Animal senses: how they
detect stimulus
• Remember that sensory stimulation is
often the starting point for behaviour.
There are five or possibly six senses and
that animal and human senses are not
necessarily the same.
Photoreceptors (vision)
• Many animals are sensitive to different ranges of
the spectrum then humans. Bees see in
ultraviolet but are less sensitive to red which is
why most red flowers are either scented or have
blue in them. Goldfish see far red and seabirds
are very sensitive to red.
• Animals detect colour in a variety of ways, many
do not have colour vision at all, eyes are set up
differently and most detect movement and speed
of movement.
Thermo receptors (heat)
• Many snakes have heat pit in front of their
eyes and can detect infrared to locate
prey.
• Most animals use their skin to detect heat.
Mechanoreceptors (touch etc)
• These receptors let an animal know which
way is up in terms of gravity, they govern
internal pressure (stomach, bladder),
recognise the position of one part of the
body to another.
• Cats whiskers are tactile receptors, human
skin, lateral line in fish
• Proprioceptors respond to tension
in muscles and joints.
Chemoreceptor (smell and taste)
• Smell is the detection of chemicals in air or
water
• Taste (gustation) is the detection of chemicals in
the liquid or solid state.
• Humans use nose and tongue but other animals
have quite different organs: flies have taste hairs
on feet, many insects smell with antenna,
reptiles have Jacobson’s organ for sensing.
• Pheromones are used to communicate between
members of the same species.
• Chemicals are used for:
– Hunting to track and detect prey
– Detecting predators
– To recognise and check if food is ripe/safe
– To recognise other members of the group
– For defence (skunk)
– For attack (spitting cobra)
– To mark territory
– For communication (especially insects)
– For sexual attraction
– To form an alarm
– To make a chemical trail
Auditory receptors (sound)
• Humans detect sound in waves with thiwer
inner easr in the range of 20-20000hz.
• Sound above this range is ultrasonic
• Bats, dogs, whales and insects can hear
ultrasonic sounds.
• Whales and dolphins also use
echolocation
Electrical fields
• Some debate over this being the ‘sixth
sense’. Some fish have an electrical field
around them and can pick up disturbance
in that field.
Magnetic fields
• Homing pigeons and some bacteria can
detect the magnetic field lines of the earth.