Hmmm, I've always wondered if animals could sense subtle things like the moons gravitational effect on the earth as it orbits. Like when corals spawn on the reef exactly 4 days after the full moon (or something like that, but it's always at the same time and at the same moment). But then home aquarists started experimenting with artificial moon light and lunar cycles and determined it was by sensing the moon's light intensity and cycle (rising and setting) that triggered their spawning behavior.
And then there's the reptiles that normally go through a cool-down period almost like hibernation (called brumation) during the winter months, and then go into breeding mode when they come out of it. Now in the wild, they have plenty of cues to tell them what time of year it is: daylight, temperature, etc. But in captivity where everything is kept fairly constant year round, they are still able to sense when it's winter time and go into brumation anyway, without any visible cues.
This is kind of a dilemma for me when breeding my bearded dragons. It seems that everyone else's bearded dragons all do the same thing, so during the winter months, it's very hard to find baby dragons, and everyone wants one. But by late spring, baby dragons show up everywhere and the pet stores won't pay as much for them because of the increased supply. Sooo, some of us try to trick our beardies into thinking it's winter sooner in the year. This can be done by gradually adjusting the light timers to shorten the length of the days (there are no windows in my herp room). The temperature is also dropped by as much as 10 or more degrees and feeding is reduced.
Sometimes this will work, but a lot of the time it doesn't.
So why doesn't it work all the time? All the visible and thermal cues are there to tell the dragons that winter is coming. Maybe there's something else that triggers their cycle. Maybe they just know when it's supposed to be winter and when it isn't.
Now the really odd thing is...when it's winter here in the upper hemisphere, it's summer in Australia, their native habitat. So whatever the trigger is, it's not a global trigger (like the earth's position in it's annual orbit around the sun). It is definitely a local trigger... but
what is it?? 