Uexküll (1934) argued that we can only appreciate how and why an
animal does what it does if we view it as the subject, rather than the
object, of the processes which influence its behaviour. He used the term
‘Umwelt’ to refer to the world around an animal as the animal sees it, and
not as it appears to us. For example, the visual space of an animal is a
function of its sensory equipment. Thus, even though dragonflies and
frogs live in the same environment, the visual space of the dragonfly, with
its compound eyes, will differ from that of the frog. Each will recognize
and respond only to those signals in the environment that are important to
its own biology. The frog might respond with a feeding strike aimed at a
flying dragonfly in the same way as it will to a black spot moving across its
visual field (Ingle, 1983). Animals also perceive time differently. For
example, the human ear does not discriminate between 18 vibrations s−^1
but perceives it as a single sound. Eighteen taps on the skin are felt as a
single pressure and, as in the movies, images must be presented at 18
frames s−^1 for us to perceive them as continuous. This temporal moment
of 8 s in humans, applies to all sensory modalities. On the other hand,
Japanese fighting fish will only recognize and attack images that are
presented at greater than 30 frames s−^1. At the other extreme, snails have
temporal moments of 4 s (von Uexküll, 1934).
Clearly, animals have unique spatial and temporal perceptions, and
we may only get close to understanding how and why parasites behave
the way they do when we get better at understanding how they perceive
their worlds. In addition, the culture and constraints of our specific
academic disciplines also have a significant impact on the way we, the
researchers, perceive our parasites and the types of questions we ask.
Thus, we shall also have to learn to appreciate how our colleagues
perceive and think about the behavioural strategies of their parasites.References
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