Challenge: help the blind to navigate their surroundings

Natural inspiration: bat sonar




An estimated 45 million people across the world are blind 1.  Artificial aids, such as the internationally-recognised white stick, can help blind people to lead full and independent lives.  In nature, many creatures have evolved to rely on senses other than sight.  Designers are looking to the adaptive responses of diverse biological organisms to find inspiration for improved aids for blind people.







Where vision cannot be used, for example in dark environments, sound provides an alternative.  Many animals, including bats, whales and shrews, use a technique called echolocation to navigate their surroundings and to hunt for food.  The animal emits a sound and analyses the returning echoes to detect nearby objects. 2  Whales can detect objects a few centimetres across at a distance of tens of metres using high-pitched sounds.  On their long migrations they navigate using low-pitched sounds, which can travel hundreds of kilometres underwater. 3



Animal use of echolocation was first demonstrated in bats in 1960. Most bat species, with the exception of the megabats (about 170 species), use echolocation. 5  Echolocation can give a level of information similar to human vision.  For example, bats cannot only locate and catch an insect in flight: they can tell what size it is and in some cases what type (e.g. soft-bodied or hard) 6




Blind people are able to learn to use echolocation to varying extents 7, but the human ear and brain have not evolved the structures necessary to detect the level of detail possible in bats.  A recent advance in technology, inspired by studying bats, enhances the ability of blind people to perceive their environment through echolocation.  Electronic devices emit ultrasonic sound and translate the echoes into cues such as vibration or audible sound that a person can detect.  Several gadgets are now available that allow the user to sense the environment around them far beyond the reach of a traditional white stick, and in much more detail. 8, 9, 10  Thus, techniques developed by nocturnal animals over thousands of years of natural selection are now enhancing the lives of human beings.







There are more than 1,100 species of bat worldwide.  They play a vital role in maintaining ecosystems: many plants, including some commercially important tree species, depend on bats for pollinating their flowers or spreading their seeds. 5 In America, the role of bats in controlling populations of insect pests is well recognised.  One study in Texas estimated the value of bats as a pest control mechanism for cotton production in the region to be as much as 741,000 US dollars per year – about 13% of the value of the crop. 11







Worldwide, about 25% of bat species are threatened with extinction and at least 12 species have already become extinct.  The main problem is destruction or disturbance of the habitats where they feed and roost. 5  Sadly, some cultures see bats as frightening or evil, but nothing could be further from the truth.  As well as providing valuable services to economies around the world, bats have inspired devices that could improve the lives of millions of blind people.






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  1. WHO visual impairment fact sheet (2009)  Accessed April 2010.
  2. Echolocation article by the Bat Conservation Trust. Accessed April 2010.
  3. Oceans of noise: a Whale and Dolphin Conservation Society Science report (2004). Accessed April 2010.
  4. Griffin, D.R. et al. (1960) The echolocation of flying insects by bats. Animal BehaviourFull article available online.  Accessed April 2010.
  5. Bat Conservation Trust. Accessed April 2010.
  6. Jones, G. (1990).  Prey Selection by the Greater Horseshoe Bat (Rhinolophus ferrumequinum): Optimal Foraging by Echolocation?  Journal of Animal Ecology, 59: 587-602
  7. Wiener, W.R. et al (1997) Audition for the traveller who is visually impaired, in Foundations of Orientation and Mobility, pp 145 – 152, AFB Press, New York.  Accessed April 2010.
  8. Sonar cane helps blind navigate. BioEd online, September 2003. Accessed April 2010.
  9. Sonar Traveller Cane. Accessed April 2010.  
  10. Bay Advanced Technologies  - BAT K-sonar device. Accessed April 2010.
  11. Cleveland, C.J. et al. (2006).  Economic value of the pest control service provided by Brazilian free-tailed bats in south-central Texas. Frontiers in Ecology and the Environment 4: 238-243.

Further reading


The secret life of bats, Natural History Museum.  Accessed April 2010.

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