Reproduction involves a highly defined series of behaviors. To locate a mate, an animal must know where and when to look. I was unable to find any evidence that animals learn the temporal aspects of this behavior. In most cases, the timing of mating behaviors appears to be a possible form of sympatric speciation. For example, the temporal staggering of male mating flights in East African army ants and the nocturnal activity patterns of moths maintains a temporal separation between species in reproductive timing (Daan, 1981).

There is a relationship between event timing and circadian rhythms in the timesharing behavior of parent doves (Streptopelia risioria) (Gibbon et al., 1984; Silver and Bittman, 1984). The female spends up to 18 h on the nest each day and is relieved by the male during one 6-h interval. If the male is prevented from starting his sit bout at the appropriate time, the female will return after 6 h regardless of the duration of the male's effort. The male, however, will dispute the rightful sitter with her until his 6 h are finished. Given that it is unknown whether the male learns the appropriate sitting interval, it is almost impossible to conclude that the dove has a generalized event timer. The male dove might simply have a genetically timed 6-h alarm clock in his brain that is started by sitting on the nest.

How might this alarm clock work? Presumably, in a way very similar to that of the operation of light on the circadian clock. In the case of the male dove, sitting on the nest causes a pulse of gene expression in the hypothetical "sit" gene. The SIT proteins degrade over time until they reach a minimum threshold level, at which point the dove gets up. This is, of course, the decay timer.

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