Hi Mike,
Thanks for your comments on this topic. Unfortunately this is one of those
topics in which many people are interested but almost none are prepared to
contribute to the discussion. So, it was good to read your comments which
provided some points that I had not considered or covered in my posting on
this topic.
I agree with your comments on red filters. Red filters are really all about
maintaining the observer's night vision and not about protecting the viewed
creature's eyes. Such filters, depending on the density of the filter
element, will also reduce the intensity of the light beam and that is
probably why some night creatures (such as bandicoots) seem less concerned
when such a light is trained on them, although, being mammals, their night
vision is also less likely to be disrupted than if an unfiltered light is
being used. However, the red filter may reduce the power of the light beam
on low powered spotlights to the point where the light becomes impractical
for spotlighting. I am not sure that spotlights with red filters are any
better, from a bird's point of view, than unfiltered lights but the
observer's night vision is less likely to be disrupted if spotlights fitted
with red filters are being flashed about willy-nilly.
Perhaps the type of colour-tinted wrap-around glasses worn by some of the
cricketers in night games would be a better proposition for participants in
spotlighting activities but that would not help the creatures being
observed.
The point about identifying snakes at night by the light of a spotlight with
a red filter is a good one. The same could be said about some bird species
as well, I am sure, but other factors would make it easy to identify birds
at night.
Incidentally, I would think that a discussion on identifying snakes has as
much relevance on a birding forum as a discussion on mammals which is
basically what this discussion on spotlighting started as.
In that same vein, I understand that invertebrates can suffer eye damage
quite easily from strong light. I wonder if any of the "bug-botherers" who
frequent BirdingAus have any comments they would wish to make publically (or
privately) on that?
Maybe the frog-fanciers could comment on the effect of spotlighting on frogs
eyes.
This document details some observations on using spotlights for observing
possums:
http://www.wettropics.gov.au/res/downloads/info/possumsSpotlight.pdf
Mike, your comments re the "very little structured scrutiny of this
activity" are apt considering that there appear to be wildlife laws in this
country concerning the use of spotlights on wild creatures.
And your comments about the economical and conservation benefits involved in
the eco-tourism industry are important as well.
Cheers
Bob Inglis
Sandstone Point
Qld
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