From:
Claire Curtis
Date: 2002-01-09 02:07:00 UTC
Subject: Re: Photoperiods
Just a footnote on the question of a natural lighting cycle --
The day/night length is determined by latitude as well as by time of
year. In the arctic, a summer day lasts several months. So length of
daylight, per se, is not especially indicative of a natural yearly
cycle.
I spent several months in northern Greenland, and was having trouble
sleeping in the 24-hr daylight. I was in a room with blackout curtains.
"Night" would fall abruptly when I drew the curtains, and "morning"
would be a shock that left me disoriented all day.
Finally I mentioned this problem to a long-time resident, who told me to
stop using the blackout curtains. He said making it dark was less
important than letting the body get a sensation of time passing. Sure
enough, after a few restless nights, my body adjusted to the changing
light of the sun moving around the horizon. I regained my sense of the
day's rhythm; I slept better and was more awake during the 'day'.
This is admittedly anecdotal, and I am unaware of any studies of
photoperiod that incorporate a changing light source to provide diurnal
cues. However, my experience suggests to me that it is unnecessary to
worry too much about exposing ferrets to artifical light in the evening.
My ferrets live in a room with large windows, and good natural light. I
don't turn on the lights until well after dark. I think that seeing the
natural dawn and dusk gives them sufficient diurnal cycle cues. I'll
then turn on the lights and they get an evening play period. I've
noticed that they are happy to call it a night much sooner in the winter
than in the summer, so I think they have caught the diurnal/seasonal cues.
The original thread dealt with photoperiods in adrenal kids, and I have
no experience with that -- but it might be worth thinking about
photoperiods as diurnal cues rather than absolute periods of light/dark.
Just a thought.
--Claire