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Wildlife Corridors - Perception, Sound and Light

30 minutes
First broadcast:
Thursday 30 October 2008

Squirrel Bridges and Wildlife Corridors

How did the squirrel cross the road? Not a joke question but one a group of conservationists wanted to answer. Quite apart from the risks of getting run over, red squirrels don’t much like coming down to the ground, meaning that a refuge for them such as the Loch Lomond and Trossachs National Park might become a fragmented habitat as far as the squirrels were concerned.

So local groups have been constructing rope bridges, linking the forest across roads and tracks at branch level. But how effective are the bridges? Do the squirrels use them? Quentin Cooper finds out from National Park ecologist Alan Bell.

Across the rest of the country, wildlife corridors are also becoming an important tool for supporting endangered species, says Jim Jones of the People’s Trust for Endangered Species. From bats to dormice, butterflies to beetles, hedgerows provide important habitats in themselves as well as ways for threatened species to expand into new areas or re-populate old habitats.

Perception, Sound and Light
What we see can sometimes depend as much on our ears as on our eyes. Think how, when watching a film, speech seems to come from the actors’ lips rather than the loudspeakers. It’s an illusion ventriloquists use to good effect. Now, psychologists are investigating it in detail.

In one experiment, Dr Elliot Freeman of Brunel University shows that the perceived direction of motion of an object – in this case, red bars across a screen - depends on minute variations in the timing of an accompanying sound - a sequence of beeps. It is the rhythm of the sounds, not their stereo position, that is changed. This provides evidence that the brain’s integration of visual and audio cues occurs at a very early stage of processing. It’s a phenomenon that has not been demonstrated before.

The research shows how our brains track moving objects, and how different sensory information gets processed in the brain. Freeman’s aim is to create a model of how the brain computes sensory information. It could explain why we see patterns where there are none – the man in the Moon, a giant animal in a rocky cliff. And there may be practical applications for display screens.

Elliot is joined in the studio by Professor Charles Spence of Oxford University who works on how we process the timing and synchronization of sensory signals. He has studied, among other things, how to design the way food is packaged or served for maximum sensory stimulation and how talking on a mobile phone affects our ability to drive a car.


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