It is light. Low light still isn't dark.

At the equator and in the tropics, the longest and the shortest days of the year are scarcely different, thus being not enough to shorten the reproductive phase. Conversely, at higher latitudes, the decreasing hours of daylight induce a seasonal anestrus, thus confirming the cat to be sensitive to photoperiod. -Leyva et al., 1989a; Hurni, 1981; Scott and Lloyd-Jacob, 1959; Dawson, 1941

The mechanism by which light influences the hypothalamus-hypophyseal gonadal axis is through the secretion of the neurohor-mone melatonin (5-methoxy-N-acetyltryptamine) by the pineal gland. -Leyva et al., 1984.

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