Foster and Kreitzman - Seasons of Life - Light pulses as triggers
Type of Spiritual Experience
So they have a number of functions which enable them to 'tell the time', except these functions must be autonomic
A description of the experience
Seasons of Life – Russell G Foster and Leon Kreitzman
So, if it is day-length that enables animals to know the time of year and synchronise conception and reproduction well in advance, how do they measure it?….
The external coincidence model is based on the concept that it is not the total duration of light exposure that matters, but the point of phase at which the light occurs after dawn that is critical. Light at dawn and dusk entrains a circadian oscillator that drives a rhythm in light sensitivity. When light falls during a photo inducible phase, the photoperiodic response is triggered…. The animal or plant does not need to actually experience a full 14, 15 or whatever hours of light to trigger reproductive events, it simply needs to experience light at dawn and then light approximately 14, 15 or whatever hours later. The time between can be spent in darkness. It is the timing of the light pulse that is critical………
Japanese quail were stimulated to breed, for example, only when the 15 minute pulse of light was between 12 and 16 hours after dawn.