60. Butterflies cross an ocean

Research just published shows that migratory Painted Lady butterflies (Vanessa cardui) found on the coast of South America had crossed the Atlantic from West Africa - and might even have started their journeys in Europe. That means they may have travelled - in total - 7000 km or more! Astonishing, even by comparison with the mighty Monarch butterfly, though the Painted Ladies would have been helped on their way by the Trade Winds.

59. The Challenge of Light Pollution

Our abuse of the natural world is causing problems which grow more terrifying with every passing day.  

Understandably, climate change and the physical destruction of entire ecosystems attract the most attention. 

But we face another environmental threat - one which is insidious and fast-growing, yet still widely ignored. 

Light pollution.

The world we inhabit was, until modern times, governed by strict astronomical laws. Day followed night, and the night was always dark - except when the moon was full. This celestial regime shaped the behaviour and biological rhythms of (almost) every living thing on the planet. 

The coming of electric light changed everything - and continues to do so. In many places true darkness now never comes. And while we may welcome that change because some of our deepest fears are associated with darkness, all that new light is causing immense damage. 

There is overwhelming evidence of the destructive effects of artificial light on the animals (and plants) with which we share the planet. 

To give just a few examples, it is likely that billions - yes, billions - of migratory birds die when they are drawn to brightly lit buildings. And even that number is dwarfed by the number of insects that suffer a similar fate. Then there are the countless, doomed turtle hatchlings that are lured away from the sea by artificial light.  

Light pollution is a major but little-noticed factor in the massive problem of biodiversity loss. 

Moreover it is increasingly clear that by banishing darkness we are also damaging our own health and well-being.

Exposure to artificial light at night is associated with a host of physical and mental disorders including diabetes, depression and even some forms of cancer.

And we are suffering other, less tangible but important injuries.

The darkness that once permitted everyone on the planet to see thousands of stars, as well as the glowing ribbon of the Milky Way - our home galaxy - has been obscured by the halo of artificial light that surrounds every town and city. The arrival of the LED has only made matters worse.

Most people living today will never see the night sky in all its glory. 

The facts are not in dispute.  In some countries (France, for example) governments are already taking practical steps to address the problems of light pollution. In the US there are many cities that have taken steps to reduce the glare of outdoor lighting.

But the British government rejected an amendment to the recent Environment Act that would have added the reduction of light pollution as a target. 

Low public awareness is a major obstacle, coupled with the common assumption that more light must be better, and a widely held (but questionable) belief that it always improves our security.  

Few people realise that the worst effects of light pollution can be reduced or eliminated by taking a few simple, inexpensive steps - such as installing lights with warmer colours, shielding them so that they don’t not spill upwards into the sky, and using motion sensors so that they only come on when needed. 

The best solution of all - just turning unnecessary lights off - has the great additional benefit of saving both energy and money.  

Often it is enough to draw someone’s attention to the problems. I recently persuaded the British Army to remove some outrageously bright lights from a military base in the middle of Chichester Harbour (a nature reserve on the South Coast of England) simply by having a conversation with the senior officer in charge. 

In the UK, the Council for the Protection of Rural England’s (CPRE) annual ‘star count’ has helped people become more aware of the problem of ‘skyglow’ - and it’s good news that several Dark Sky Parks have been designated in the UK.  

But while some UK charities take an interest in light pollution, none treats it as a priority. Because all their efforts are small and fragmented, progress in tackling the problem has been painfully slow.

 Much more needs to be done. 

 So here are a few ideas: 

Why don’t British environmental charities devise and adopt a code of conduct in relation to light pollution? 

Why don’t those same charities ask all their grant recipients to follow a similar code of conduct? Perhaps they could offer extra funding for this purpose. 

A good way of raising public awareness in the UK would be to establish an annual prize in recognition of outstanding achievements in tacking light pollution. Who would like to take this on? 

Above all, policy change is needed. Will one of our leading environmental charities launch a campaign to get the government to regulate light pollution? 

Yes, it’s a big challenge, but it’s also an urgent one.  

58. New National Geographic channel series: INCREDIBLE ANIMAL JOURNEYS

This spectacular - and very beautiful series - is now available on Disney + and if you’re interested in animal journeys you’ll really want to watch it!

I was asked to help the production team at Plimsoll Productions and had fun trying to answer their questions about the navigational tools employed by a pretty diverse set of animals.

It was very nice to be given an on-screen credit as a ‘series consultant’!

28.Green turtles aren’t perfect navigators - but they don’t have to be

Charles Darwin was one of the first scientists to speculate about how sea turtles navigate on the open ocean. It’s a fascinating question and two whole chapters of Incredible Journeys are devoted to it.

One of the experts I interviewed was Paolo Luschi whom I visited at the University of Pisa. Paolo has spent many years doing experiments on turtles in the field, and he warned me to be sceptical of claims that these animals - remarkable though they are - are brilliant navigators.

A fascinating new piece of research reinforces his point.

Graeme Hays and his colleagues (including Paolo) tracked 33 green turtles migrating from their nesting beaches on the remote Indian Ocean island of Diego Garcia to their habitual feeding grounds dotted around the western part of that vast expanse of sea. The turtles travelled anything from a few tens of kilometers to more than 4,000.

Several interesting things emerge from the analysis of their data.

Firstly, the animals very seldom went directly to their destination - sometimes they massively overshot and they often strayed wildly off track. Nevertheless, they were still able eventually to locate their targets.

Secondly, the turtles were mostly swimming in such deep water that they had no chance of seeing the seafloor beneath them (they don’t normally dive deeper than 50m). In these circumstances it would be hard for them to make use of underwater topography to guide them. However, when they got close to their destinations and entered shallower water, they were able to head fairly directly towards them. This suggests that they were making use of ‘landmark’ information - possibly acquired on previous trips.

This study also compared what the real turtles did with what they might have done based two different assumptions about how they navigate.

The first, stringent assumption was that the turtles are true ‘map and compass’ navigators - able, that is, both to work out where they currently are and where they need to go to reach their goal.

The second, much simpler one was that the turtles only had access to a compass of some kind that would enable them to maintain a steady course. This would of course give them no positional information.

When the actual tracks followed by the turtles were compared with the ‘virtual tracks’ that emerged from the simulations, it became clear that the turtles were not perfect map and compass navigators. They lacked ‘the ability to always locate small isolated targets with pinpoint accuracy’.

But, since they were still able to find their targets, it looks as if the turtles must have access to some kind of ‘map’, though plainly not a very detailed or precise one.

Such a map is very likely to involve geomagnetic cues, though other factors might also be involved. (Ken Lohmann’s studies of captive loggerhead turtle hatchlings have already shown their acute sensitivity to geomagnetic information - see Incredible Journeys chapter 22 for a summary.)

It’s also clear that the turtles don’t rely on following a single, fixed compass course. This makes very good sense as such a crude mechanism would make them vulnerable to the disturbing effects of ocean currents that deflected them from their proper course..

The researchers found no evidence that, in the final stages of their journeys, turtles were making use of olfactory information - either smells in the air or tastes in the water - carried to them from their target. This is quite surprising, especially as hints of such an ability have emerged from earlier research.

This new study illustrates an important principle. Evolution doesn’t favour the emergence of perfect systems of navigation (or anything else), when merely adequate ones will enable animals to survive and reproduce successfully.

Good enough is good enough!

17.Amazing cuckoos

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There’s no better way of getting a sense of what migratory birds can do than to look at the maps that record their journeys.

The Mongolian Cuckoo Project has been using tracking devices to follow the amazing journeys of cuckoos returning home from Southern Africa in recent weeks. Do please visit their excellent website to see the achievements of Onon, Bayan and the other birds. It’s a real model of public engagement in science.

Quite apart from the extraordinary distances the birds have been covering, I’m struck by the close similarity between the routes they have been following. It would be fascinating to know exactly how they perform such impressive navigational feats.

Presumably, like many other migratory birds, cuckoos have a sun and star compass as well as a magnetic one. And when they have made their first migratory journey, it’s safe to assume that they use familiar landmarks to help them retrace their route. But of course there are no landmarks over the ocean!

And cuckoos face a special problem. Their unusual lifestyle means that when they first head south, they must do so alone - because their parents will have left before them.

So how on earth do they find their lonely way over thousands of miles of land and ocean to the areas in Africa where they pass the winter months? Some kind of genetic program must be involved. But how does that work? We just don’t know.

One last thing: why not lend your support to this brilliant project by following this link?

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