacht; how did this change your ability to navigate using the sky?”
Colin McMullen, a retired naval officer, invited me to join
him on his 35 ft ‘Saxon’ class yacht ‘Saecwen’ for a trans-Atlantic cruise,
when I was only 19. I had been fascinated by the idea of celestial navigation
for some time, and Colin taught me how to use the sextant. In the last 20 years
or so, there has been a navigation revolution; instead of celestial and natural
world observations, using our senses combined with reasonable inferences; we
can now use GNSS and know our position with no intellectual effort at all!
However, by becoming too dependent on technology, we are losing something very
valuable. The RIN is very concerned about the extreme vulnerability of GNSS;
satellite signals are very easy to jam, and now to spoof too, resulting in
false positions! But more profoundly, our increasing dependency on these
systems is affecting our relationship with the world around us and even our
spiritual health, as described in both books.
“With that in mind, what do you think the future holds for
instruments like traditional sextants, compasses and charts?”
The traditional answer is that we should go on learning those
skills as a ’safety net’, because the electronic stuff might go down, or there
might be a solar storm or lightning. That’s right; but I also think you would
actually be missing out on a rewarding aspect of sailing. If you are not
already adept, I would recommend getting into it; and it’s a lot easier now
because there are ‘Apps’ which do all the maths and reduce the workload a lot.
However, we still need to be able to take a sight, which is a real skill. Learn
celestial navigation for fun and enter into a much more profound and
spiritually rewarding relationship with the world around you!
“What are the key virtues of the Sextant itself, compared
to Quadrants and other earlier
instruments?”
A sextant measures bigger angles: up to about 120 degrees,
but it uses the same ideas as the earlier Quadrant. It was invented in the
1750s to enable sailors to make use of the Moon & Sun, and calculate the
‘Lunar Distance’ to determine Longitude; a breakthrough at the time! You could pick
up a very old instrument and still be able to use it today. Accurate and
robust; it’s an instrument that opens a gate into infinity! My book brings the
sextant to life.
“I want to draw you back to 1714, when the Longitude Act
established a prize of up to £20,000 for someone who could demonstrate
determining longitude.”
To explain the significance of the problem, Latitude could be
determined accurately, eg by measuring the altitude of Polaris. However,
astronomical tables are needed to use the Sun, and the earliest tables of solar
declination appeared in the late fifteenth century. So, in the early sixteenth
century, on the great voyages of Portuguese and Spanish captains, they had to
be very cautious when sailing out of sight of land, because their Longitude wasn’t
known. The various great naval powers offered prizes to try to solve the longitude
problem, and two solutions emerged. One
was Harrison’s Chronometer, described in detail in the book ”Longitude” by Dana
Sobell; but this was only part of the story, as chronometers were hugely
expensive and very unreliable. Captain Cook carried several valuable
chronometers, but they could go wrong, or start to be fast or slow. The 2nd
solution was to use ‘Lunars’ which were popular from around 1760 to the 1840s;
nowadays there’s even an ‘App’ for Lunars!
“Are
there any animal navigation methods which don’t require any sense of knowing
time, or is time something which is essential?”
Yes: using
Beacons doesn’t need time; also, using a scent trail doesn’t need time; so, many
animals don’t use time. Also, it’s not necessary to have a super-accurate idea
of time; eg, a time-compensated sun-compass sense just has to be good enough;
but time seems essential for many navigational challenges.
“I agree
on the desirability of learning to use a sextant, but with an understanding of
the shortcomings of GPS, it does enable sailing in areas which you wouldn’t
have been able to go to before; eg remote Pacific islands, or when navigating
under cloud cover.”
Yes, for
parts of the world like the Amazon or for small atolls or islands in the
Pacific which aren’t accurately charted, or with adverse weather, having access
to GPS enables visits that were too difficult or dangerous in the past.
“Would
the debate about over-dependency on GPS and having to learn traditional
methods, have had a parallel when ‘new-fangled’ chronometers were invented by
Harrison?“
When the
Royal Navy tried to impose a requirement to learn new methods of navigation
using chronometers, it met a lot of resistance from traditionalist masters.
“Watching
films with my grand-daughters, there’s a Disney film called ‘Moana’ with a lot
of discussion about finding your way across the Pacific using the waves. Isn’t
that a good thing to tell children about“?
Yes; as
mentioned, there was a special cadre of Polynesians that did this.
“I read
about a breed of moths in Australia that live in location A, but fly thousands
of miles to location B to breed; then they die, but the offspring make their
way back home to location A. How can that be possible?”
My favourite
insect, the Bogong Moth lives in Queensland until the Summer heat arrives, then
migrates South to the Snowy Mountains in New South Wales, covering distances of
over 1000 Km. The moths hide in crevices and go into suspended animation; but
at the end of the Summer they don’t die, it’s the same moths that return to
Queensland, making the round trip over 2000 Km.
I spent time with researcher Eric Warrant and joined in some
experiments, described in ‘Incredible Journeys’; the moths have a
magnetic-compass sense enabling them to accurately set a course and in
addition, they use the Milky Way.
“If the
moths were moved by scientists to a new location, would they identify with the
new location, or the old one?”
Translocation
hasn’t been tried with Bogong Moths, but it has been with some bird
species. Birds mostly use their magnetic
sense, the nocturnal migrants have a star-compass, some birds also use their
sense of smell and some may also use infrasound. Experiments have shown that Reed
Warblers can find their way back to their destination if displaced from their
migration route, but only if they have migrated before; juvenile birds can’t do
this!
“How do
Homing Pigeons get home?”
Pigeons have
a time-compensated sun-compass, a magnetic sense; and they can recognise
landmarks around their lofts, and out to about 10-15 Km from the loft. However,
even if they are anaesthetised and moved in a sealed box, they can still
usually find their way back from, say, 300 km away! This question has puzzled
scientists for many years, and about 40 years ago, it was shown that the birds
only returned if their sense of smell was intact; but this seemed
preposterous! Hundreds of experiments
showed that olfaction was important at both long and short distances, although
other factors may also have been involved, and Pigeons might be able to detect
the signature infrasound of their loft location.
“How can
domestic Cats and Dogs find their old home, after a house move?”
In the last
2 or 3 years, there has been some new research in the Czech Republic; it seems
that Hunting Dogs can use two navigation methods: a magnetic compass sense, and
their sense of smell. They stand for a while, aligned with the earth’s magnetic
field before setting off on a course. They may, like humans, have a map sense
too!
“What
unsolved animal navigation questions are there?”
The methods
of magneto-reception are largely unknown. A huge amount of effort is going into
trying to understand this. It is also fascinating how tracking studies have
shown that marine mega-fauna, like whales and sharks, make breathtakingly
accurate migrations and returns across vast oceans, using unknown methods.
“Please
comment on Anthropocentrism”
This is the
idea that we humans are the most important things on the planet. However, other
creatures often astound in their capabilities, and exceed human ones in some
areas. The more we can recognise that we are only a part of creation and that
we are ‘all in it together’ with millions of other species, the better. One
advantage of all this study of animal navigation is realising that we are not
the most special animal, after all!