Information about the environment can be detected in many ways. Electro-magnetic waves, chemicals in the air or water, vibrations, and even magnetic and electric fields
It is a mistake to try to understand animal senses in our human terms. Do not try to imagine what a fly ‘sees’, or what a spider ‘feels’. This is to fall into the trap of Anthropomorphism. Most (all?) animals lack the sort of ‘consciousness’ that we humans possess, so it is probably best to think of then as ‘responding appropriately to stimuli’.
Sight
Many type of ‘eye’ have evolved (independently) in the animal world. Perhaps the most amazing is that of the Mantis Shrimps. These creatures have some of the most advanced eyes of all and they can ‘see’ much more than we can. (Perhaps it is better to say that they detect a far wider range of stimuli with their eyes than us.)
It is not just a question of which wavelengths of light can be detected by an animal, but also of how many eyes there are and how the nervous system (brain) deals with the information. We process the information from two eyes (binocular vision) to allow true three-dimensional awareness, whereas the Mantis Shrimp has three parts to each eye and potentially trinocular vision from just one eye. It is difficult to understand what extra information this kind of vision might allow.
Furthermore, many invertebrates can detect light of wavelengths far beyond our reach, allowing them to process information invisible to us. In addition they often have ‘compound eyes’, and we can only imagine what they might be able to do! ‘Seeing’ the polarisation of light is another trick, as is the ability to detect heat. The Kissing Bugs can find their hosts by moving towards the heat they give off and also by detecting the carbon dioxide they breathe out.
Smell and Taste
‘Smelling’ carbon dioxide is a trick employed by many of the blood-sucking invertebrates, and many animals also use their chemical senses for communication. Humans have a very poor sense of smell – we only have to think of dogs to realise that – but some invertebrates can detect individual molecules of certain chemicals at a distance. Taste is simply the ‘close-up’ version of smell, in other words the ability to detect chemicals in the mouth.
Touch
Touch-at-a-distance is something we find hard to imagine, but spiders do it through their webs, snakes do it through the ground and fish do it through water. The responses that Woodlice show when they find crevices warns us not to try to interpret these senses by reference to our own conscious thought-processes, it is better to keep to the ‘stimuli provoking responses’ way of thinking.
Other Senses
Vision, chemical and vibrational senses are not all. Some fish can detect (and navigate by) electrical impulses, Bats (and Dolphins) can use echo-location and many species are aware of magnetic fields. There are probably many other ‘environmental clues’ that animals can detect, and it is perhaps no too ‘far-fetched’ to suggest that we ourselves might be able to respond to some things that never reach our consciousness (such as dowsing for water?).
Other articles by John Blatchford
