Analysis of the Reingestion Rhythm in Confined Cottontails

Reingestion in caged cottontails occurs as a well—synchronized diel rhythm coinciding with or following sunrise. On a reversed lighting regimen rabbits slowly adjust their rhythmic functions so that reingestion is closely fixed to the light time. When they are exposed to sunlight the relationship between the onset of reingestion and sunrise differs during the seasons. As the days become longer reingestion begins later in the morning. This daily and seasonal relationship appears to follow very closely the condition found in unconfined populations. A gastrocolic reflex appears to govern the rate of hard pellet defecation, but another answer apparently must be found to explain the cyclic production of soft feces. The transition from soft feces to hard pellets occurs previous to and is independent of the evening feeding activity. If rabbits are not allowed to feed in the evening a second period of reingestion occurs, at least in some animals.