Friday, January 29, 2016

Which way to go? How do they do it?


Image above: The extraordinary navigation skills of the pigeon

Related links to Spatialworlds
GeogSplace (a teaching blog for Year 12 geography)
Geogaction (geography professional learning blog)
Spatialworlds website
GeogSpace

Australian Geography Teachers' Association website
manning@chariot.net.au


The mystery of spatial orientation

For years I have been fascinated with the disparity of the spatial intelligence/orientation between individuals and even more amazed by the spatial intelligence of animals such as cats and pigeons that seem to have an in-built GPS to find their way from place to place with uncanny, and unfathomable skills. In a Spatialworlds posting last year I discussed the parts of the brain that have been identified as our spatial control room with GPS capacity.
My thinking on this was particular prodded by my experience with my son when he was younger. I could walk around large cities all day that he had never been to before and then say lets go back to the hotel - and he would negotiate the streets of places like Hong Kong, without a map and take me back to the hotel, whilst I was hopelessly lost and searching for a map to orientate myself. Maybe that is why I became a geographer, because my spatial control centre was so bad that I had to learn to use maps to orientate myself. After this happened time and time again, I realised that my son had a much better spatial orientation than me, despite his limited knowledge and experience - was it just an innate ability? The following posting explores several examples of the extraordinary spatial orientation skills of some people and animals and suggest some reasons why.


The pigeon's spatial ability

 For years, scientists have struggled to explain carrier pigeons' directional challenges in certain areas, known as release-site biases. This "map" issue, or a pigeon's ability to tell where it is in relation to where it wants to go, is different from the bird's compass system, which tells it which direction it's headed in.
 
Pigeons have extraordinary navigational abilities. Take a pigeon from its loft and let it go somewhere it has never been before and it will, after circling in the sky for while, head home. This remarkable capacity extends to places tens even hundreds of kilometres from its home and is all the more remarkable to humans because we are apparently incapable of it ourselves. Humans have long made use of the pigeon’s homing ability, principally for carrying messages in the past -  especially in war.

Out of direct contact with home, and out of the landscape to which birds have become familiar, there must nonetheless be large-scale cues available to the navigating bird with which it can estimate its position relative to home. Many theories have been forwarded to explain the navigational ability of pigeons, from reading the sun’s arc to the detection of long-distance infra-sounds. Both unfounded in science! 

Another theory is that pigeons can use the predictable gradients of intensity and dip-angle in the earth’s magnetic field to map their position relative to known values at home. Again scientifically unsubstantiated. It is true that many birds do have a magnetic compass which gives them a sense of direction when they cannot see the sun. A compass helps make long-distance movement efficient and is central to migration, but it cannot help them navigate if they do not know the direction of the goal. This requires a map. It seems this map turns out almost certainly to be olfactory – pigeons, and perhaps all birds, navigate using smell. Pigeons deprived of the ability to smell cannot navigate. Scientist have fooled them with air from the wrong site and they fly in the wrong direction. However there are still experts who doubt it on reasonable grounds.

Another theory relates to the sense of smell. The case is pretty strong that birds learn the rough composition of atmospheric volatiles characteristic of their home area. Considering that this varies with winds that come from different directions, they are able to extrapolate to unfamiliar places if they are blown off-course or taken there by a human and released. Even over the open oceans, birds may use odours to navigate.It seems that olfactory deprivation has little effect on a pigeon’s orientation, and it seems that they switch to a second mechanism dominated by visual landscape cues. 

Recently, through access to miniature on-board tracking technologies such as GPS, birds can be followed with precision to unravel the mechanisms of their spatial cognition in the wild. Spatial tracking has shown that pigeons repeatedly released from the same site soon learn a habitual route home which they stick to faithfully even if it is not the quickest. Routes often follow linear landscape features, such as roads or field margins, but are learnt most effectively over landscapes of intermediate complexity. So if the pigeon’s brain contains a network of learnt routes, how are these memories acquired and how do they interact? Recently,  Andrea Flack and Dora Biro showed that having to learn three routes in parallel doesn’t cause pigeons any additional confusion. Route-learning is memorised independently, regardless of whether the sites they are released from are encountered sequentially, randomly intermingled or in strict rotation.

Other ideas to explain the power of animal navigation over unknown landscapes

It seems that there are places around the world that seem to confuse birds — areas where they repeatedly vanish in the wrong direction or scatter on random headings rather than fly straight home. Geophysicist Jon Hagstrum proposes an intriguing theory for homing pigeon disorientation—that the birds are following ultralow frequency sounds back towards their lofts and that disruptions in their ability to "hear" home is what screws them up. Called infrasound, these sound waves propagate at frequencies well below the range audible to people, but pigeons can pick them up.

"They're using sound to image the terrain [surrounding] their loft," he said. "It's like us visually recognizing our house using our eyes."
Other research supports the theory that homing pigeons use magnetic field lines to find their way home. What homing pigeons are using as their map probably depends on where they're raised. In some places it may be infrasound, and in other places [a sense of smell] may be the way to go."

The pigeon in war
The story of a WWII hero whose feats of navigation saved hundreds of lives. The hero? A pigeon named G.I. Joe. Homing pigeons can find their way home from more than 500 kilometres away and at speeds of 100 Kilometres per hour, said Mindy Rosewitz, curator at the U.S. Army Communications Electronics Museum in Fort Monmouth, N.J.

The fox! 
The foxes spatial orientation to North when hunting mice is an amazing example to affirm the thinking of the magnetic field capacity of the pigeon - this rather amusing video on the red fox is worth a look and wonder about their spatial ability.


The following summary is from the article about the research of Jaroslav Červený that appeared in the Discovery Magazine blog.

Cerveny found that when red foxes pounce, they mostly jump in a north-easterly direction. He thinks that they’re using the Earth’s magnetic field to hunt. Červený spent over two years studying wild red foxes in the Czech Republic, with the help of a 23-strong team of wildlife biologists and experienced hunters. The team recorded almost 600 mousing jumps, performed by 84 foxes at a wide variety of locations and times. They found that foxes strongly prefer to jump in a north-easterly direction, around 20 degrees off from magnetic north. This fixed heading was important for their success as hunters. They were more likely to make a kill if they jumped along their preferred axis, particularly if their prey was hidden by high cover or snow. If they pounced to the north-east, they killed on 73% of their attacks; if they jumped in the opposite direction, they success rate stayed at 60%. In all other directions, only 18% of their pounces were successful. Could the foxes be taking their direction from the environment? Červený thinks not. He found that the animals leapt in the same direction regardless of the time of day, season of year, cloud cover, or wind direction. Červený thinks that the only remaining explanation is that foxes align their pounces to the Earth’s magnetic field.

Many living things can sense magnetic fields. In his New Scientist article Cerveny concluded that other animals have a magnetic sense too, such as sharks and rays, turtles, ants, lobsters, beetles, bats and mole rats. The list also includes cow and deer. In 2008, he found that herds of cow and deer also tend to align in a north-south line like living compass needles. Spying on the animals with Google Earth satellites, it was found that that they tend to face magnetic north regardless of wind strength, time of day, or the position of the sun. A year later, they found more evidence that these animals are influenced by a magnetic sense: their neat lines could be disrupted by high-voltage power lines, which produce strong magnetic fields. The nearer the herds get to the lines, the more chaotic their positions.
In all of these cases – be they cows of birds – it’s not entirely clear what the point of having a magnetic sense is. For example, it’s reasonable to think that magnetic compasses and maps could help migrating animals to find their way, especially when visibility is poor or landmarks aren’t obvious. That makes sense, but there’s little hard data to back it up. Červený’s study is one of the first to demonstrate a clear benefit – red foxes hunt more successfully if they jump in the right direction.

So how do foxes and other animals log into the magnetic fields of the earth? Scientists suggest that animals sense magnetic fields using one of two basic methods. 

The first involves clustered crystals of magnetite, an iron mineral that line up according to magnetic fields. Depending on their direction, the crystals either repel or attract one another, creating tiny forces that could be picked up by proteins. The moving crystals could even open or close molecular gates on the surface of nerve cells. Either way, the crystals convert a magnetic field into a nervous signal.

The second method is used by birds and involves a molecule called cryptochrome, which is found in the retina. When light strikes cryptochrome, it shunts an electron over to a partner molecule called FAD. The result is a pair of ‘radicals’ – molecules with a solo electron. These unpaired electrons have a property called “spin” and they can either spin together, or in opposite directions. The two states can flip from one to another, and they lead to different chemical outcomes. This is where the Earth’s magnetic field comes in: it acts like a switch that influences the flips. In doing so, it can affect the outcome of the radical pair’s chemical reactions. All of this happens in the eyes of common birds, such as robins or warblers. This is why you can deactivate a robin’s internal compass by blindfolding it. In fact, you could make it lose its bearings by blindfolding just its right eye, or covering it with a frosted goggle. Some scientists have suggested that robins and other birds can literally see magnetic fields, as a sort of heads-up display. The fields could appear as light or dark patches (or even colours) that lay on top of what the bird normally sees.

Overall, after reading all this research and trying to piece together a coherent summary of the causes of the amazing spatial orientation of animals, I am more confused than ever!!


Going beyond the spatial skills of animals, here is an interesting human example of unexplainable spatial cognition.

Lera Boroditsky once did a simple experiment: She asked people to close their eyes and point southeast. A room of distinguished professors in the U.S. pointed in almost every possible direction, whereas 5-year-old Australian aboriginal girls always got it right. She says the difference lies in language. Boroditsky, an associate professor of cognitive science at the University of California, San Diego, says the Australian aboriginal language doesn't use words like left or right. It uses compass points, so they say things like "that girl to the east of you is my sister."