SOLENT & SOUTH NEWS - an event report by Graham Purchase

On February 2^nd, 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 2^nd 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 2^nd 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!