The Cloak and the Snake.

[Lady Macbeth]

No: HPFGUIDX 74375

Tzvi Said:
>>>I love you all, but there is a reason that we are HP for GROWNUPS.
For all of you that know anything about snakes, they can see infra-red
on the light spectrum. I would assume that the cloak would have to
make all things invisible to the naked eye, but there is still the
matter of the heat that any of the invisible people are giving off. I
would think that the larger the snake, the more developed his heat
seeking capabilities. I would assume JKR would be using a snake that
would even be able to detect invisible people. Perhaps moody's eye can
see the full spectrum from ultraviolet to infra-red as well.<<<

Lady Macbeth:
If we're going there, however, it should be noted that Parseltongue
would be adequate at best, unless the Parselmouth were interested in
communicating with only certain species - snakes' hearing varies from
species to species, ranging from keen hearing (being able to detect
human voice frequencies at ten feet) to profoundly deaf.  Many species
that are considered "deaf" (do not detect frequencies within normal
human hearing range) pick up sound through vibrations transmitted from
the ground to receptors in their bellies.  Parseltongue, generated in
airwaves, would be undetectable to them.  The "general" rule is that
most species kept for pets might indeed recognize their name - their
hearing is just sharp enough that a person in a quiet room close
enough to be talking to them would be heard.  (This would also fit
with the "movie contamination" of the constrictor apparently not
hearing the argument between Harry and Dudly, but after it was quiet
hearing Harry's apology and explanation.  Parseltongue or no, it
wouldn't have been able to distinguish Harry's voice over those of the
Dursleys or the other park visitors who walked by at that time.)

Also, a snake being able to communicate back in an eloquent fashion
could be a chancey venture.  Not all snakes hiss - those that do
usually produce a breathy "HA" sound by rapidly expelling air from
their lungs.  The sound IS detectable by other snakes and animals,
including people - some species of snake and crocodillians use it in
mating and territorial disputes.  Others, however, are the "silent
type" - that's why people who are bitten by them don't see or hear
them until they're bitten.  All snakes generally give warning (unless
you jump down on top of it or something) but posturing or tail-waving
doesn't work on people who can't see them in the first place.

Vision likewise varies from species to species, with the same extremes
- from keen with detailed color vision to completely blind. 
(Completely blind being unable to see even infrared spectral
reflections.)  As a "general" rule, snakes have minimalistic vision
that allows them to see movement and size, and not much else - they
could distinguish between a human and a mouse, but not between a
hamster and a gerbil.

Snakes DO have special heat receptors in their heads for detecting
warmth - this is how they do a good percentage of their navigating
while hunting or seeking shelter/sun.  When other senses are dulled,
such as in travel when sounds would blend together or disappear and
the world would run together in a blur of color and/or shapes, the
heat receptors will steer the snake toward a target that has a higher
temperature than the surrounding environment - this usually means a
living being, but it's also how a lot of snakes end up on the highway.
 Flat rocks and similar "sunbathing places" for snakes reflect
sunlight and become hot in a manner similar to road surfaces, so roads
are sometimes mistaken for a good place to soak up rays before
continuing on a journey. 

-Lady Macbeth