14 © T. Atkinson, 2018. Practical Feline Behaviour (T. Atkinson)
2. The Senses
Because pet cats share our lives and our homes it can be easy to assume that their
experience and perception of surrounding stimuli is the same as ours. But their sen-
sory abilities, which have not changed from their wild ancestry, enable them to see,
hear and smell things of which our senses leave us completely unaware. In a few
respects, however, our senses are slightly better or at least just dissimilar but the over-
all effect is that the cat’s view of the world is quite different to our own.
Sight
Night vision
There are a number of ways in which a domestic cat’s vision differs from human eyesight.
The most well-known of these is the cat’s ability to ‘see in the dark’. In truth cats cannot
see any better than we can in complete darkness but in low light conditions specific struc-
tures of the feline eye allow them to utilize any available light far better than we can.
● The retina of mammalian eyes contains two types of photoreceptors: rods and
cones. Cones function best in bright light and are responsible for colour vision.
Rods are more light sensitive and function better in reduced light to allow vision
in low-light conditions. A cat’s retina contains far more rods than cones, with the
total number of rods being around three times greater than is found in the human
eye (Steinberg et al., 1973).
● The rod photoreceptor cells are not connected to fibres in the optic nerve individ-
ually but are joined together in bundles, so that more visual receptors are con-
nected to each nerve cell, resulting in even greater light detection. The disadvantage
of this, however, is that it also reduces the clarity of the image (Miller, 2001).
● Cats have very large eyes in relation to body size. At 22 mm in diameter, they are
only slightly smaller than human eyes, which are 25 mm. The large size of the eyes
along with elliptical pupils allow for pupil dilation that is at least three times greater
than our own, enabling a large amount of light to enter the eyes when required.
In bright light the elliptical pupil can be reduced by constriction of the iris to a very
small vertical slit only 1 mm wide to protect the retina from damage. (Fig. 2.1).
● A layer of reflective cells behind the retina called the ‘tapetum lucidum’ – more
specifically the tapetum cellulosum in cats and some other carnivores – reflects
light that has not yet been absorbed by the photoreceptor cells back into the eye to
allow another chance for absorption. This increases the efficiency of the eye in low
light conditions by up to 40% (Bradshaw et al., 2012). The tapetum is responsible
for the characteristic reflective shine whenever a light is shone into a cat’s eyes.
